Hydrocarbon separation process and apparatus
First Claim
1. A process for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, which process comprises:
- (a) cooling the gaseous feed to produce a partially condensed stream, (b) separating the partially condensed stream to form a first liquid stream and a first gaseous stream, (c) subcooling at least a portion of the first liquid stream, (d) expanding said subcooled stream, (e) passing at least a portion of the expanded stream from (d) as a liquid feed to a fractionation column, (f) producing a cooled stream by cooling a separated lights fraction of the feed, and (g) recovering said heavier hydrocarbon fraction as a bottoms fraction from said column, characterised in that (i) at least a part of the subcooling required in subcooling step (c) is provided by transfer of heat to the expanded stream from (d), (ii) at least a portion of the cold required to cool the separated lights fraction to produce said cooled stream (f) is provided by transfer of heat to the expanded stream from (d), and (iii) at least a portion of said cooled stream (f) is introduced to an upper part of the column.
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Abstract
A process is described for separating the heavier hydrocarbons from a gaseous hydrocarbon feed wherein a first separator is employed to separate partially condensed gaseous feed and wherein the vapour portion undergoes work expansion and is fed to a fractionation column. The liquid portion is subcooled in heat exchange with the overhead vapour from the fractionation column, expanded, evaporated to provide refrigeration at a low temperature level, and fed to the fractionation column. The rewarmed residual vapour is subsequently compressed to a pressure suitable for export, with a portion of the compressed gas being cooled, condensed and recycled back to reflux the top section of the fractionation column.
Also described is a process wherein a first separator is employed to separate partially condensed gaseous feed and wherein the vapour portion undergoes work expansion and is fed to a high pressure wash column. The liquid portion is expanded and fed to the base of the high pressure wash column. Bottoms liquid from the wash column is subcooled in heat exchange with the overhead vapour from a fractionation column, expanded, evaporated to provide refrigeration at a low temperature level, and fed to the fractionation column. Vapour from the high pressure wash column is partially condensed, with the liquid portion used to provide reflux to the high pressure wash column and the fractionation column.
The processes are especially applicable to recovery of ethane and heavier components from natural gas. Overall process power requirements are reduced, recovery of the desired heavy hydrocarbons is increased or both of these effects are realised.
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Citations
43 Claims
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1. A process for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, which process comprises:
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(a) cooling the gaseous feed to produce a partially condensed stream, (b) separating the partially condensed stream to form a first liquid stream and a first gaseous stream, (c) subcooling at least a portion of the first liquid stream, (d) expanding said subcooled stream, (e) passing at least a portion of the expanded stream from (d) as a liquid feed to a fractionation column, (f) producing a cooled stream by cooling a separated lights fraction of the feed, and (g) recovering said heavier hydrocarbon fraction as a bottoms fraction from said column, characterised in that (i) at least a part of the subcooling required in subcooling step (c) is provided by transfer of heat to the expanded stream from (d), (ii) at least a portion of the cold required to cool the separated lights fraction to produce said cooled stream (f) is provided by transfer of heat to the expanded stream from (d), and (iii) at least a portion of said cooled stream (f) is introduced to an upper part of the column. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. Apparatus for the separation of a heavier hydrocarbon fraction from a gaseous feed comprising a mixture of hydrocarbons, wherein said mixture is cooled, partially condensed, separated into a first liquid stream and a first gaseous stream and at least a portion of each of the first liquid stream and the first gaseous stream are passed to a fractionation column in which said separation is carried out, which apparatus comprises:
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(i) conduit means for transferring at least a portion of the first liquid stream to a heat exchanger in which said portion is subcooled, (ii) means for expanding said subcooled stream, (iii) conduit means for transferring at least a portion of said expanded stream to the heat exchanger in which the subcooling is effected, whereby at least a part of the subcooling is provided by transfer of heat to the expanded stream, and (iv) conduit means for introducing a cooled stream produced by cooling a separated lights fraction of the feed to an upper part of the column, at least a portion of the cold required to cool the separated lights fraction being provided by transfer of heat to said expanded stream. - View Dependent Claims (41, 42, 43)
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Specification