Lng Process Train

PROCESS SCHEMES FOR LNG TRAIN

MOHAMMED SHARIQUE KHAN 23. 07. 2009

LIQUIFIED NATURAL GAS • LNG is predominantly methane, CH4 converted to liquid for ease of storage and transportation by cooling it to -260 0F or -160 0C. • LNG takes up 1/600th the volume of natural gas in the gaseous form. • LNG is an odorless, non-toxic and non-corrosive liquid if spilled would not result in slick. Absent an ignition source LNG evaporates quickly and disperse leaving no residue. • No environmental cleanup needed for LNG spills on water or land

LNG TRADE •

LNG accounted for 7% of the world’s natural gas demand.

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The global trade in LNG has increased at a rate of 7.4 % per year over the decade from 1995 to 2005 and expected to grow substantially.

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LNG demand is heavily concentrated in Northeast Asia– Japan, Korea and Taiwan at the same time Pacific Basin supplies dominated world LNG trade.

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By the end of 2007 there were 15 LNG exporting countries and 17 LNG importing countries.

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LNG trade volumes increased form 140 MT in 2005 to 158 MT in 2006, 165 MT in 2007, 172 MT in 2008 and is forecasted to be increased to about 300 MT in 2012.

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The Biggest LNG exporters in 2007 were Qatar(28 MT), Malaysia (22MT)

LNG TRANSPORTATION

• LNG is transported in especially designed ships with double hulls protecting cargo and ship from leaks and damage. • Ships are designed with insulated walls in which LNG is kept at its boiling point by the process of Auto refrigeration.

LNG PROCESS

LNG PROCESS •

A typical LNG process the gas is first extracted and transported to processing plant .

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Purified by removing condensates such as water, oil, mud, as well as other gases like CO2 and H2S and some times mercury by amine treatment.

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The gas is then cooled down in stages until it is liquefied. LNG is finally stored in storage tanks and can be loaded and shipped.

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Reducing volume makes LNG cost effective to transport over long distances by LNG carriers.

LIQUEFACTION TECHNOLOGY

LNG TRAIN

SCHEMES FOR LNG TRAIN • APCI Propane Pre cooled mixed refrigerant process( MCRTM ). • Phillips optimized cascade process. • Black & Veatch PRICO Process. • Statoil / Linde mixed fluid cascade process(MFCP). • Axens liquefin process.

APCI Propane Precooled mixed refrigerant process

APCI Propane Precooled mixed refrigerant process •

APCI accounts for about 81% of the world’s baseload LNG production capacity.

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Train capacities of 4.7 MTPA were built or are under construction.

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Two main refrigerant cycles are used in this process. i) Propane Precooling cycle: It uses propane at four different pressure level and cool process gas to -40 0C & also partially liquefy the MR. ii) Mixed refrigerant liquefaction and sub-cooling cycle : It is used in main cryogenic exchanger(MCHE) & the partially liquefied refrigerant is separated into vapour and liquid and subcool the process stream form -35 0C to -160 0C.

Phillips Optimized Cascade Process

Phillips Optimized Cascade Process • Three pure components used for refrigeration. i) Propane pre-cooling ii) Ethylene iii) Methane • Loss of one train does not cause plant shut down. • Production carries on with reduces capacity. • Easily shift from LNG recovery to LPG recovery to ethane recovery. • Utilization of pure components minimized the risk of two phase flow. • Many plant still being designed and built using the cascade process—simple and reliable.

Axens LiquefinTM process

Axens LiquefinTM Process

Axens LiquefinTM Process •

Two mixed refrigerants are used which are made up of methane , ethane , propane, butane, and nitrogen.

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It uses reduced number of main equipment items and uses plate-fin heat exchangers.

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Easy adjustment of pre-cooling temperature and can operate with significant variations in feed gas composition and pressure.

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Process feedstock containing high concentration of mercaptans and benzene.

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Efficiency remains the same over a large spectrum of production rate from 3 MTPA to 8 MTPA

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Uses limited number of control loops.

Statoil/Linde mixed Fluid cascade process(MFCP) •

Three mixed refrigerants are used to provide cooling and liquefaction duty.

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Pre-cooling is carried out in PFHE by mixed refrigerant .

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Sub-cooling and liquefaction is carried out in a spiral wound heat exchanger by other two refrigerant.

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This process is selected for SnØhvit LNG project (Ekofisk, Norway) it is a single train of 4 Million TPY Plant.

Black & Veatch PRICO Process •

PRICO uses a single-mixed refrigerant loop for natural gas liquefaction.

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It is a simplified refrigeration system require minimum equipment and simplified control.

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Flexible in feed gas composition receives natural gas from multiple sources.

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It has lowest capital cost of all competing technologies hence suitable for midsize train.

AP-X Hybrid LNG Process TM

AP-X Hybrid LNG Process TM

• It is a hybrid of Propane Pre cooled APCI Process. • Uses both Propane Pre-cooling and Nitrogen subcooling for LNG Liquefaction. • Train capacities up to 8 Mta are feasible. • AP-X achieves high efficiencies and low production cost by using both cycles to their best advantage. TM

• Retrofitting of APCI process change it to AP-X Hybrid TM

Process.

Technology Selection • Technology selection of LNG process and equipment will mainly based on technical and economical considerations. • Technical consideration includes process and equipment experience, reliability , process efficiency ,site conditions and environmental impact. • Economic issues include capital cost, operating cost and lifecycle costing. • Technical risks associated with a process relate to the track record of the process in operation. • Other selection include deciding heating and cooling medium , compressors and drivers and equipments.

References • http://www.adgas.com • http://www.pdfcoke.com • http://www.freepatentsonline.cm • www.lngindustrys.com • www.toodoc.com • www.lngfacts.org • www.naturalgas.org • www.adventuresinenergy.org