LNG: Basics of Liquefied Natural Gas

The UniversiTy of Texas aT aUsTin • PeTroleUm exTension service

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Table ofContents

FIGURES vTABLES viFOREWARD viiACKNOWLEDGEMENTS ixABOUT THE AUTHORS xi 1.0 INTRODUCTION 1 2.0 OVERVIEW OF LNG INDUSTRY 3

History of LNG Industry 3Baseload LNG 5Snapshot of Current LNG Industry 7Developing an LNG Project 10References 12

3.0 BASELOAD LIQUEFACTION PLANT 13Liquefaction Technologies 13

Propane Precooled Mixed Refrigerant Process 14 Description of Air Products C3MR LNG Process 14 Liquefaction 17 LNG Flash and Storage 17Cascade Process 17 Description of ConocoPhillips Optimized CasadeSM (COPOC) 18

Liquefaction 20 LNG Flash and Storage 20Other Liquefaction Processes 20 Description of Linde MFC® LNG Process 21 Precooling and Liquefied Petroleum Gas (LPG) Recovery 22 Liquefaction and Subcooling 23

Trend in LNG Train Capacity 23Strategy for Grassroots Plant 24References 26

4.0 RECEIVING TERMINAL 27Receiving Terminals in the U.S. 28Main Components and Process Descriptions 30

Marine Facilities 30Storage Capacity 31Process Descriptions 32

Integration with Adjacent Facilities 33Gas Interchangeability 34

Nitrogen Injection 36Extracting C2+ Components 37 Comparing Two Methods of Compositional Adjustment 38

References 395.0 LNG SHIPPING INDUSTRY 41

LNG Fleet 41Types of LNG Ships 43

Moss 44Membrane 46Prismatic 48

Reducing Greenhouse Gas Emissions 49References 50

6.0 MAJOR EQUIPMENT IN LNG INDUSTRY 51Cryogenic Exchangers 51

Spiral-Wound Heat Exchangers 52

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iv LNG: Basics of Liquefied Natural Gas

Plate-Fin Heat Exchangers 55Cold Boxes 58

Compressors and Drivers 59Centrifugal Compressors 60Axial Compressors 61Reciprocating Compressors 62Gas Turbines 62

LNG Pumps and Expanders 64LNG Pumps 64Liquid Expanders 66

Loading Arms 68LNG Tanks 69LNG Vaporizers 74

Submerged Combustion Vaporizers 74Open Rack Vaporizers 76Shell and Tube Vaporizers 78 Direct Heating with Seawater 78 Indirect Heating with Seawater 80Ambient Air Vaporizers 82 Direct Heating with Ambient Air 82 Indirect Heating with Ambient Air 84

References 867.0 SUPPORTING FUNCTIONAL UNITS IN LNG PLANTS 87

Gas Pretreatment 87Slug Catcher 87NGL Stabilizer Column 89Acid Gas Removal Unit 90Molecular Sieve Dehydrator 92Mercury and Sulfur Removal Unit 92

NGL Recovery 93Integrating NGL and LNG Plants 94

Nitrogen Rejection 95Helium Recovery 96References 97

8.0 SAFETY, SECURITY, AND ENVIRONMENTAL ISSUES 99Safety Design of LNG Facilities 99Security Issues for the LNG Industry 103Environmental Issues 105References 106

9.0 OFFSHORE APPLICATIONS 107Offshore Design Considerations 107Offshore Receiving Terminal 110Offshore LNG Production 111Offshore LNG Transfer 111References 112

10.0 SPECIAL TOPICS 113Nonconventional LNG 113Risk-Based Analysis for an LNG Project 113References 114

APPENDICES 115Appendix A. Conversions Factors 115Appendix B. Properties of LNG 117Appendix C. Figures 119

GLOSSARY 125INDEX 137

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About the Authors

vDr. Stanley Huang has a specialty area in cryogenic applications, par-

ticularly in LNG and gas processing. He has worked on many projects of LNG baseload plants and receiving terminals since 1996. Dr. Huang has contributed to the process

and technology improvements through more than 20 publications and corporate reports. He worked for IPSI (an affiliate of Bechtel) and KBR, before joining Chevron. Currently he is a Staff LNG Process Engineer.

By training Dr. Huang is an expert in thermodynamics, in which he still maintains keen interest. He graduated from National Taiwan University with a B.S. degree and attended Purdue University in 1981. He earned his Master and Ph.D. degrees there, all in Chemical Engineer-ing. Additionally, he also acquired a Master of Science in physics. After leaving school he worked for Exxon Research and Engineering Company as a post-doctoral Research Associate. Then he joined DB Robinson and Associates in Alberta, Canada for six years. Dr. Huang contributed more than 30 papers and corporate reports before 1996, including a molecularly-based equation of state, called Statistical Associated Fluid Theory (SAFT), which is still popular in polymer applications today.

Dr. Huang is a Registered Professional Engineer in Texas. He gave seminars on thermodynamic applications at Chinese Petroleum Corporation, National Chung-Yan University, and National Institute of Industrial Technology in Taiwan. In recent years he also gave seminars on gas processing and LNG industry at Association of Chinese American Professionals (ACAP) meetings, Universities of Houston and Wyoming.

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xii LNG: Basics of Liquefied Natural Gas

vDr. Chen-Hwa Chiu has worked on many baseload LNG and LNG re-

ceiving terminal projects, and participated in the startup of Arun LNG plant. He has contributed to technological development, energy integration, safety, and cost reduc-

tion in large-scale baseload LNG plants and LNG terminals. A Fellow of American Institute of Chemical Engineers, he served as the Chair of its Fuels and Petrochemicals Division. He has won the George Lappin Na-tional Program Committee Service Award, AIChE, 2006, and the Distin-guish Service Award, Fuels and Petrochemicals Division of AIChE in 2004.

Dr. Chiu was an author of a Chapter in a Wiley Encyclopedia on Environmental Remediation and Analysis. He has over 80 publications, encyclopedia chapters, proceedings, and 2 patents. A frequent speaker on major international conferences on LNG, he is the chief organizer of the LNG sessions for the Topical Conference on Natural Gas Utilization and editor of its 7 proceedings from 2001 to 2007 for AIChE.

He has established and conducted the popular “Fundamentals of LNG Technology” for the Chevron professionals since 2000. He has lectured at Chinese Petroleum Corporation, National Taiwan University, National Cheng Kung University, and recently at the Lamar University on LNG Industry. Dr. Chiu graduated from National Taiwan University with a B.S. and earned his Master of Engineering and Ph.D. from the University of Oklahoma, all in Chemical Engineering. He is a Registered Professional Engineer in Texas and Pennsylvania. He has worked for Lummus, Air Products, Exxon, M.W. Kellogg, Bechtel, Fluor, and Texaco, before Chevron. Dr. Chiu is a senior technology advisor of Chevron Energy Technology Company.

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About the Authors xiii

vDr. Doug Elliot has over 40 years experience in the oil and gas busi-

ness, devoted to the design, technology development, and direction of industrial research. Doug is currently President, COO and cofounder (with Bechtel Corpo-

ration) of IPSI LLC, a company formed in 1986 to develop technology and provide conceptual design services to oil and gas producing and EPC companies. Prior to IPSI, Doug was Vice President of Oil and Gas with Davy McKee International. Doug started his career with McDermott Hudson Engineering in the early 1970s following a post-doctoral research assignment under Professor Riki Kobayashi at Rice University, where he developed an interest in oil and gas thermophysical properties research and its application. Doug has authored or coauthored over 65 technical publications plus 12 patents.

Doug served as a member of the Gas Processors Association (GPA) Research Steering Committee from 1972 to 2001 and as Chairman of the GPSA Data Book Committee on Physical Properties. Doug served as Chair-man of the South Texas Section and Director of the Fuels and Petrochemical Division of the AIChE; and is currently a member of the PETEX Advisory Board. He holds a B.S. degree from Oregon State University and M.S. and Ph.D. degrees from the University of Houston, all in chemical engineer-ing. Doug is a Bechtel Fellow and a Fellow of the American Institute of Chemical Engineers.

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Theliquefied natural gas(LNG)industryintheU.S.canbetracedbackto the1940s.However, the industrynever receivedmuchattention

from thegeneralpublicuntil thebeginningof this century.Firstly,mostLNGproducedintheU.S.isusedforpeakshavingpurposes.Evenforthisfunction,LNGcannotdistinguishitselffromothermechanismsfornaturalgasstorage,suchassaltcaverns.Secondly,domesticgasproduction,withthehelpofpipelineimportsfromCanada,hasbeenmostlyself-sufficientuntiltheendofthepastcentury,sotherewasnoneedtoimportLNGinanysignificantquantity.UsingLNGasabaseloadfuelhadafalsestartinthe1970s.OfthefourLNGimportterminalsbuiltatthetime,onlytwo(EverettinMassachusettsandLakeCharlesinLouisiana)managedtostayinopera-tionduringthattime.

Withtheincreasedconsumptionanddwindlingdomesticnaturalgasproductioninrecentyears,LNGimportsareprojectedtoincreasesignificantlyinthenearfuture.Therehavebeencloseto50proposalsforconstructingnewLNGreceiving terminalsonbothcoastsandtheGulfofMexicoareas.ThepublicinterestinLNGisalsoarousedbytheunprecedentedhighnaturalgasprices.

Inresponsetotheheightenedinterest,thisbookprovidesacompre-hensivecoverageofalldomainsintheLNGindustry.OneintendeduseofthisbookisforthetrainingclassespresentedbythePetroleumExtensionService(PETEX)ofTheUniversityofTexas.ThereadersofthisbookareassumedtobemanagersnewtotheLNGindustryoroperatingpersonnelwhohavealreadyaccumulatedsuitabletechnicalbackground.ThefocusofthematerialswillbeontheprocesssidesoastopresentanoverallpictureregardinghowLNGliquefactionandregasificationfacilitiesworkandwhytheindustryhasevolved.Ofcourse,nodescriptionscanbecompletewithouttouchingthekeyequipment,particularlythoseitemsspecifictotheindustry.

Thewaywe acquire informationhas changeddramatically in theinformationage.Thepaceofchangeacceleratedinthepasttenyearsafterhigh-speedinternetconnectionsandpowerfulsearchenginesbecamegener-allyavailable.Itisalmostadailyexperiencethatweprovideonlythe“keywords”andgainaccesstomyriadsofinformationcomingfromtheinternet.Thepresentationstyleofthisbookreflectsthisreality.Insteadofdetaileddescriptionsofachosentopic,weprovidebriefbutcomprehensivecoverageoftheideasinvolved.Interestedreaderscanpickupthecorrectkeywordstoeasilygainaccesstomoredetailedinformationfromtheinternet.Moreimportantly, comprehensivecoveragewill enable the reader to judge therelevanceofsearchedinformationandnotgetlostinaseaofinformation.

Outofthehundreds,probablythousands,ofWebsitesrelatedtotheLNGindustry,thesiterunbythe Oil and Gas Journal(OGJ)hasbeenheavilyreferenced.Throughouttheyears,OGJhasbecomeanindustriallyrecognizedleaderinprovidinginformationinthehydrocarbonindustry.Additionally,thedatabase,whichismaintainedbyOGJafter1990,isuser-friendlyandcomprehensive.

1 Introduction

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2 Overview of LNG Industry

ThischapterprovidesanoverviewoftheLNGindustry,fromthede-velopmentofcryogenictechnologytothemodern-daygasmonetization

mega-projects.Ahistoricalperspectiveishelpfulinappreciatingthecurrentstatusoftheindustry.

Therearefourdistinctivephasesinthelifecycleofanindustry:devel-opment,expansion,saturation, thendeclineor transformation.Twowell-knownexamplesarethecokeandsteelindustries(AndersonandDeLawyer,1995).Intheverybeginning,asthedevelopingtechnologyisseekingpublicacceptance,theindustrialscaleissmallandexpansionisusuallyslow.Oncethesehurdlesintechnologydevelopmentandacceptanceareovercome,afastexpansionphasefollows.Thesaturationphasesetsinwhenthewidelypracticedtechnologyischallengedbyotheremergingonesorparallelcom-petitionsreducetheprofitmargintoamerelysustainablelevel.Atthispoint,theindustryeithercandeclineortransformandrejuvenatethelifecycle.

ItisdifficulttopinpointtheexactphaseofLNGindustryatthepresentmoment.However,thereareindicationsthatithaspasseditsdevelopmentstageandisenteringtheexpansionphase.ThisiswitnessedbythesurgeofannouncedLNGprojectsinthepastfewyears.However,howlongthistrendwilllastandtowhatextentitwillcontinueprobablyonlyfuturehistorianswillbeabletotell(True,2006).

Thefirst sectionof this chapterprovidesabriefhistoryof theLNGindustry,describingthetechnologicaladvancesthatcontributedtoitswideacceptancenowadays.Thesecondsectiondescribestheemergenceofthebase-loadLNGindustryandtheessentialcomponents.ThethirdsectionprovidesasnapshotofthecurrentLNGindustryanditsroleinglobalgastrading.ThelastsectionprovidesabriefdescriptionofstepsinforminganLNGproject.

HISTORY OF LNG INDUSTRYAlthoughthecryogenicdisciplinesforgasliquefactionweredevelopedinthelate19thCentury,theearlycommercialeffortsweredirectedtowardairliquefactionandseparation.Manycompaniesformedatthattime,suchasBritishOxygenCompany(BOC),AirLiquide,andLinde,remainfamiliartradenamestoday(Scurlock,1992).

Theadvantagesofusingliquefactiontoreducegasvolumesandvaporpressuresforfluidstorageandtransportationwerenoticedbythenaturalgasindustry.ThefirstpilotplantfornaturalgasliquefactionwasbuiltinWestVirginiain1939.Theresultsweresoencouragingthatin1941thefirstcommercialLNGplantwascompletedinCleveland,Ohio.Inthenextfewyears,severalrelativelylargesphericalstoragevesselswereadded.In1944,alargecylindricalLNGtankwithanovelbase-constructiondesignfailed,becauseinsufficientmetallurgicalknowledgeatthetimeallowedthetanktobebuiltwith3.5percentnickelsteel.TheleakedLNGdischargedintothesewagesystemofaneighboring,congestedcommunityandresultedinacatastrophicexplosion,whichdemolishedtheentirecommunityandcaused128deaths.ThisincidenthaltedLNGdevelopmentforadecade.

ThedevelopmentoftheLNGindustryresumedafteritwasconcludedthat9percentnickelsteelwasadequateforLNGstorageapplications.Thisspecificationisstillinusetoday.

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Theliquefactionplantisthemostcapital-intensivelinkintheentireLNGmonetarychain.Thischapterprovidessomedetaileddescriptions

ofthecryogenicliquefactionunit,thetechnicalcoreofthislink.ThereareothersupportingunitsinanLNGplant,suchasgas sweetening,dehydration,NGLremoval,andnitrogen(N2)rejection.TheywillbecoveredinChapter7.

ThebasisofthefollowingdiscussionisasingleLNGtrain.CombiningseveralLNGtrainstoformanLNGplantorcomplexforutility-sharingwillnotbeaddressed.Theseissuesaremorerelatedtotheplantlayout,reliability,andeconomics.Also,onlytheonshoreapplicationswillbecoveredinthischapter.OffshoreapplicationsaremainlyextensionsofonshorecounterpartsandwillbecoveredinChapter9.

ThefirstsectionofthischapterdescribesthreeLNGprocessestofa-miliarizereaderswiththetechnicaldomain.Thesecondsectiondescribestrain-capacitytrendsresultingfromtechnologicaladvances.Thelastsectiondescribeschallengesfacedbytheindustryduringtheconstructionofabase-loadLNGplant.Experiencesareprovidedforreferencesinfutureprojects.Itshouldbeemphasizedthateachprojecthasitsowncharacteristicfeaturesanddifficulties.Pastexperiencesmayserveasusefulguidelines toavoidthesametraps.However,discretionshouldbeusedastotheapplicabilityoftheseexperiencesonspecificprojects.

ThedevelopmentofanLNGliquefactionprocessisanon-goingen-deavor.Notonlyarenovelprocessesbeingpatented, improvementsandvariationsofexistingonesareconstantlybeingproposed,studied,andin-stalled.Cumulatively,alltheseinnovationsandincrementalimprovementscontributetothesuccessoftheLNGindustrytoday.TheLNGplantstodayareefficient,safe,andcost-effective.Inparticular,theirsafetyrecordsareexemplaryintheenergysector.

LIQUEFACTION TECHNOLOGIES

Therearemorethan100patentsintheU.S.alonedescribingdifferentpro-cessesforLNGliquefaction.However,onlyahandfulofprocesseshavebeeninstalledcommercially.Amongthoseinstalled,someencounteredoperationalandreliabilitychallenges.Afterwards,theywereneverusedagain.Othersemergedonlyrecentlyandarestillintheprocessofconstruction.

ProcessselectionsignificantlyaffectstheoutcomeofanLNGproject.Extensivediscussionsareavailable in theopendomain toaddress issuesrelatedtoprocessefficiency,plantconstructabilityandoperability,economicperformances,andenvironmentalconcerns(Chiu,Dimitroff,andShah,2006;MokhatabandEconomides,2006;YostandDiNapoli,2003).

ThreeexamplesarepresentedbelowtohighlightthemainfeaturesofLNGprocesses.Thecriteriaforchoosingthethreeexamplesincludetheircommercialsuccessorperceivedcommercialpotential.Thethreeprocessesare:propaneprecooledmixedrefrigerant(C3MR)liquefactionprocessoftheAirProductscompany, ConocoPhillipsOptimizedCascadeSM Process(COPOC),andmulti-fluidcascadeprocess(MFC®)ofLinde.

3 Baseload Liquefaction Plant

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ThereceivingterminalisanindispensablelinkbetweenLNGshipsandthetargetedpipelinegrid.Theterminalservesthreefunctions:(1)to

receiveandstoreship-deliveredLNG,(2)toregasifytheLNG,withoptionalcompositional adjustments,and(3)todelivercontractedvolumesofgasintothedesignatedpipelinegridatspecifiedtimes.Thus,thestoragecapacityinareceivingterminalalsoprovidesadequatebufferingshouldinclementmarineconditionsinterrupttheLNGdeliveryforafinitenumberofdays.

Theglobaloperational capacityofLNGreceiving terminals shouldmatchthatoftheproduction,asshowninTable2.1.JapanisthelargestLNGimportingcountrywhichaccountsforabout40percentofglobalLNGtrade.Incontrast,theU.S.currentlyimportslessthan10percentofglobalLNGsupplies.Thescenarioisprojectedtochangebytheyear2025,whentheU.S.isexpectedtoimportabout30percentoftheglobally-tradedLNG,matchingthelevelofJapanatthattime.Also,theimportedLNGwillaccountfor20percentoftheU.S.domesticgasbalance(Shanleyetal.,2004;Martin,2005).

Theglobal-installedcapacityofLNGreceivingterminalsexceedsthatofproduction.ThisexcessreceivingcapacityisusedbysomecountriesasanassuranceagainstpossibleinterruptionsintheLNGdeliverylinks.Forexample, there isnonationalgaspipelinegrid in JapanandeachpowercompanyisexpectedtoprovideitsownLNGsparecapacity.Asaresult,thereisexcessLNGcapacityinJapanifviewedfromanationalperspective.AnotherexampleofexcessreceivingcapacityisintheU.S.,wheretwooffourterminalsweremoth-balledduetounfavorableoperatingeconomicsinthepast30years.

Since theU.S.market is themajordriving forcebehind the currentglobalLNGboom, this chapterwill focuson theU.S.LNGmarket.Thechapter isdividedinto foursections.ThefirstsectiondescribesreceivingterminalsintheU.S.Thesecondsectionprovidestechnicaldescriptionsofa typical receiving terminal.The thirdsectiondiscusses thepossibilityofintegratingtherefrigerationinareceivingterminalwithotherfacilitiesinitsvicinityinordertoimprovetheoverallthermodynamicefficiencyofthewholesystem.Thefourthsectiondescribestheissueofgas interchangeability,whichassuresthatimportedLNG,afterbeingregasifiedanddeliveredintotheexistingpipelinegrid,iscompatiblewithexistingdomestically-producedgas.Thisassuranceeliminatespossibleadverseimpactsonendusersduetocompositionalchanges.

4 Receiving Terminal

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5 LNG Shipping Industry

Shipping is a key link in theLNGmonetization chain. In currentLNGcommercialpractices,where there areminimumactivities in

spotmarkets,fewLNGshipsarebuiltonnoncommittedbases.EachLNGprojectincludesitsowndedicatedLNGfleet.Theoccasionaltransportationneeds createdby spotmarket activities aremetby chartering shipswithspareloadcapacityavailableatthedesiredtimesandlocations.LNGspotmarkettransactionsareexpectedtoincreaseinthefuture,aswillthevolumeofLNG transportedbynondedicated ships charteredafter constructiononvariableterms.

Thischapterisdividedintothreesections,thefirstofwhichprovidesaglobalviewofthecurrentglobalLNGshipfleet.Asanticipated,theupsurgeofLNGcapacityinthenextfewyearswillbematchedbyexpansionoftheLNGfleet.ThesecondsectionisfurtherdividedintothreesubsectionstodescribethreetypesofLNGships:Moss,membrane,andprismatic.ThethirdsectiondescribesthemeasurestheLNGshippingindustrytakentoreducegreenhouse gasemissions.

LNG FLEET

Similar to efforts to expand theproduction capacityofLNGproductiontrains,LNGship-buildershavebeenstrivingtoincreaseshipsizetocapturetheeconomyofscale.However,theadvancesinship-buildingtechnologyappearasquantumleapscomparedtothegradualexpansionoftheLNGtraincapacities.ThemaximumsizeofLNGshipsrecentlyincreasedto210,000m3afterlanguishingatabout140,000m3since1975(Choetal.,2005).Asaresultofthislongplateau,thecapacitiesofmostcurrentLNGshipsfallbetween100,000m3and140,000m3.Figure5.1showstheglobalship-sizedistributionasof2005(Rajvanshy,2005).

Figure 5.1 Sizes of global LNG ships in 2005

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TherearehundredsofequipmentitemsinanLNGplant.Itwouldbedifficult todescribeeverything inasinglebook.Fortunately,many

ofthesameequipmentitemsarealsousedinthegasprocessingindustry.ExcellentgeneralreferencesontheWeborinprintareavailablefortheseitems(GPSA,2000;PerryandGreen,1997).Examplesincludevessels,tow-ers,aircoolers,shellandtubeexchangers,centrifugalandpistonpumps,compressorsanddriversand,optionally,gasexpanders.

ThischapterfocusesonselecteditemsspecifictotheLNGindustry.Theseitemsincludecryogenic exchangers,largecompressorsanddrivers,LNGpumpsandliquidexpanders, loading arms,LNGtanks,andLNGvaporizersused in receiving terminals.Large compressors anddrivers are includedbecausetheirsizemakestheirapplicationsunique.

EachitemofLNGequipmentisexplainedinthefollowingsevensec-tions.Thephotosusedtoillustratethisequipmenthavebeenreprintedwithpermission fromkindmanyLNGvendors currently supplying theLNGindustry.

CRYOGENIC EXCHANGERS

Aluminum,becauseof its superior thermal conductivityandmechanicalstrengthatlowtemperatures,isafavoredmaterialforcryogenicapplications.Forcleanandnoncorrosive(NC)fluids,aluminum-basedconstructionshouldbeconsidered,ifthetemperatureisbelow35°C.Thelarge-scaleapplicationofaluminum-basedcryogenicexchangersisanimportantfactorcontributingtothesuccessofmoderngasprocessingandLNGplants.

Therearetwocommonmethodsinconstructingthealuminum-basedcryogenicexchangers:spiral-wound heat exchangers (SWHEs)andplate-finheatexchangers(PFHEs).SometimesPFHEsarealsocalledbrazed-aluminumheatexchangers(BAHEs).Spiral-wounddesignscanbetracedtotheearlydevel-opmentofcryogenicprocessesforairliquefactionbyDr.CarlvonLindeinMay1885.Intheearlydays,threeimportantmanufacturerswereLindeandHampsoninEurope,andTriplerintheU.S.Thebrazed-aluminummethodwasdevelopedrelativelylate,afterWorldWarII.Thismethodrevolutionizedthecryogenicexchangerdesignbecauseitmadepossiblethecomplexmul-tipassarrangementsandnarrowtemperatureapproaches(Scurlock,1992).

Intoday’scompetitivecommercialenvironment,severalplayersineachmanufacturingmethodarecompetingforthemarket.Thefirsttwosubsec-tionsbelowwilldiscussthetwomethodsseparately.Thethirdsubsectionwilldescribean insulation techniquecalled“coldbox,”whichcanhouseseveralpiecesofcryogenicequipmentitems.Thismethodofinsulationiscommonincryogenicplants.

6 Major Equipment in LNG Industry

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There are many functional units inside an LNG plant besides the core cryogenic and liquefaction units covered in Chapter 3. Figure 7.1 pres-

ents a schematic showing the relations between different functional units. Those units covered in Chapter 3 are highlighted in the figure. This chapter will cover the other supporting functions, including gas pretreatment, natural gas liquid (NGL) recovery, nitrogen rejection, and helium recovery.

There are four sections in this chapter. The first section covers the gas pretreatment unit, which includes gas receiving, NGL stabilizing, gas sweet-ening, gas precooling, and gas dehydrating. Inlet gas must be sweetened and dried before it can be directed to the cryogenic unit. The second section cov-ers the NGL recovery operation, the purpose of which is to meet a specified LNG heating value as well as compositional specifications. The third section discusses the nitrogen rejection unit (NRU), the purpose of which is to meet nitrogen composition specifications. Finally, the fourth section discusses he-lium recovery. In some LNG plants, where inlet gases contain relatively high proportions of helium, helium recovery can enhance the economic attractive-ness of an LNG project.

These operations are not unique to the LNG industry and also are stan-dard operations in gas processing industries. There are many good technical references (GPSA, 2000; Kohl and Nielsen, 1997; Dinh et al., 2005) to help explain more about these operations in publications and on the Web. This chapter will only provide brief functional descriptions for these supporting units to give readers a complete picture of typical LNG plants.

GAS PRETREATMENT

This section describes the following units: gas reception, NGL stabilization, acid gas removal, molecular sieve dehydration, and sulfur and mercury removal. The first two units sometimes are referred to as upstream facilities.

Slug CatcherA slug catcher is a buffering apparatus at the end of a pipeline, which includes a storage vessel sized to hold periodic in-flows of large volumes of liquids created by pigging or liquid surges. The slug catcher also acts as a means of ensuring steady outlet flows to downstream liquid handling facilities. Figure 7.2 shows a photo of the slug-catching facilities (foreground) of the Statoil Snøhvit LNG plant in Melkøya Island, Norway.

The initial separation of gas, liquids, and chemicals takes place in the slug catcher. Sometimes chemicals are injected into upstream pipelines to control corrosion or to prevent formation of hydrates or solids. Gas continues to downstream pretreatment facilities while hydrocarbon liquids are processed in the NGL stabilization plant. Chemicals, such as hydrator inhibitor, need to be reclaimed in specially designed regeneration facilities.

Structurally, a slug catcher may be a single large vessel or a collection of manifolded pipelines. The finger-type slug catching facilities shown in Figure 7.2 are visible in the foreground. When this LNG facility was under construction, the slug catcher was fabricated in a construction yard elsewhere and barged

7 Supporting Functional Units in LNG Plants

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The U.S. has a long history of working with LNG starting with peak shaving applications. Today there are more than 100 LNG

facilities scattered around the country, as shown in Figure 2.1, page 4. Baseload LNG applications have not proliferated since being intro-duced in the U.S. in the early 1970s. Rapid growth of U.S. LNG-import capacity began in the early 2000s because of dwindling domestic gas production.

Overall, the LNG industry has demonstrated an excellent safety record (Foss, 2003). In addition, dedicated journals address safety issues and con-cerns periodically to propagate awareness among industrial players (West and Chiu, 2005).

LNG safety, security, and environmental imperatives changed pro-foundly after the terrorist attack on the World Trade Towers in New York City on September 11, 2001. An LNG ship or storage tank contains a tremen-dous amount of energy. Upon sudden breach of the containment system, the released LNG poses a real safety concern. How to mitigate the potential hazard is still actively debated.

As a source of energy, LNG will play an evermore important role in U.S. domestic gas markets. With current public focus on mitigating CO2 emissions and energy efficiency, the LNG industry is proactively respond-ing to these concerns.

This chapter is divided into three sections: industrial safety, security, and environmental issues.

Safety Design of LNG Facilities In the safety domain, LNG has the following advantages over other industries:

1. The physical and chemical properties of LNG are well understood. LNG exists only under cryogenic conditions. In order to manufac-ture LNG on a large scale, these properties are required to support industrial designs.

2. The industry has evolved around a tradition of safe designs and operations which includes rigorous personnel training. To create and preserve cryogenic conditions economically, it is of utmost im-portance to minimize unscheduled process interruptions. Short-cuts lead to increased plant downtime contrary to economic principles. Hence, the LNG industry intrinsically self-regulates toward safe designs and operations.

3. Codes and regulations have been evolving synchronously with the LNG industry rather than being developed only after major indus-trial accidents.

8 Safety, Security, and Environmental Issues

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INDEXaboveground membrane tank materials, 72acid gases, 90acid gas removal unit (AGRU), 90–92alkanolamines, 90aluminum plate-fin heat exchangers (PFHE), 22ambient air

with direct heating, 82direct heating with, 82with indirect heating, 84indirect heating with, 84

ambient air vaporizers (AAVs), 82–85amine solution, 90, 92AP-X process, 14atmospheric storage tank designs, 69axial compressors, 17, 61

barg, 30baseload fuel, 1baseload liquefaction plant, 13–25baseload LNG, 5-7batch management vs. methane content, 35Bishop Process, 110Bluewater Big Sweep technology, 111BOG reliquefaction units, 49boil-off gas (BOG), 32boil-off gas (BOG) facilities, 30boil-off vapors, 17Boom to Tanker (BTT) technology, 111bottoms, 16, 22bottoms pentanes-plus product, 22brazed aluminum, plate-fin heat exchangers (PFHE), 20brazed-aluminum heat exchangers (BAHEs), 51

C2+ extraction schemes, 37C3MR process, 14canned LNG pumps, 32canned pumps, 64–65capacity, globalhistorical and projected, 4of LNG receiving terminals, 27capacity trends of LNG trains, 23–24capital cost (CAPEX), 38carbonyl (COS), 92Cascade Process, 17centrifugal compressors, 17, 60Chiksan LNG swivel joint, 68codes, 102cold boxes, 20, 51, 58combined cycle gas turbine (CCGT), 33

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138 LNG: Basics of Liquefied Natural Gas

commodity market, 10compander, 95Composite System (CS1), 46compositional adjustment comparison, 38compositional adjustments, 27, 38compressors and drivers, 59ConocoPhillips Optimized CascadeSM Process

(COPOC), 13, 17-19constant speed liquid expanders, 67construction phase, 11containment tanks, 37contracts, 10core-in-kettle configuration, 56cryogenic exchangers, 51cryogenic liquefaction unit, 13

debottlenecking, 10, 25debutanizer, 16deethanizer, 16demethanizer (DeC1), 38depropanizer, 16desuperheated propane vapor, 16development phases, 11development strategy for grassroots plant, 24–25diesel-electric propulsion systems, dual-fuel, 49diethanolamine (DEA), 90diglycolamine (DGA), 90direct heating

with ambient air, 82with seawater, 78

discharge pressure, 32double-containment tanks, 70–71double mixed refrigerant (DMR) process, 20double nitrogen expander loop process, 20downstream equipment pluggage, 14dual-fuel diesel-electric propulsion systems, 49

economics, breakeven, 8emergency release systems (ERSs), 68emissions, 104Energy Bridge, 110environmental agencies and organizations, 100–101environmental issues, 105 equipment, major, 51–84

cold boxes, 51, 58compressors and drivers, 59cryogenic exchangers, 51liquid expanders, 66–67LNG pumps, 64LNG tanks, 69LNG vaporizers, 74–85loading arms, 68

equipment, supporting functional, 87–92

gas pretreatment, 87–91helium recovery, 96NGL recovery, 93–96nitrogen reinjection, 95–96

ethylene glycol (EG), 80Eurodim technology, 111exchangers, 14expander based NGL recovery, 94expanders, 17expansion phase, 11exporting and importing countries, 9extraction of C2+ components, 37-38

Federal Energy Regulatory Commission (FERC) rulings, 28

feed gas, 14flaring, 108flash and storage, 17, 20flash vapors, 17floating production, storage, and operations (FPSO)

vessels, 107formation phase, 11fractionation column, 89fractionation unit, 16freon, 80front-end design NGL plant, 94full-containment tanks, 70functional units schematic, 88

gas interchangeability, 27, 34–35gas liquefaction, 3, 7,14gas monetization chain, 3, 6gas odorization, 30gas pretreatment, 87–91Gas Processors Association (GPA), 100gas production, 6–7gas recovery LPG, 22gas reservoirs, 96gas sweetening, 13gas turbines, 62–63Gaz Transport (GT) No. 96, 46–47global consumption, 7global gas market, 8grassroots plant strategy, 24–25greenhouse gas emissions, 49, 104

handholes, 52heat exchangers, 20heat transfer fluids, 80heavy hydrocarbons, 14heavy removal unit, 22

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Index 139

helium recovery, 96high heating values (HHV), 34–35high heating values (HHV) vs. methane content, 35high-pressure gaseous nitrogen (GAN), 36hydrates, 87hydrocarbon recovery step, 14

importing, exporting countries, 9indirect heating

with ambient air, 84with seawater, 80–81

inground tanks, 69in-tank pumps, 32, 64–65intercooling, 17intermediate fluid vaporizer (IFV), 81isobutane, 80

jacket-insulated pipelines, 111

Kvaerner’s Moss design, 44–46

life cycle cost (LCC) analysis., 38Linde MFC process, 20–22liquefaction, 7, 6, 17, 20liquefaction, gas, 7, 3, 14liquefaction and subcooling, 23liquefaction facilities, 1liquefaction flow schemes

C3MR process, 15COPOC process, 18Linde MFC process, 21, 22

liquefaction processes, 20liquefaction technologies, 13liquefied plant, 13liquefin process, 20liquid expanders, 15, 66–67LNG (liquefied natural gas), described, 2LNG fleet, global

numbers of, 42sizes of, 41types of, 43

LNG industry history, 1, 3–4LNG pumps, 64-65LNG receiving terminals

process descriptions, 32storage capacity of, 31–32

LNG ships, 5, 41LNG tanks, 69-74LNG trains, 10, 23–24LNG vaporizers, 74–85

loading arms, 51, 68long-term operating cost (OPEX), 38LPG recovery. See NGL recovery

MFC process, 21-22main cryogenic heat exchanger (MCHE), 14manifolded pipelines, 87marine facilities, 30–31membrane designs, 108membrane materials, 72membrane ships, 41membrane tank designs, 46–47membrane tank materials, 72mercaptans, 90, 92mercury and sulfur removal unit, 92methane loop, 18methyldiethanolamine (MDEA), 90mid-train design NGL plant, 95mixed refrigerant (MR) loops, 14molecular sieve dehydrator, 92monetization, 3monoethanolamine (MEA), 90Moss design, 108Moss ships, 41, 44–46multi-fluid cascade process (MFC), 13Mustang design, 84

National Fire Protection Association (NFPA), 100natural gas liquid (NGL), 2NGL and LNG plants integration, 94-95NGL recovery, 93–96

expander based, 94schematic of, 93

NGL Stabilizer, 89–90nitrogen injection, 36–37nitrogen rejection., 2, 95–96nonconventional LNG, 113noncorrosive (NC) fluids, 51non-dedicated ships, 41NOx, 75

odorization, 30Offshore Cryogenic Loading (OCL) technology, 111offshore design considerations, 107–111offshore LNG production, 111offshore LNG transfer, 111offshore receiving terminal, 110–111Oil and Gas Journal (OGJ), 1open rack vaporizers (ORVs), 75, 76–77operational capacity of receiving terminals, 27operation phase, 11

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140 LNG: Basics of Liquefied Natural Gas

overhead, 16overhead butanes product, 22

peak shaving facilities, 1, 4, 74, 75pigging, 87pipeline grid, 7pipeline transmission, 7pipeline vs. LNG economics, 8plate-fin heat exchangers (PFHEs), 51, 55–57positioning monitoring systems, 68precooling and liquefied petroleum gas (LPG) recovery,

22pressurized LNG, 113prestressed concrete (PC) containment tanks, 73primary containment, 100primary containment materials, 72prismatic (SPB) design, 48prismatic ships, 41prismatic tank design, 108process descriptions, 32process trains, 52project development, 10project risk-based analysis, 113propane precooled mixed refrigerant (C3MR)

liquefaction process, 13propane precooled-mixed refrigerant process, 14pumps

canned, 64–65canned LNG, 32canned LNG pumps, 32in-tank, 32, 64–65LNG, 64send-out, 32submerged electric motor, 64vessel-mounted (canned), 64

quick connect/disconnect couplers (QCDC), 68

reboiler, 89receiving terminals, 1, 27–38

existing and proposed, 29main components and process descriptions, 30operational capacity of, 27potential, 30in the U.S., 28-29

reciprocating compressors, 62recondenser, 32refrigeration loops, 18refrigeration needs, 59regasification facilities, 1, 7regasification terminal, 33

regulations, 100–101regulatory authorities, 100rejection of refrigeration in seawater, 33reservoirs, 96risk-based analysis, 113

safeguard systems:, 100safety agencies and organizations, 100–101, 102safety design and issues, 99–102SBM Soft Yoke technology, 111scoping phase, 11scrub column, 16, 22seawater

direct heating with, 78with indirect heating, 80–81indirect heating with, 80–81rejection of refrigeration in, 33

secondary containment, 100secondary containment materials, 72security agencies and organizations, 100–101security issues, 103–104self-supporting prismatic (SPB) design, 48self-supporting prismatic (SPB) ships, 44send-out pumps, 32separation, 16separation distance:, 100September 11, 2001 terrorist attacks, 99, 103shell and tube vaporizers (STVs), 78–79shipping, 7shipping industry, 41–48ships

LNG, 5, 41membrane, 41Moss, 41, 44–46non-dedicated, 41prismatic, 41

self-supporting prismatic (SPB), 44single-containment tanks, 37, 70slug catcher, 87–88Society of International Gas and Tanker and Terminal

Operators (SIGTTO), 100solvents, 90Soot Index, 36sparging, 74spiral-wound heat exchangers (SWHEs), 22, 51, 52–55standards, 102steam turbine propulsion, 49storage, regasification, and send-out, 7storage boil-off recovery system, 17storage capacity, 27, 31–32storage facilities, 4, 7straddle design NGL plant, 95stranded gas, 7, 113subcooling, 14

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Index 141

submerged combustion vaporizers (SCVs), 74–75submerged electric motor pump, 64subsea cryogenic LNG pipelines, 111sulfur removal unit, 92superheaters, 80swivel joint, 68

tanksaboveground membrane materials, 72atmospheric storage designs, 69containment, 37double-containment, 70–71full-containment, 70inground, 69LNG, 69membrane designs, 46–47membrane materials, 72prestressed concrete (PC) containment, 73prismatic design, 108single-containment, 37, 70type A and B, 43

Technigaz Mark III, 46–47The Deep Water Ports Act (DWPA), 100thermal integration, 33–34trains, LNG, 10, 23–24type A and B tanks, 43

unloading arms, 30–31upstream facilities., 87U.S. Coast Guard (USCG), 100, 103, 104U.S. Department of Transportation (DOT), 100U.S. Environmental Protection Agency (EPA), 100U.S. Federal Energy Regulatory Commission (FERC),

100, 103, 104U.S. LNG market, 27

vacuum-insulated pipelines, 111vaporization heat, 33vaporizers, 30variable speed liquid expanders, 67vessel-mounted (canned) pumps, 64

Waterway Suitability Assessment (WSA), 103weather-vane effect, 108Wobbe Index, 36

Yellow Tip Factor, 36

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To obtain additional training materials, contact:

PETEXThe University of Texas at Austin

Petroleum extension service10100 Burnet Road, Bldg. 2

Austin, TX 78758

Telephone: 512-471-5940or 800-687-4132

FAX: 512-471-9410or 800-687-7839

E-mail: petex@www.utexas.eduor visit our Web site: www.utexas.edu/ce/petex

To obtain information about training courses, contact:

PETEXlearning and assessment center

The University of Texas4702 N. Sam Houston Parkway West, Suite 800

Houston, TX 77086

Telephone: 281-397-2440or 800-687-7052

FAX: 281-397-2441E-mail: plach@www.utexas.edu

or visit our Web site: www.utexas.edu/ce/petex

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Catalog No. 3.12010ISBN 0-88698-217-0

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