Plant Block Schematic Hydrocarbon Recovery Chapter 12
advertisement
Hydrocarbon Recovery Chapter 12 Based on presentation by Prof. Art Kidnay John Jechura – jjechura@mines.edu Updated: April 4, 2016 Plant Block Schematic John Jechura – jjechura@mines.edu Updated: April 4, 2016 2 Topics • Introduction Retrograde Condensation • Process Components Refrigeration System Turboexpansion Heat exchange Gas-Liquid Separators Fractionation • Recovery Processes Dew Point Control and Fuel Conditioning Low C2+ Recovery High C2+ recovery • Safety and Environmental Considerations John Jechura – jjechura@mines.edu Updated: April 4, 2016 3 Reasons for Hydrocarbon Recovery • Field Operations Reduce liquid content of high GPM gases in gathering systems Eliminate or reduce potential for condensation (dew-pointing) Reduce Btu content of gas for use in engines (fuel conditioning) • Plant Operations Reduce Sales gas Btu content to spec (950 to 1150 Btu/scf) Eliminate possible condensation Recover valuable C2+ liquids John Jechura – jjechura@mines.edu Updated: April 4, 2016 5 Retrograde Condensation 1500 B 1250 Pressure, Psia C 1000 750 A 500 Vapor Liquid 250 0 -300 -250 -200 -150 -100 -50 0 50 100 Temperature, °F John Jechura – jjechura@mines.edu Updated: April 4, 2016 6 External Refrigeration When inlet pressures to Hydrocarbon Recovery are too low to provide required cooling by expansion we can obtain additional refrigeration by: • Compressing inlet gas to higher pressure • Compressing propane in refrigeration cycle Compressing propane is usually the best choice John Jechura – jjechura@mines.edu Updated: April 4, 2016 8 Basic Refrigeration System Condenser Compressor Suction Drum Receiver J-T Valve Chiller/ Evaporator John Jechura – jjechura@mines.edu Updated: April 4, 2016 9 Refrigeration cycle Pressure Critical Point Liquid Phase Vapor Phase C B * D A Enthalpy John Jechura – jjechura@mines.edu Updated: April 4, 2016 10 1 Stage C3 Refrigeration System Condenser Compressor 250 Psia Suction Drum Receiver ~120°F 240 Psia J-T Valve Chiller/ Evaporator -40°F, 16 Psia John Jechura – jjechura@mines.edu Updated: April 4, 2016 11 Refrigeration cycle B C D John Jechura – jjechura@mines.edu Updated: April 4, 2016 A 12 2 Stage C3 Refrigeration System 60 Psia 250 Psia Condenser JT-Valve - 40°F 16 Psia 25°F 62 Psia Interstage Economizer 25°F 62 Psia Chiller/ Evaporator Receiver ~120°F 240 Psia JT-Valve Chiller / Evaporator -40°F, 16 Psia JT-Valve John Jechura – jjechura@mines.edu Updated: April 4, 2016 13 2 Stage C3 Refrigeration System 60 Psia 250 Psia Condenser JT-Valve - 40°F 16 Psia 25°F 62 Psia Interstage Economizer Receiver ~120°F 240 Psia JT-Valve Chiller / Evaporator -40°F, 16 Psia John Jechura – jjechura@mines.edu Updated: April 4, 2016 14 Refrigeration cycle B C D A John Jechura – jjechura@mines.edu Updated: April 4, 2016 15 Benefits of Staging Number of Stages 1 2 3 Reduction in Compression Power 0 19% 23% Reduction in Condenser Duty 0 8% 10% Condenser Temp = 100oF Chiller Temp = -40oF John Jechura – jjechura@mines.edu Updated: April 4, 2016 16 Expansion Paths Joule-Thomson (J-T) Expansion (ΔH = 0) Turboexpansion (ΔS = 0) No work from ΔP Obtain work from ΔP Simple system Complex system Inexpensive Relatively expensive Extensively used Increasingly used Expands liquid, vapor and liquid-vapor mixtures Expands only gases John Jechura – jjechura@mines.edu Updated: April 4, 2016 19 20 Turboexpanders • Provide Maximum possible cooling Work which can drive compressors • Operate Over wide temperature range At high speeds, > 15,000 rpm • Require clean gas • Can handle up to 50 wt % liquid formation provided droplet size < 20 μm John Jechura – jjechura@mines.edu Updated: April 4, 2016 21 Turboexpander Cutaway Compressor Expander Mafi-Trench John Jechura – jjechura@mines.edu Updated: April 4, 2016 22 Recovery Processes • Dew Point Control and Fuel Conditioning High recovery not needed Operating temperatures ~0oF for fractionation • Low C2+ Recovery < 60% C2+ recovery needed Operating temperatures ~ -35oF for fractionation • High C2+ recovery ~ 90% C2+ recovery needed Operating temperatures ~ -165oF for fractionation John Jechura – jjechura@mines.edu Updated: April 4, 2016 24 Dew Point Control and Fuel Conditioning Traditional technology: • Low Temperature Separators (LTS or LTX) Standard technology (>60 years old) Newer technologies: • Membrane System Newer technology (~10 years old) • Twister Newest technology (~5 years old) John Jechura – jjechura@mines.edu Updated: April 4, 2016 25 Low Temp Separator with Glycol Injection Gas from Field Water Knockout J-T Valve Low Temperature Separator Condensate Stabilizer Condensate Water Glycol Regenerator Rich Glycol Residue Gas John Jechura – jjechura@mines.edu Updated: April 4, 2016 26 Membrane for Fuel Conditioning Rich Gas Compressor Cooler C3+ Lean Fuel Gas Membrane Fuel Gas Slipstream Compressor Engine C3+ Enriched Gas Permeate John Jechura – jjechura@mines.edu Updated: April 4, 2016 27 Twister • Modular, flow dependent • Depends upon pressure ratio, ΔP ~ 20 to 30% • Slip gas is 10 to 15% • Used for dehydration and liquids removal • Is being tested in subsea application http://twisterbv.com/PDF/resources/Twister_-_How_Does_It_Work.pdf John Jechura – jjechura@mines.edu Updated: April 4, 2016 28 Refrigerated Process Air Cooler Compressor Residue Gas Cold Separator Fractionator C3 Chiller Inlet Gas Reboiler NGL Product John Jechura – jjechura@mines.edu Updated: April 4, 2016 31 Effect of Composition on C3+ Recovery 90 C3+ Recovery, % 80 7 GPM 70 5 GPM 60 50 40 3 GPM 30 20 -40 -30 -20 -10 0 10 20 Process Temperature, °F John Jechura – jjechura@mines.edu Updated: April 4, 2016 32 Recovery Efficiency of C2 and C3 90 7 GPM 80 5 GPM Recovery, % 70 C3 60 7 GPM 50 40 3 GPM 5 GPM 30 C2 3 GPM 20 10 -30 -25 John Jechura – jjechura@mines.edu Updated: April 4, 2016 -20 -15 -10 -5 Process Temperature, °F 0 5 10 33 High C2+ Recovery Requires cryogenic separation • Processes involve: Propane refrigeration (unless high inlet gas pressure) Multipass heat exchangers (gas-gas) Expansion, turbo and JT Demethanizer column • Two processes: “1st Generation” – simplest Gas Subcooled Process (GSP) – more efficient, higher recoveries and commonly used John Jechura – jjechura@mines.edu Updated: April 4, 2016 34 1st Generation Cryo Process John Jechura – jjechura@mines.edu Updated: April 4, 2016 35 GSP Schematic John Jechura – jjechura@mines.edu Updated: April 4, 2016 36 Effect of Inerts on Max C2 Recovery Maximum Ethane Recovery, % 100 90 80 70 60 50 1.5 GPM 40 3.0 GPM 5.0 GPM 8.0 GPM 30 0 2 4 6 8 10 12 14 Nonhydrocarbon Content, mol % John Jechura – jjechura@mines.edu Updated: April 4, 2016 37
