Introduction PAGES SAMPLE - Amazon S3 · 2013-11-13 · Fractional distillation column at a petroleum refinery The boiling points of organic compounds increases with molecular mass,

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Unit 12.5 Natural Resources and Chemical Industries in Papua New Guinea

Topic 1: Extraction of oil and gasTopic 1 covers the extraction of oil and gas in Papua New Guinea, by discussing:• The carbon cycle.• Petroleum refining.• Natural gas and liquefied natural gas.

IntroductionPapua New Guinea is not only a consumer; it is also an active participant in developing and using the principles of chemistry. Papua New Guinea has long been known as region with rich oil and gas deposits. Large-scale exploration began after the 1970s Arab oil embargo, at which time Papua New Guinea was still a colony of Australia.

This exploration established the Hides Anticlines, an area in the Southern Highlands, as the richest area in oil, with the main discoveries taking place within this tectonic region.

All of Papua New Guinea’s existing oil and gas fields are located in the region of the Papuan Fold Belt. ‘Fold belt’ is a geological term that refers to a region of the Earth’s surface where the rocks have been subjected to severe folding and thrusting.

The major oil and gas reserves in Papua New Guinea are shown on the following map.

SANDAUN

Vanimo

Wewak

Wabag

MountHagen

Madang

Goroka

Lae

Popondetta

Alotau

Rabaul

Kavieng

Kerema

Port Moresby

Hoskins

EAST SEPIK

ENGAWESTERNHIGHLANDS

EASTERNHIGHLANDS

SIMBU

MADANG

MANUS

MOROBE

GULF CENTRAL

ORO

WEST NEWBRITAIN

MILNE BAY

EAST NEWBRITAIN

NEWIRELAND

WESTERN

WES

T P

AP

UA

SOUTHERNHIGHLANDS

AUTONOMOUSREGION OF

BOUGAINVILLE

Lorengau

Petroleum projectsOil projectGas projectPossible oil or gas projectOil export projectProposed gas pipeline

Pnyang

Elevala

KetuJuha

Angore

DouglasKimu

Uramu

Pandora

LehiGobe

Moran

S.E. ManandaKutubu

ElkBwata

Barikewa

Hides

0 100 200 km

N

Petroleum projects in PNG

The carbon cycleCarbon dioxide makes up about 0.04% of air. In normal circumstances, this value is kept constant by the cycling of CO2 through nature by the processes of photosynthesis and respiration in the carbon cycle, shown in the following flow diagram.

23_SAV_CH12_78805_TXT_4pp.indd 269 24/07/13 2:18 PM

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270 Unit 12.5 Natural Resources and Chemical Industries in Papua New Guinea


CO2 in atmosphere

Photosynthesis

CO2 diffusion

Respiration and metabolism

Respiration by marine animals

Fossil fuels

Green plants

Soil decomposition

Death and decay

Animals

CO2diffusioninto sea

Photosynthesisby marineplants

Burning (combustion)

Basic carbon cycle flow diagram

The main pathway of the carbon cycle is the:

• conversion by plants of CO2 gas in the atmosphere into glucose.

6CO2(g) + 6H2O C6H12O2(aq) + 6O2(g)

• conversion of glucose in organisms back to CO2 gas in the atmosphere.

C6H12O2(aq) + 6O2(g) → 6CO2(g) + 6H2O + energy

Plants take in about 25% of the CO2 gas from the atmosphere and photosynthesise it into carbohydrates in the presence of the green pigment chlorphyll. Some of the carbohydrate is consumed during plant respiration and the rest is used to build plant tissue and growth. Animals consume the carbohydrates and return CO2 to the atmosphere during respiration. Carbohydrates are also oxidised by small organisms, returning CO2 gas to the atmosphere. Through the process of photosynthesis and respiration, carbon is cycled in nature.

Fossil fuels are coal, petroleum and natural gas. These formed when ancient life forms were buried and decomposed. When fossil fuels are burnt to generate electricity, to run industries and for transportation, they also generate carbon dioxide and release it to the atmosphere. This process is contributing to rising levels of CO2 in the atmosphere.

Unit 12.5 Activity 1A: The carbon cycle1. Write the general word equation and chemical equation for animal respiration.

2. Write the general word equation and chemical equation for photosynthesis.

3. Research and explain the chemical composition of chlorophyll as an important substance in photosynthesis.

4. Explain the importance of oceans in the carbon cycle.

sunlightchlorophyll


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Topic 1: Extraction of oil and gas 271


CoalCoal is a black or brownish-black rock composed of a mixture of carbon, hydrocarbons, nitrogen, sulfur and water. It formed from plants that lived hundreds of millions of years ago. Coal is the most abundant of the fossil fuels. Some countries have large deposits of coal.

Example ACoalLarge coal mines are found in areas such as the Hunter Valley in New South Wales, Australia. There are no coal mines in Papua New Guinea.

Coal has many uses. In some countries coal is used directly for heating. The main use of coal has been for generating electricity. Coal is also used to purify iron in a blast furnace, where it removes oxygen from iron oxide (Fe2O3) via a metal reduction process.

Example BCoal and iron extractionCoal reacts with oxygen to produce carbon monoxide gas, which reduces iron oxide in the blast furnace in the following series of reactions:

C(s) + O2(g) → CO2(g)C(s) + CO2(g) → 2CO(g)

Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g)

Unit 12.5 Activity 1B: Coal1. Describe the physical appearance of coal.

2. Explain the uses of coal.

3. Write the general reaction equation for the reduction of a metal compound, MX, by a reducing agent, R.

4. Research and explain the reduction of iron oxide in a blast furnace.

Oil (petroleum)Oil formed from the remains of animals and plants that lived millions of years ago. Over time, the remains became covered by layers and layers of mud. The heat and pressure from these layers caused the animal and plant remains to turn into crude oil.

Petroleum literally means ‘rock oil’. It is a complex mixture of hydrocarbons and other chemicals. The hydrocarbons are mostly alkanes, cycloalkanes and aromatic hydrocarbons. Their relative proportions vary depending on where and how the pertoleum was formed. The composition of crude oil varies from one deposit to another.

Generally, the elemental composition of crude oil is carbon (83–7%), hydrogen (11–15%), sulfur (1–6%), nitrogen (0.1–2%), oxygen (0.05–1.5%) and metals (<0.1%).

The amount of sulfur in crude oil also varies from one deposit to another. Crude oil with a high sulfur content is referred to as ‘sour’ crude oil. Crude oil with a low sulfur content is referred to as ‘sweet’ crude oil.


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Crude oil is the source of most of our liquid fuels, and petroleum oil is used in the forms of petrol and diesel that power most vehicles. Other useful crude oil products include propane, butane, fuel oil, lubrication oil, greases, paraffin wax and bitumen. Petroleum products have a wide range of uses, including in the manufacture of polymers and fibres, adhesives and sealants, cosmetics, fragrances and food additives, paints and packaging.

Example CArabian heavy crude oil and light crude oil have the same components but in different proportions.

Example DSweet and sourAustralian crude oil is sour crude – it has a high sulfur content. Papua New Guinean crude oil is sweet crude – it has a very low sulfur content.

Unit 12.5 Activity 1C: Oil (petroleum)1. Write the chemical formulae for propane and butane.

2. Find out where the following products are used.

a. Fuel oilb. Paraffin waxc. Bitumend. Kerosene

3. Research and explain the difference between kerosene and jet fuel.

Oil refiningAlthough petroleum refineries are generally similar, operations can vary from one refinery to another because of the type of crude oil and the type of products required. The following operations are carried out in many refineries.

Desalting is usually the first process in crude oil refining. Salt, minerals and other water-soluble impurities are removed from the crude oil by washing it with water. The salt dissolves into the water. After desalting, the remaining salt content is usually measured in PTB (pounds of salt per thousand barrels of crude oil).

Desalting is necessary to protect refinery equipment against plugging, corrosion and catalytic poisoning.

Example EDesaltingCalcium, sodium and magnesium chlorides are the most common salts in crude oil. They are removed by desalting.

Petroleum can be separated and purified into the different hydrocarbons in two ways: non-chemically and chemically.


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Non-chemical separation methodsSeparation methods that don’t involve chemical reactions include solvent extraction, absorption, distillation and crystallisation.

Solvent extractionSolvent extraction removes impurities that would affect the performance of the final petroleum product. It removes heavy aromatic compounds from lubricating oils. It also removes impurites that would contribute to corrosion and poisoning of catalysts in subsequent processes at the refinery.

Solvent extraction and solvent dewaxing usually remove these impurities at intermediate refining stages or just before the product is sent to storage.

The specific processes and solvents used depend on the type of petroleum being treated, the contaminants present and the finished product requirements.

Example FExtraction solventsThe most widely used extraction solvents are phenol, furfural (an aromatic aldehyde) and cresol. Furfural is used to remove coloured compounds containing sulfur and oxygen.Other solvents include liquid sulfur dioxide, nitrobenzene and 2,2′-dichloroethyl ether. Ethylene glycol is used to extract the aromatic compounds benzene, toluene (methylbenzene) and xylene (1,4-dimethylbenzene) (also known as the BTX fraction).

AbsorptionMolecular sieves are materials with microscopic holes that block large molecules and let smaller molecules pass through into the sieve. The larger molecules pass by with the solvent and the smaller molecules are trapped (adsorbed) in the sieve until desorption occurs. The holes are measured in Ångstroms (1 Å = 10−10 m) or nanometres (1 nm = 10−9 m). The petroleum industry uses molecular sieves consisting of porous aluminosilicates, which adsorb linear hydrocarbons in preference to branched ones.

Example GMolecular sieves in petroleum refiningDuring petrol refining, moleculer sieves with 3–10 Å pores are used to separate mixtures of the C4 compounds 2-methylpropene (isobutene), 1-butene, 2-butene and butane. 2-Methylpropene is cleanly separated as it is too bulky to be absorbed.

DistillationThe next step in the refining of oil is fractional distillation. This is carried out in tall steel towers up to 50 metres high. Crude oil is heated in a furnace to about 600°C and then fed into the bottom of a fractionation tower.


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Crude oil

150°C

200°C

300°C

370°C

400°C

Furnace

Gas20°C

Gasoline(petrol)

Kerosene

Diesel oil

Fuel oil

Lubricating oil,Paraf�n wax,Asphalt

Fractional distillation column at a petroleum refinery

The boiling points of organic compounds increases with molecular mass, so distillation separates crude oil into fractions of different size and boiling points, from gases to heavy oils, waxes and asphalt. The chemicals that result from the first fractional distillation are called straight-run fractions. They are listed in the following table.

Straight-run fractions from petroleum distillation

Fraction Boiling point (°C)

Uses Sent to

Gases (C1–C4 compounds)

<20 Natural gas Gas processing

Light naphtha (C5–C8 compounds)

20–150 Jet fuel Petroleum blending

Heavy naphtha (C9–C12 compounds)

150–200 Feedstock for fuel, chemicals Catalytic reforming

Kerosene (C9–C16 compounds)

175–275 Jet fuel Hydro-treating

Gas oil (C15–C25 compounds)

200–400 Diesel, cracking to olefins Distillate fuel blending

Lubricating oil >350 Lubrication and catalytic cracking to lighter fractions

Fluid catalytic cracking

Heavy fuel oil >350 Boiler fuel and catalytic cracking for lighter fractions

Fluid catalytic cracking

Asphalt Paving, coating and construction purposes

Coking


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The C1–C4 alkanes (methane (CH4) to butane (C4H10)) are gases, which are sent to the gas processing unit. The C5–C8 alkanes (pentane (C5H12) to octane (C8H18)) are refined into petroleum. The C9–C16 alkanes (nonane (C9H20) to hexadecane (C16H34)) are refined into diesel fuel and kerosene. Higher alkanes are refined into fuel oil and lubricating oil. At the heavier end of the range is wax and asphalt, which can be converted to more valuable products.

CrystallisationWaxes are removed from lubricating oil fractions by crystallisation. A solvent such as a benzene/butan-2-one mixture is added to the oil and the solution is then cooled to about −20°C. The wax precipitates out as crystals and can be removed.

Unit 12.5 Activity 1D: Processes in oil refining1. Explain how waxes are removed from petroleum by crystallisation.

2. Research petroleum refining further to explain the separation of fractions by linearity and aromaticity.

3. Name the natural gases in the C1–C4 range.

Chemical separation methodsStraight-run fractions from petroleum distillation are further refined to produce fuels for high-compression engines. The refining converts hydrocarbons greater than C10 or smaller than C4 into hydrocarbons in the petrol range (C4–C10).

The aim is to produce compounds with a high octane rating. The octane rating (or octane number) of a fuel is a measure of its performance. The higher the octane rating, the more it can be compressed before it spontaneously ignites, which causes damaging engine ‘knocking’. The rating is based on a scale on which isooctane (2,2,4-trimethylpentane) is 100 (minimal knock) and heptane is 0.

Example HOctane rating 92Petrol with an octane rating of 92 has the same knock as a mixture of 92% isooctane and 8% heptane. This does not mean that the petrol contains these hydrocarbons in these proportions. It simply means that it has the same resistance to spontaneous ignition as the described mixture.

Some fuels are even more knock-resistant than isooctane, so the scale has been extended to allow for octane numbers higher than 100.

Example IOctane ratings >100Petrol with the same knocking characteristics as a mixture of 90% isooctane and 10% racing fuels, avgas, liquefied petroleum gas (LPG) and alcohol fuels, such as methanol, may have octane ratings of 110 or significantly higher.


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An octane rating is not an indicator of the energy content of a fuel. It is only a measure of the fuel’s tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner.

Lead in the form of tetraethyl lead was once a common fuel additive because it reduced knocking, but since the 1970s its use in fuels has been progressively phased out worldwide, because of lead’s negative effects on the environment and health.

Other chemicals that are added to fuel to increase its performance include aromatic hydrocarbons such as toluene, ethers, alcohol and isooctane.

Thermal crackingThermal cracking is the use of high temperatures(400–900°C) to convert alkanes to alkenes (ie form double bonds). At the cracking temperature, a C–C bond breaks and two free radicals form. Radicals are atoms or groups of atoms that contain one or more unpaired electrons (represented by a single dot in the formula). They are very reactive.

Example JThermal crackingIn thermal cracking, octane forms ethene or propene and a shorter-chain radical:

CH3(CH2)6CH3→ CH3(CH2)3CH2•+ •CH2CH2CH3

CH3(CH2)3CH2•→ H2C=CH2 + •CH2CH2CH3

ethene shorter radicalCH3(CH2)6CH3→H2C=CHCH3 + CH3(CH2)3CH2

•

propene shorter radical

Fluid catalytic crackingFluid catalytic cracking is a process that uses heat and catalysts such as zeolite to convert long-chain alkanes to aromatics and branched-chain molecules.

Example KFluid catalytic crackingGas oil (C15–C25) breaks up to form 2-methyl-1-butene and 2-methyl-2-butene.

Hydrocracking and hydrotreatingHydrocracking is a chemical process that converts long-chain alkanes in crude petroleum into shorter-chain alkanes, alkenes and aromatic compounds and then hydrogenates them. Catalysts such as palladium on zeolite are used in the hydrocracking process.

The result is a relatively large amount of isobutane (methylpropane), which is used in later alkylation and isomerisation reactions (to produce high-quality jet fuel).

Hydrotreating is a catalytic hydrogenation process that removes contaminants such as oxygen, sulfur, nitrogen, metals and unsaturated hydrocarbons from liquid petroleum fractions. Hydrotreating catalysts are usually transition metals, such as cobalt and molybdenum. The contaminants are converted to ammonia, hydrogen sulfide and water.


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PolymerisationIn this process, two short-chain alkenes, such as ethene, propene or butene, combine to form a longer-chain alkene, at high temperatures and pressures and using a catalyst of phosphoric acid (H3PO4) on clay. The process is terminated at the dimer or trimer stage and the products are blended with petrol or added to the petroleum feedstock.

Example LPolymerisationIsobutene combines with propene to yield a C8 or C12 alkene mixture for detergent manufacture.

AlkylationReactions of short-chain alkenes are useful for producing hydrocarbons in the petrol range with more branched products. Catalysts such as sulfuric acid and hydrofluoric acid are used. The process is very useful in the petrol refinery. The alkylate product consists of a mixture of heptane and octane isomers and so can be added to petrol.

Example MAlklyationAlklyation of isobutene and isobutane produces branched products such as 2,2,4-trimethylpentane and the 2,3,4- and 2,3,3-trimethyl isomers.

CH3

Isobutane(2-methylpropane)

Propene 2,2,4-Trimethylpentane

CH3H3C

CH2

H3C

H3C CH3C

H3C

C C

H2

CH3 CH3

CH3H

+ →

Catalytic reformingCatalytic reforming is the opposite process to cracking and is the most widely used method for petroleum production. The process converts low-octane compounds to high-octane products, called reformates, and hydrogen. This is achieved by rearranging some hydrocarbons and breaking other hydrocarbons into smaller molecules. The catalysts are Pt or Pt–Re on alumina and the process occurs at high temperatures and pressures.

Example NCatalytic reformingCatalytic reforming of octane forms 2,5-dimethylhexane. Methylcyclohexane rearranges to form toluene and 3 moles of hydrogen.Catalytic reforming of the hydrocarbon C15H32 breaks it down into ethene, propene and octane.


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The less valuable product of the reaction can be converted to other, more commercially valuable hydrocarbons.

Example OMetathesisPropene breaks up to form ethene and butene. The reaction is applicable to many alkenes and is called metathesis.2CH2=CHCH3 → CH2=CH2 + CH3CH=CHCH3

Propene Ethene Butene

Unit 12.5 Activity 1E: Conversion methods1. Explain how catalytic reforming works.

2. Define octane rating and explain how it affects motor vehicles.

3. Draw structures for:

a. isobutene.b. isobutane.c. 2,2,4-trimethylpentane.

4. Write the chemical reaction for the catalytic reforming of:

a. methylcyclohexane to toluene and 3 moles of hydrogen.b. octane to 2,5-dimethylhexane.

Petroleum refining in PNGThe ten top oil-producing countries are Saudi Arabia (producing 12% or the world’s oil), Russia (11%), United States (9%), Iran (5%), China (4.5%), Canada (4%), United Arab Emirates (3%), Mexico (3.6%), Kuwait (3%) and Iraq (3%). Australia produces 0.70% of the world’s oil and Papua New Guinea produces 0.04%.

The refining of oil in Papua New Guinea began in 2004. The InterOil Napa Napa Oil Refinery is the only oil refinery in Papua New Guinea. InterOil gets its crude oil from Kutubu in Southern Highlands Province and some from overseas. The refinery has the capacity to produce 36 000 barrels per day.


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Napa Napa Oil Refinery

Petroleum products such as diesel, kerosene, petrol and liquefied petroleum gas (LPG) are used domestically. Products such as naphtha are not used in Papua New Guinea and are exported to China and Australia.

The following table compares the crude compositions of products from the Napa Napa Oil Refinery and Australian Mutineer oil.

Comparative yields of products made from local Kutubu crude oil and Australian Mutineer crude oil

Stream Volume (%)

PNG Australia

Fuel gas 0.4 0

Propane (LPG) 0.6 0

Butane (LPG) 3.9 0

Light virgin naphtha 11.6 5

Mixed naphtha 11.4 13

Unleaded petrol 10.7 8.9

Kerosene 7.7 7.4

Diesel 38.0 57.8

Low-sulfur waxy residue 15.7 7.8


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Unit 12.5 Activity 1F: Petroleum in PNG1. Like all oil from PNG, Kutubu crude oil is referred to as ‘sweet’ crude. Explain why

this is.

2. The Napa Napa Oil Refinery imports crude oil from Australia and Asia. Use the information from the table to justify this practice.

3. From the information in the table, should Mutineer Oil Refinery import crude oil from PNG? Explain.

Natural gas and liquefied natural gasNatural gasNatural gas formed from the decaying remains of ancient plants and animals. Natural gas is found deep underground, often near oil deposits. It is extracted by using drilled wells.

Natural gas can be considered the most environmentally friendly fossil fuel, for two reasons:

• It has the lowest CO2 emissions per unit of energy.• It is suitable for use in combined-cycle power stations, which use waste heat from the

power station to make steam to generate additonal electricity.

The major constituent of natural gas is methane, CH4(g). It also contains other hydrocarbons, CO2, nitrogen and hydrogen sulfide.

Liquefied natural gasLiquefied natural gas (LNG) is produced relatively cheaply both worldwide and in Papua New Guinea. LNG is produced when natural gas is cooled below its boiling point to −160°C through a process known as liquefaction. Liquefaction removes or reduces the levels of hydrocarbons, water, carbon dioxide, oxygen and some sulfur compounds. This increases the methane concentration to 80–90% and is known as ‘sweetening’. Liquefaction also reduces the density to 1/600th of that of the original gas, making transport more economically viable.

Liquefied natural gas is:

• clear, colourless, odourless, non-corrosive and non-toxic.• less than half as dense as water and floats on water.• not explosive in its liquid state.

LNG does not burn by itself. It needs to be in vapour form in an enclosed space and mixed with air. It is only combustible at concentrations of 5–15% by volume of natural gas in air.

LNG is cleaner burning than diesel fuel. It is particulary suited to heavy-duty vehicles because of its high storage density and low nitrogen oxides (NOx) and particulate emissions.


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Example PLNGLNG is used by garbage trucks, local delivery (eg grocery) trucks and transit buses. Vehicles that are classified as Class 8 (above about 15 000 kg, gross vehicle weight) typically use LNG. LNG is also used in gas stoves and heaters.

Unit 12.5 Activity 1G: Liquefied natural gas1. What is LNG?

2. Draw the structure of methane.

3. What is the difference between natural gas and liquefied natural gas?

4. Under what conditions does liquefied natural gas become explosive?

Gas refining in PNGThe countries with the largest natural gas reserves are Algeria, Australia, Brunei, Indonesia, Libya, Malaysia, Nigeria, Oman, Qatar, Trinidad and Tabago, and Papua New Guinea.

The ExxonMobil and Oil Search Port Moresby LNG plant is the only gas refinery in Papua New Guinea. The consortium gets its gas from the Hides gas fields at Kutubu in Southern Highlands Province.

There are five steps involved in getting natural gas into homes and businesses in the cities from gas fields in remote locations.

1. Natural gas is pumped from below ground at the Hides gas fields to the surface. The gas is transported from the site through pipelines to Australia and Port Moresby.

2. The gas is liquefied in Port Moresby to produce a stable liquid ready for shipping.3. Transportation to China occurs in double-hulled ships specifically designed to handle

the low temperature required for LNG. These carriers are insulated to limit the amount of LNG that evaporates. The LNG is off-loaded as a liquid and pumped from the jetty to storage tanks at the terminal. The LNG remains at –160ºC throughout.

4. When LNG is received at the terminals, it is transferred to insulated storage tanks specifically built to hold LNG. Tanks can be above or below ground and keep the liquid at low temperature to avoid evaporation. Full containment systems use two tanks – an inner tank that contains the LNG, and an outer tank to contain any leaks from the inner tank. The tanks are well insulated to keep the natural gas at −160°C to avoid evaporation.

5. Re-gasification of the LNG occurs when it is pumped out of the tanks and warmed so that it returns to its natural gaseous state. The natural gas is then pumped into the natural gas transmission system to cities and towns.


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L N G

L N G

1. Extraction

2. Liquefaction

3. Transportation

4. Storage

5. Regasi�cation

Processes in LNG in Papua New Guinea

Unit 12.5 Activity 1H: LNG refining1. How is LNG transported?

2. How is LNG stored?

3. Is LNG flammable or explosive?

4. What are the benefits of LNG in transportation applications?

5. What vehicles or niche markets use LNG?


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Introduction PAGES SAMPLE - Amazon S3 · 2013-11-13 · Fractional distillation column at a petroleum refinery The boiling points of organic compounds increases with molecular mass,