Natural Gas Refrigeration
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Transcript of Natural Gas Refrigeration
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Prepared By:
Shafaat KhanChemical Engineering
University of Engineering & Technology Peshawar, Pakistan
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Cooling of Natural Gas by Refrigeration Process
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Contents
Natural Gas Composition Main Uses Natural Gas Processing Cooling Cooling Methods Refrigeration Parts of MRU
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Contents (Cont…..)
Refrigerant Cycle Recommendations
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Natural Gas
Natural gas consisting mainly of methane.
Nonrenewable fossil fuel. It is found associated with fossil fuels, in
coal beds.
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Composition
Methane 70-90% Ethane 5-15% Propane 5% Butane 5%
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Main Uses
Power generation Domestic use Transportation Fuel Fertilizer Aviation Hydrogen
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Natural Gas Processing Dehydration Desulphurization Cooling
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Dehydration
Removal of water content from natural gas.
Because:
i). Water forms hydrates
ii). Water causes corrosion
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Desulphurization
Removal of Sulpher content from natural gas is called Desulphurization.
Because
i). Sulpher pollutes the environment.
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Cooling
Lowering the temperature of the raw gas so condensates can be removed.
Control the Hydrocarbon Dew Point.
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Cooling Methods
Refrigeration Turbo Expander JT Valve
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Refrigeration
Mechanical Refrigeration Unit is used for refrigeration Process
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Parts of MRU
Coalescer Filter Unit Gas-Gas Exchanger Gas-Liquid Exchanger Chiller Low Temperature
Separator De-Ethanizer MEG Injection
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Coalescer Filter Unit
It consist of two sections
i). Coalescer Element
ii). Double Pocket Vane It removes initially free liquid contents
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www.amistco.com
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Gas-Gas Exchanger
Gas-Gas Exchanger is used to cool the gas by exchanging heat with the cooled residue gas.
MEG is used in this step It is a mixture of water(20%) and Mono
Ethylene glycol(80%).
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Gas-Liquid Exchanger
Condensate Enters form Shell side Raw Gas from Gas-Gas Exchanger enters
the tube side. Raw Gas temperature lowers from 70ºF to
50ºF Condensate temperature rises from -15ºF
to 30ºF
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Chiller
Pre cooled gas from gas-gas exchanger enters the chiller.
The function of chiller is to further reduce the temperature of raw gas before it enters LTS.
It is just like a heat exchanger and propane is used as a refrigerant.
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Low Temperature Separator High pressure horizontal vessel. It consist of deflector plates. It separates the liquid from gas on the
basis of gravity and retention time.
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De-Ethanizer
Hydrocarbon Liquids passes through the liquid gas heat exchanger.
From gas liquid heat exchanger it enters the De-Ethanizer and Showered from top of De-Ethanizer.
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Mono ethylene Glycol Injection
MEG is injected along with raw gas before it enters the Gas/Gas exchanger.
It enters the tube side of the gas/gas Heat exchanger.
It prevents Hydrates formation. It is 80% MEG and 20% water.
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Refrigerant cycle
It recovers the refrigerant.
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Refrigerant Accumulator A horizontal high pressure vessel. For maintaining high pressure,
regulators are installed. It accumulates the refrigerant.
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Dessicator
It consist of silica gel, which acts as moisture absorbent.
Acts as filter for removal of impurities.
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Overhead Heat Exchanger It is a U type Shell and tube Heat
Exchanger. It cools the refrigerant prior to the
throttling valve.
Refrigerant Shell Side
De Ethanizer Vapor Tube Side
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Expansion Valve
Refrigerant passes through it. Sudden expansion occurs. Due to which pressure drops and
temperature lowers.
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Economizer
Reduces the load on the compressor. Make the process economical. Consist of the level control valve which
works as an expansion valve. Pressure drops and temperature lowers.
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Evaporator
Just like a heat exchanger.
Refrigerant Shell side
Gas Tube side After Heat exchange the refrigerant
enters the compressor
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Compressor
Compressor draws the refrigerant vapors from evaporator.
Rises the pressure and temperature. Sends the compressed refrigerant to the
condenser.
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Condenser The condenser accepts the high
pressurized refrigerant from the compressor.
Exchanges the heat with the atmosphere.
Here phase change occurs. Refrigerant Liquefies. Liquefied Refrigerant back to the
accumulator.
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Recommendations
Refrigerant Selection Magnetic Refrigeration
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Factors affecting Refrigerant
Properties Operating condition System components Chemical stability Cost Environmental Friendly
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Properties
Temperature Pressure Toxicity Heat Capacity
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Operating Conditions
Environmental Effect on the operation Temperature Difference
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System Components
Temperature Withstand Corrosiveness
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Selected
Ammonia Toxic, High Temp, Environment
R-134 Corrosive R-122 Selected
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Magnetic refrigeration Working principle are based on the
magnetocaloric effect. MCE is the lowering of temperature. Temperature as low as 0.3K MCE is the phenomena in which a material
temperature is changed by exposing it to the changing magnetic field.
Paramagnetic salt is used as refrigerant. e.g. cerium magnesium nitrate.
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References
www.processgroup.com.au www.britannica.com www.wipo.int www.naturalgas.org www.pfaudler.com www.amistco.com
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