Design of LNG Facilities

Design of LNG Facilities

Evaluation of LNG Production Technologies Ayema Aduku Oluwaseun Harris Valerie Rivera Miguel Bagajewicz University of Oklahoma Outline LNG Background Objective Simulation Specifications Liquefaction Techniques Heat Exchanger Types Simulation Method Results

Flow Diagram for a Typical LNG Plant NATURAL GAS CO22/H22S REMOVAL DEHYDRATION HEAVY COMPONENT REMOVAL NATURAL GAS LIQUEFACTION TRANSPORTATION LNG (Liquefied Natural Gas) Basics Combustible mixture of hydrocarbons Dry

VS. Wet NGL Extraction Dehydration/Scrubbing Liquefied Natural Gas Target temperature for Natural gas:-260F Reduces volume by a factor 600 Objective Main Objectives Simulate Processes

Optimize Processes Minimize compressor work Compare Processes based on Capital cost Energy cost Total cost per capacity(Ton) Liquefaction Processes Mixed Refrigerants Pure Refrigerants Both Linde Process CoP Simple Cascade

APCI C3 MR Axens Liquefin Process CoP Enhanced Cascade APCI AP-X Dual Mixed Refrigerant Linde 2006 Technip-TEALARC ExxonMobil Dual Multi-component Black and Veatch Prico Process

Technip- Snamprogetti * Italicized processes signify Patent searched processes. * Bolded processes signify processes not included in scope of project. Other BP Self refrigerated process ABB Randall TurboExpander Williams Field Services co. Mustang Group Flow diagrams Black and Veatchs PRICO

Process Axens Liquefin Process C3MR: Air Products and Chemical Inc ExxonMobil Dual Multi-Component Cycle AP-X: Air Products and Chemical Inc. Technip- TEALARC System BP- Self Refrigerated Process DMR- Dual Mixed Refrigerant

Linde/Statoil -Mixed Fluid Cascade Process ConocoPhilips Simple Cascade Linde- CO2 MFCP Simulation Specifications Natural Gas composition Methane: 0.98 Ethane: 0.01 Propane: 0.01

Inlet conditions Pressure: 750 psia Temperature: 1000F Outlet conditions Pressure: 14.7 psia Beihai City, China Temperature: -260oF Capacity: Common min. to max. capacity of process Common min. Capacity: 200,000 lbs/hr Liquefaction Techniques

Different Liquefaction techniques include : Single Refrigeration cycle Multiple Refrigeration cycles Self Refrigerated cycles Cascade Processes The cooling of natural gas involves the use of refrigerants which could either be pure component refrigerants or mixed component refrigerants. Liquefaction Techniques Schematic of a Simple Refrigeration Cycle COOLING WATER LOW TEMPERATURE


LOW TEMPERATURE NO PRESSURE CHANGE GAS HIGH TEMPERATURE Liquefaction Techniques Mixed refrigerants are mainly composed of hydrocarbons ranging from methane to pentane, Nitrogen and CO2. Pure component Refrigerants

Specific operating ranges for each component Mixed Refrigerants Modified to meet specific cooling demands. Helps improve the process efficiency Liquefaction Techniques T-Q Diagrams Natural gas cooling curve THIS WOULD SIGNIFY A

REDUCTION IN THE WORK DURING THE COOLING PROCESS AND AN INCREASE IN EFFICIENCY. THE MAIN GOAL IS TO REDUCE THE DISTANCE BETWEEN THE TWO CURVES. Area between curves represents work done by the system Liquefaction 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 Black and Veatch: PRICO Process Condenser Compressor Inlet Gas 100oC

Cold Box Residue -260oC Expander LNG Single mixed refrigerant loop and single compression system Limited capacity (1.3 MTPA) Low capital cost

Great Pilot Process Refrigeration Cycles and Natural Gas Liquefaction COOLING WATER Compressor Inlet Gas Simple Refrigeration Cycle Cold Box GAS LNG

Black and Veatch- PRICO Process LIQUEFACTION TECHNIQUES TAKE ADVANTAGE OF MODIFIED REFRIGERATION CYCLES Liquefaction 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. Air Products and Chemical Inc: C3-MR

LNG Inlet Gas Mixed Refrigerant APCI processes are used in almost 90% of the industry Good standard by which to

judge the other processes Capacity of about 5 MTPA Utilizes Propane (C3) and Mixed Refrigerants (MR) Liquefaction 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. BP Self Refrigerated Process

Residue Gas Inlet gas LNG Neither refrigerants, compressor, nor expanders present in setup. Cost include mainly capital costs and electricity.

Low Production rate (51%) Capacities of over 1.3MTPA attainable . Liquefaction 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. ConocoPhilips Simple Cascade

Ethylene 3 stage pure refrigerant process Propane Ethylene Methane Methane Propane Residue Gas Sub-Cooling Inlet Gas

Pre- Cooling Liquefaction LNG 5 MTPA Capacity Equipment Plate Fin Heat Exchanger VERY COMPACT DESIGN BUT LIMITED IN OPERATING RANGE Spiral Wound Heat Exchanger LARGE OPERATING RANGE BUT ROBUST DESIGN

Spiral Wound Heat Exchanger TUBE BUNDLES WRAP AROUND CENTRAL HOLLOW TUBE Equipment Comparison Plate-Fin-Heat-Exchangers Coil-Wound-Heat-Exchangers Extremely compact Compact Multiple streams Multiple streams

Single and two-phase streams Single and two-phase streams Fluid Very clean Clean Flow-types Counter-flow Cross counter-flow

Characteristics Cross-flow Heating-surface 300 - 1400 m/m 20 - 300 m/m Materials Aluminum Aluminum Stainless steel (SS) Carbon steel (CS) Special alloys

Temperatures -269C to +65 C (150 F) All Pressures Up to 115 bar (1660 psi) Up to 250 bar (3625 psi) Applications Cryogenic plants Also for corrosive fluids

Non-corrosive fluids Also for thermal shocks Very limited installation space Also for higher temperatures Our 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 Details of methodology Conditions after each stage of refrigeration were noted

After making simple simulations mimic real process, variables were transferred to real process simulation Optimization- Refrigerant composition Optimization- Compressor work Restriction needed- Heat transfer area Restriction needed- Second law of thermodynamics All cells in LNG HX must have equal area Check temperature of streams Utilities

Obtain cooling water flow rate CO2 Pre-cooled Linde Process Inlet Gas 100oC Pre- Cooling

-70oC Liquefaction -140oC Sub-Cooling -260oC LNG High Pressure Low Pressure

Modification of the Mixed Fluid Cascade Process Three distinct stages using 3 mixed refrigerants with different compositions Carbon dioxide is sole refrigerant in pre-cooling stage Separate cycles and mixed refrigerants help in the flexibility and thermodynamic efficiency Process is safer because hydrocarbon inventory is less 8 MTPA Capacity TQ DIAGRAMS FROM PRO II SIMULATION

Results Cost 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



3.41 4.83 12.58 19.20 31.73 24.77 25.35 12.93 20.15 Max capacity (MTPA) 1.20 6.00 4.80 4.80 7.80 7.20 7.20

6.00 4.80 5.00 Analysis Our results may not match market trends Operating temperature and pressure range as well as flowrate information unavailable Precedents to compare results unavailable Information on cost to use process unavailable (licensing, proprietary production fees, etc.) Analysis

We may be trapped in local minima and failed to identify better conditions Work Local Minimum Global Minimum Temperature Conclusions

We successfully simulated several LNG production plants We obtained capital and operating costs and determined a ranking Some connection with existing trends were identified, but other results do not coincide with market trends We discussed why discrepancies may arise. Questions? References

"Overview: LNG Basics." Center for Liquefied Natural Gas. 2008. Center for Liquefied Natural Gas. 3 Feb 2008. . Fossil Energy Office of Communications. U.S. Department of Energy: Fossil Energy. 18 Dec 2007. U.S. Department of Energy. 3 Feb 2008. .. "Mustang receives U.S. patent for LNG liquefaction process." Scandanavian Oil and Gas

Magazine. 14 Dec 2007. 3 Feb 2008. . 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 Flynn, Thomas N. Cryogenic Engineering. Second edition. Marcel Dekker. New York- NY. 2005

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