Linde brochure2

Linde Technology 1/2003

World Trade in LNG

The Snøhvit Project

Large-Scale Helium Extraction

Liquid-Hydrogen-powered Mobility

On-Site Gas Supply

Reports on Science and Technology

Key components of natural gas liquefaction plants: coil-wound heat exchangers, like they are used in the Snøhvit project (p.12)

Editorial

Dear Readers,

For many years, the intent of Reports on Science and Technology has been to arouseyour interest in some of the latest research and engineering trends. Today that effort is more important than ever: in fact, know-how and the ability to innovate are among the most important factors for success in an environment marked by rapid technological change. In addition to that, both media and public interest in scientificconcepts in general have been growing steadily in recent years. These are two good reasons for modernizing a proven concept.

With the first edition of Linde Technology we hope to inspire you in an up-to-date form with fascinating concepts from the areas of gases and engineering. Scientists and engineers are reporting about the growing importance of world trade in liquefied natural gas and the construction of Europe’s largest natural gas liquefaction plant innorthern Norway. Other articles focus on the versatile inert gas, helium, and on hydro-gen as a guarantee of our future mobility. We also report on processes for on-site supply of industrial gases to refineries.

Linde Technology, which will be published twice a year, will give you an insight into our company. We will be pleased if this first edition arouses your interest, and we wish you an exciting read.

Dr.-Ing. Aldo Belloni, Member of the Executive BoardLinde AGGas and Engineering

Linde Technology

Reports on Science and Technology

Contents

Liquid Energy 4Natural gas trade routes and liquefaction processesWolfgang Förg

The Snøhvit Project 12The MFC® (Mixed Fluid Cascade) Process for the first European Baseload LNG Production PlantEginhard Berger, Wolfgang Förg, Roy Scott Heiersted, Pentti Paurola

From the pipeline to storage 24Large-scale helium extraction and liquefactionMax Bräutigam, Jürgen Clausen

LH2 makes you mobile 30Liquid-Hydrogen Technology for VehiclesJoachim Wolf

Reliable Temperature Control 36Cryogenic temperature-control system for low-temperature processesHans-Jürgen Reinhardt,Dieter Dürr

Tight at Cryogenic Temperatures 40High performance Butterfly Valve for pipelines with cryogenic liquidsM. Metin Gerceker

Less pollutants in petroleum 43On-site supply of industrial gases to refineriesGebhart Scholz, Dirk Schweer,Michael Heisel

1/2003

Partial view of a coil-wound heat exchangerduring assembly (p. 12)

CAD drawing of the LNG baseload plant underconstruction at Hammerfest (p. 12)

New high performance cryogenic butterfly valve (p. 40)

Heating value

1toe = 41.9 x 109 J

1 t LNG ~ 55.0 x 109 J = 131%

World trade volumes

1996 72.6 x 106 t LNG

2001 106.65 x 106 t LNG ≈ +8% annually

Price (in US $ per toe) for natural gas in large quantities (as per 2001)

in Europe 166.3

in USA 161.6

in Japan 184.2

4 Linde Technology I 1/2003

Natural gas trade routes and liquefaction processes

Liquid Energy

Wolfgang Förg

About a fourth of the international trade in natural gas is as liquefied natural gas (LNG). In 2001, thatamounted to 106.6 million tons. The Linde Statoil LNGTechnology Alliance is attempting to use new conceptsto reduce the costs of natural gas liquefaction plantsand, at the same time, to reduce construction time.

Fig. 1 shows a primary energy consumption of the worldin 2001 of 9.126 billion tons of oil equivalent (toe). Thesmall increase of 0.34% reflects the small growth in the industrialized world. Coal and nuclear energy – so tospeak, the home-grown resources – have the highest increase, while consumption of oil and hydropower havedecreased [1].

Germany consumed 335.2 million tons of oil equiva-lent, or 3.7% of the total world consumption. Some 23% of the natural gas supply was traded internationally,and a fourth of that was as liquefied natural gas (LNG).

Fig. 2 shows some important figures for the LNGindustry. One ton of oil equivalent equals 41.9 billion Joules, and one ton of LNG equals approximately 55 bil-lion Joules. This means that the heating value of LNG perunit of weight is about 31% greater than that of oil.

In 2001, world trade in LNG was 106.6 million tons.This is 1.53% of the world primary energy consumption.In 1996, it was 72.6 million tons, an increase of 46.9% in five years. It can be expected that this considerable increase of 8% per annum will continue for some time. In 2001, the price for natural gas in large quantities, in dollars per toe, was $166.30 in Europe, $161.60 in theUSA and $184.20 in Japan.

Since in Japan only LNG is used, this price can be considered as an average price for LNG. In the USA,the price for natural gas has increased considerably to$161.60. Therefore, in the future, larger quantities of LNGwill find their way into the USA. In Europe the natural gasprice of $166.30 is between that of Japan and the USA so that even there LNG can compete against pipeline gas.

Figure 2: Important numbers for the LNG industry

Figure 1: World consumption of primary energy

2001 % 2000 Changein Mio.toe in Mio.toe 01/00 %

Oil 3510.6 38.47 3519.0 -0.24

Coal 2255.1 24.71 2216.8 + 1.73

Natural gas 2164.30 23.72 2157.5 + 0.32

Nuclear 601.2 6.59 585.0 + 2.77

Hydroelectric 594.5 6.51 619.0 - 3.96

Total 9125.0 100.0 9095.2 + 0.34

Germany 335.2 3.67

At present, there are 15 sites of baseload liquefaction plants:Algeria (2) Brunei (1)Libya (1) Australia (1)Abu Dhabi (1) Alaska (1)Qatar (2) Oman (1)Malaysia (1) Nigeria (1)Indonesia (2) Trinidad/Tobago (1)

Other plants are being built, such as Damietta, Egypt;Hammerfest, Norway; and Sakhalin, Russia, and othersare being planned in Africa and South America.

In Europe, there are these LNG receiving terminals with regasification plants:Belgium (1) Italy (1)France (2) Greece (1)Spain (3) Turkey (1)

5Linde Technology I 1/2003

World trade in LNG

One LNG terminal in Canvey Island, UK, was shut downand dismantled as was another one in Nantes, France.

The majority of regasification plants (19) are locatedin Japan. There are also LNG terminals or regasificationplants in Taiwan and Korea. Aside from the two alreadyoperating in Korea, a third one is being built. In the USAthere are still three terminals in use, while a fourth one,Cove Point, Maryland, was converted into a peak shavingplant, but will be turned back into a receiving terminalthis year.

Fig. 5 shows the historical development of LNG exports. In 1964, Algeria started to export LNG from itsCamel plant in Arzew. Numerous plants in Alaska, Libya,Brunei, Abu Dhabi and Indonesia were added in the 60sand 70s. Indonesia quickly became the world’s biggestexporter. In 1983, Malaysia started to export LNG, in1990, the North West Shelf Project in Australia followed.In the meantime, Qatar, Trinidad & Tobago, Nigeria andOman have joined the group [2].

Figure 3: The usual trade

routes for LNG

Figure 4: Liquefaction and

RegasificationPlants in Europe

Liquefaction

Regasification

The first importer was the UK with a terminal in CanveyIsland at the mouth of the river Thames (see fig. 6).Although, the UK stopped importing in 1981, as enoughgas could be supplied by pipeline from the North sea.France and Japan started to import LNG in 1965 and 1969respectively. Japan soon became the biggest importer.Then Spain, Italy and the USA joined the group. It is worthmentioning that, in 1979, the USA imported their largestquantity up to now. In 1980, as a consequence of thesecond oil price crisis and the fact that the price of LNGwas coupled to the oil price, the American importer wasunable to sell the LNG and filed for bankruptcy. Naturally,the shipments by the Algerian exporter decreased.

Even Germany bought LNG through the French termi-nal in Fos sur Mer. As China, India, Mexico and Brazil areplanning imports, the forecasted growth will continue.

Fig. 7 shows the LNG sources for 2001, the quanti-ties and the fractions of the total.

Fig. 8 shows that Europe and the USA together consume only 29%, and Japan, Korea and Taiwan 71% ofthe total of LNG produced.

The enormous investments are the greatest problemin building up LNG supply chains. They require long-termcontracts between financially strong and reliable partnerson both the buyer and seller's side. A certain spot markethas indeed developed in recent years. For instance, for along time the USA only purchased through short-termcontracts on the spot market. But that is not a basis forbuilding new liquefaction plants or new ships. Assumingthe specific investment costs per ton of annual liquefac-tion capacity to be $300 (only very recently has the costdecreased below that), the installed capacity representsan investment of 32 billion dollars. In 2001, 128 LNGships were in operation. These ships have a value ofabout 25 billion dollars. At the same time, 40 regasifica-tion plants were in operation, representing an invest-ment of at least 12 billion dollars. Those numbers do notinclude the costs of gas production, collection and pipingto the liquefaction plant, nor the distribution of the reva-porized gas. These numbers emphasize the enormouseffort necessary to provide only 1.5% of the primaryenergy supply of our world.

New customers will be added to the existing lique-faction plants. India, China and Brazil are already more orless advanced. The outstanding efficiency of gas turbineand steam turbine power plants and the relative envi-ronmental acceptability of natural gas make LNG a preferred source of primary energy for “independentpower producers” (IPP) which will establish themselvesin the heavily populated coastal regions. One project ofthis type was completed in Puerto Rico in 2000.


Peakshaving plants

In contrast to baseload

plants, which operate

through the entire year and

cover the basic requirement

for natural gas, the peak-

shaving plants are used to

cover peak requirements.

They are needed because

the energy supply compa-

nies buy larger amounts of

gas during the warmer sea-

sons than are needed for

average consumption. The

excess is liquefied and sto-

red. During the cold season,

the liquid natural gas is

used to cover the peak con-

sumption. It is first raised

to the required supply pres-

sure, revaporized in regasifi-

cation plants of special

design, and provided to the

consumer net.

The liquefaction capaci-

ties of peakshaving plants

are roughly from 100 to

20,000 std. cubic meters per

hour. Baseload plants can

liquefy up to 800,000 std.

cubic meters of natural gas

per hour (5 million tons per

year), depending on the

particular liquefaction line.

Figure 5: LNG exports by country

Figure 6: LNG imports of individual countries

LNG-Exports 2001

Mio. m3 Mio. t % Change (%)(liquid) 2001/2000

Algeria 42.298 19.373 18.16 - 3.64

Abu Dhabi 11.396 5.219 4.89 2.53

Qatar 27.394 12.547 11.76 20.37

Libya 1.278 0.585 0.55 - 0.16

Nigeria 12.519 5.733 5.38 27.16

Oman 11.975 5.484 5.14 164.17

Middle East/Africa 106.860 48.941 45.88 14.38

Trinidad & Tobago 6.174 2.838 2.65 - 4.16

USA 2.996 1.72 1.29 0.71

Americas 9.170 4.200 3.94 - 2.62

Indonesia 52.422 24.009 22.51 - 11.76

Malaysia 33.662 15.417 14.46 0.77

Australia 16.155 7.399 6.94 1.19

Brunei 14.600 6.687 6.27 - 0.14

Australasia 116.839 53.512 50.18 - 5.32

Total 232.869 106.653 100.00 2.93

Figure 7: The major LNG exporting countries


LNG-Imports 2001

Mio. m3 Mio. t % Change (%)(liquid) 2001/2000

France 19.546 8.952 8.39 2.51

Spain 17.188 7.872 7.38 13.43

Belgium 3.745 1.715 1.61 - 45.82

Türkey 8.038 3.682 3.45 12.59

Italy 5.809 2.660 2.49 - 0.68

Greece 0.879 0.403 0.38 3.53

Europe 55.205 25.284 23.70 + 0.43

USA 11.130 5.097 4.78 3.96

Puerto Rico 0.903 0.414 0.39 57.04

Americas 12.033 5.511 5.17 6.67

Japan 120.071 54.992 51.56 1.34

Korea 35.198 16.121 15.11 10.66

Taiwan 10.362 4.746 4.45 6.79

Asia 165.631 75.859 71.13 3.52

Total 232.869 106.654 100.00 2.93

Figure 8: Imports of LNG

People in the LNG industry have often wished for morecompetition and new concepts to reduce the costs andconstruction time for liquefaction plants. Because of that,the Norwegian Oil and Gas Producer Statoil and Linde AGformed an alliance at the beginning of 1996 with the objective of developing new concepts for:■ the liquefaction process■ the manufacturing of cryogenic heat

exchangers and■ the design and construction of the entire plant.

First, all existing liquefaction processes had to be evaluated. We can distinguish between three differentprocesses:■ the Classical Cascade■ the Single Flow Mixed Refrigerant, and■ the Propane Precooled Mixed Refrigerant Process

Both the Classical Cascade and the SFMRP have been established at three locations (figures 10 and 11).

The three processes with simple mixed flow may haveremarkable differences within their designs, but they have in common that one mixed refrigerant stream iscompressed by one single compressor.

The most successful process so far, however, hasbeen the Propane Precooled Mixed Refrigerant Process of APCI, which has been used with start-up dates from1972 to 2001 in more than 55 liquefaction plants in eight different countries [10].

The liquefaction plant represents approx. 50% of the investment cost of the entire LNG value chain. The Alliance therefore scrutinized and compared the existingprocesses.

Fig. 12 shows the Classical Cascade Process (CCP). A three-stage propane precooling cycle is followed by athree-stage ethylene liquefaction cycle and a three-stagemethane subcooling cycle. While propane is compressedleaving the different suction drums at its dew point, ethylene and methane are vaporized and superheatedbefore being compressed.

Fig. 13 shows the Single Flow Mixed RefrigerantProcess (SFMRP) which was the result of extensive optimization work. The first objective of the Alliance, development of an improved process, led to design ofthe Mixed Fluid Cascade Process (see also page 12)

Comparison of existing liquefaction processes

Location Country Process Year of Start-up

Arzew Algeria TEAL 1965 [3]

Kenai Alaska Phillips Petroleum 1969 [4]

Point Fortin Trinidad & Tobago Phillips Petroleum 1999 [5]

Figure10: Applications of the classical cascade

Location Country Process Year of Start-up

Marsa el Brega Libya APCI 1970 [6] [7]

Skikda Algeria TEALARC 1972 [8]

Skikda Algeria PRICO 1981 [9]

Figure11: Applications of the Single Flow Mixed Refrigerant Process


Fig. 14 shows a sketch of this process, which con-sists of three mixed flows connected in cascade. The pre-cooling cycle consisting of a mixture of C2H6 and C3H8 iscompressed in compressor C1, liquefied in sea water cooler CW1 and subcooled in cryogenic heat exchangerE1A. One part is throttled to an intermediate pressureand used as refrigerant in E1A. The other part is furthersubcooled in heat exchanger E1B, throttled to the suctionpressure of compressor C1 and used as refrigerant in heatexchanger E1B. The liquefaction cycle is compressed incompressor C2, cooled in sea water coolers CW2A andCW2B, further cooled in heat exchangers E1A, E1B andE2. It is throttled and used as a refrigerant in liquefier E2.The subcooling cycle is compressed in compressor C3,cooled in sea water coolers CW3A and CW3B, further cooled in heat exchangers E1A, E1B, E2 and E3, expandedin liquid turbine X1 and used as refrigerant in subcoolerE3. All compressor suction fluids are slightly superheated

Process MFCP C3MRC SFMRP CCP

compressor shaft power % 100 103.3 114.2 115.5at 100% adiabatic efficiency

Heating surface, % 100 100 88.4 105.1cooling water section

Heating surface, % 100 99.1 106.8 94.2refrigerant section

Heating surface total % 100 99.4 100.5 98.0

Number of compressor 3 3 2 3casings

Number of suction lines 4 4 1 9

Maximum flow in m3/h 120.000 200.000 315.000 112.000suction line approx. eff.

Figure 12: Comparison of the principal data for various liquefaction processes

above their dewpoints. One German and several inter-national patents have been granted for this process in themeantime.

Figure 15 shows a comparison of the principal data forthe processes mentioned above.

A special effort was made to investigate the differ-ent processes on a comparable basis. Linde's proprietarydesign optimization program Optisim® was used for thispurpose [11]. We attempted to have similar heat transfersurfaces for all processes within the cooling water andthe cryogenic section. This was not always possible asthe limitation of a minimum temperature difference wasgiven priority.

Under these assumptions the compressor shaftpower at 100% adiabatic efficiency for the refrigerationcycles turned out to be 70.4 MW for the Mixed Fluid Cascade Process. If one compares the compressor shaftpower with real adiabatic efficiencies the advantage ofthe MFCP versus the C3MRC may disappear, because noaxial machine can be applied at the MFCP, while com-pressor C2 in the C3MRC can be built as an axial machine,with higher adiabatic efficiency.

In spite of that Linde sees an advantage for theMFCP, since heat exchangers E2 and E3 of this process areof similar size and well within the limits of manufactura-bility of spiral wound heat exchangers. That means thatthose heat exchangers are not the limiting factor for thesize of a liquefaction train.

As far as the SFMRP is concerned we believe that thelimits of manufacturability are exceeded in several areas,e.g. suction line, separators D1 to D3 and compressor C1.Thus this process can be used only for smaller lines withcapacities not exceeding 2 million tons per year.

Fig. 16 indicates the optimum capacities for the differentliquefaction processes. While the Single Flow MixedRefrigerant Process best covers the capacity up to 2 mil-lion tons per annum, the Dual Flow Mixed RefrigerantProcess and the Propane Precooled Mixed RefrigerantProcess are suited for 1 to 4.5 million tons p.a. and theMixed Fluid Cascade Process for 3 to 8 million tons p.a..


Figure 13: The classical cascade process (CCP)

Figure 14: The single flow mixed refrigerant process (SFMRP)

Figure 15: The mixed fluid cascade process (MFCP)

Figure 16: Optimal capacities of the different liquefaction processes.


The work done by the Statoil - Linde LNG Technology Alliance with respect to process design, selection of maincomponents, manufacturing of cryogenic heat exchangersand the installation of the process plant on a purpose built barge has led not only to significant savings in investment cost but also to a considerable shortening ofthe project execution time. The decision to build theHammerfest plant was a result of this (see also page 12).

Conclusion

Figure 17: This modern LNG ship (Moss Rosen-berg system) was built in Finland. It travels between Abu Dhabi and Japan. Length 290 meters; beam 48.1 meters; draft 11.8 meters.135,000 m3 or 60,000 tons of LNG cargo in 4 aluminum spheres 40.4 meters in diameter.0.15% per day boil-off. 30 MW steam turbine,19.5 knots cruising speed. Cost about$250,000,000.

Figure 19: The North West Shelf LNG plant in Australia

Figure 18: A modern LNG terminal at Ogishima in Tokyo Bay. Almost all the partsof the plant here are underground. The pieris parallel to the coast to allow faster maneuvering. A 50 m shaft extends fromthe pier to the bottom of the sea. From there, a 500 m tunnel extends to the shore.It opens into another shaft from which atunnel runs 1.5 km to the tank farm. Thetwo tanks, almost completely underground,each hold 200.000 m3, allowing an annualLNG turnover of million tons.

Foto

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Literature

[1] The LNG Industry 2001; GIIGNL; Seite 1[2] Fundamentals of the Global LNG Industry

Petroleum Economist, March 1998; Seite 29[3] Pierot, M.: Operating Experience of the Arzew Plant,

LNG 1, Chicago, Illinois, USA, April 7-12, 1968; Session No. 2, Paper 10b

[4] Houser, C. G.; Krusen, L. C.: Phillips Optimized Cascade LNG Process, Gastech '96, 17th Int.LNG/LPG Conf., Vienna, Dec. 3-6, 1996, Conf. Papers

[5] The LNG Industry 1996; GIIGNL; Seite 9[6] Latimer, D. M.: Esso Libya Venture,

LNG 1, Chicago, Illinois, USA, April 7-12, 1968; Session No. 3, Paper 15

[7] Gaumer, L. S.; Geist, J. M.; Harnett, G. J.; Pfannen-stiel, L. L.: The Design, Fabrication and Operation of Large Cryogenic Heat Exchangers, LNG 3, Wash-ington D. C., Sept. 24-28, 1972; Session II, Paper 15

[8] Bourget, J. M.: Experience of Arzew and it’s Effect on the Design of the Skikda Natural Gas Liquefaction Plant, LNG 3, Washington D. C., Sept. 24-28, 1972; Session V, Paper 6

[9 ] Price, B. C.; Mortko, R. A.: PRICO – A Simple, Flexible Proven Approach to Natural Gas Lique-faction, Gastech '96, 17th Int. LNG/LPG Conf., Vienna, Dec. 3-6, 1996, Conf. Papers

[10] James C.: The Air Products Propane Precooled/ Mixed Refrigerant LNG Process Bronfenbrenner,LNG Journal, Nov./Dec. 1996, page 25-27

[11] Burr, Peter S.: The Design of Optimal Air Separation and Liquefaction Processes with theOPTISIM equation-oriented Simulator and it’s Appli-cation to on-line and off-line Plant Optimization,AIChE Spring National Meeting, Houston, Texas,April 7-11, 1991; Paper 50a

[12] Diery, W.: The Manufacture of Plate-Fin Heat Exchangers, Linde Reports on Science and Technology 37/1984

[13] Scholz, W. H.: Coiled Tubular Heat Exchangers,Linde Reports on Science and Technology 18/1973

[14] Foerg, W.: The History of Air Separation,MUST 1996, Refrigeration Science and Technology Proceedings Munich (Germany) Oct. 10-11, 1996

[15] Steinbauer, M.; Hecht T.: Optimized Calculation of Helical-Coiled Heat Exchangers in LNG Plants,Eurogas 96 Conference, Trondheim, Norway, June 3-5, 1996

[16] Abadzic, E. E.; Scholz, H. W.: Coiled Tubular Heat Exchangers, Advances in Cryogenic Engineering, Vol. 18, Plenum Press, 1973

[17] Hausen, H.: Wärmeuebertragung im Gegenstrom,Gleichstrom und Kreuzstrom, Springer Verlag, 1950

[18] Neeraas, B. O.: Condensation of Hydrocarbon Mixtures in Coil-Wound LNG Heat Exchangers,Thesis, University of Trondheim, Norwegian Inst. of Technology, 1993

Wolfgang Förg

Wolfgang Förg (64) came to Linde AG in 1963 when hecompleted his academic study of physics. In 1966 he became head of a newly formed group for process designand calculation for natural gas and synthesis gas plants.He was given the title of General Manager for Gas Plantsin 1976. From 1982 to 1990 he was President of the Linde daughter company, Lotepro Corporation, one of the leading US plant constructors. From 1993 to 1998 he represented the managerial staff on the Supervisory Board of Linde AG. As a member of the Steering Com-mittee of the Linde Statoil LNG Technology Alliance, heparticipated in development of new technologies, oneresult of which was construction of Europe’s largest natural gas liquefaction plant at Hammerfest. Retired since the end of 2000, Wolfgang Förg holds numerouspatents and has authored many papers in his specialty.

The Author

This paper is about the historical development and current importance of liquefied natural gas as a source ofprimary energy. At the beginning of 1996, the Norwegiancompany Statoil and Linde AG established a LNG Technol-ogy Alliance. The second part of the paper describes the results of that alliance, that achieved a reduction ofcosts and construction times.

Abstract

[19] Fredheim, A. O.: Thermal Design of Coil-Wound LNG Heat Exchangers Shell-Side Heat Transfer andPressure Drop, Thesis, University of Trondheim,Norwegian Inst. of Technology, 1994

[20] Barbe et al.: Echange de Chaleur et Pertes de Charges en Ecoulement Diphasique dans la Calandre des Echangeurs Bobines,Proceedings of the XIII International Congress onRefrigeration, Vol. 2


The MFC® (Mixed Fluid Cascade) Process for the first European Baseload LNG Production Plant


The development of LNG production processes for base-load operation are targeted at the following main criteria:■ Minimizing cycle compressor shaft power requirement■ Reducing investment cost by increasing single train

LNG production capacity, or, in other words providingthe benefits of higher train capacity.

This minimum shaft power criterion drives the arguments– investment cost and environmental friendliness – toget-her with other criteria, in a positive direction, althoughthis may frequently be considered as contradictory:■ With minimum shaft power the costs for the cycle

compressors, the drivers (mostly gas turbines) and thecooling system are minimized. That represent a majorportion of the plant investment cost together withminimized instrumentation, electrical, piping, struc-tural steel, construction work, etc.

■ Space and weight of the plant are minimized, which is of great importance for land-based and, inparticular, 9 for offshore installations.

■ The simultaneous reduction of fuel gas consumption reduces the operating cost

■ The minimized fuel gas consumption consequently results in low emissions to the environment.

Increased economy of a LNG baseload plant makes itpossible to increase the capacity for an individual processtrain up to 8 to 10 MTPA LNG production. Two major pieces of LNG plant equipment limit capacities to about 5 MTPA in the single and double mixed fluid processes:■ The centrifugal cycle compressors, which have

fabrication limits at about 90 MW shaft power requirement, along with the gas intake volumes

■ The main cryogenic heat exchanger (coil-wound heat exchanger)

The trend toward large LNG production capacities can be observed at the Snøhvit LNG project. The first approach was a capacity of 3.4 MTPA in one train, which was finally increased, to the current 4.3 MTPA.

Given those benchmarks, Linde-Statoil TechnologyAlliance subjected the potential process options to detailed examination, taking into consideration the thermophysical properties of the natural gas and the possible coolant-cycles.

From that basis, Linde-Statoil Technology Alliancedeveloped the MFC® LNG baseload process (Figure 2).(See also page 4).

This process consists of three mixed refrigerant cy-cles. The precooling cycle consisting of a mixture of C2H6

Development of the Mixed FluidCascade (MFC®) Process

To reduce costs and construction times of natural gas liquefaction plants, the Linde-Statoil Technology Alliance has developed a new process: the Mixed FluidCascade (MFC®). The first European plant using this proc-ess is now being built in the Barents Sea off the northernNorwegian coast. The Snøhvit project – named after thegas field there – has one further unusual feature otherthan the new process: The entire LNG baseload plant isbeing almost completely preassembled and transportedto its operating location by barge.

For a long time, the LNG industry has demanded innova-tions to reduce the costs and construction times of lique-faction plants. Because of that, Linde AG and Statoil foun-ded the Linde-Statoil LNG Technology Alliance in June,1996. The objectives of the alliance were improvementof LNG baseload technology, improvement of projectdevelopment procedures and strategies, cost reduction,and shortening of the construction time, along withdevelopment of economical LNG concepts. After severalyears of comprehensive activities in selection, investiga-tion, and optimization, the results of the joint technologydevelopment peaked with a new LNG process, the MFC®

process (Mixed Fluid Cascade Process) and in numerousjoint accompanying patents.

Eginhard Berger, Wolfgang Förg, Roy Scott Heiersted, Pentti Paurola

Hammerfest

HammerfestMelkøya

Snøhvit

and C3H8 is compressed in compressor C1, liquefied in sea water cooler CW1 and subcooled in cryogenic heatexchanger E1A.

The first European LNG baseload plant operatingwith the newly developed Linde-Statoil MFC® process is currently being built on Melkøya Island off the Nor-wegian coast near Hammerfest, to recover the Snøhvithydrocarbon deposit in the Barents Sea.

The MFC® process is distinguished by several noteworthyadvantages:■ No separator is needed. As that is a relatively

large item of equipment, the cost can be kept low.■ Less circulating hydrocarbon is needed. That has

good effects with respect to the volume and safety of flammable hydrocarbons. It is particularly importantfor compact installations such as that on the SnøhvitLNG process barge or on floating LNG productionplants.

■ The mixed circulation can be adapted directly for the three mixtures, and does not depend on two-phase equilibrium in a separator.

■ The loop portion in the liquefier-heat exchanger need not be overheated out of its subcooling. That is linked with lower heat exchanger dimensions and lower costs.

The MFC® Process has other benefits:■ The three cycle compositions enable optimized match

to the three sections of the cooling curve compared toonly one or two cycle mixtures. That offers excellentefficiency or low energy requirement.

The split of the refrigerant duty to three cycles and compressors instead of one or two allows LNG productioncapacities of up to 8 MTPA in one train, where the otherprocesses have to install costly 2 x 50 % train configura-tions for the compressors and heat exchangers.


Figure 2: The Linde-Statoil MFC® (Mixed Fluid Cascade) process

The compressors of the first LNG baseload plants weredriven by steam turbines with the advantage of havingany required capacity available, more or less stepless.However, the low efficiency, the large equipment and the larger cooling system caused the investors to changeto direct gas turbine drive.

For the Snøhvit LNG baseload plant a great numberof prime mover concepts have been investigated. The following option was initially considered to be the mostpromising:

Selection of Main Drives

Figure 1: Location of the Snøhvit field in the Barents Sea and the LNG plant on Melkøya Island near Hammerfest

Linde is the only manufacturer to produce both the types of cryogenic heat exchangers conventionally usedin LNG baseload plants:■ Plate-fin fin heat exchangers (Figure 3)■ Coil-wound heat exchangers (Figure 4)

Each of these heat exchanger types has specific benefitsand disadvantages. Among others the single plate-fin heat exchanger core is relatively competitive. But largeLNG plants require numerous plate-fin heat exchangers in parallel. Part of the cost advantage of the individualexchangers is reduced by the complexity of the pipingneeded to connect numerous plate-fin heat exchangers.The coil-wound heat exchangers are very robust whenexposed to thermal stresses which may be encounteredin the low temperature sections during start-up or impro-per operation.

Selection of Heat Exchangers

■ A General Electric Frame 7 gas turbine driving the pre-cooling and liquefaction cycle compressor directlyon a single shaft together with a starter/helper motor

■ A steam turbine driving the two-stage sub-cooling cycle compressor also on a single shaft

The steam would be generated by waste heat recoveryfrom the Frame 7 gas turbine exhaust gas stream.This scheme showed the lowest investment cost. Howe-ver, an availability study by Statoil showed that an all-electric drive configuration would provide higher LNGproduction rates per year due to more onstream days.The higher LNG sales revenues would compensate thehigher cost of the electric power system, which resultedin improved internal rate of return figures.

Therefore, Statoil decided to install 5 highly efficientGeneral Electric LM 6000 gas turbines with electrical generators. The back-up would be provided by the localpower grid.

This all-electric drive scheme for Snøhvit is unprece-dented. However, it is considered as the most advancedsystem providing the highest availability for single train installations. The concept is expected to be adaptedto further LNG plant projects both for land-based and foroffshore installations. One additional benefit is thedecoupling of the train capacity from the drive sizes, be-cause the electrical drive motors for the compressors canbe operated almost stepless. If the compressors were tobe driven directly by the gas turbines, there would belimitations because only certain sizes of gas turbines areavailable.


After a detailed comparison it could be demon-strated that each heat exchanger type has specific meritsat the proper place. Therefore, it was decided to use theplate-fin heat exchanger for the pre-cooling section and the coil-wound heat exchanger for the liquefactionand for the sub-cooling section in the Snøhvit project.

In most of the large LNG baseload plants the cryo-genic heat exchangers have individual insulation. That istrue of both the plate-fin and the coil-wound heatexchangers. This insulation mainly consists of polyure-thane foam or of foam glass.

For the Snøhvit LNG project, however, the alternativeinsulation method has been chosen: the cold box. Coldboxes are often installed in cryogenic processes such asair separation and LNG peakshaving plants. A cold box isa box of normal carbon steel plates enclosing the cryo-genic equipment and piping. The void space is filled withthe insulation material perlite, a powdery mineral. Figure5 shows the typical structure of the interior of a cold box.

Establishment of the operating conditions for the SnøhvitLNG plant had to take various feed gas compositions intoconsideration, as well as the prevailing climatic condi-tions at the site and the sea water available for cooling.The feed gas flow to the LNG plant from the incomingmultiphase pipeline is 20.8 million standard cubic metersper day. The plant design is based on maximizing LNGproduction for the given feed rate. The production targetfor the plant is at least 5.58 billion standard cubic metersper year at 330 operating days.

The feed gas is supplied from 3 different gas fields,the Snøhvit, Askeladd and Albatross fields. They areabout 150 km offshore from the plant site on Melkøya Island near Hammerfest. Five different feed gas composi-tions had to be considered for operating the LNG plant.

These feed gases have different compositions. Particularly important data for the process steps andequipment are the maximum concentrations of nitrogen,carbon dioxide, and heavy hydrocarbons.

In normal operation of the offshore and onshore production facilities, the feed gas pressure is controlledbetween 50 and 90 bar by adjusting the offshore pro-duction rates.

As the Snøhvit field is depleted, the feed stock pressure will decrease to a final pressure of 35 bar. In the future, that may require onshore compression of thefeed gas downstream from the slug catcher (condensateseparator). Depending on the pressure of the feed gas,its temperature can range from –4°C to +5°C.

Feed gas conditions for the Snøhvit LNG plant:


Figure 3 (above): Typical plate-fin heat exchanger for LNG plants

Figure 5 (left): Typical structure of the piping and equipment inside a cold box

The so-called ‘cold box‘ offers a numberof advantages insulating low-temperatureprocesses:■ The cryogenic process equipment and

piping are all welded together and laidout as compactly as possible, resultingin minimal material and thermal lossesand maximal safety.

■ The cold box can be constructedmechanically in workshops under opti-mized conditions

■ The cold box provides externalmechanical protection during transpor-tation and in the plant itself

■ Apart from the “all welded” principleof the cold box interior, which is con-sidered as the safest installation mode,the cold box enables detection of

possible leakages by use of a pulsedflow of nitrogen through the perlite-insulated space.

Fire resistance requirements can be metwith a cold box in an efficient way. This isparticularly relevant for the compactSnøhvit plant layout as well as offshoreLNG plant designs in general.

Figure 4: Typical coil-wound heat exchanger for LNG plants

The cold box and its advantages


The particular ambient conditions cause specific problemsfor man and material both during the construction phaseas well as during plant operation. The visibility, humidity,temperatures, snowfall and wind chill are especiallyimportant.

The ambient temperatures on Melkøya Island rangefrom –20.5°C to +27°C for a 100 year prediction and from–17°C to +22°C in a corresponding 1 year prediction period. The extreme one hour wind speed 10 m aboveground is 35 m/s in the 100 year prediction. The meanrelative humidity is 75%. The extreme daily precipitationis 70 mm for a 100 year period and 50 mm for a 50 yearperiod. It is assumed that the expected snow depth will be similar to Hammerfest with 230 cm for a 100 yearprediction period and 210 cm for a 10 year period. Reduced visibility due to heavy snowfall or blizzards willoccur during September to May. Reduced visibility fromfog will have a more or less even probability throughoutthe year.

Heavy icing with more than 5 cm of accumulated icethickness can be expected in February and March. Thecooling effect of combinations of wind and low tempera-tures shows that uncomfortable cooling of human bodymay occur throughout the whole year. In wintertimeabout 50% of the time the cooling (wind chill) is uncom-fortable on unprotected skin. In about 10% of the time inwinter frostbite may occur on unprotected skin. Longdarkness and sleet are further phenomena, which needspecial attention.

One consequence on the adverse weather conditionswas the decision to install as much as possible of theprocess plant onto a steel barge in order to reduce theconstruction effort and time on site.

Ambient Conditions on the Melkøya Island Site:

Cooling medium

One of the special benefits of the Melkøya location is the availability of cold seawater for process cooling, It iscollected at 80 m water depth and has a temperature of 5°C. This low temperature allows LNG production with about 20 to 30% less power consumption than at locations in warm regions, where most of the existingLNG plants are located. This benefit extends also to reduced CO2 emissions as well as reduced investmentcosts of the cycle compressors, the drives, and the cool-ing system, including the seawater coolers.

This seawater is considered to be clean. Thereforethe heat exchangers need not be designed for mechani-cal cleaning on the seawater side. The installation of a hypochlorite injection unit to prevent marine growth isnot presently foreseen.

The following plant components are provided in order tominimize consumption of feed gas or fuel gas. (Figure 6):

■ The highly efficient MFC® Process with 3 mixed refrigerant cycles and plate-fin heat exchangers forpre-cooling and a coil-wound heat exchanger each for the liquefaction and for the sub-cooling section, all arranged in a cold box

■ Highly efficient GE LM 6000 gas turbines drive electric power generators (5 gas turbines with back-up from the local grid)

■ The 5 gas turbines are equipped for waste heat recovery with heat exchangers in the exhaust ducts,where a hot oil cycle is re-heated to provide processheat, mainly for the CO2 removal and for the dehydration unit.

The gas turbines utilize 41% of the heating value of the fuel gas. Together with the hot oil heating by the gasturbine exhaust gas, the overall thermal utilization of the fuel gas very high. Therefore Snøhvit is a projectwhich is very responsible ecologically.

MFC® Process, with Power-Heatcoupling

The recoverable reserves of the hydrocarbons in theSnøhvit, Askeladd and Albatross deposits are in excess of300 billion cubic meters. With the feed rate of 6.9 billioncubic meters envisaged for the LNG plant a production time of more than 40 years is envisaged, so that a second train with the same capacity could be justified. The two plants together would then have a production life of more than 20 years each.

The following hydrocarbons will be produced from the6.9 billion cubic meters feed stream:■ LNG: 4.3 mtpa (million tons per year) (mostly

methane with small proportions of ethane, propaneand butane)

■ LPG: 0,2 mtpa (LPG: Liquefied Petroleum Gas; propane and butane)

■ Condensate: 0.8 mtpa (mostly heavy hydrocarbonssuch as pentane, hexane, etc.)

About 6% of the feed flow is used as fuel for the gas turbines. 7% of the feed gas is inert / sour gas compo-nents. The N2 is released into the atmosphere, and theCO2 is returned to a subsea reservoir.

Production volumes and energy consumption

17Linde Technology I 1/2003Linde Technology I 1/2003

Figure 6: MFC® Process with

Power-Heat coupling

Process and utility units within the Snøhvit LNG project

The production of LNG requires a great number of proc-ess, treatment, liquefaction, utility and support units.The natural gas arrives at the plant boundary through asubsea pipeline. Possible condensate slugs have to beseparated in a large finger type slug catcher. The compo-nents CO2 and H2O must be separated, because theywould freeze out and plug the pipes. Mercury can alsooccur. It must also be separated, because it would causedestruction of the aluminum plate-fin heat exchangersespecially when it is present in combination with air. An activated methyldiethanolamine (aMDEA) wash unit isused to remove CO2, which may be present in the differ-ent feed gases at from 5.2 up to 7.9 mol%, while thewater is separated in a fixed bed molecular sieve adsor-ber station.

The MFC® liquefaction process operates in plant Unit25. The cryogenic heat exchangers are arranged in a coldbox together with the piping. The dimensions of the cold box are 12 m x 17 m x 48 m. The compressors withintercoolers and seawater aftercoolers together with thenecessary auxiliary equipment like separators, valves andhydraulic turbine expanders are also part of Unit 25.

The LNG from the Unit 25 is routed to the LNG stor-age tanks in Unit 42. These tanks are 2 x 125 000 m3 full-containment steel tanks with concrete shells. From thesetanks the LNG is periodically loaded onto shuttle LNG

carriers. The gas formed during loading, which comprisesdisplacement, flash and boil-off gas, is returned to theland LNG tanks, from where it is recompressed jointlywith the boil-off gas from the land LNG tanks.

The different feed gases contain between 0.8 and3.6 mol% nitrogen, which has to be removed to below 1 mol% in the product LNG. This is performed in a cryo-genic process in Unit 24 with a column and plate-fin heatexchanger in a separate cold box with dimensions of 3,6 m x 4 m x 32 m.

The CO2 from the wash unit is recompressed andreinjected into an offshore reservoir.

Heavy hydrocarbons are recovered after the pre-cooling section of the natural gas liquefaction unit. Theyare fractionated into ethane, propane and butane. Thesecomponents are used as refrigerant make-up, as the los-ses through the compressor seals have to be replenishedin the cycle mixtures.

Fractionation Unit 26 produces LPG (Liquefied Petro-leum Gas), a mixture of propane and butane, which istemporarily stored in a 45 000 m3 cryogenic full contain-ment steel tank with concrete outer shell. From there theLPG is periodically loaded onto tankers.

The heavy fractions are combined with the conden-sate streams from feed gas treatment. Condensate is stored in a 75 000 m3 conventional steel tank at atmos-pheric conditions, from where it is offloaded periodicallyto shuttle tankers.


The Snøhvit LNG-Plant is being erected north of the PolarCircle on the remote Melkøya Island under extreme climatic conditions without sufficient infrastructure closeto the site. Therefore keeping the manpower required onsite to an absolute minimum has been a major concern.

In a very early stage of the project it was decided tobuild the process plant as a preassembled and completelytested unit, which would be as ready to go into operationas possible, at a European site with favorable constructionconditions. In order to be able to transport the processplant to Melkøya Island, it was decided to erect the proc-ess plant on a floating barge hull. Figure 8 shows a CADmodel of the process plant layout (topside) on the barge.

The process plant can be transported either by “wettow” or by a “Heavy Lift Vessel” (HLV). The HLV optionwas chosen because of several advantages. This conceptprovides the minimum construction costs and simultane-

Barge Concept for Plant Construction

ously the shortest construction time, because all the other activities can be accomplished on site in parallelwith production of the process barge.

The barge hull design considers all the requirementsof the process plant, the loads from the steel structures,equipment and piping as well as all dynamic influencesduring construction on the barge deck, floating out, andtransportation of the completed process barge from theyard to Melkøya Island.

Dimensions of the box-like barge hull are defined asbeam 54 m, length 154 m, and draft 9 m. It weighs10,300 tons. The barge hull is being fabricated in a yardin Northern Spain and will be towed to the outfittingyard.

During the pre-engineering phase it was determinedthat conventional construction rather than modularizingof the process plant on top of the barge would result in a significant reduction of structural steel. Therefore it was decided to erect the process plant primarily in con-ventional construction on the self-supporting barge deck.

Figure 7: Block diagram of the Snøhvit LNG-plant.


Figure 8: CAD model of the process plant on the barge with electrical generation equipment.

The box-like barge is currently being assembled at theIzar shipyard in northern Spain. It will be mechanicallycomplete in the Fall of 2003. Immediately thereafter, thebarge will be towed to the Dragados Offshore integrationshipyard at Cadiz in southern Spain, where it will be to-wed alongside an outfitting dock, ballasted, and sunk tothe bottom of the sea. The sea bottom will be specially

Assembly and outfittingon the barge

Some process plant units such as■ 5 LM 6000 gas turbines ■ the electrical substation■ and other smaller process and utility unitswill be installed preassembled on the barge deck. All other stationary and rotating equipment as well as steelstructures and piping will be erected on the barge deckin a conventional structure.

prepared to hold the planned final weight of the barge.Dragados Offshore has also been contracted to preparethe base for the barge and to integrate the process andauxiliary equipment on it.

The process plant plot on the deck of the barge is dividedin three areas by access routes:■ The main process area■ The refrigeration and compression area■ The power generation and substation area.

That provides for good accessibility of these areas during the construction, which will be done in parallel in those areas.■ A permanent weight control and deflection monitor-ing procedure has to be installed from the very beginningand maintained throughout the construction period.

After the barge arrives at the shipyard, the deck will beprepared for the plant installation. The barge preparationactivities include installation of foundations for the largeand heavy equipment as:

After completion of commissioning all necessary meas-ures for weather and transport protection must be instal-led, such as sea fastening of heavy pipes and equipment,etc. Defined detachments of bolts piping and mechanicalshaft couplings will be released according to a transportflexibility analysis. Necessary temporary equipment likeballast pumps, bollards, ropes, winches, navigation lights,stress and acceleration monitoring equipment, etc. for themarine transportation and site docking will be installedaccording to the approved transport manual. All loose-shipped items like hook-up materials and spools locatedonboard will be thoroughly fastened and registered inthe Ship Loose Parts Register. That also applies to all thepieces of assembly equipment.

In preparation for transport to Melkøya Island, allequipment and piping must be preserved carefully. Allopenings, break points and loose ends must be closedand sealed properly. Certain systems have to be filledand slightly pressurized with nitrogen, with control gauges installed on those systems. All nitrogen-pre-served systems must be marked as such by significantlabeling. Machines and their oil units must be filled up with preservative oil and properly vented according to manufacturer’s requirements. Electrical and instrumen-tation equipment must be preserved as specified by themanufacturers.

The next step will be preparation for floating thebarge and towing it to the specified handover point atthe HLV in Cadiz harbor.

Completion of outfitting and hook-up work must be donestrictly according to the detailed construction plan so that the complete system will be ready for “punch-out”(checking of the documentation and installation), pressure testing and release by the following disciplines.Inspection, testing verification and documentation ofmechanical completion will be an ongoing activity duringthe completion of outfitting. Prior to handover to com-missioning, punch-out will be organized. The first areasor systems have to be handed over in parallel with the ongoing construction work. Some of the equipmentvendors are required to supervise installation, testing andcommissioning of their equipment.

Mechanical Completion andHand-over

Preservation and Preparationfor Transport


Figure 9:Typical Heavy Lift Vessel (HLV) as a potential carrier for the process barge. The most importantdata for the ship:Length overall 217.0 mBeam 42.0 mGross deadweight capacity 56,000 mtOpen deck length 178.2 m or 157.2 mOpen deck area more than 7215 m2

Cruising speed 14.5 knots

■ Electrical substation■ Power generation and associated equipment

and structures■ Main structural members■ Deck-mounted equipment.

Rather than with modular construction, with the individ-ual installation method the erection of the equipmentand piping for each level can be started and completed inthe three defined subareas.

The heavy equipment, such as premounted columnsor gas turbines is being installed so that the individual loads are distributed as evenly as possible across the bargedeck in order to avoid uneven load distribution, whichcould cause deflections or stresses within the barge hull.

After installation of the substation, the five LM 6000Gas Turbines, the other equipment and parts will be installed so that the construction of defined regions,including provision of pipelines, on-site mounted instru-ments, electric motors, etc., can be completed.


The concept foresees a fully equipped and pre-commis-sioned process barge. The process barge is transported tothe site on the Norwegian coast of the Barents Sea. Itwill weight approximately 35,000 tons during transporta-tion.

The marine activities are critical to the project. Mari-ne transportation of the barge could be accomplished bytowing from any European yard. However, using a specialtransportation solution based on a HLV (heavy lift vessel)reduces the transportation schedule and improves theoverall safety of the transportation to Melkøya Island. A typical Heavy Lift Vessel as a potential process bargecarrier is shown in Figure 9.

Transport to Melkøya Island

Figure 10: Solidly installed process bargeat the site on Melkøya Island, in a CAD model.

Figure 11: Overall view of the Snøhvit LNG installation on Melkøya Island, in the CAD model.

The site preparation on Melkøya Island was started inmid-2002 with construction of a camp, rock blasting, andleveling. An access tunnel under the water between theisland and the mainland has been commenced andshould be completed in September 2003.

A dock for the process barge will be excavated withthe relevant length, depth and width. On arrival at Melk-øya Island, the process barge will be docked inside theLNG plant and ballasted down, providing a permanentfoundation for the process systems. The area under thebarge will be backfilled with gravel. After docking, theprocess barge will be given a concrete deck and becomean integral part of the overall LNG facility, see Figure 10.

Site Preparation and Installation on Melkøya Island

Besides the process barge there are other units, buildings and equipment which will be installed on Melkøya Island including:■ Pig receiver and slug catcher■ Tank farm with 2 LNG tanks, 1 LPG tank and

a condensate tank■ Metering stations for LPG and condensate■ Transfer station for LNG, LPG and condensate■ Construction jetty for site supply■ Construction jetty for construction activities■ Utility service station for offshore/

subsea production■ Ethane and propane refrigerant drum■ Hot oil drain drum■ MEG (methyethylene glycol) tanks■ Fresh and deminaralized water tanks■ High and low pressure flares with separators■ Cooling water intake and pump pit , sump,

outlet and weir box (or equivalent pipe design)■ Fire-extinguishing water system■ Effluent treatment plant■ Electrical power network, substations for tank

storage and harbor■ Buildings for the central control room, offices,

canteen, first aid, bathrooms, maintenance facilities,warehouse, fire station, garage parking lots, guardhouses/check points at tunnel entrance as well as on island (including fence between two areas), harbor offices, chemical storage, storage for gas bottles, laboratory, harbor facilities for tug and mooring boats

■ Permanent camp■ Temporary camp■ Subsea tunnel, roads, helicopter landing area■ Rock protection walls■ Service harbor

In addition, spaces for future extensions, for instance, for a second process train parallel to the process barge,will be provided. Eventually an area of about 1000 m x300 m will be occupied by the Snøhvit LNG baseloadplant, see Figure 11.

Other plant installations onMelkøya Island


The Snøhvit license partners made their final commit-ment to commercialize the gas and condensate reservesof the Snøhvit area in September 2001. The NorwegianParliament approved the plan for development and oper-ation of the Snøhvit area in March 2002.

The Snøhvit LNG chain will begin operation in Octo-ber 2006 and will be the first LNG base load plant inEurope. The capacity of the LNG chain is 4.3 mtpa in asingle train. The capacity selection is based on an overallrisk assessment, including potential technology qualifica-tions.

The Snøhvit LNG chain is a valuable contribution toan eco-responsible future, which will probably see an in-creased share of natural gas in the primary energy mix.

The combination of the Linde-Statoil MFC® processwith an energy system based on gas turbines derivedfrom aircraft engines, delivering electric power and proc-ess heat is obviously the right technology, providing low-est environmental emissions at high economic viability.

Summary and Outlook

The Snøvit project on the internetYou can find current information about theSnøhvit project, including seasonal impressionsfrom the construction site by Webcam, on theinternet at: http://www.statoil.com/statoilcom/snohvit/svg02699.nsf

Eginhard Berger

Eginhard Berger (60) graduated in mechanical engineer-ing at the Technical University, Munich. He worked in the aerospace industry before joining the Linde AG, Engineering Division, Höllriegelskreuth, Munich, in 1969.He was first involved in computerizing the physical properties of natural gas components. As a project andsales manager he later was decisively involved with the

LNG projects at Snøhvit (Norway) and Xinjiang (China). For the past threeyears he promoted the application of the newly developed Mixed Fluid Cascade Process to offshore LNG production concepts. Eginhard Berger is,among other things, a member of the European Technical Committee for the standardization of LNG plants.


With the Snøhvit LNG project, the Linde-Statoil LNGTechnology Alliance joins the select circle of companieswhich can provide highly efficient LNG technology forbaseload plants. The liquefied natural gas from theBarents Sea, the site of the Snøhvit project, is the firstmajor LNG project in Europe. It will bring positive chan-ges and effects not only for the industry affected, butalso for consumers. The article describes the specialfeatures of the MFC® process and the Snøhvit LNG pro-ject, with all the important details.

Abstract

Wolfgang Förg

Wolfgang Förg (64) came to Linde AG in 1963 when hecompleted his academic study of physics. In 1966 hebecame head of a newly formed group for process designand calculation for natural gas and synthesis gas plants.He was named General Manager for Gas Plants in 1976.From 1982 to 1990 he was President of the Linde daugh-

ter company, Lotepro Corporation, one of the leading US plant constructors.From 1993 to 1998 he represented the managerial staff on the SupervisoryBoard of Linde AG. As a member of the Steering Committee of the LindeStatoil LNG Technology Alliance, he participated in development of newtechnologies, one result of which was construction of Europe’s largest natu-ral gas liquefaction plant at Hammerfest. Retired since the end of 2000,Wolfgang Förg holds numerous patents and has authored many papers inhis specialty.

The Authors

Roy Scott Heiersted

Roy Scott Heiersted was awarded a Master of Science de-gree in 1968 from the Norwegian Institute of Technology,Division for Refrigeration Technology. He has been invol-ved in both LNG technology and business developmentsince he joined Statoil ASA in 1984. In 1997, he was ap-pointed Alliance Manager of the technology alliance with

Linde AG. He presently holds the position of Technology Manager in theSnøhvit LNG Project.

Pentti Paurola

Pentti Paurola of Statoil ASA (Norway) was awarded a Master of Science degree in 1972 from the University of Technology, Helsinki (Finland) in Chemical Engineering.He has a vast experience in both engineering and operation of refinery and petrochemical plants and holdsseveral international patents in this field. He presently

is a Lead Process Engineer in the Snøhvit LNG Project.

Literature

[1] Roy Scott Heiersted, Statoil: Snøhvit LNG Project – Concept Selection for Hammerfest LNGPlant, GASTECH 2002, Qatar 13-16 October 2002

[2] W Förg, W Bach, R Stockmann, Linde and R SHeiersted, P Paurola, A O Fredheim, Statoil:A New LNG Baseload Process and Manufactur-ing of the Main Heat Exchangers. LNG 12 Conference, Perth, May 1998.

[3] R S Heiersted, S Jacobsen, S Nystrøm, Statoil:Project Execution Strategy for the HammerfestLNG Plant, Snøhvit LNG Project. Gastech 1998,Dubai, December 1998.

[4] S W Jensen, E Herløe, S Jacobsen, R S Heiersted,Statoil: New Project Execution Strategy for Base Load LNG Plants. Eurogas 99, Bockum,May 1999.

[5] R S Heiersted, Statoil: Cost Reduction Potentialof the Execution Strategy for the Snøhvit LNG Plant. IBC’s International Forum on LNG, London, October 1999.

[6] R S Heiersted, Statoil: Commercializing Snøhvit- An Atlantic Basin LNG Chain. CWC Group, World LNG Summit, London, September 2000.

[7] S W Jensen, Statoil: Developing the Snøhvit LNGChain. Gastech 2000, Houston, November 2000.

[8] R S Heiersted, R E Jensen, R H Pettersen, S Lillesund, Statoil: Capacity and Technologyfor the Snøhvit LNG Plant. LNG 13 Conference,Seoul, May 2001.


Max Bräutigam, Jürgen Clausen

Large-scale helium extraction and liquefaction

From the pipeline to storage

Algeria has very large natural gas fields. Most of the natural gas is sold to Europe through pipelines and as liquid. Two of the four existing pipelines run from the gasfields in the Sahara to Italy and Spain. The other twopipelines run to Arzew near the Moroccan border and toSkikda, near the boundary with Tunisia. This natural gas is liquefied at Arzew and Skikda for transportation (seealso p. 4).

Before the natural gas goes into the cryogenic partof the plant to be liquefied, it must first be dried and carbon dioxide must be removed to prevent blockages in

Plants for natural gas processing and liquefaction

Industrial demand for helium is growing steadily.Separation from natural gas is the most importantprocess for recovering the inert gas. Design of newproduction installations certainly adds complexrequirements for plant engineering. For the plannednew plant for helium extraction and liquefaction at Skikda, Algeria, Linde engineers are showing thatthey have mastered the complete process fromextraction to storage.

The inert gas helium has many attractive chemical andphysical properties: it is colorless, odorless, tasteless,nontoxic, noncorrosive; and it is the only element in theperiodic system that remains liquid at normal pressuredown to absolute zero. Except for neon, it is the only ele-ment for which no chemical compounds are known. Thesum of these special properties is the basis for its manyuses in industry and research (Figure 1). Helium use isrising, for instance, in the fields of fiber optics, welding,breathing gases, leak detection, laser technology, super-conduction technology and particle physics.

Annual helium production for the world is about 160 million standard cubic meters (Nm3). Approximately85% of the helium produced is from natural gas sourcesin the USA. The helium consumption in Europe in 2002 was calculated at about 30 million Nm3. It was providedfrom wells in Poland (Odolanov), Russia (Orenburg) andAlgeria (Arzew), and from the US gas fields. Increasingdemand in recent years has been satisfied by added natural gas imports from the US. The annual growth rateshave been from 5% to 10%. Publications in magazines in

that field indicate an annual growth of about 8%. Giventhe limited production capacities over the world, and the increasing dependency on the gas market in the US,future helium supply will remain a bottleneck.

Extraction from natural gas is the only commerciallyfeasible source for helium. The helium concentration innatural gas depends on the location of the gas field.Recovery of helium as a byproduct in natural gas produc-tion and treatment is a complex problem.

Based on the invention of air liquefaction by Carl vonLinde a hundred years ago, the know-how and experi-ence of Linde AG in process engineering, plant operationand gas distribution have improved enormously. Lindetechnology for■ gas processing■ natural gas liquefaction■ cryogenic gas separation to remove nitrogen■ recovery of crude helium■ helium purification and storagehas become the state of the art throughout the world.Linde technology will also lead to future innovations inplant design. A large new helium extraction and liquefac-tion plant will be completed in Algeria, at the Skikda siteon the Mediterranean Sea, by 2005. It will have a capac-ity of 15 million Nm3 per year.

Protective gas welding (laser, MIG/MAG) 18%

Heat treatment (annealing ovens, glass fibers) 16%

Pressure testing (helium leak tests) 6%

Aerospace (rocket propulsion, Zeppelins) 7%

Medicine (magnetic resonance tomography) 5%

Science/Research (superconduction, cryogenics) 24%

Recreation (ballooning, diving) 3%

Gas chromatography; test gas in spectrometry 5%

Inert gas in semiconductor technology 16%

Figue 1: The major uses of helium in industry and research


the heat exchangers because of water and carbon diox-ide freezing out. Algerian natural gas contains only tracesof helium, but, because the quantities of gas handled inthe liquefaction plants is very large, the total amount ofhelium is of interest for commercial recovery.

In the LNG plant, the natural gas is cooled with a refrigerant and liquefied. Low-boiling components suchas nitrogen, hydrogen, argon, and the helium in the gascannot be liquefied at the temperatures which are lowenough to liquefy natural gas, so they remain as gas. So when the natural gas is cooled in a separator, anexpansion stage produces a gas in which the helium isenriched up to several percent by volume, along withmethane and nitrogen. Results of analyses at this pointdepend on the liquefaction process. Figure 4 shows typical data of the helium recovery plant feed stock.

Natural gas liquefaction always handles very largeamounts of gas in order to attain the highest efficiency.But these plants are usually designed as multiple linesfor reasons of feasibility. As a result, capacities of individ-ual lines now in operation are up to 460,000 Nm3/hour.Plants with capacities of 660,000 Nm3/hour per line areunder construction.

The limits of line size in these large plants are due to the drive systems for the compressors and for the heatexchangers, which are coil-wound heat exchangers inalmost all plants. The coil-wound heat exchanger inwhich the natural gas is chilled and liquefied (Figure 2)is the most important static component.

Figure 3 shows, as an example, a natural gas processing plant built some years ago with a capacity ofabout 400,000 Nm3/hour. Other natural gas processingplants with capacities of up to 3,000,000 Nm3/hour areunder construction.

Figure 2: Coil-wound heat exchanger

Figure 3: Large plant for natural gas liquefaction

Gas volume: 50.000 Nm3/hour

Pressure: 0.5 MPa

Composition: 55 55 mole-percent N2

40 55 mole-percent CH4

5 55 mole-percent He

Figure 4: Typical data for the feed gas for the helium extraction plant

A cold box design, as shown in Figure 9, was selected forthe cryogenic gas separation plant. Such a design allowsthe apparatus and pipelines involved in the low-tempera-ture processes to be insulated simply. They are built in abox which is then filled with a powdered insulator. Ifrepairs are necessary later, the flowable insulating pow-der can be removed easily.

All the components are placed in the cold box:■ plate-fin heat exchangers■ columns■ connecting pipes■ cryogenic control valves, and■ supporting equipmentThe cold box is assembled in the factory, utilizing experi-ence and know-how from the somewhat similar designof air separation plants.

Heat exchange in cryogenic plants usually takesplace in aluminum plate-fin heat exchangers becausethey allow heat exchange of multiple streams simultane-ously. The plate-fin heat exchangers are hard-brazedwithout flux at about 600 °C in a vacuum chamber.Because of that, the heat exchange units are very cleanafter brazing. Figure 8 shows the most important techni-cal data (limits) for one of the heat exchangers.

The crude helium from the cryogenic separationplant still contains too much nitrogen and methane for itto be liquefied directly. Those compounds would freezeout during helium liquefaction. Therefore, those compo-nents are removed, except for traces, by a pressure-swing adsorption plant at ambient temperature. Theproduct from that plant is almost pure gaseous helium,containing 99.999% pure helium.

Specific surface: 1 400 m2

Maximum unit dimensions: 1.5 m x 1.5 m x 8.0 m

Material: Aluminium

Maximum pressure: 11.5 MPa

Figure 8: The most important technical data (limits) for one of the heat exchangers.


Helium extraction from natural gas

Figure 5:Cryogenic gas

separation plant

Figure 7:Plate-fin heat

exchanger

Figure 6:Natural gas

treatment and C2+ separation

Helium extraction from natural gas is a cryogenic processin which the mixture He/N2/CH4 must be separated. Theprinciple of the separation – cooling and liquefaction – issimilar to the LNG production, as described above. As thegas contains helium, it cannot be completely liquefied,and a residue of gas remains. That residue containsgreatly concentrated crude helium, containing about 80%helium. The cryogenic liquid is separated into its compo-nents, nitrogen and methane, in a distillation column,and the two products, as well as the crude helium, arewarmed back to ambient temperature (figure 12).


Helium liquefaction and storage of liquid helium

There have been changes in both the capacities and thesizes of helium liquefaction plants over the past decades.Design of the first air-liquefaction plant goes back to Carlvon Linde in 1895. The process was based on a heatexchanger and an expansion valve. That configurationhas become known as the Linde process. Linde built thefirst helium liquefier in 1932. It was based on the sameprinciples, but used three stages of chilling. In the pio-neering days of cryogenics, the capacity was around 3 to4 liters/hour. Today, a single helium liquefaction plant in continuous operation can produce 3,500 liters/hour ormore.

Helium, just like natural gas, is liquefied for transportation. That requires the following process steps and installations:■ helium liquefaction with adsorption of trace impurities■ storage of liquid helium■ preparation and filling of the transport containers.

The helium feed gas is sent from the helium recoveryand purification unit to the liquefier (cold box) at a pres-sure of about 2.0 MPa (Figure 9). The helium is chilledand liquefied in a modified Helium Brayton cycle usingliquid nitrogen.

Helium is cooled from ambient temperature to about80 K by return of cold helium gas and vaporization of liquid nitrogen. Gas-bearing turboexpanders (Figure 10)are placed at different temperature levels along the process. They provide chilling to nearly the liquefactiontemperature. Finally, the feed gas is expanded and partially liquefied in a Joule-Thompson stage. The liquid-gas mixture is taken to the storage container, where theliquid collects. The gaseous portion is returned to the cold box, warmed in that, and taken to the input of theliquefaction plant. The heat exchanger required for thecryogenic process are vacuum-brazed plate-fin heatexchangers which are suitable for the low temperature,down to about 4 K, as well as for the external vacuum-insulated space.

The storage tanks for liquid helium are double-wal-led pressure containers with multilayer vacuum insulationand a radiation shield chilled with liquid nitrogen. Eachone has a capacity of 30,000 gallons (114,000 liters). Theboil-off rate is in the vicinity of 0.3% per day.

The liquid helium is filled into ISO containers withcapacities of 11,000 or 15,000 gallons and shipped toEurope. After the warm and/or contaminated containersare returned, they must be recleaned before they can beused again. Any remaining helium gas is recovered andsent to the plant intake for reprocessing.

Figure 9 (left): The cold box of what is currently the largesthelium liquefier

Figure10 (right): Gas-bearing turbo-expander


Figure 12: Typical helium liquefac-

tion process

Figure 11: Survey of the overall

process of helium extraction

Natural gas is a mixtures of gases, of which meth-ane is the major component. Other componentsinclude heavy hydrocarbons, sour gas, nitrogen,and occasionally low proportions of helium. Natu-ral gas is a very important primary energy source.It is found in large fields that are often far fromthe users.

Use of natural gas will become more importantbecause of environmental considerations. Theexhaust from natural gas combustion contains less

carbon dioxide, sulfur, and solids than when otherheavier hydrocarbons are used.

The world consumption of natural gas was 2,400billion Nm3/year in 2001. Of that, 550 billionNm3/year was shipped across national bounda-ries. Natural gas is transported in high-pressurepipelines or as liquefied natural gas (LNG) inocean-going freighters. About 25% of the world-wide natural gas trade, or about 150 billionNm3/year, is liquefied for transportation reasons.

Natural Gas

The Brayton cycle is a process in which the coolant remains gaseous within the cycle anduptake of heat from the object being cooledalways results in heating of the coolant. Cooling is produced by expansion in an expansion

machine to produce work. The modified Braytoncycle (applied by G. Claude in 1902) for gas liquefaction uses a subsequent Joule-Thomsonstage in which the coolant is liquefied.

Helium Braytoncycle


High annual growth rates are predicted for the heliummarket. More helium extraction plants must be built tosupply the steady increase in demand. Large natural gasliquefaction plants like Skikda are a suitable source. Itsfuture output will amount to about 10 % of the worldhelium production. By obtaining the construction order,Linde prevailed against strong international competition.Furthermore, as joint-venture partner of the Algerianenergy supplier Sonatrach, Linde is an owner and opera-tor of the plant, which offers the possibility to sell theprecious gas on the world markets.

Prospects

This paper describes large-scale application of cryogenicengineering to recover helium from natural gas and toliquefy the helium. The entire process is described usinga block diagram, from the pipeline to the natural gasstorage site to storage of the liquid helium, including theindividual process steps, special parts, and the designand fabrication requirements. The state of the art forprocesses and apparatus in this area is presented. Exam-ples of parts for the planned big new helium extractionand helium liquefaction plant at Skikda, Algeria, are presented.

Abstract

The Authors

Max Bräutigam

Max Bräutigam is Sales Engineer in the Linde EngineeringDivision at Höllriegelskreuth, Munich. He began his trainingas a coppersmith at Linde in 1953, and later received hisdegree in Mechanical engineering. Because of his variedexperiences in technical and managerial assignments, MaxBräutigam is a proven expert on natural gas projects. He isparticularly interested in use of LNG in motor vehicles, and is active in several committees and panels on that subject.

Johann Jürgen Clausen

Johann Jürgen Clausen, joined Linde AG in 1981 aftercompleting his study in Mechanical engineering at theTechnical College, Munich, and at the Technical University,Munich. Since 1984 he has been intensively involvedwith cryogenic engineering, initially as Project Managerfor development, manufacture, and operation of a heliumchilling plant for MRI (Magnetic Resonance Imaging)magnets. He was delegated to the Linde daughter com-pany Lotepro Corp. at Valhalla (NY) from 1992 to 1997.He returned to Europe, specifically to Linde CryotechnikAG at Pfungen (Switzerland) in 1998. There he has beenresponsible for sales and marketing of cryogenic plantssince 2003.

As a rough overview of the comparison between LH2

and CGH2, three major aspects have to be considered:■ What is the energy content of the

state of aggregation?■ What is the effort required to prepare a

certain state of aggregation?■ What is the total volume and weight of the

relevant tank system?The energy content of the different states of aggregationof LH2 and CGH2 at different pressures is illustrated in Figure 1. For a LH2 tank system, the typical nominaloperational pressure is in the range from 0.1 MPa up to0.35 MPa. Grading for CGH2 considers 24 MPa a common pressure today and 35 MPa common in the near future.


Liquid-Hydrogen Technology for Vehicles

LH2 makes you mobile

Joachim Wolf

Liquefaction of hydrogen (LH2), with a cryogenic tempe-rature of 20 K (-253°C), has been produced and distribu-ted in a safe and reliable manner by the gas industry for all kinds of industrial needs for more than 70 years.Twenty years ago, car manufacturers began the imple-mentation of LH2 applications in prototype cars. Theexpected public use of cryogenic fuels like LH2 willrequire suitable, safe, and reliable storage and fillingfacilities; in particular, safe and easy-to-use filling equip-ment comparable to conventional gas stations. This arti-cle outlines the advantages of LH2 in comparison withcompressed gaseous hydrogen (CGH2). The necessity ofpurpose-designed tank systems to fit the restricted avail-able space within vehicles will be highlighted. A her-metic, clean, and leak-free break coupling for the fillingand refilling of cryogenic fuel systems will also be dis-cussed. This coupling enables the safe and easy handlingof LH2, short filling and coupling times, and a high fillingrate (number of vehicles filled per unit of time).

Pressures up to 70 MPa reflect an envisaged technicalgoal. As can be seen in the figure, the specific energycontent of LH2 is higher than that of CGH2, within not only the common pressure range for both fuels, but alsocompared with the envisaged CGH2 pressure of 70 MPa or more.

As illustrated in Figure 2, the extra work for lique-faction based on a mid-sized liquefier is of the order of30% of the specific energy content. The entire work for agaseous compression unit, in comparison, is up to 18% ofthe specific energy content. Nevertheless, the use of LH2

for vehicle applications offers many advantages thatclearly stand out and compensate the greater work requiredto prepare the liquid state of aggregation. As can be seenin Figure 2, the comparison of storage volume and stor-age weight highlights the advantages of LH2, especiallyconcerning its use as a vehicle fuel.

To round out the comparison of the states of aggregation of hydrogen, it is useful to look at the current methods of commercial transport for LH2 andCGH2. Figure 3 shows a trailer for LH2 (total weight, 40tons; hydrogen load 3370 kg). Compare this with the trailer for CGH2 (total weight 40 tons; hydrogen load, 530 kg at 20 MPa). The LH2 trailer is able to transportmore than six times the hydrogen load of the CGH2 trailer(Figure 4).

Liquid Hydrogen and CompressedGaseous Hydrogen: A Comparison

The storage of cryogenic liquids like LH2 requires specialequipment. These so-called cryostats are metallic dou-ble-walled vessels with insulation sandwiched betweenthe walls. To avoid or minimize thermal losses, threebasic mechanisms of heat input have to be considered:thermal radiation, thermal convection, and thermal con-duction.

Liquid-Hydrogene Storage

A few years ago it was just a vision. Today it is reality: Hydrogen-fueled vehicles on the road. For distribution, liquid hydrogen (LH2)appears to be an alternative to compressed gaseous hydrogen.But refueling vehicles with liquid hydrogen requires special equip-ment. A coupling just developed by Linde assures a hermeticallysealed, clean, and leak-free path from the storage tank to thevehicle tank. It allows safe and simple handling of LH2 and short filling times.

31Linde Technology I 1/2003Linde Technology I 1/2003

Figure 1:Energy content of the different states of aggregation of liquid hydrogen (LH2) and compressed gaseous hydrogen (CGH2) at different pressures.

Driving range100 l LH2 / 100 l GH2

@ 200 bar

Storage volume6,4 kg LH2 / 6,4 kg GH2

@ 200 bar

Storage weight6,4 kg LH2 / 6,4 kg GH2

@ 200 bar

Effectiveenergy content

Primary energy content

Figure 2:Comparison of LH2 and CGH2 on a basis of 6.4 kg hydrogen: LH2 at 0.1 MPa in a vacuum-insulated cryostat; CGH2 at 20 MPa in a conventional steel bottle. The primary energy content is the energy necessary to compress or liquefy the hydrogen.Approximately 15% of the specific value will be necessary to compress hydrogen up to 200 bar, and approximately 28% will be necessary for liquefaction.

0,1 MPa 0,35 MPa 70 MPa 35 MPa 25 MPa

100% 90% 58% 35% 25%

8,49

7,63

LH2 CGH2

Ener

gy C

onte

nt (

MJ/

l)

0 % 20 % 40 % 60 % 80 % 100 % 120 %

100%

22%

495 liter

110 liter

>> 610 kg

86 kg

120 kJ/g

120 kJ/g

156 kJ/g

142 kJ/g

4,93

2,952,16

■ LH2 Liquid Hydrogen

■ CGH2 Compressed Gaseous Hydrogen


A schematic illustration of a typical LH2 tank system for vehicles is shown in Figure 5. The final layout,design, and dimensions of such a system ultimatelydepend on its destination, whether in a bus, a truck, or a passenger car.

The shape of the cryogenic storage system (i.e., ofthe cryostat itself) has to be fitted to the restricted avail-able space. Basing the shape of the tank system on theavailable mounting space within the vehicle naturallyresults in different useful volumes. For example, the use-ful volume can be increased from approximately 50% ofthe available space when a conventional (cylindrical)tank system is installed to nearly 100% if the design ofthe tank system is fitted to the available space.

Vehicle ApplicationsPurpose-Designed Tank Systems

To minimize the heat input via thermal radiation, the inner vessel that contains the cryogenic hydrogen isinsulated with so-called multilayer insulation, consistingof a number of layers of a metallic foil with spacer mate-rial (a thin layer of glass wool) between each foil layer toprovide a thermal barrier. The insulated inner vessel ismounted within the outer vessel by means of speciallydesigned internal fixtures. The resulting volume betweenthe two vessels is evacuated to avoid heat leaks caused by thermal convection. Vacuum superinsulation isanother common name for this kind of insulation. Tominimize heat leaks caused by thermal conduction, aspecialized knowledge of cryogenics is required for the proper design and materials selection of the internalfixtures of the vessel and the tube system for injectingand extracting the hydrogen.

Enginecooling water

Enginecooling water

Figure 5:Schematic illustration of a typical LH2 tank system.

Figure 3: Trailer for LH2 transport (total weight 40 tons; hydrogen load, 3370 kg).The LH2 trailer is able to transport more than six times the hydrogen loadof the CGH2 trailer.

Minimizing Boil-Off

In addition to the shape of the tank system, special meas-ures are required for the storage of LH2 in vehicles. Basedon the principle of a thermal flask that keeps cold drinkscold, an insulated LH2 tank provides the liquid hydrogenwith a high degree of proetction from unwanted heatingress. Nevertheless, it is a physical law that cryogenicliquids will evaporate (also known as boil-off) due to theimpact of heat on the tank system. This heat impact canbe minimized but not avoided. In the course of time, thepressure in the tank rises because of the effects of heatingress. As a result, if the vehicle is not used for a rela-tively short time (about three days), a critical pressurevalue is reached that results in unacceptable hydrogenevaporation losses.

However, that is now no longer the case. An innova-tion for which a patent has been applied makes possiblea significant extension of the time (>12 days) before

Figure 4: Trailer for GH2 transport (total weight 40 tons; hydrogen load, 530 kg at 20 MPa).


The transfer of cryogenic liquids like LH2, requires specialtransfer lines. To avoid unacceptable heat ingress duringthe filling/refilling sequence, the transfer lines have tobe adequately insulated, applying insulation methodssimilar to those used in the cryogenic storage system. For ease of handling, the transfer lines have to be some-what flexible, and they have to be mountable and dis-mountable.

The weak link in a cryogenic transfer chain is the dismountable part, the “cryogenic coupling“. The surfaceof the connection region of two cryogenic transfer lines has to be designed to provide adequate thermal insulation; this tends to be a costly, delicate, and notcompletely fail-safe process. Conventional cryogeniccouplings require skilled, specialized operators wearingprotective gloves and goggles. Thermal leaks may freezethe two lines together; dismantling them requires heating and takes time. The components also need to becleaned after each use.

To avoid these problems, a novel cryogenic couplingwas developed by Linde nine years ago. This coupling fulfills all of the basic requirements for public use andhas been continually improved since its introduction.

Cryogenic Filling Equipment

Outer vessel

Hydrogen

Radiation shield

Inner vessel

Heat exchanger

Ambient air

Dried airLiquefied air

Figure 6:Principal design of a novel recooling system to minimize evaporation losses in a LH2 storage tank.

evaporation losses occur. When the vehicle is in opera-tion, this time can be extended further, even indefinitely.The solution is an efficient re-cooling system that mini-mizes evaporation losses. Linde AG has developed such a re-cooling system, called CooLH2 (Figure 6). The surrounding air is drawn in, dried, and then liquefied bythe energy released as the hydrogen increases in tem-perature. The cryogenically liquefied air (-191°C) flowsthrough a water cooling jacket surrounding the inner tankand thus acts like a refrigerator. This leads to a significantdelay in the temperature increase of the LH2 and a sensible use for the energy stored in the liquid hydrogen.Since the cooling system can be accommodated in theexisting insulating layer of the tank, it does not affect thesize of its tank.

In its liquid form (-253°C), hydrogen has a considera-bly higher energy density than in its gaseous form. LH2

thus enables vehicles to cover almost the same drivingrange that can be covered using normal fuel systems. Theenergy stored by the liquefication of hydrogen was, how-ever, not put to good use previously, but was actuallyremoved in a cooling water heat exchanger because theoperation of a fuel cell or an internal-combustion enginerequires hydrogen at room temperature.

The principal design is illustrated in Figure 7. Eachcounterpart, one on the vehicle side, the other on thefuel station side, consists primarily of a ball valve that isclosed in its normal state. Only when the counterpartsare connected can the ball valves be opened together.After the ball valves have been opened, a common tubular volume is created that is hermetically protectedagainst the outside environment. Within this tubular volume, the “cold finger“ on the fuel station side will beextended deep into ist counterpart on the vehicle side.Thus, a coaxial, well-insulated, and hermetically closedconnection between both parts of the coupling is estab-lished.

The innermost line of this connection, which is sepa-rately insulated, performs the transfer of the cryogenicLH2 from the fuel station to the vehicle tank system. Anouter coaxial line, which is also insulated, guides the ventgas back to the fuel station. Once the tank is filled, thecold finger is retracted to a safe and covered position within the fuel station side of the coupling. The internalcounterpart in the vehicle side of coupling remains in itssafe and covered position. Only when the cold finger has been retracted can the ball valves be closed and thecoupling disengaged.

Decoupling can be accomplished without any warming up, flushing, or cleaning of the coupling. Thenext filling/refilling sequence can be started immedi-ately – there is no waiting time between filling/refillingsequences.

For a LH2 vehicle tank system with a fuel content ofabout 100 l, this filling sequence takes less than 2 min.Compared with the conventional LH2 filling procedure, the operation is much shorter, safer, and simpler. Thereturn gas system is passed back to the fuel station viathe coaxial LH2 clean break coupling.

In summary, the main features of the hermetic cleanbreak coupling are■ easy and safe handling,■ minimization of LH2 losses,■ avoidance of cold valves to minimize

condensation and contamination,■ short filling/refilling times,■ short coupling/decoupling times,■ high filling rate (number of vehicles filled

per unit of time), and ■ high potential for further optimization.


Figure 7:Principal design of the cryogenic coaxial clean break coupling developed by Linde AG

Figure 8:Linde built the completely automatic tank system for theworld‘s first hydrogen filling station at the Munich airport,and is also providing the necessary hydrogen


To supply vehicles with LH2, a suitable fuel station is nec-essary. This station needs to be connected to an adequateLH2 storage tank and must have the necessary equipmentto manage the cryogenic transfer from the storage tankto the vehicle tank. A typical filling/refilling sequence bymeans of a manually operated LH2 fuel station usingexisting LH2 technology involves the following steps: thecoupling is done manually. By means of a push-buttoncontrol on the fuel station, the coupling is flushed withgaseous helium to clean the small volume enclosed bythe connected counterparts. A hand-operated lockingmechanism provides a gas-tight connection between thevehicle tank and the fuel station. By using a second lever,the ball valves on the vehicle side and on the fuel stationside are simultaneously opened. The cold finger insidethe fuel station side of the coupling is driven pneumati-cally into the vehicle side of the coupling and ensures aproper cryogenic connection. When the vehicle tank isfull, a “tank-full“ signal from the vehicle automaticallystops the filling procedure. The cold finger is retracted,the ball valves are closed, and the locking mechanism is released. Finally, the coupling is manually returned toits holder.

A public LH2 filling station of this type is currently in operation at Munich Airport, using the hermetic cleanbreak coupling described here (Figure 8).

This is an edited and abridged version of an article that will appear in the Handbook of Fuel Cells, to be published by John Wiley & Sons Ltd. In 2003.

Liquid-Hydrogen Fuel Stations

This survey focuses on the use of liquid hydrogen as anautomotive fuel in comparison with the use of com-pressed gaseous hydrogen. The energy penalties associ-ated with liquefaction versus gas compression are com-pared, followed by an examination of the weight ofhydrogen relative to carrier weight for the two alterna-tive approaches. The optimum form and design of LH2tanks are discussed, followed by the important topic ofhow to achieve quick and easy transfer of LH2 from astorage tank to a vehicle.

Abstract

The Author

Joachim Wolf

Joachim Wolf (51), a physicist, coordinated a low-temperature research group at the Max Planck Institutefor Metals Research in Stuttgart before joining Linde AGin 1987. He worked on the development of the ISO(Infrared Space Observatory) satellite at the Linde Engineering Division in Munich. He became Director ofSpace Technology in 1990, and later Director of Alterna-tive Fuel and Helium Systems within the Gas Division. As a part of the strategic business development, JoachimWolf has been responsible for the newly formed “virtual hydrogen division” since 2002, coordinating allLinde missions and projects in this area.


Cryogenic temperature-control system for low-temperature processes

Reliable Temperature Control

Hans-Jürgen Reinhardt, Dieter Dürr

Low-temperature processes are becoming increas-ingly important for fine chemicals. For example, temperatures down to –110 °C are currently beingused for syntheses and for crystallization processes.That places special requirements on temperature control systems for chemical reactors.

Efficient development of new products and technologiesis one of the factors which distinguish development infine chemicals. Low-temperature processes have animportant role in that. Syntheses in particular, and alsocrystallizations, are being done increasingly at low temperatures to■ improve selectivity,■ reduce costs for product processing, and■ attain high product quality.

Although temperatures of –20 °C to –40 °C were oftenadequate in the past, there is now more need for temperatures down to –110 °C. In fine chemicals andpharmacy, temperatures below –40 °C are produced mosteffectively by using liquid nitrogen, which has a boilingpoint of –195.8 °C at a pressure of 1.013 bar. The principal reasons are:■ Refrigeration machinery for such temperatures

is expensive.■ The processes are usually batch processes which

do not require continuous chilling power.■ The gaseous nitrogen can also be used for

inerting and for flushing.

There are various requirements in chemical and pharma-ceutical production for low-temperature systems com-bined with effective and reliable nitrogen supply. Lindehas worked with the chemical industry and engineeringto develop both standardized and client-specific solutionswhich are being optimized continuously.

Area of application

Syntheses [1] as well as crystallizations are the majorareas of application in fine chemicals and pharmaceuti-cals. The low temperature, cooling power, and inertingaction of nitrogen can all be used advantageously forprocess control.

Typical low-temperature processes are [1]:■ asymmetric syntheses■ Birch-Hückel reduction (hydrogenation of aromatic

compounds with sodium and ammonia)■ Grignard syntheses■ reduction of metal hydrides■ Wittig reaction■ low-temperature crystallization

The pharmaceutical industry prefers to use standardizedplants. They have the advantages that they are availablemore rapidly and are more economical. On the otherhand, tailored plants based on standardized processingmethods and plant elements make it possible to attain a broader range of use economically with respect to temperature and capacity. In addition to that, the specialrequirements of clients can be taken into considerationalready in the design of the plant. Those include, forexample:■ materials■ use of special instruments for

measurement and control■ integration into existing temperature-control

systems■ integration into the process control system■ consideration of plant specifications.

Tradename Chemical Usable range, Boiling- Freezing- Litera-name in °C point, in°C point, in °C ture

Paracryol Oil Aliphatic - 39 to 180 192 - 274 [2]hydrocarbons

Marlotherm X Alkylbenzenes - 80 to 315 ~ 180 [3]

GILOTHERM 12 Synthetic - 85 to 260 59 [4]hydrocarbons

Syltherm XLT Poly (dimethyl- - 100 to 260 47 - 111 [5]siloxane)

Methyl- Methyl- - 120 to 130 72 -142 [6]cyclopentane cyclopentane

Figure 1: Survey of selected heat-transfer media.

Various methods have been developed for chilling chemical industrial processes with liquid nitrogen:■ direct cooling of the reaction mass by

injecting liquid nitrogen■ cooling of the reactor contents by feeding

liquid nitrogen into a built-in cooling coil or into a cooling jacket

■ cooling and/or heating the reactor through a secondary loop, with the heat-transfer fluid being cooled by liquid nitrogen.

The third variant is gaining favor. One reason is becauseof the high requirements for maintaining the specifiedtemperatures. Another reason is that one often workswith a series of process steps in which the individualsteps must be accomplished at different temperatures (in a batch reactor, for instance). That is done by integrat-ing heating and cooling into a high and low temperaturesystem. The advantages of such a solution are:■ Several process steps can be carried out in

a single reactor with a simply controlled change of temperature.

■ The process can be run more effectively when theprocess temperature can be changed quickly.

■ Short heating and cooling times.■ Process reliability through precise selection of

temperature.■ High flexibility because the temperature control

can be modified easily.

The low-temperature system requires a heat-transfermedium which makes it possible to attain a very broad temperature range. The temperature ranges are,for instance, between –120 °C and +130 °C. Criteria for selection of the heat-transfer medium are:■ viscosity■ solidification temperature■ thermal stability■ corrosion properties (not corrosive to ordinary steels)■ cost.

The viscosity is a particularly important criterion to assurethat the medium can be pumped well. The solidificationtemperature is important to prevent the heat-transfermedium freezing to the heat exchanger wall.

The heat-transfer oils often utilized can be used fromabout –80 °C to +260 °C. Figure 1 shows the ranges ofuse of selected heat-transfer media which were selected


Methods of chilling

Heat-transfer media

The selection and design of the heat exchangers are critical for the capacity of the plant. Heat exchangerselection depends on the following criteria:■ temperature range■ heat-transfer medium■ allowable pressure loss■ space requirement.

Tube-bundle heat exchangers and plate-fin heat exchan-gers are used primarily. Tube bundle heat exchangers are used because they have a low pressure loss and are particularly insensitive to large temperature differences.When tube bundle heat exchangers are used in a second-ary loop, the nitrogen being vaporized is usually runthrough the tubes while the heat-transfer medium runsthrough the jacket space. The advantage of this is that it reduces the danger of freezing up the heat exchanger,or a slight freezing can be accepted.

Plate-fin heat exchangers, in comparison, have higher pressure losses and are sensitive to freezing up.There are also absolute limits to the temperature range.However, plate-fin heat exchangers are less expensiveand require less space.

Various computer programs are available for designcomputations. They must be adapted to the particular situation with values derived from experience. It is particularly important to determine correctly the propor-tion of gas in the heat exchanger nitrogen flow. It has a great effect on the capacity of the heat exchanger.

Heat exchangers

particularly from the viewpoint of use at low tempera-tures. Other heat-transfer media, such as 2-methylpen-tane, can be used for the low-temperature range.


This case involves temperature control of a reactor containing the reaction mass to be cooled or heated. The reactor has a coil of tubing, through which the heat-exchange medium passes, at its outer edge. The cryogenic temperature-control system establishes thenecessary temperature of the heat-transfer medium.

As Figure 3 shows, the core parts of the system area heat exchanger for cooling (W1) and a heat exchangerfor heating (W2), the corresponding closed loop, and thecompensating tank. The heat-transfer medium, methylcy-clopentane, is chilled with liquid nitrogen in heat exchan-ger W1. Then the chilled methylcyclopentane is pumpedthrough the reactor, cooling it and the reaction mass tothe required reaction temperature. Methylcyclopentane isalso used for heating. It is heated in heat exchanger W2.The changes in volume of the methylcyclopentane at thedifferent temperature settings are compensated by thecompensating tank. This volume change is about 30% ifthe temperatures vary between –110 °C and +130 °C. The temperature of the heat-transfer medium is con-trolled by a process control system which uses controlvalves to regulate the energy input of the liquid nitrogenand the heating loop.

The liquid nitrogen is supplied to the cooling systemfrom a vacuum-insulated pressure-regulated tank and a supply line which is also vacuum-insulated. Aside fromthe liquid nitrogen supply, it is also possible to providegaseous nitrogen if necessary. That is accomplished separately through an air-heated finned-tube evaporator without energy input, or through a water bath evaporatorheated with steam. If gaseous nitrogen is needed at higher pressure, it is often better to supply it from a sep-arate tank.

A low-temperature system that was developed anddesigned to meet the specific requirements of a client ispresented as an example. Various technical data andrequirements were specified.■ temperature range: -110 °C to +130 °C■ coolant: liquid nitrogen■ heat transfer medium in the secondary loop:

methylcyclopentane■ maximum pressure in the heat transfer loop:

10 bar■ cooling and heating power: 25 kW each

Requirements■ Zone 1 explosion-proof ■ low space requirement■ fast switching from heating to cooling and back■ programmable memory control (over a Profibus

connected to the higher-level process control system)■ expansion vessel to compensate for volume changes

due to temperature changes.

Low-temperature system

Figure 3:Basic flow diagram of the heating and cooling system with reactor

Figure 2:Cryogenic tem-perature-control system withoutinsulation for reactor chilling.


System Design

Given the objective of building the most compact possi-ble plant for the reactor heating and cooling loop, all therequired equipment has been contained within a frame-work 3100 mm long, 1800 mm wide, and 2400 mm high(Figure 2). That includes both the heat exchangers, thecompensating tank, the redundant pair of pumps, and allthe valves needed for operation (remotely controlled andmanually operable), as well as the field instrumentation.The material used in the plant is stainless steel 1.4571 or better. The allowable temperature range for all parts isfrom –200 °C to +200 °C, and the allowable pressurerange is from –1 bar to +16 bar.

The following are required for operation of the plant:■ electrical power to drive the pumps■ compressed gas supply for the pneumatically

operated valves■ pipe connections for supply and return of the energytransfer medium, optionally for the filling and draining of the heat-transfer medium, for the nitrogen supply andfor the waste gas produced, for evacuation in case of fire,for filling the system, and for the collecting line from thesafety valves.

A cryogenic temperature control system is presented. It is based on surveys of use of low-temperature systems,cooling methods and selection of heat-transfer mediaand heat exchangers. The system is used for effectivecooling and heating of chemical reactors.

Linde is currently working on further development of the temperature control system, with particular attentionto extending the range of use of the system.

[1] Lesar, Jeffray, A.: Constructing a Frigid Process Facility, Chemical Engineering, June 2001,pages 74-78

[2] Product information from Sulzer[3] Holstein, E.; Hons, G.: Sicherheit bis 360°C

(“Safety up to 360 °C”), cav 2/2000, page 14[4] Product information from Monsanto Europe, S.A.[5] Product information from Dow[6] Patent DE 42 40306 C2, held by Bayer AG,

51373 Leverkusen

Outlook

Literature

Dieter Dürr

Dieter Dürr is also in the Gas Division of Linde AG, atUnterschleissheim. He is Project Manager in the area of Market Development for the chemical industry. He was active at the University of Munich and in themechanical engineering sector before joining the company in 1982. In recent years his major emphasis has been development and design of hardware fornitrogen applications, especially for deburring andrefrigerating machines.

Hans-Jürgen Reinhardt

Hans-Jürgen Reinhardt received his Doctorate in ProcessEngineering, and was in the chemical industry for many years before coming to the Gas Division of LindeAG in 1996. As a Department Manager, he is responsi-ble for development and introduction of processes andhardware for use of gases in refineries and in thechemical industry. At present he is primarily concernedwith applications of nitrogen and with processes foruse of oxygen.

Abstract

The Authors


High performance Butterfly Valve for pipelines with cryogenic liquids

Tight at Cryogenic Temperatures

M. Metin Gerceker

The seal between cryogenic liquids and the atmos-phere is very important in cryogenic processingplants and storage-tanks, because losses of the liquids are expensive. The high pressure and temper-ature differences in plants place special requirementson the sealing elements. A newly developed highperformance Butterfly Valve from Linde-MAPAG assures trouble-free operation and long life.

Processing plants have been working entirely automati-cally for years. They are controlled and monitored byprocess control systems. Some manufacturers have builtcentral control stations. Plants can be operated and moni-tored by such systems even over great distances. Theoperators have high requirements for■ availability, ■ plant safety, ■ minimal maintenance cost, ■ very economical operation, and ■ maximum product purity.

These requirements apply for cryogenic processingplants such as air-separation plants, liquid natural gasplants, hydrogen plants and helium plants. Because ofthe continually increasing requirements for the process-ing plants, the requirements for the individual units are also increasing to match.

Linde AG presented those requirements to theMAPAG plant, and has developed a cryogenic ButterflyValve for installation in pipelines carrying cryogenic liquids down to –270 °C. This Butterfly Valve meets thehighest requirements for tightness at high pressure differentials. The pressure range for the cryogenic Butterfly Valve is from vacuum to 400 bar, at nominaldiameters up to DN 2500 mm. The cryogenic ButterflyValve is used for the liquids oxygen, nitrogen, argon,hydrogen, helium and LNG.

Butterfly valves are used primarily in cryogenicprocessing plants and storage tanks for isolation, or foralternating use of units such as pumps and vaporizers.Their principal function is to block or seal off the cryo-genic liquids, which are sometimes at high pressure,against the atmospheric conditions during maintenancework. In that way, the maintenance personnel are assu-red that the units can be maintained safely and quickly.Loss of the expensive cryogenic liquid is very low.

Application for space engine test facility

The design and capacity features have convinced evenNASA of the high quality of thenew Butterfly Valve. Valves ofthis type have been used successfully at the NASA SpaceEngineering Test Facility to shutoff liquid hydrogen and liquidoxygen. This NASA decision confirms the state of the artdesign, high quality, and relia-bility of the Butterfly Valve.

Figure 1: A team from Linde-

MAPAG assembling thenew butterfly valve.


All the materials used were specially selected for use at low temperature. The Butterfly Valve body and the shut-off disc were designed according to AD LeafletW10 1.4581 / 1.4308 and according to ASTM A351 CF8M or CF3.

Bearing tolerances are selected so that the ButterflyValve is easily accessible for service in the warm area, i. e., at ambient temperature as well as during operation.Functional reliability is assured for rapid temperaturechanges.

The connection between the actuator and the But-terfly Valve is designed so that the factory adjustment of the shut-off disc to the sealing elements in the valvebody is not affected on removal and replacement of theactuator. The gives complete assurance that the ButterflyValve will seal reliably even after maintenance work.

There is an extended shaft between the actuator andthe shut-off disc, with a covering tube, so as to minimize

Special design features

heat flow from the atmosphere to the liquid medium.Depending on the specification for the Butterfly Valve,the actuator can be pneumatic, electrical, hydraulic ormanual.

The individual parts are produced on numericallycontrolled machines. Quality control following specifiedproduction steps is assigned the highest priority so thatthe specified requirements are met reliably. Once all theparts have been produced, checked and cleaned, they areassembled in a special assembly area. No later mechani-cal work is allowed.

The actuator and Butterfly Valve are assembled and adjusted according to the specification. Every Butter-fly Valve is subjected to a functional test and a leak test according to the required standard before shipment.

Other tests can also be done before shipmentaccording to the well-known international “Low-tempera-ture test standards“ and the Linde-MAPAG in-house “Low temperature test procedure“. Linde air-separationplants can provide the liquid nitrogen required for thesetests whenever needed.

Figure 2:The sealing systemwas designed in-house for differentoperations and applications.PTFE Sealing

Copper Sealing

Disk

Disk

Disk

Copper Sealing

PTFE Sealing

Copper Sealing

Copper Sealing

Sealing system for use in liquid nitrogen, liquid oxygen and LNG

The sealing system is made up of a combination of PTFE and copper, developed at Linde MAPAG. This sealingsystem reliably seals butterfly valves with rapid tempera-ture changes. It is used primarily in pump butterfly valves in the cryogenic region. In a low-temperature testat Linde MAPAG the measured helium leakage was at-196°C 5 x NPS cm3/minute.

Sealing system for use in liquid hydrogen

This sealing system consists of a combination of a copperand a PTFE sealing element. Both sealing elements are supported by springs to assure tightness with any temperature fluctuation. The measured helium leakage in the low-temperature test at Linde MAPAG was at-196°C 0.1 mbar x 1/s. These butterfly valves are usedprimarily in liquid hydrogen installations such as theSpace Engineering Test Facility.

Sealing system for use in liquid helium

The sealing system consists of a combination of twospring-supported copper sealing elements. This sealingsystem is used primarily at extremely low temperatures.The measured helium leakage in a low-temperature testat Linde MAPAG was at -196°C 0.1 mbar x 1/s.


With this “High performance cryogenic Butterfly Valve“,Linde-MAPAG has developed a valuable product whichmeets the highest requirements for sealing in pipelinescarrying cryogenic liquids at high pressure differences, aswell as high availability and easy operation. Extensivereferences available provide information about quality,long life and trouble-free operation.

These cryogenic Butterfly Valves have been usedsuccessfully world-wide in air separation plants, liquidnatural gas plants, and in the “Space Engine Test Facili-ties” at NASA and DLR. At present, high performance cryogenic Butterfly Valves are being shipped for a LNGplant in Qatar. Linde-MAPAG has numerous orders forthese cryogenic Butterfly Valves for 2003.

The high performance Butterfly Valve is undergoingcontinuous development at Linde-MAPAG, with the focus of bringing intelligent butterfly valves “i-cryovalve“to the market.

Conclusion and outlook

Linde-MAPAG has developed a new “high performancecryogenic Butterfly Valve“. It meets the highest requirements for sealing at high pressure differences in pipelines carrying cryogenic liquids. This report describes the special design features of the high performance Butterfly Valve.

Abstract

M. Metin Gerceker

M. Metin Gerceker (41), a graduate engineer, is the Business Development Manager at the MAPAG plant, Horgaunear Augsburg, part of the

Linde Engineering Division. With Linde since1986, he is now responsible for sales and marketing as well as for development of highperformance cryogenic butterfly valves, aspeciality of the MAPAG plant.

Figure 3:MAPAG Cold Shock Test

Figure 4: Linde-MAPAG’s newly developed high-capacity butterfly valve for cryogenic fluidpipelines.

The Author


With on-site supply of industrial gases, the gas suppliertakes on the investment in the plant and operates it at itsown risk. The customer usually provides the materials.The refinery operator has the required gases delivered,and need not be concerned with operation of the gasrecovery plant. Of course, the investments for the gassuppliers are relatively high, and so the industrial life ofthe gas plant is linked with the term of the contract withthe refinery. That term is usually 15 years. The contractterm can be even shorter for smaller standardized con-tainer plants, especially those supplying nitrogen. It iseasier to reuse those plants for other customers after thecontract runs out. The advantages of this supply conceptfor the customers are■ economical gas cost which can be firmly

calculated in advance;■ no investment outside their core business;■ no labor costs;■ no operating risk, and■ highly reliable supply because the gas supplier

is specialized in operating such plants.

Usually on-site plants do not require oxygen, nitrogen orhydrogen in liquid form. That saves the high liquefactionenergy that would be needed for production. Omission of truck shipments reduces costs and is also environmen-tally friendly. That makes on-site plants an economicallyattractive variant for refinery gas supply.

The concept of on-site supply of industrial gasesbegan to spread in the 1980s. Since then it has spreadthrough the industrial countries and the usual “purchaseplants” have mostly been replaced. If the basic conditionsare favorable, gas costs can be reduced by double-digitpercentages with on-site supply. The on-site plants mustbe selected properly for them to be used with optimaleconomy. In the following, the various plants for theindustrially important gases, H2, O2 and N2, are discussed,with the economically reasonable load ranges for eachand the amounts of gases which they typically produce.

On-site supply of industrial gases to refineries

Less pollutants in petroleum

Gebhart Scholz, Dirk Schweer, Michael Heisel

Environmental protection and legal requirementsrequire reduction of pollutants in Diesel fuel and gasoline. One efficient way to accomplish that is to useindustrial gases for various purification processes in oil refineries. Large quantities of gases are produced inso-called on-site plants in the immediate vicinity of the users. That is an extremely economical possibilityof refinery operation.

The great increase in road and air traffic has led to sub-stantial environmental stress. Because of that, increas-ingly more stringent regulations are being issued withrespect to the environmental compatibility of fuels. In the European Union (EU), for instance, the “Auto/Oil Pro-gram” requires that contents of pollutants in gasoline andDiesel fuel must be reduced substantially, particularly forsulfur and aromatics. Substantial quantities of hydrogenare required to react with those components. Reductionin capacity of Claus plants due to greater desulfurizationcan be compensated by using oxygen.

Aside from the legal requirements for environmentalprotection, refineries must react to long-term markettendencies and shift their product range. That also requi-res use of industrial gases:■ The proportion of Diesel vehicles is increasing in the

EU. That means that more Diesel fuel will be used, incomparison with gasoline [1].

■ Growing air traffic requires more kerosene.■ It is getting harder to sell heavy heating oil with

high sulfur content [7], so that refineries must try toprocess it into more valuable products.

We can handle heavier residues than are in the currentfeedstock in fluid catalytic crackers (FCCs) to producemore Diesel fuel and kerosene. At the same time, thatreduces the amount of heavy heating oil, for which themarket is vanishing. It is primarily regeneration that limits the capacity of the FCC. That bottleneck can bebypassed with only minor investment by use of oxygen.The growing number of refineries using this methodshows that it is economical.

The examples show that the use of industrial gasesoffers possibilities for meeting the new requirements placed on refineries. It requires reliable supply of largeamounts of industrial gases from plants near the users,known as on-site plants.

What on-site supply means


Hydrogen consumption by refineries increases rapidlywith more stringent desulfurization, because theamounts of substances other than sulfur compoundswhich are hydrogenated also increase. That is particularlythe case for nitrogen compounds. Figure 1 shows a typical example for the increase in hydrogen require-ments [6]. One can see that large volumes of hydrogenare used, which can be produced economically by on-site supply.

For such large users, it is economically feasible togenerate the hydrogen on-site with the steam reformingprocess. In principal, one might also consider generationby a partial oxidation plant, such as one using the Texacoprocess. That can be done practically in only a few cases,though, in which it is either necessary to process resid-ues, or to produce a synthesis gas, as if the supply is formethanol production. Therefore we can limit the descrip-tion here to steam reforming.

On-site supply of hydrogen

Figure 1 shows a block flow diagram of the process. Thestarting materials could be natural gas, naphtha, LPG [liquefied petroleum gas] or refinery gases (feed and fuel).

The feed gas, hydrocarbon from natural gas (meth-ane) to naphtha, and perhaps refinery gas that wouldotherwise be used only as a fuel within the plant, is pas-sed through a desulfurization plant with a small quantityof recycling hydrogen. This unit includes a hydrogenatorand a zinc oxide bed for the actual sulfur removal. Thehydrogenator converts unsaturated hydrocarbons, whichtend to crack, to alkanes. In parallel, sulfur compoundsare converted to hydrogen sulfide. The sulfur compoundsare trapped in the zinc oxide bed.

The steam reforming process

Degree of desulfurization 90% 98% 99%

Added H2 as % by weight of the feed 0.51 0.74 0.94

H2 requirement for a refinery ca. 60,000 Nm3/hr ca. 87,000 Nm3/hr ca. 110,000 Nm3/hrwith a crude oil throughput of 9,000,000 tons/year*

* Example of a US refinery from [6]. Numbers are different for other refineries and other crude oils, but the order of magnitude of the requirement remains the same.

Figure 1: A typical example of the increasing H2 requirement of refineries with more stringent desulfurization

The desulfurized feed gas is preheated by a counter-current flow of the hot exhaust gases or hot products,and is mixed with steam. In the steam reformer, the gas-steam mixture is converted to hydrogen and carbonoxides. The principal reactions are:

CnHm + n H2O ➔ nCO + (n + 1/2m) H2

(Steam-Reforming)

CH4 + H2O ➔ CO + 3 H2

(Steam-Methane-Reforming)

The reformer reactions are endothermic. The reactionheat is introduced by using many reformer tubes inwhich the actual reaction occurs which are externallyheated by burners. The reaction is catalyzed by nickel andoccurs at about 800 °C. The hot gas from the reactor iscooled by feed gas and then directed to the CO conver-sion, where the CO is reacted with steam to give CO2 andmore hydrogen:

CO + H2O ➔ CO2 + H2

(CO conversion)

After further cooling and separation of the process condensate, the crude hydrogen is purified by pressureswing adsorption (PSA) (Figure 2). In this process, thegas mixture flows over various adsorbers on which all thecomponents except hydrogen are retained. After sometime, the adsorbent is saturated and must be regener-ated. To do so, the gas flow is switched to a differentadsorber and purified there. The pressure on the loadedadsorber is reduced so that some of the contaminants areremoved. Then the container is flushed with fresh hydro-gen, producing fresh adsorbent. Finally, the pressure isbuilt up again with fresh hydrogen for another adsorp-tion, before the gas mixture from CO conversion is againsent to the container. This cycle is repeated continuously.

The residual gas from flushing the container containsthe impurities. It is collected in a vessel where the pres-sure and composition become uniform. Then that purgegas is burned with added fuel gas to heat the reformer.

The steam used in reforming and in the CO conver-sion is generated by the waste heat from burning. Some

Figure 2 (left): Block diagram of the steam reformingprocess


Displacement of air oxygen and combustible gases withinert gases is a proven process for preventing oxidationand danger of fire and explosion. Processes often used inrefineries are:■ pressurizing■ permanent flushing, and■ controlled metering of inert gasusing nitrogen. Nitrogen is used particularly often toblanket liquids in storage tanks to prevent reaction with air oxygen. In those cases, nitrogen is usually takento the consumers through the plant’s own piping. It istypical for the entire refinery to use several hundredNm3/hour continuously.

Discontinuous use of nitrogen is primarily for thearea of industrial service. That covers a wide range ofservices, such as catalyst flushing or catalyst cooling, leakdetection, pipeline flushing, and pipeline cleaning. Someof that work is done in cooperation with service compa-nies. It is typical to a refinery to use several million Nm3

N2 in a complete turnaround.Three processes are used for nitrogen recovery. Aside

from the classic cryogenic process, adsorption and mem-brane processes for nitrogen recovery have developed tothe point of being ready to market.

On-site supply of nitrogen

Figure 3 (above): View of the Leunasteam reformer

steam can even be exported. The air needed for burningis preheated in the exhaust gas duct to increase the effi-ciency.

Figure 3 shows the steam reformer at Leuna. Theplant produces 35,000 Nm3/hour hydrogen from naturalgas. It supplies hydrogen to a refinery and about 20 othercustomers through a pipeline network.

High-hydrogen gases already present in the refinerysystem can also be used to produce hydrogen in refiner-ies. If hydrogen-containing gases already present aremerely purified, the investments are usually lower thanfor producing hydrogen with synthesis gas generation inthe steam reformer. Pressure-swing adsorption processesare often adequate to purify refinery gases.

Linde’s largest gas facility is located at Leuna. Thecenter supplies more than 40 major customers inthe central German triangle with oxygen, nitro-gen, hydrogen and carbon monoxide through apipeline network with more than 300 miles (500km) of pipe. Linde started up its fourth hydrogenplant at Leuna at the beginning of 2003 becauseof the continuing high demand in the chemicalsector. That increased the hydrogen productioncapacity to 140,000 m3 per hour. Linde has inves-ted more than 500 million Euro in the regionsince reunification.

The Leuna-Buna-Bitter-feld refinery triangle


Membrane plants

Nitrogen can be purified economically down to about 1%residual oxygen in membrane plants (figure 4 and 5).The actions of the ultra thin polymer membranes andtheir separating ability depend on the pressure, tempera-ture, composition of the gas stream, and the flow geom-etry. In membrane plants, compressed pre-purified airflows through long hollow fibers with semi permeablewalls. Molecules of oxygen, carbon dioxide and waterpass through these membranes faster than nitrogen. Thatresults in separation of the air. The oxygen, carbon diox-ide and water diffuse into the outer volume around thehollow fibers and are released as residual gas (perme-ate). Much of the nitrogen remains inside the hollowfiber, where it becomes concentrated and finally leavesthe ends of the fibers as retentate.

The hollow-fiber membranes are assembled intomodules. The modular design of a membrane plantallows flexible operation. The capacity of a membraneplant depends, among other things, on the number ofmodules connected in parallel. It can be expanded orreduced at any time if the requirement changes.

Membrane plants are used primarily for smaller consumptions up to 1000 Nm3/hour. They do not needmuch space or investment, and are robust and simple to operate.

Adsorption plants

In adsorptive nitrogen recovery, one uses the differentdynamics of gas molecules on adsorption on special acti-vated charcoals. These “carbon molecular sieves” (CMS)have many pores and cavities with dimensions similar tothose of oxygen and nitrogen molecules. As the oxygenmolecules are somewhat smaller than the nitrogen mol-ecules, they can penetrate into the cavities of the CMSfaster than the nitrogen molecules.

Adsorptive pressure-swing (PSA) plants for nitrogen havebasically four units:■ air compression, with air preparation if necessary■ adsorptive N2/O2 separation■ product storage, with product recompression

if necessary■ evacuation (only for vacuum plants)There are several processes for industrial nitrogen recovery by adsorption, but the most widely used oneis the “1 bar/8 bar” process, which was developed in the 1970s.

Outside air is drawn in through a filter by a com-pressor and compressed to about 8 bar. This process airflows through adsorber A. Water, in particular, is adsor-bed in the lower part of the adsorber, while oxygen is

Figure 4 (above): Diagram of a membrane plant

Figure 5 (left): Membrane plant for 120m3/h N2


adsorbed preferentially in the rest of the adsorber. Nitro-gen, or a nitrogen-rich product, is removed at the headand goes to the product buffer.

In parallel with this adsorption step, container B,which previously operated in the adsorption phase, isregenerated by decompression to atmospheric pressurethrough a sound damper. When adsorber A has becomeloaded, after 40 to 60 seconds, the pressure is equili-brated between the containers at both ends. That makesoptimal use of the remaining pressure and purity poten-tial of the loaded adsorber. The pressure balancing lastsfor 1 to 3 seconds, after which the system is adjusted toan intermediate pressure of about 4.5 bar. After the pres-sure balancing, adsorber A is regenerated by depressuriz-ing to atmospheric pressure and adsorber B is switch tothe adsorption phase. That is, it is loaded with process air.

Some basic rules must be followed for reliable long-term operation of the plant in this process. The CMS mustbe fixed absolutely firmly in place, because any “agita-tion” of the CMS leads to excessive dust formation due to abrasion. The process air must be free of oil, which can actually be assured only by using oil-free compress-ors. Appropriate measures must be employed to preventthe moisture in the air making the CMS unusable in thelong term.

Cryogenic nitrogen plants

The process of cryogenic air separation for nitrogenrecovery is made up of the following steps:■ air compression■ air purification■ air chilling■ separation in the rectification column and

recovery of the cooling potential.

In cryogenic nitrogen recovery, the materials are usually separated in a single column. In special cases,though, it may be appropriate to use two columns fornitrogen recovery, to save energy, for instance.

As cryogenic nitrogen plants are economical even asrelatively small units, these plants often do not requiretheir own refrigeration using a turbine, and instead injectsmall amounts of liquid nitrogen.

Small cryogenic plants (figure 6 and 7) are assem-bled, ready to use, in the shop and then subjected to atest run. That assures that customers will later be able toput them into operation with a brief and reliable start-up.For larger plants, the individual units are prebuilt and tested at the plant. That also speeds up on-site assemblyand start-up.

Hydrogen has always been used in refineries. Use of oxygen is not as common, though. That may change soonunder the new rules. There are two reasons for that:1. Excess capacities for petroleum production are beingreduced for better economy. However, the new environ-mental laws require added capacities in some plants. Asnoted above, for instance, that occurs for some plantssuch as fluid catalytic crackers to utilize heavier feed oils,or in Claus plants, where more sulfur and considerablymore ammonia appear from the hydrotreaters. Then thelack of capacity can be provided by oxygen enrichment,which requires only minor changes in existing plants.Similarly, wastewater treatment plants capacities can beincreased by use of oxygen.

On-site supply with oxygen

Figure 6: Cryogenic nitrogen plant for 620 Nm3/hour

Figure 7: Process diagram for a small nitrogen plant


Figure 8: Diagram of a nitrogenPSA plant

2. Oxygen gasification of residues makes it possible to establish a broader economic basis for a refinery andto make it more flexible and economical. The gasificationgas can be used for many purposes, particularly forhydrogen recovery, as synthesis gas, especially in C1chemistry, and as fuel gas in an IGCC (Integrated Gasifica-tion Combined Cycle) power plant.

Pressure-swing adsorption (PSA) and cryogenic processesare generally used for oxygen recovery.

Use of fuels without sulfurresults in a distinct reduc-tion in emission of the pol-lutants nitrogen oxides(NOx) and hydrocarbons(HC). Sulfur-free gasolineand Diesel fuel are beingoffered at German fillingstations since the begin-ning of 2003. The maxi-mum sulfur content is 10parts per mission. By theend of 2004 the maximumsulfur content in gasolinewill be 150 mg/kg. ForDiesel fuel, the limit willbe 350 mg/kg. After 2005,the maximum sulfur con-

tent for both fuels will be50 mg/kg. Then, probablyafter 2009, the maximumsulfur in all fuels will be 10mg/kg.

In 1990 the sulfur contentof fuels for gasoline engi-nes was still 1000 ppm,and 2000 ppm for Dieselfuels. That is 100 and 200times what it will be in thefuture.

Sulfur-free fuels

Oxygen adsorption plants

Oxygen recovery using adsorption technology is based onthe property of porous adsorbents, “molecular sieves”, tobind gases at their surfaces. The two major componentsof air, oxygen and nitrogen, are adsorbed to differentextents, depending on the pressure and temperature. Thepressure dependence is utilized to separate the oxygenfrom the nitrogen. The process operates at elevated pres-sure in the adsorption phase and under vacuum in regen-eration. Therefore such plants are called vacuum-pressureswing adsorption plants, or, briefly, VPSA plants (figure 9and 10).

There are systems with one, two, or three adsorbers.In each adsorber, the cycle is generally made up of threesteps:■ adsorption phase (collection of the product)■ desorption phase (regeneration of the adsorber)■ pressure buildup (preparation for the

adsorption phase).

A cycle lasts for about 60 to 180 seconds at full load. Asargon, another component of the air, has adsorptionbehavior similar to that of oxygen, the maximum purityof oxygen from adsorption plants is 95 to 95.5%. Thatcorresponds to the proportions of oxygen and argon inthe air. For economic reasons, most plants produce puri-ties of 90% to 93%.

Adsorptive oxygen recovery is done industrially bypassing air into a container of a molecular sieve so thatthe pressure in the container rises to 1.5 bar. Almost100% of the nitrogen in the air is adsorbed by the molec-ular sieve, but only about half of the oxygen and argon.The unabsorbed oxygen and argon are drawn off as theproduct, temporarily stored in a buffer tank, compressed,and sent to the consumer. When the adsorber is satu-


rated with nitrogen, the system switches to a secondadsorber after a partial pressure equilibration betweenthe two containers. The adsorber which has just com-pleted its adsorption phase is regenerated by evacuationto 200 – 400 mbar. Near the end of this desorptionphase, product oxygen gas is added to the adsorber fromabove, increasing the desorption of the gas molecules.This flush completes the regeneration of this adsorberand the adsorption cycle starts again. The system mustbe adjusted so that the adsorption phase is just as longas the desorption phase required.

Adsorption plants have been built since the 1970s,and have been developed steadily. Modern plants havetwo adsorbers standing vertically to save space, withhigh-capacity molecular sieve. They have replaceableguard beds for removal of air moisture and to protect themolecular sieve from harmful components of the air. Theoperating times between overhauls is several years. Theplants have matured control systems which allow reliableremote monitoring. Modular design makes almost tailor-made plants available for nearly every need.

The advantages of these plants over cryogenic oxy-gen plants are their low investments, more favorableenergy requirement, and quick start-up and shut-down.The sensitivity of the molecular sieve to air pollution iscritical. However, pollutants can be trapped by guardbeds. The lifetime of the molecular sieve is almost unlim-ited if the guard bed is monitored and replaced whennecessary. The oldest VPSA plants have been operatingfor more than 15 years and we can assume that they willcontinue to operate for many more years.

Cryogenic oxygen plants

On-site supply from cryogenic plants (figure 11 and 12)is an economical alternative to VPSA plants whereverhigher purities and larger volumes of product are requi-red. Depending on the customers’ requirements, thisprocess can recover gaseous and/or liquid oxygen, oxygen and nitrogen, and, with a large air throughput,even nitrogen. The costs of cryogenic plant products arecomparable with or lower than those of VPSA plantswhen the plants are large, if nitrogen is recovered alongwith oxygen.

A cryogenic air separation plant consists essentially of the following process steps:■ air compression■ process air purification■ chilling in the main heat exchanger■ separation in the rectification column■ recovery of the cooling power.

The products are obtained by distillative separation of the air in a dual column in which the air components areseparated by their different boiling temperatures. Theseparation takes place in the temperature range of about–117 °C to –196 °C, according to the boiling points of theair components, and depending on the pressures in therectification column.

After dust particles have been removed in filters, the process air is compressed in an air compressor to theprocess pressure, typically 6 bar. Then it is led to themolecular sieve station. At this station, containers of spe-cial adsorbers operate in cycles to remove water, carbondioxide and many hydrocarbons from the process air.

The process air, purified in that manner, is chilled in the main heat exchanger in countercurrent to the pro-ducts from the rectification column. Part of the air is

Figure 9 (left): Process diagram of a VPSA plant

Figure 10 (down)VPSA plant with a capacity of 1,600 Nm3/hour O2


expanded in an expansion turbine to provide the coolingrequirement of the plant and fed into the upper column.Most of the compressed air is cooled nearly to the lique-faction temperature in the last part of the main heatexchanger and then taken to the lower part of the pres-sure column. The more volatile nitrogen accumulates inthe gas phase, due to the rectification, and can be drawnoff as compressed nitrogen at the upper part of the column. Most of the gaseous nitrogen is liquefied in thecondenser and is returned as reflux to the pressure column or the low-pressure rectification column.

The oxygen-rich liquid which collects at the base ofthe pressure column acts as the reflux for the low-pres-sure columns, which the final separation into pure oxy-gen and nitrogen takes place. Oxygen can be removed atthe lower art of the low-pressure column in both liquidand gaseous forms, while there is pure and nearlyunpressurized nitrogen at the head of that column.Impure nitrogen (residual gas) is removed through anot-her outlet in the upper portion of the column. It is suita-ble for regenerating the molecular sieve because it isnoncombustible and extremely dry.

Figure 11 (right): Flow diagram for a cryogenic oxygen plant

Figure 12: Cryogenic oxygen plant for 1,500 Nm3/hr oxygen

Linde can produce hydrogen from practically all hydrocar-bons: gaseous methane, naphtha, heavy oil, asphalt orcoal. Lindsay has the entire range of processes for hydro-gen generation: steam reforming, autothermal recordingunder the GIAP license, gasification under the Texacolicense, and prereforming under license from British Gas.Autothermal reforming and partial oxidation have as yetbeen used only in a handful of refineries, so they are nottreated in detail here. Favorable solutions can usually befound for purifying hydrogen-containing refinery gases.

Linde is also a leader in air separation for recoveringoxygen and nitrogen. Cryogenic air separation was inven-ted by Carl von Linde, the founder of the company. It hasbeen improved steadily since then. Linde’s leading posi-tion in this area appears, for instance, in its shipment ofthe world’s largest air separator for enhanced oil recovery(oil recovery by injection of nitrogen into fields) at Cantarell in Mexico. The air throughput there is 500,000Nm3/hour in each of four plants. Each one supplies335,000 Nm3/hour nitrogen at 120 bar pressure.

For each application, there is an optimal economyfor the gas supply. It depends on many conditions. Figure13 shows the optimal ranges of use for the various gasproduction systems for most applications.

Linde gas separation plants

Reprinted with permission from HYDROCARBON PROCESSING, February 2003, Copyright 2003, by Gulf Publishing Co., all rights reserved.

Gas Gas volume Purity Plant type NotesNm3/hour % by volume

H2 Up to about 400 > 99.9 Trailer up to about 400 kg H2 per hour Gaseous

100 to 100,000 > 99.9 PSA, on-site supply Recovery from residual refinery gases. Load range typically 30 to 100%

300 to 200,000 > 99.9 Steam reformer plus CO shift plus PSA, Load range typically 50 to 100%On-site supply

N2 0 to about 1000 > 99.99% Liquid from tank Also for highly variable withdrawals

About 50 to 1000 < 99% N2- membrane, Load range typically 30 – 100%On-site supply

About 100 to 5,000 < 99.5% N2-PSA, Load range typically 30 – 100%On-site supply

About 200 to 300,000 > 99.99% Cryogenic air separator, Load range typically 50 – 100%On-site supply

O2 0 to about 1000 > 99.5% Liquid from tank Also for highly variable withdrawals

About 300 to 5000 < 94% O2-PSA (VPSA) Load range typically 30 – 100%On-site supply

About 1000 to 100,000 > 99.5% Cryogenic air separator, Load range typically 50 – 100%On-site supply

Figure 13: Typical range of use for gas supply systems


Industrial gases help to meet the new requirements forrefineries under the “Auto/Oil Program” and to attainlower emissions without the need for refinery operatorsto make large investments. In particular, the hydrogenneeded for dearomatization and greater desulfurizationcan be provided. In this way, hydrotreaters can attain thelow sulfur values needed to meet the EU requirements.The lack of sulfur capacity which often appears in theClaus plants can then be made up by oxygen enrichment.The ammonia produced in hydrotreating can also beremoved at the same time without difficulty. Oxygenenrichment in fluid catalytic cracker regeneration makesit possible to process a wider range of feedstocks, and inparticular, to utilize heavier feedstocks. At the same timeit increases flexibility with respect to crude oil quality.Finally, inert gases help to improve economy and safetyin the refinery.

Conclusion

On-site plants can provide economical and reliablesupply for all these applications. A refinery operator can decide to have the gas plant built and operated bya gas company. Then he need not be concerned about the investment in such a plant, its maintenance, or itsoperation. That allows him to concentrate on his corebusiness, to react flexibly to market fluctuations, and toimprove the economy of the refinery.


[1] Purvin; Gertz: European Refining, The Quality Challenge, The European Refining Technology Conference, Paris, Nov. 22.-24., 1999

[2] Paskall, H.G.; Sames, J.A.: Sulfur Recovery by the modified Claus Process, Calgary, 1992

[3] Reinhardt, H.-J.; Heisel, M.: Increasing thecapacity of Claus plants with oxygen,Linde Reports on Science and Technology, no. 61 (1999), page 2

[4] Sadeghbeigi, R.: Fluid Catalytic Cracking Handbook, Gulf Publishing, Houston/Texas, 1995

[5] Aitani, A.M.; Ali, S.A.: Hydrogen Management in modern refineries,Erdöl Erdgas Kohle, 48 (1995), page 19-24

[6] Shorey, S.W.; Lomas, D.A.; Keesom, W.H.:Use FCC pretreating methods to remove sulfur,Hydrocarbon Processing, 78 (1999), Nummer 11, page 43

[7] N.N.: 1998 Annual Report of the PetroleumEconomics Association, Hamburg 1999, page 55

[8] Reinhardt, H.-J.; Heisel, M.; Obermeyer, H.D.:Use of industrial gases in oil refineries,Linde Reports on Science and Technology, no. 62 (2000), page 7

[9] Heisel, M.P.; Kummann, P.; Tsujino, T.:Cleaning up on economics, Power EngineeringInternational, Dec. 1999, page 15

Literature

Gebhart Scholz

Gebhart Scholz (58) is Technical Manager for stand-ard plants with the Global On-Site Business of theLinde Gas Division at Höllriegelskreuth. He holds anEng. (physics) degree from the Technical University ofMunich. His responsibilities include sourcing anddevelopment of standardized systems for generationand delivery of gaseous nitrogen and oxygen. Geb-hart Scholz has been with Linde since 1973. Duringthat time he has been involved with air separation,VPSA and ECOVAR plants.

The Authors

Michael Heisel

Dr. Michael Heisel studied Process Engineering at theTechnical University, Munich, and joined Linde AG in1973. After assignments in the Engineering Division,such as in environmental engineering at Linde-KCA-Dresden, he has since 1999 been responsible forgas supply to refineries with the Gas Division at Lohhof. His works have been awarded several inter-national prizes.

Dirk Schweer

Dr. Dirk Schweer (36) is Sales Manager for hydrogen,carbon monoxide and synthesis gas plants at LindeGas, Höllriegelskreuth, at Munich. He studied chemistry at the Ruhr University, Bochum, where hisDoctoral research was on the subject of natural gasrefining. He joined Linde in 1996.

Linde Technology 1/2003

World Trade in LNG


Large-Scale Helium Extraction

Liquid-Hydrogen-powered Mobility

On-Site Gas Supply

Reports on Science and TechnologyPublisher: Linde AGAbraham-Lincoln-Straße 21D-65189 Wiesbadenwww.linde.com

Editor: Stefan [email protected]

Enquiries and orders to:Linde AG, Corporate Center, Corporate Communications Postfach 4020, D-65030 Wiesbaden

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