Process for the purification of gases
AssigneeUop LLC
InventorPaulino Forte
Life of this patent
Estimating the term…
Abstract
A process is disclosed for the purification of natural gas in which the reduction of the nitrogen content of a natural gas stream is achieved by a combination of absorption, purification, flashing, and reflux steps. More specifically, the process achieves the rejection of inert components such as nitrogen from natural gas without operating in the cryogenic temperature range. The process uses a lean solvent to absorb the non-rejected components in a recovery zone of an absorber and uses a portion of the off-gas from the flashing zone to purify the rich solvent in a purification zone of the absorber. In a further embodiment, solvent entrained in off-gases from low and medium pressure flash zones is recovered in a high pressure flash zone by washing the off-gases with recovered lean solvent.
Claims25
A process for the rejection of a light component from a gas mixture thereof with hydrocarbons comprising:
- (a) contacting the gas mixture with a lean solvent stream in a recovery zone to provide a light component rich stream and a first rich solvent stream;
- (b) passing said first rich solvent stream to a purification zone and therein countercurrently contacting said first rich solvent stream with a light gas stream to displace the light component from said first rich solvent stream and to provide a second rich solvent stream;
- and
- (c) flashing said second rich solvent stream in a flash zone to provide a gas product stream and the lean solvent stream.
A process for separating nitrogen from a natural gas stream comprising nitrogen and methane comprising the following steps:
- (a) passing said natural gas stream to recovery zone and contacting said natural gas stream with a lean solvent stream in said recovery zone to provide a nitrogen-rich stream and a first rich solvent stream;
- (b) passing said first rich solvent stream to a purification zone and countercurrently contacting said first rich solvent stream with a reflux stream and withdrawing a second rich solvent stream;
- (c) flashing said second rich solvent stream in a first flash zone at a first flash zone pressure and at a first flash zone temperature effective to provide the lean solvent stream and a nitrogen-reduced stream;
- (d) recycling at least a portion of said lean solvent stream to the recovery zone;
- (e) withdrawing the nitrogen-reduced stream at a product pressure to provide a nitrogen-reduced product;
- and
- (f) passing at least a portion of said nitrogen-reduced product to the purification zone to provide said reflux stream;
A process for separating nitrogen from a natural gas stream comprising nitrogen and methane comprising the following steps:
- (a) passing the natural gas stream at a feed pressure to a recovery zone, said natural gas stream countercurrently contacting a lean solvent stream in said recovery zone to provide a nitrogen stream and a first rich solvent stream;
- and withdrawing said nitrogen stream from said recovery zone;
- (b) passing said first rich solvent stream to a purification zone and countercurrently contacting therein said first rich solvent stream with a reflux stream and withdrawing a second rich solvent stream;
- (c) passing said second rich solvent stream to a high pressure flash zone, said flash zone being maintained at a high pressure of between about 1/5 and about 1/2 of a product pressure to provide a high pressure off-gas and a high pressure liquid;
- (d) passing said high pressure liquid to a medium pressure flash zone said medium pressure being maintained at a medium pressure of between about 1/5 and about 1/2 the high pressure to provide a medium pressure off-gas and a medium pressure liquid;
- (e) passing said high pressure off-gas stream to a first stage of at least a two-stage compressor, having the first stage and a second stage and passing said medium pressure off-gas stream to said second stage of said compressor to raise the pressure of said off-gas streams to the product pressure to provide a product gas stream;
- (f) passing said medium pressure liquid to a low pressure flash zone, said low pressure flash zone being maintained at a low pressure of between about 1/5 and about 1/2 the medium pressure to provide a low pressure off-gas and the lean solvent stream;
- (g) recompressing said low pressure off-gas to provide a compressed off-gas stream;
- (h) passing a portion of said compressed off-gas stream to the purification zone to provide the reflux stream of step (b);
- and
- (i) withdrawing the product gas stream.
A process for separating nitrogen from a natural gas stream comprising nitrogen and methane comprising the following steps:
- (a) passing the natural gas stream to an absorber, having an upper recovery zone and a lower purification zone, said natural gas stream entering said adsorber at a point between said upper recovery zone and said lower purification zone, said natural gas stream countercurrently contacting a lean solvent stream in said upper recovery zone to provide a nitrogen stream and a first rich solvent stream, and withdrawing said nitrogen stream from said upper recovery zone;
- (b) passing said first rich solvent stream to said lower purification zone in said absorber and countercurrently contacting therein said first rich solvent stream with a reflux stream and withdrawing a second rich solvent stream from said lower recovery zone;
- (c) passing said second rich solvent stream to a high pressure flash zone at conditions effective to provide a high pressure liquid and introducing a combined gas stream comprising lean solvent to said high pressure flash zone and contacting said high pressure liquid with said combined gas stream to provide a high pressure off-gas essentially free of lean solvent;
- (d) passing said high pressure liquid to a medium pressure flash zone at conditions effective to provide a medium pressure off-gas and a medium pressure liquid;
- (e) passing said medium pressure liquid to a low pressure flash zone at conditions effective to provide a low pressure off-gas and said lean solvent stream;
- (f) passing said low pressure off-gas to a first-stage of at least a 3-stage compressor having the first stage, a second stage, and a third stage, and passing said medium pressure off-gas to the second stage of said 3-stage compressor, and passing said low pressure off-gas to the first stage of said 3-stage compressor to provide said combined gas stream comprising lean solvent, and withdrawing said combined gas stream from said second stage and sithdrawing a product gas stream from said third stage;
- (g) passing at least a portion of said product gas to said lower purification zone to provide said reflux stream of step (b).
Dependencies are inferred from the claim text.