NGL Recovery
NoDoC designs the cost models for Natural Gas Liquids (NGL) for the following methods:
• Absorption
• Adsorption
• Condensation
NoDoC cost estimation models and simulations are based on the following criterias:
REFRIGERATED ABSORPTION
The gas is first cooled in conventional dewpoint control facilities down to -30 to -35°F. the gas then passes through an oil absorber where the various components are absorbed. The gas leaves the tower and is sent to a presaturator where the oil is saturated with methane and ethane. The gas then is returned to the chilling system for cooling the incoming gas.
The oil that leaves the absorber is called rich oil and contains all the absorbed compounds. The condensed hydrocarbon liquids from the chilling section joint this stream. The rich oil is heated and reduced in pressure to about half of the absorbing pressure in the rich oil flash tank. A considerable amount of the absorbed methane is flashed off in this vessel. The oil is then further heated and sent to a de-ethanizer where most of the ethane and the remaining methane are fractionated out of the oil stream. Finally the oil is sent to a Hp still where the absorbed products are produced as the overhead product and the bottoms produced is lean oil which is cooled and recirculated to the absorber. The absorbed products are sent to the fractionating facilities.
ADSORPTION
For deep cut plants only carbon adsorption plants have been used to any extent. The particular problem is the wide temperature variations experiences between adsorption and regeneration. Two process using charcoal as the adsorbent are commercially used. The process is quite simple. One bed is on the adsorbing cycle, one bed is regenerated and one bed is cooled.
CONDENSATION ( CRYOGENIC OR EXPANDER PLANT)
The raw gas enters into an inlet separator where any liquids are separated. The gas is dried to about -150°F dewpoint.(about 10°F below the lowest expected temperature). The gas is then cooled in gas-to-gas exchangers. Condensed liquids are removed and then the gas is sent to an expander. This is a turbine that reduces the pressure to about half the entrance pressure and cools the gas by taking work out of it(down to -130°F or lower). The liquid hydrocarbons are again separated and then fed to a demethanizer in which the methane is removed,then to the de-ethanizer for production of specification ethane and propane. The lean gas is used, along with the other liquids to cool the incoming gas. It is then recompressed to the required outlet pressure using the energy available in the pressure drop and considerable additional energy from outside to get it back to its original pressure.
• Absorption
• Adsorption
• Condensation
NoDoC cost estimation models and simulations are based on the following criterias:
REFRIGERATED ABSORPTION
The gas is first cooled in conventional dewpoint control facilities down to -30 to -35°F. the gas then passes through an oil absorber where the various components are absorbed. The gas leaves the tower and is sent to a presaturator where the oil is saturated with methane and ethane. The gas then is returned to the chilling system for cooling the incoming gas.
The oil that leaves the absorber is called rich oil and contains all the absorbed compounds. The condensed hydrocarbon liquids from the chilling section joint this stream. The rich oil is heated and reduced in pressure to about half of the absorbing pressure in the rich oil flash tank. A considerable amount of the absorbed methane is flashed off in this vessel. The oil is then further heated and sent to a de-ethanizer where most of the ethane and the remaining methane are fractionated out of the oil stream. Finally the oil is sent to a Hp still where the absorbed products are produced as the overhead product and the bottoms produced is lean oil which is cooled and recirculated to the absorber. The absorbed products are sent to the fractionating facilities.
ADSORPTION
For deep cut plants only carbon adsorption plants have been used to any extent. The particular problem is the wide temperature variations experiences between adsorption and regeneration. Two process using charcoal as the adsorbent are commercially used. The process is quite simple. One bed is on the adsorbing cycle, one bed is regenerated and one bed is cooled.
CONDENSATION ( CRYOGENIC OR EXPANDER PLANT)
The raw gas enters into an inlet separator where any liquids are separated. The gas is dried to about -150°F dewpoint.(about 10°F below the lowest expected temperature). The gas is then cooled in gas-to-gas exchangers. Condensed liquids are removed and then the gas is sent to an expander. This is a turbine that reduces the pressure to about half the entrance pressure and cools the gas by taking work out of it(down to -130°F or lower). The liquid hydrocarbons are again separated and then fed to a demethanizer in which the methane is removed,then to the de-ethanizer for production of specification ethane and propane. The lean gas is used, along with the other liquids to cool the incoming gas. It is then recompressed to the required outlet pressure using the energy available in the pressure drop and considerable additional energy from outside to get it back to its original pressure.
