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
LNG (Liquefied Natural Gas) Basics
Combustible mixture of hydrocarbons
Dry
VS. Wet
NGL Extraction Dehydration/Scrubbing Liquefied Natural Gas
temperature for Natural gas:-260F Reduces volume by a factor 600
Target
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 Other
Linde Process Axens Liquefin Process Dual Mixed Refrigerant
CoP Simple Cascade CoP Enhanced Cascade
APCI C3 MR APCI AP-X Linde 2006
Technip-TEALARC
ExxonMobil Dual Multi-component Black and Veatch Prico Process Technip- Snamprogetti
BP Self refrigerated process ABB Randall TurboExpander Williams Field Services co. Mustang Group
* Italicized processes signify Patent searched processes. * Bolded processes signify processes not included in scope of project.
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
Linde- CO2 MFCP
ConocoPhilips Simple Cascade
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 o Temperature: -260 F 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
Expander
Compressor
Heat Exchanger
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
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
Single mixed refrigerant loop and single compression system Limited capacity (1.3 MTPA) Low capital cost Great Pilot Process
Expander
LNG
Refrigeration Cycles and Natural Gas Liquefaction
Compressor
Inlet Gas
Simple Refrigeration Cycle
Cold Box
LNG
Black and Veatch- PRICO Process
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
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)
Mixed Refrigerant
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
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 .
Inlet gas LNG
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
Methane Ethylene Propane
Residue Gas Sub-Cooling
3 stage pure refrigerant process
Propane Ethylene Methane
5 MTPA Capacity
Inlet Gas
Pre- Cooling Liquefaction
LNG
Equipment
Plate Fin Heat Exchanger
Spiral Wound Heat Exchanger
Spiral Wound Heat Exchanger
Equipment Comparison
Plate-Fin-Heat-Exchangers Coil-Wound-Heat-Exchangers
Characteristics
Extremely compact
Multiple streams Single and two-phase streams
Compact
Multiple streams Single and two-phase streams Clean Cross counter-flow 20 - 300 m/m Aluminum Stainless steel (SS) Carbon steel (CS) Special alloys
Fluid Flow-types
Very clean Counter-flow
Cross-flow
Heating-surface Materials
300 - 1400 m/m Aluminum
Temperatures Pressures Applications
-269C to +65 C (150 F) Up to 115 bar (1660 psi) Cryogenic plants Non-corrosive fluids Very limited installation space
All Up to 250 bar (3625 psi) Also for corrosive fluids Also for thermal shocks 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
All cells in LNG HX must have equal area Check temperature of streams Obtain cooling water flow rate
Restriction needed- Second law of thermodynamics
Utilities
CO2 Pre-cooled Linde Process
Inlet Gas
100oC
Pre- Cooling
-70oC
Liquefaction
-140oC
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
Sub-Cooling
-260oC
LNG
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
Results
10
Results
10
Results
Process Prico Liquefin ExxonMobil DMR APX MFCP MFCP(CO2) TEALARC C3MR Conoco
Cost per ton ($) 5.12 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. <http://www.lngfacts.org/About-LNG/Overview.asp>. http://www.globalsecurity.org/military/systems/ship/tanker-lng-history.htm www.fpweb.com/200/Issue/Article/False/67449/Issue Fossil Energy Office of Communications. U.S. Department of Energy: Fossil Energy. 18 Dec 2007. U.S. Department of Energy. 3 Feb 2008. .<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 2007. 3 Feb 2008. <http://www.scandoil.com/moxie-bm2/news/mustangreceives-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=F eb-2006> Flynn, Thomas N. Cryogenic Engineering. Second edition. Marcel Dekker. New York- NY. 2005
