LNG Production

1. UTT, PEOP1010
Prepared by Safiyyah Wahid

2.  Trinidad & Tobago has one LNG facility known as Atlantic LNG,
based in Pt. Fortin.
 There are 4 refrigeration “trains” having a total capacity of
100,000 m3 per day.
 In 2013, ALNG was the main user of natural gas, accounting for
some 57% of the total usage of natural gas in that year. Most
of the gas received by ALNG is utilized in the production of
LNG, while some natural gas liquids are also produced at the
plant and transported along a pipeline to PPGPL for separation
into propane, butane and natural gasoline.
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3. 3
http://www.energy.gov.tt/our-business/lng-
petrochemicals/

4.  World trade in LNG has more than tripled over the last 20
years, growing from 8.5 Bcf/d (billions of cubic feet per
day) in 1994 to nearly 32 Bcf/d in 2013.
 Current LNG consumers are mainly found among the
energy-hungry economies of Asia, as well is in a number
of the more developed Western European countries.
 Worldwide natural gas consumption is predicted to
increase from 310 Bcf/day in 2010 to 507 Bcf/day in
2040.
Much of this increase is due to the anticipated growth in
the use of natural gas for power generation as countries
take advantage of the cleaner-burning properties of this
fuel
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5.  Atlantic LNG uses the Phillips Optimised Cascade Process
developed by Phillips Corporation, that was first used
successfully at the Phillips plant in Kenai, Alaska.
 Liquefaction is the most efficient way to reduce the
volume of natural gas so that it can be transported. Pure
LNG produced is piped to heavily insulated storage
tanks.
-161°C
Vol. Reduction 600:1
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Natural Gas LNG
PLANT
LNG

6.  Natural gas specifications have several purposes,
including corrosion prevention, avoiding liquid drop out in
pipelines, and burner performance.
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Component Limit Reason
CO2 50 ppm Avoid freezing in cryogenic
processing unit
H2S 5 mg/Nm3 Avoid catalyst
poisoning/acid formation
S 18-30 mg/Nm3 Avoid catalyst
poisoning/acid formation
HHV 940-1205 Btu/scf permits maximum use of
infrastructure by moving
greater combustion heat
capacity for a given volume

7.  To prevent liquid dropout, natural gas pipeline
companies limit the amount of butane, pentane
and heavier components. LNG plants must
remove heavier hydrocarbon components to
prevent freezing in the liquefaction process, and
the heavies removed become a natural gasoline
by-product.
 Water is limited to less than 1 ppm to prevent
hydrate formation.
 Mercury is limited to 10 ng/m3 of gas product.
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8. 3 main sections:
Pre-
Treatment
Liquefaction Storage
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9.  Acid Gas Removal – CO2 & H2S
 Dehydration
 Mercury Compounds Removal
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10. http://www.newpointgas.com/services/amine-treating-plants/
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11.  Sour gas enters the contactor tower and rises through the
descending amine.
 Purified gas flows from the top of the tower.
 The amine solution is now considered Rich and is carrying
absorbed acid gases.
 The Lean amine and Rich amine flow through the heat
exchanger, heating the Rich amine.
 Rich amine is then further heated in the regeneration still
column by heat supplied from the re-boiler. The steam rising
through the still liberates H2S and CO2, regenerating the
amine.
 Steam and acid gases separated from the rich amine are
condensed and cooled.
 The condensed water is separated in the reflux accumulator
and returned to the still.
 Hot, regenerated, lean amine is cooled in a solvent aerial
cooler and circulated to the contactor tower, completing the
cycle
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12.  Gas dehydration is the process of removing a sufficient
amount of water from the natural gas so that the
specification for maximum allowable water content in the
treated gas is met. It also prevents the formation of
hydrates.
 Natural gas hydrates are formed when natural gas
components, for instance methane, ethane, propane, iso-
butane, hydrogen sulfide, carbon dioxide, and nitrogen,
occupy empty lattice positions in the water structure, thus
solidification occurs considerably above the freezing point
temperature of water.
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13.  Hydrate formation is favored by low temperature and
high pressure.
Factors essential for hydrate formation are:-
 Presence of “free” water - No hydrate formation is possible if “free”
water is not present.
 Low temperatures, at or below the hydrate formation temperature
for a given pressure and gas composition.
 High operating pressures.
 High velocities, or agitation, or pressure pulsations, in other
words turbulence can serve as catalyst.
 Presence of H2S and CO2 promotes hydrate formation because
both these acid gases are more soluble in water than the
hydrocarbons.
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14.  Molecular Sieve Beds (Predominantly used)
 Glycol Dehydration (Absorption):
 the aim here is to remove as much water vapour as possible
(through condensation and absorption) by using cold glycol to
lower the dew point of the gas. This is known as dew point
depression.
 Dehydration will take place at temperatures between 50 - 130°F.
 Over a normal pressure range up to 1200 psi, about 3 - 5 gallons
of glycol must be circulated for every pound of water removed at
a 55 °F dew point depression.
 Since the main objective of natural gas dehydration is maximum
dew point depression for maximum condensation and removal,
relatively high glycol concentrations are used. 97-99% favors
maximum dew point depression.
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15.  Generally, the level of mercury in natural gas is low, being only
a few parts per billion. However, even these low levels of
mercury will cause problems.
 Mercury will damage aluminum heat exchangers commonly
used in LNG plants, cryogenic hydrocarbon recovery plants,
and petrochemical plants. A number of production plants have
experienced sudden heat exchanger failures resulting in
unscheduled plant shutdowns, costly repairs, and even fires.
 Mercury can also concentrate and drop out as liquid in the
colder sections of the plant where subsequent plant
maintenance becomes difficult. In petrochemical plants,
mercury can deactivate downstream catalyst. Mercury in the
plant inlet gas has caused an ammonia production gas plant
explosion.
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16.  Mercury removal occurs simultaneously with the water
removal by the molecular sieve bed dehydration process
(regenerative mercury removal).
 The mercury removal function can be easily added to the
dehydrator performance by replacing some of the
molecular sieve with a mercury removal adsorbent. The
mercury is sorbed during the dehydration step, and then
regenerated off the adsorbent and the mercury leaves
the vessel with the spent regeneration gas.
 Depending on the amount of mercury present in the feed
fluid, and on the process conditions in the spent
regeneration gas knockout separator, potentially all of the
mercury can be collected and recovered as liquid
mercury by a Sulphur-based adsorbent bed.
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18. https://www.google.tt/imgres?imgurl=https://upload.wikimedia.org/wikipedia/co
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Basic_Dehydration_Unit.jpg&imgrefurl=https://en.wikipedia.org/wiki/Glycol_de
hydration&h=401&w=605&tbnid=NqwOA4oqz-
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z2pcOHjdM&usg=__C57u4shZxRl6JzlbbHMD1qF33uo=&sa=X&ved=0ahUKE
wiV0sbYnvnRAhVCRCYKHQdqDL4Q9QEIITAA#h=401&imgrc=NqwOA4oqz-
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19. http://lnglicensing.conocophillips.com/what-we-do/lng-
technology-licensing/Pages/optimized-cascade-process.aspx
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21.  At atmospheric pressure, LNG liquefies at -260°F.
 Thus tanks are heavily insulated to maintain the
cryogenic conditions for storage. LNG tanks are always
of double-wall construction with extremely efficient
insulation between the walls.
 LNG when vaporized back to a gaseous state, only burns
when the natural gas-to-air ratio is between 5 and 15%.
When the mixture of natural gas to air is less than 5%
there is not enough gas to burn. Also, when the mixture
is more than 15% natural gas to air, there is not enough
oxygen for it to burn.
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23.  http://www.trinidadexpress.com/business-magazine/Changing-
trends-in-the-LNG-world-210786531.html
 http://www.guardian.co.tt/business/2016-07-
21/atlantic%E2%80%99s-lng-cross-newly-expanded-panama-canal
 https://www.e-education.psu.edu/png520/m21_p3.html
 “Natural gas specification challenges in the LNG industry” – Koyle,
De la Vega, Kurr
 “Optimized mercury removal in gas plants” – Markovs & Clarke
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24. 1. Compare and contrast the regenerative & non-
regenerative mercury removal system technologies.
2. What are the major export markets for Trinidad’s LNG?
3. Have recent worldwide surge in other countries’ natural
gas production impacted on Trinidad’s LNG production,
and export markets? If yes, explain how.
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