Hydrocarbon gas processing
First Claim
1. In a process for separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane together comprising a major portion of said feed gas, wherein(a) said feed gas under pressure is cooled sufficiently to partially condense said gas forming thereby a liquid portion of said feed gas and a vapor feed gas;
- (b) at least some of the liquid portion is expanded in an expansion means to a lower pressure whereby a part of said liquid portion vaporizes to cool the expanded liquid portion to a refrigerated temperature; and
(c) at least some of the expanded liquid portion is subsequently treated in a fractionation column to separate said relatively less volatile fraction;
the improvement comprising(1) combining at least part of liquid portion (a) with a process stream having a bubble point below the bubble point of said liquid portion (a), to form thereby a combined stream;
(2) supplying said combined stream to said expansion means at a temperature which is below the bubble point of said liquid portion (a);
(3) expanding said combined stream to said lower pressure, whereby the refrigerated temperature achieved in expansion step (b) is reduced;
(4) thereafter supplying at least some of said expanded combined stream to said fractionation column at a first feed position; and
(5) expanding at least a portion of said vapor feed gas in a work expansion engine to said lower pressure, and supplying the expanded vapor to the fractionation column at a second feed point, said second feed point being at a lower column position than said first feed point.
1 Assignment
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Accused Products
Abstract
A process for separating hydrocarbon gases is described for the recovery of gases such as ethane and heavier hydrocarbons from natural gas streams or similar refinery or process streams. In the process described, the gas to be separated is cooled at a high pressure to produce partial condensation. The liquid from the partial condensation is further cooled and then expanded to a lower pressure. At the lower pressure, the liquid is then separated into fractions in a distillation column. The basic separation process is improved by combining the condensed high-pressure liquid with a stream having a lower bubble point, with cooling of one or both streams prior to expansion.
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Citations
32 Claims
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1. In a process for separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane together comprising a major portion of said feed gas, wherein
(a) said feed gas under pressure is cooled sufficiently to partially condense said gas forming thereby a liquid portion of said feed gas and a vapor feed gas; -
(b) at least some of the liquid portion is expanded in an expansion means to a lower pressure whereby a part of said liquid portion vaporizes to cool the expanded liquid portion to a refrigerated temperature; and (c) at least some of the expanded liquid portion is subsequently treated in a fractionation column to separate said relatively less volatile fraction; the improvement comprising (1) combining at least part of liquid portion (a) with a process stream having a bubble point below the bubble point of said liquid portion (a), to form thereby a combined stream; (2) supplying said combined stream to said expansion means at a temperature which is below the bubble point of said liquid portion (a); (3) expanding said combined stream to said lower pressure, whereby the refrigerated temperature achieved in expansion step (b) is reduced; (4) thereafter supplying at least some of said expanded combined stream to said fractionation column at a first feed position; and (5) expanding at least a portion of said vapor feed gas in a work expansion engine to said lower pressure, and supplying the expanded vapor to the fractionation column at a second feed point, said second feed point being at a lower column position than said first feed point. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In a process for separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane together comprising a major portion of said feed gas, wherein
(a) said feed gas under pressure is cooled sufficiently to partially condense said gas, forming thereby a liquid portion of said feed gas and a vapor feed gas; -
(b) at least some of said liquid portion is expanded in an expansion means to a lower pressure, whereby a part of said liquid portion vaporizes to cool the expanded liquid portion to a refrigerated temperature; and (c) at least some of the expanded liquid portion is subsequently treated in a fractionating column to separate said relatively less volatile fraction, the improvement comprising (1) dividing at least part of the liquid portion resulting in step (a) into a first stream and a remaining stream; (2) expanding said first stream to said lower pressure, whereby a portion thereof vaporizes to cool the expanded first stream; (3) directing said expanded first stream into heat exchange relation with the remaining part (1) of said liquid portion; (4) combining said remaining part with a process stream having a bubble point below the bubble point of the liquid portion from step (a), thereby to form a combined stream; (5) supplying said combined stream to an expansion means at a temperature which is below the bubble point of said liquid portion (a); (6) expanding said combined stream to said lower pressure, whereby the refrigerated temperature achieved in said expansion is lower than the refrigerated temperature achieved in step (2); (7) thereafter supplying at least some of said expanded combined stream to said fractionation column at a first feed position; and (8) expanding at least 25% of the vapor feed gas resulting from step (a) in a work-expansion engine, and supplying the expanded vapor to the fractionation column at a second feed point, and said second feed point being at a lower column position than said first feed point, the amount of said feed gas vapor which is work expanded being sufficient to reduce the risk of carbon dioxide icing in the fractionation column.
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9. In a process for separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane together comprising the major portion of said feed gas, wherein
(a) said gas under pressure is cooled sufficiently to partially condense said gas forming thereby a liquid portion of said feed gas and a vapor feed gas; -
(b) the liquid portion at a temperature below its bubble point is expanded in an expansion means to a lower pressure whereby a part of said liquid portion vaporizes to cool the expanded liquid portion to a refrigerated temperature; (c) at least some of said expanded liquid portion is subsequently treated in a fractionation columm to separate said relatively less volatile fraction; the improvement comprising (1) combining a portion of said vapor feed gas and at least a part of the liquid portion (a) prior to expansion thereof to form thereby a combined stream; (2) supplying said combined stream to said expansion means at a temperature below the bubble point of said liquid portion (a); (3) expanding said combined stream to said lower pressure whereby the refrigerated temperature achieved in expansion step (b) is reduced; (4) thereafter supplying at least some of said expanded combined stream to said fractionation column at a first feed point; and (5) expanding the remaining portion of the vapor feed gas in a word expansion and supplying the expanded remaining portion to said fractionation columm at a second feed point, said second feed point being at a lower column position than the first feed point. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. In an apparatus for the separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed containing hydrocarbons, methane and ethane comprising the major portion of said feed gas, said apparatus having
(a) cooling means to cool said gas under pressure sufficiently to partially condense said gas and form thereby a liquid portion of said gas and a vapor feed gas; -
(b) expansion means connected to said cooling means to receive said partly condensed feed gas and to expand it to a lower pressure, whereby it is further cooled; and (c) a fractionation column connected to receive at least a portion of the expanded feed gas from said expansion means (b), said distillation means being adapted to separate said relatively less volatile fraction, the improvement which comprises (i) means for combining at least part of the liquid portion obtained from said cooling means (a) with a process stream having a bubble point below the bubble point of said liquid portion (a) to form thereby a combined stream; (ii) cooling means for cooling at least one of said part of said liquid portion, said process stream and said combined stream sufficiently that said combined stream has a temperature below the bubble point of said liquid portion (a); (iii) means connecting said expansion means (b) to receive said combined stream at a temperature below the bubble point of said liquid portion (a), wherein said combined stream is expanded to said lower pressure; (iv) means connecting said expansion means (b) to said fractionation column to supply at least a portion of the expanded combined stream as a feed to said fractionation column at a first feed point; and (v) work expansion means connected to said cooling means (a) to receive at least some of the vapor feed gas and to expand said lower pressure, said work expansion means being further connected to supply the expanded vapor feed gas to said fractionation column at a second feed point, said second feed point being at a lower column position than said first feed point. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. An apparatus for the separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane together comprising the major portion of said feed gas, said apparatus having
(a) cooling means to cool said gas under pressure sufficiently to partially condense said gas and form thereby a liquid portion of said gas and a vapor feed gas; -
(b) expansion means connected to said cooling means to receive said partially condensed feed gas and to expand it to a lower pressure whereby it is further cooled; and (c) a fractionation column connected to receive at least a portion of the expanded feed gas from said expansion means (b), said fractionation column being adapted to separate said relatively less volatile fraction, the improvement which comprises (i) dividing means connected to receive at least part of said liquid portion (a), and to divide said part into a first stream and a remaining part; (ii) expansion means connected to said dividing means to receive said first stream and to expand it to a lower pressure, whereby a portion thereof vaporizes to cool the expanded first stream; (iii) heat exchange means connected to said expansion means to receive the remaining part of said liquid portion, said heat exchange means further being connected between said cooling means (a) and said dividing means (i) to direct the expanded first stream into heat exchange relation with said remaining part of said liquid portion; (iv) means connected to said dividing means to receive said remaining part and to combine said remaining part with said process stream havung a bubble point below the bubble point of said liquid portion (a) to form said combined stream having (v) heat exchange means connected between said means (iv) and said expansion means (iii) adapted to further cool said combined stream prior to expansion thereof sufficiently that said combined stream has a temperature below the bubble point of said liquid portion (a); (vi) means connecting said expansion means (b) to receive said combined stream at a temperature below the bubble point of said liquid portion (a), wherein said combined stream is expanded to said lower pressure; (vii) means connecting said expansion means (b) to said fractionation column to supply at least a portion of the expanded combined stream as a feed to said fractionation column at a first feed point; and (viii) work expansion means connected to said cooling means (a) to receive at least 25% of the feed gas vapor and to expand it to said lower pressure, said work expansion means being further connected to supply the expanded vapor feed gas to said fractionation column at a second feed point, said second feed point being at a lower column position than the first feed point, said work expansion means further being adapted to expand a sufficient amount of feed gas vapor to reduce the risk of carbon dioxide icing in the fractionation column.
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25. In an apparatus for the separation of a feed gas into a volatile residue gas and a relatively less volatile fraction, said feed gas containing hydrocarbons, methane and ethane, together comprising the major portion of said feed gas,
said apparatus having (a) cooling means to cool said gas under pressure sufficiently to partially condense said feed gas and to form thereby a liquid portion of said feed gas and a vapor feed gas; -
(b) expansion means connected to said cooling means to receive said liquid portion and expand it to a lower pressure, whereby a part of said liquid portion vaporizes to cool the expanded liquid portion; and (c) a fractionation column connected to receive at least some of said expanded liquid portion and to separate said relatively less volatile fraction, the improvement wherein said exchange means includes (i) means connected to said cooling means (a) for combining a portion of said vapor feed gas and at least part of said liquid portion prior to expansion thereof to form thereby a combined stream; (ii) means for cooling at least one of said liquid portion, said vapor feed gas and said combined stream sufficiently that said combined stream has a temperature below the bubble point of said liquid portion (a) prior to expansion thereof; (iii) means connecting said expansion means (b) to receive said combined stream at a temperature below the bubble point of said liquid portion (a), wherein said combined stream is expanded to said lower pressure; (iv) means connecting said expansion means (b) to said fractionation column to supply at least a portion of the expanded combined stream to the fractionation column at a first feed point; and (v) work expansion means connected to said cooling means (a) to receive the remaining portion of the vapor feed gas and to expand it to said lower pressure, said work expansion means being further connected to supply the expanded remaining part to the fractionation column at a second feed point, said second feed point being at a lower column position than the first feed point. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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Specification