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DRIVER SELECTION FORDRIVER SELECTION FORLNG COMPRESSORS LNG COMPRESSORS
1414thth December 2004December 2004
Dr Sib AkhtarDr Sib AkhtarMSE (Consultants) LtdMSE (Consultants) Ltd
Carshalton, Surrey SM5 2HWCarshalton, Surrey SM5 [email protected]@mse.co.uk
http://www.mse.co.uk Tel: 020 8773 4500http://www.mse.co.uk Tel: 020 8773 4500
© MSE 2004
Driver Selection for LNG CompressorsDriver Selection for LNG CompressorsDriver Selection for LNG Compressors
Introduction
Drivers Used in Past & Present Projects
Factors Influencing Driver Selection
Potential Future Applications
Pros & Cons of:Steam TurbinesIndustrial Gas TurbinesAero-derivative Gas TurbinesElectric Motors
Conclusions and Observations
© MSE 2004
IntroductionIntroductionIntroductionHistoryEarly LNG Trains Steam DrivenDevelopment of Gas TurbinesThe LNG Growth Pause
US & UK became self sufficient in GasJapan and later Korea needed secure energy-LNGJapan remains the biggest importer of LNG
Re-emergence of LNG Demand New MarketsGas Shortages in US Re-opening of LNG terminalsExpansion of LNG in Europe UK to become net importer of Gas
© MSE 2004
Common LNG Process SystemsCommon LNG Process SystemsCommon LNG Process Systems
Phillips Cascade ProcessThree Pure Components
PropaneEthyleneMethane
APCI (Air Products)Two Components
Propane Mixed Component Refrigerant
© MSE 2004
New Emerging LNG Process SystemsNew Emerging LNG Process SystemsNew Emerging LNG Process Systems
Linde Process Three Mixed Refrigerants
Axens Liquefin ProcessDual Mixed Refrigerant
Shell ProcessDual Mixed Refrigerant
© MSE 2004
Factors Influencing Compressor Driver SelectionFactors Influencing Factors Influencing Compressor Driver SelectionCompressor Driver Selection
Plant Capacity
Process Used – Choice and Number of Refrigerant Streams
Compressor Configuration
Plant Location; Ambient Conditions
Plant Availability
Operational Flexibility
Economic Factors - CAPEX & OPEX
© MSE 2004
Gas Trade FlowsGas Trade FlowsGas Trade Flows
Source: Energy Information Administration – The Global LNG Market Status & Outlook
© MSE 2004
LNG Import CapacityLNG Import CapacityLNG Import Capacity
Source: Energy Information Administration – The Global LNG Market Status & Outlook
© MSE 2004
LNG Export CapacityLNG Export CapacityLNG Export Capacity
Source: Energy Information Administration – The Global LNG Market Status & Outlook
© MSE 2004
LNG ProcessesLNG ProcessesLNG Processes
Phillips Optimised Cascade and Air Products (APCI) processes dominate the LNG plants currently under design, construction & operation
New processes include:Axens (DMR)Linde (Statoil)Turbo-Expander (BHP)
© MSE 2004
Phillips Cascade ProcessPhillips Cascade ProcessPhillips Cascade Process
Many plant still being designed and built using the cascade process – simple and reliable
Three pure components used for refrigeration:Propane pre-coolingEthyleneMethane
© MSE 2004
Phillips Cascade ProcessPhillips Cascade ProcessPhillips Cascade Process
Propane pre-coolingCentrifugal compressorsTypically 2 x ~30 MW Gas Turbines (e.g. Frame 5)
Ethylene and Methane cyclesCentrifugal compressorsTypically 2 x ~30 MW Gas Turbines (e.g. Frame 5) for each cycle
© MSE 2004
Phillips Cascade ProcessALNG – TrinidadPhillips Cascade ProcessPhillips Cascade ProcessALNG ALNG –– TrinidadTrinidad
Propane pre-coolingCentrifugal compressors2 x Frame 5 C – upgraded to D
Ethylene and Methane cyclesCentrifugal compressors2 x Frame 5 C upgraded to D for each cycle
Plant Capacity 3 MTPA – Raised to 3.3 MTPA
High Availability 95-96%
© MSE 2004
Phillips Cascade ProcessALNG – Optimised DesignPhillips Cascade ProcessPhillips Cascade ProcessALNG ALNG –– Optimised DesignOptimised Design
Phillips Cascade Process
© MSE 2004
Phillips Cascade ProcessPhillips Cascade ProcessPhillips Cascade Process
Simple to design and operateSimple cycle Frame 5 gas turbines mechanical driveNo helper turbine or large motor needed for start-upIncreased size with two gas turbine trains for each refrigerant processParallel compressor trains avoids capacity limitsIncreased CAPEX due to more (six) trains offset by increased availability 95-96% with parallel train operationLoss of one train does not cause plant shut downProduction carries on with reduced capacity Refrigerant and exchangers temperature not affected by one train trip enabling quick restart
© MSE 2004
APCI ProcessAPCI ProcessAPCI Process
Most of existing plant are using the APCI process with 3 – 3.3 MTPA Fr 6 / Fr 7 combination
Train capacities up to 4.7 MTPA built or under construction using Fr 7 / Fr 7 combination
Higher Capacities to 7.9 MTPA being announced with Frame 9 GT
Two main refrigeration cycles:Propane pre-coolingMixed refrigerant liquefaction and sub-cooling
© MSE 2004
APCI ProcessAPCI ProcessAPCI Process
Propane pre-coolingCentrifugal compressor (to 15 – 25 bar)Side-streams at 3 pressure levelsTypically requires a ~40 MW Gas Turbine (e.g. Frame 6) plus Helper Motor or Steam TurbineCompressor sizes reaching maximum capacity limitsAdded aerodynamic constraint; high blade Mach numbers due to high mole weight of propane (44)Prevents utilisation of full power from larger gas turbines (Frame 7)
© MSE 2004
APCI ProcessAPCI ProcessAPCI Process
Mixed refrigerant liquefaction and sub-coolingAxial LP for Shell Advised PlantCentrifugal HP compressor (45 – 48 bar)Typically requires ~70 MW Gas Turbine (e.g. Frame 7) plus Helper Motor or Steam Turbine
© MSE 2004
© MSE 2004
ELLIOTT IN LNGA HISTORY OF FIRSTS
World’s first large-scale liquefaction plant (CAMEL – Arzew, Algeria) World’s first baseload refrigeration plant (Phillips - Kenai, Alaska)World’s first gas turbine driven LNG compressors (Phillips, Alaska)World’s first single-mixed refrigerant (APCI) process compression (Esso (Exxon) – Marsa el-Brega, Libya)World’s first dual-shaft (GE Frame 5) gas turbine driven compressor strings (P.T. Arun (Mobil) – Indonesia)World’s first C3-MR (APCI) process compression (P.T.Arun – Indonesia)World’s first GE Frame 7 driven Propane MR compressor (Ras Gas 1&2 – Ras Laffan, Qatar)World’s largest four-section Propane MR compressor (Ras Gas 3 – Ras Laffan, Qatar - UNDER CONSTRUCTION)
© MSE 2004
Partial List - ELLIOTT LNG Plants
End User Process Capacity MM T/Yr # of Units Service C.A.M.E.L.
Arzew, Algeria Cascade 1.3 3
3 3 3 3
Propane Ethylene
Methane 1 Methane 2
Vapor
Phillips Petroleum Kenai, Alaska
Cascade 1.1 2 2 1
Propane Methane 1 Methane 2
Esso Libya Marsa El Brega,
Libya
Mixed Refrigerant 3.2 4 4
MR-1 MR-2
Sonatrach Arzew, Algeria
Mixed Refrigerant &
Propane
16.4 6 6 6
MR-1 MR-2
Propane
Abu Dhabi Liquefaction Co.
Das Island, Abu Dhabi
Mixed Refrigerant &
Propane
3.0 2 2 2 2
Feed Gas Feed Gas Feed Gas Propane
P. T. Arun Liquefaction Co. Lhokseumawe,
Indonesia
Mixed Refrigerant &
Propane
9.0 6 6 6
MR-1 MR-2
Propane
Ras Laffan Liquefaction Co.
Qatar
Mixed Refrigerant &
Propane
6.0 2 2 2
MR-1 MR-2
Propane
© MSE 2004
APCI ProcessAPCI ProcessAPCI Process
Mixed refrigerant liquefaction and sub-cooling
Large volumetric flows
Two casing arrangements (LP and an HP)Axial LP / centrifugal HP compressor (45 – 48 bar)Typically requires ~70 MW Gas Turbine (e.g. Frame 7) plus Helper Motor or Steam TurbineLP and HP compressor speeds compromisedLP axial compressor (higher efficiency)HP centrifugal compressor
© MSE 2004
APCI ProcessAPCI ProcessAPCI Process
APCI
© MSE 2004
Example of APCI Process EvolutionExample of APCI Process EvolutionExample of APCI Process Evolution
Petronas MLNG, located in Bintulu, Sarawak
First trains designed in the ’70s:3 x Centrifugal compressors3 x Steam Turbine drivers ~ 37 MW each
© MSE 2004
Example of APCI Process EvolutionExample of APCI Process EvolutionExample of APCI Process EvolutionExtension trains designed in the ’90s:
Propane pre-cooling:Centrifugal compressor30 MW Gas Turbine & 7 MW Steam Turbine
Mixed component refrigeration (MCR):LP axial compressor & HP centrifugal compressor64 MW Gas Turbine & 7 MW Steam Turbine
© MSE 2004
RAS GAS I & II – RAS LAFFAN, QATARRAS GAS I & II RAS GAS I & II –– RAS LAFFAN, QATARRAS LAFFAN, QATAR
© MSE 2004
RAS GAS III (&IV), RAS LAFFAN, QATARUNDER CONSTRUCTION
RAS GAS III (&IV), RAS LAFFAN, QATARRAS GAS III (&IV), RAS LAFFAN, QATARUNDER CONSTRUCTIONUNDER CONSTRUCTION
© MSE 2004
Axens Liquefin ProcessAxensAxens LiquefinLiquefin ProcessProcess
Mixed refrigerants for pre-cooling, liquefaction and sub-cooling dutiesLiquefin development studies presently oriented towards increasing capacity to 6 MTPA with:
2 x Frame 7 Gas Turbines for main compression2 x Frame 5 Gas Turbines for power generation
Higher capacities possible using:Frame 9 GTsElectric motorsSteam turbines etc.
© MSE 2004
Axens Liquefin ProcessAxensAxens LiquefinLiquefin ProcessProcess
Similar to APCI with Propane compressor replaced with Mixed Refrigerant for pre-cooling
Allows more balanced flows, refrigeration loads and power between the two compressors
Avoids the process design limits associated with Propane compressors
© MSE 2004
Axens Liquefin ProcessAxensAxens LiquefinLiquefin ProcessProcess
Axens
© MSE 2004
Shell DMR ProcessRef O G J July 16 2001
Shell DMR ProcessShell DMR ProcessRef O G J July 16 2001Ref O G J July 16 2001
Similar to Axens but with twin parallel compressor trains for each process stream
Use of aero-derivative or VSD motors
Shell claim 4.5 - 5.5 MTPA and lower cost
© MSE 2004
Linde ProcessLinde ProcessLinde Process
Mixed refrigerants for pre-cooling, liquefaction and sub-cooling duties
Minimum of Three Gas Turbine or electric motors needed for compressor driver
4.3 MTPA plant under construction with VSD motor drivers and onsite power generation with aero-derivative gas turbines
© MSE 2004
Linde ProcessLinde ProcessLinde Process
© MSE 2004
Process Design, Driver Ratings& Compressor ConfigurationProcess Design, Driver RatingsProcess Design, Driver Ratings& Compressor Configuration& Compressor Configuration
APCI process uses larger and larger gas turbines to reduce CAPEX in a single train configuration; bigger gas turbine have lower $/kWFrame 7EA used for Mixed RefrigerantFrame 6 being replaced by Frame 7 for Propane for larger plantsThe plants are “single train” i.e. each machine is designed for 100% capacity and arranged in series
© MSE 2004
Process Design, Driver Ratings& Compressor ConfigurationProcess Design, Driver RatingsProcess Design, Driver Ratings& Compressor Configuration& Compressor Configuration
Phillips Optimised Cascade process have used 2x50% compressor configuration and achieved cost savings and high availability
Shell DMR process appears to favour twin train configuration and achieves 4.5 - 5.5 MTPA with larger aero-derivative
© MSE 2004
Gas Turbines Used in LNG PlantGas Turbines Used in LNG PlantGas Turbines Used in LNG Plant
Heavy Duty Gas Turbines:Mechanical drive shown in bluePower generation shown in yellow
© MSE 2004
Aero-Derivative Gas Turbines for LNG Plant – Potential AeroAero--Derivative Gas Turbines Derivative Gas Turbines for LNG Plant for LNG Plant –– Potential Potential
Aero-derivative Gas Turbines:
© MSE 2004
Combined Cycles and LNG Plant – PotentialCombined Cycles and LNG Combined Cycles and LNG Plant Plant –– PotentialPotential
Combined Cycles:ISO Power (kW) Heat Rate (kJ/kWh) Efficiency (%)
LM1600PE 18591 7605 45LM2500PE 31048 7186 50LM2500+ 6STG 40912 6981 52LM6000PC 55007 6764 53LM6000PD Sprint 59142 6876 52RB211-24GT RT62 39760 7005 51.4Trent 50 64458 6780 53.1Trent 60 72268 7189 50.1
© MSE 2004
Economies of ScaleEconomies of ScaleEconomies of Scale
Source: Gower and Howard, “Changing Economics of Gas Transportation”
© MSE 2004
Economies of ScaleEconomies of ScaleEconomies of Scale
Source: Introduction to LNG, University of Houston Institute for Energy, Law and Enterprise
© MSE 2004
Steam Turbines - ProsSteam Turbines Steam Turbines -- ProsPros
Several established VendorsSize; may be built to exact process specificationMechanical drive up to 130 MW not a problemConstant speed power generation 600–1100 MWHigh reliability; 30 years life is achievableHigh availability; compressors & steam turbines may both achieve 3 years non-stop operation, no need for inspectionSteam is often required elsewhere in processMixed fuel; boilers can utilise varying fuel mix whereas gas turbines require fuel specification to be maintainedHigher thermodynamic efficiency than simple cycle GT (but lower efficiency than GT-steam combined cycle)Power output relatively unaffected by ambient conditions
© MSE 2004
Steam Turbines - ConsSteam Turbines Steam Turbines -- ConsCons
Perceived as old “Victorian” technology
Physically very large; boilers, condensers, desalination plant (for make-up water), water polishing plant etc.
CAPEX of steam turbine plant is higher than simple cycle GT (but similar cost to combined cycle)
Overhaul of steam turbine similar to large frame GT (but interval between overhauls is twice as long!)
Added complexity in steam auxiliaries, including feed heating, boiler feed pumps etc.
© MSE 2004
Industrial Gas Turbines - ProsIndustrial Gas Turbines Industrial Gas Turbines -- ProsProsSimple cycle GT is uncomplicated in its design
Low CAPEX
Economies of scale when using large frame GTs
Extensive operational experience with mechanical drive applications
Large population; perceived as low risk technology
Skid mounted; easier to install than a steam system
Smaller plant footprint; less extensive civil works
Lower NOX than Aero-derivative GT
Range of sizes available:
~ 110 MWFrame 9~ 75 MWFrame 7~ 40 MWFrame 6~ 30 MWFrame 5
© MSE 2004
Industrial Gas Turbines - ConsIndustrial Gas Turbines Industrial Gas Turbines -- ConsCons
Paucity of Vendors!Low thermal efficiency, high CO2 emissionsMaintenance is intensive, involving prolonged on-site work which reduces plant availabilityFixed sizes and fixed optimal speedsProcess and compressors must be designed around the GT (unlike steam turbines)Process may not make full use of the GT powerPower output highly sensitive to ambient conditions e.g. typical large GT:
At 40 °C~82% power
At 30 °C~88% power
At 20 °C~95% power
At 15 °C 100% power
© MSE 2004
Aero-Derivative Gas Turbines - ProsAeroAero--Derivative Gas Turbines Derivative Gas Turbines -- ProsProsHigher thermal efficiency than Industrial GT; 38-42% compared to 28-32% for similar size Industrial GTs in simple cycle
Smaller footprint area than Industrial GT because of aero design
Shorter maintenance period; modular design allows gas engine and power turbine sections to be swapped out
Off-site maintenance (in factory)
Thus, higher plant availability
Most engines have free power turbines for variable speed operation (within a range)
Large helper motors or steam turbines may not be needed for start-up
Range of sizes available:
~ 55 MWTrent~ 40 MWLM6000~ 30 MWRB211
© MSE 2004
Aero-Derivative Gas Turbines - ConsAeroAero--Derivative Gas Turbines Derivative Gas Turbines -- ConsConsPaucity of Vendors (essentially only 2)!Higher NOX than Industrial GTsEngines need more care and maintenance due to higher operating pressures and temperatures and design complexityFixed sizes and fixed optimal speedsProcess and compressors must be designed around the GT (unlike steam turbines)Process may not make full use of the GT powerPower output highly sensitive to ambient conditionsFuel quality is critical – even more than in Industrials!Limited operating experience for LNG, although extensive for offshore mechanical drive and power generationPowers greater than 60 MW not available in simple cycleDry Low Emissions (NOX) technology adds complexityHigher risk technology than Industrial GTs
© MSE 2004
Combined Cycles - ProsCombined Cycles Combined Cycles -- ProsPros
Mitigates some of the cons of Industrial GTs
Adds some of the pros of Steam Turbines
Essentially, 50% extra power / 50% extra thermal efficiency / 50% lower CO2 emissions
Allows optimisation of process and compressors
Steam turbine can be used for start-up and additional power
Steam may be required elsewhere in the process
© MSE 2004
Combined Cycles - ConsCombined Cycles Combined Cycles -- ConsCons
High CAPEX, increased complexity, more extensive civil works… same as for Steam Turbine
Combined cycles are not presently favoured by LNG plant designers, but may be considered when CO2 is taxed!
© MSE 2004
Variable Speed Electric Motors - ProsVariable Speed Electric Motors Variable Speed Electric Motors -- ProsProsCan be made to suit, allowing optimisation of process and compressorsHigher availability of LNG plant than if using GTs or Steam TurbinesReduced manning levelsMay avoid gearboxes for 3000-3600 rpm compressor speeds (large flow capacity compressors)Power generation may be off-siteLower CAPEX if power is bought from the gridSimple layout, reduced civil works
© MSE 2004
Variable Speed Electric Motors - ConsVariable Speed Electric Motors Variable Speed Electric Motors -- ConsConsMost LNG plant are in remote locations; off-site power generation of 400-500 MW not available!
Very high CAPEX if power generation is built alongside LNG
High OPEX (although savings may be possible)
Limited experience with high power VSDs; 45-55 MW is achievable, 65 MW is the maximum
Electrical issues at compressor start-up; grid peak current and fault levels
Power generation using GTs must happen somewhere; CO2, NOX and sensitivity to ambient conditions is similar to a GT (unless power generation is using a combined cycle)
© MSE 2004
Conclusions and ObservationsConclusions and ObservationsConclusions and ObservationsLNG drivers are predominately Industrial Heavy Duty Gas Turbines e.g. GE Frames 5, 6, 7 … even 9!Frame 5s generally used on older LNG plant, although ALNG in Trinidad was recently fitted with Frame 5Ds; these are demonstrating high overall availability at low CAPEX… 3.3 MTPA with 6 x Fr 5Fr 6 / Fr 7 combinations replaced Steam Turbines at MLNGNow Fr 6 / Fr 7 commonly used at NLNG, Oman LNG, Qatar LNG… 3.3 – 3.5 MTPAFr 7 / Fr 7 combinations used at Qatar LNG, but with poor use ofGT power because of non-optimal process, process had to be redesigned… ~4 MTPALarger and larger trains are pushing the limits of compressor technology i.e. Axials for Mixed Refrigerant and largest centrifugals for Propane
© MSE 2004
Conclusions and ObservationsConclusions and ObservationsConclusions and Observations
When parallel trains are used (instead of series) e.g. ALNG:
Smaller driver sizes can be used e.g. Frame 5sCompressor capacities are halved, so centrifugals may be used instead of axialsPlant availability is enhancedImproved operability, re-starting after a train failure is simpler and quickerPlant costs are surprisingly lower