3Heavy Component Removal Natural Gas Liquefaction Flow Diagram for a Typical LNG PlantNatural GasCO2/H2S RemovalDehydrationHeavy Component RemovalNatural Gas LiquefactionTransportation
4LNG (Liquefied Natural Gas) Basics Combustible mixture of hydrocarbonsDry VS. WetNGL ExtractionDehydration/ScrubbingLiquefied Natural GasTarget temperature for Natural gas:-260°FReduces volume by a factor 600
5Objective Main Objectives Simulate Processes Optimize Processes Minimize compressor workCompare Processes based onCapital costEnergy costTotal cost per capacity(Ton)
6Liquefaction Processes Mixed RefrigerantsPure RefrigerantsBothOtherLinde ProcessCoP Simple CascadeAPCI C3 MRBP Self refrigerated processAxens Liquefin ProcessCoP Enhanced CascadeAPCI AP-XABB Randall Turbo-ExpanderDual Mixed RefrigerantLinde 2006Williams Field Services co.Technip-TEALARCMustang GroupExxonMobilDual Multi-componentBlack and Veatch Prico ProcessTechnip- Snamprogetti* Italicized processes signify Patent searched processes.* Bolded processes signify processes not included in scope of project.
8Black and Veatch’s PRICO Process Axens Liquefin ProcessC3MR: Air Products and Chemical IncExxonMobil Dual Multi-Component Cycle
9AP-X: Air Products and Chemical Inc. Technip- TEALARC SystemBP- Self Refrigerated ProcessDMR- Dual Mixed Refrigerant
10Linde- CO2 MFCPLinde/Statoil -Mixed Fluid Cascade ProcessConocoPhilips Simple Cascade
11Simulation Specifications Natural Gas compositionMethane: 0.98Ethane: 0.01Propane: 0.01Inlet conditionsPressure: 750 psiaTemperature: 1000FOutlet conditionsPressure: 14.7 psiaTemperature: -260oFCapacity: Common min. to max. capacity of processCommon min. Capacity: 200,000 lbs/hrBeihai City, China
12Liquefaction Techniques Different Liquefaction techniques include:Single Refrigeration cycleMultiple Refrigeration cyclesSelf Refrigerated cyclesCascade ProcessesThe cooling of natural gas involves the use of refrigerants which could either be pure component refrigerants or mixed component refrigerants.
14Liquefaction Techniques Mixed refrigerants are mainly composed of hydrocarbons ranging from methane to pentane, Nitrogen and CO2.Pure component RefrigerantsSpecific operating ranges for each componentMixed RefrigerantsModified to meet specific cooling demands.Helps improve the process efficiency
15Liquefaction Techniques T-Q DiagramsNatural gas cooling curveThe main goal is to reduce the distance between the two curves.This would signify a reduction in the work during the cooling process and an increase in efficiency.Area between curves represents work done by the system
16Liquefaction Techniques Single Refrigeration Cycle One refrigeration loop that cools the natural gas to its required temperature range.Usually requires fewer equipment and can only handle small base loads.Lower capital costs and a higher operating efficiency
17Black and Veatch: PRICO Process Inlet GasLNGCold BoxCompressorCondenserSingle mixed refrigerant loop and single compression systemLimited capacity (1.3 MTPA)Low capital costGreat Pilot Process100oCResidue-260oCExpander
18Refrigeration Cycles and Natural Gas Liquefaction Cooling WaterGasInlet GasLNGCold BoxCompressorSimple Refrigeration CycleBlack and Veatch- PRICO ProcessLiquefaction techniques take advantage of modified refrigeration cycles
19Liquefaction Techniques Multiple Refrigeration cycles Contains two or more refrigeration cycles. Refrigerants involved could be a combination of mixed or pure component refrigerants.Some cycles are setup primarily to supplement cooling of the other refrigerants before cooling the natural gas.More equipment usually involved to handle larger base loads.
20Air Products and Chemical Inc: C3-MR Inlet GasLNGMixed RefrigerantAPCI processes are used in almost 90% of the industryGood standard by which to judge the other processesCapacity of about 5 MTPAUtilizes Propane (C3) and Mixed Refrigerants (MR)
21Liquefaction Techniques Self Refrigerated Cycles Takes advantage of the cooling ability of hydrocarbons available in the natural gas to help in the liquefaction process.Numerous expansion stages are required to achieve desired temperatures.Considered as a safer method because there are no external refrigerants needing storage.
22BP Self Refrigerated Process Inlet gasLNGNeither refrigerants, compressor, nor expanders present in setup.Cost include mainly capital costs and electricity.Low Production rate (51%)Capacities of over 1.3MTPA attainable .Residue Gas
23Liquefaction Techniques Cascade Processes A series of heat exchangers with each stage using a different refrigerant.Tailored to take advantage of different thermodynamic properties of the refrigerants to be used.Usually have high capital costs and can handle very large base loads.
26Plate Fin Heat Exchanger Very compact design but limited in operating range
27Spiral Wound Heat Exchanger Large operating range but robust design
28Spiral Wound Heat Exchanger Tube bundles wrap around central hollow tube
29Equipment Comparison Extremely compact Compact Multiple streams Plate-Fin-Heat-ExchangersCoil-Wound-Heat-ExchangersCharacteristicsExtremely compactCompactMultiple streamsSingle and two-phase streamsFluidVery cleanCleanFlow-typesCounter-flowCross counter-flowCross-flowHeating-surfacem²/m³m²/m³MaterialsAluminumStainless steel (SS)Carbon steel (CS)Special alloysTemperatures-269°C to +65 °C (150 °F)AllPressuresUp to 115 bar (1660 psi)Up to 250 bar (3625 psi)ApplicationsCryogenic plantsAlso for corrosive fluidsNon-corrosive fluidsAlso for thermal shocksVery limited installation spaceAlso for higher temperatures
30Our Evaluation Methods Data on operating conditions (Temperatures, Pressures, Flowrates, etc) for all these processes is not widely available (Only some is reported).We decided to perform simulations using our best estimates.We used minimum compression work as guide.We identified non-improvable points
31Details of methodology Conditions after each stage of refrigeration were notedAfter making simple simulations mimic real process, variables were transferred to real process simulationOptimization- Refrigerant compositionOptimization- Compressor workRestriction needed- Heat transfer areaAll cells in LNG HX must have equal areaRestriction needed- Second law of thermodynamicsCheck temperature of streamsUtilitiesObtain cooling water flow rate
32CO2 Pre-cooled Linde Process Modification of the Mixed Fluid Cascade ProcessThree distinct stages using 3 mixed refrigerants with different compositionsCarbon dioxide is sole refrigerant in pre-cooling stageSeparate cycles and mixed refrigerants help in the flexibility and thermodynamic efficiencyProcess is safer because hydrocarbon inventory is less8 MTPA CapacityInlet Gas100oCPre- Cooling-70oCLiquefactionHigh Pressure-140oCLow PressureSub-Cooling-260oCLNG
35Cost Basis Economic Life of 20 years New train required at the documented maximum capacity of each specific process.Average cost of electricity and cooling water throughout the US used in analysis.Energy cost evaluated at a minimum capacity of 1.2 MTPA
36Results10Spikes in chart represent points at which new train of process is installed
37Results10Energy cost includes electricity and cooling water cost
38ResultsThe Liquefin Process is reported as fast becoming a popular LNG technique.The Prico process results were expected.Numerous equipment usually leads to higher overall costs.ProcessCost per ton ($)Max capacity (MTPA)Prico5.121.20Liquefin3.416.00ExxonMobil4.834.80DMR12.58APX19.207.80MFCP31.737.20MFCP(CO2)24.77TEALARC25.35C3MR12.93Conoco20.155.00
39Analysis Our results may not match market trends Operating temperature and pressure range as well as flowrate information unavailablePrecedents to compare results unavailableInformation on cost to use process unavailable (licensing, proprietary production fees, etc.)
40AnalysisWe may be trapped in local minima and failed to identify better conditionsWorkTemperatureLocal MinimumGlobal Minimum
41Conclusions We successfully simulated several LNG production plants We obtained capital and operating costs and determined a rankingSome connection with existing trends were identified, but other results do not coincide with market trendsWe discussed why discrepancies may arise.
43References"Overview: LNG Basics." Center for Liquefied Natural Gas Center for Liquefied Natural Gas. 3 Feb <http://www.lngfacts.org/About-LNG/Overview.asp>.Fossil Energy Office of Communications. U.S. Department of Energy: Fossil Energy. 18 Dec U.S. Department of Energy. 3 Feb <http://www.fossil.energy.gov/programs/oilgas/storage/index.html>."Mustang receives U.S. patent for LNG liquefaction process." Scandanavian Oil and Gas Magazine. 14 Dec Feb <http://www.scandoil.com/moxie-bm2/news/mustang-receives-us-patent-for-lng-liquefaction-pr.shtml>.Spilsbury, Chris; Yu-Nan Liu; et al. "Evolution of Liquefaction Technology for today's LNG business." Journees Scientifiques Et Techniques (2006)Process Selection is Critical to onshore LNG economics.” World-Oil Magazine. February 2006 com <http://www.worldoil.com/Magazine/MAGAZINE_DETAIL.asp?ART_ID=2808&MONTH_YEAR=Feb-2006>Flynn, Thomas N. “Cryogenic Engineering.” Second edition. Marcel Dekker. New York- NY. 2005