Low pressure chilling train for olefin plants
First Claim
1. A method of processing, at a relatively low pressure, a cracked gas feedstream containing hydrogen, methane, C3 to C5 hydrocarbons and C6 and heavier hydrocarbons to separate hydrogen and methane and produce a hydrogen stream at a relatively high pressure comprising:
- a. compressing said feedstream to a pressure of less than 27 bars;
b. cooling said compressed feedstream to a temperature in the range of 10°
to 25°
C. thereby forming a first condensed portion and a first vapor portion of said compressed feedstream and separating said first condensed portion and said first vapor portion;
c. drying said first condensed portion and said first vapor portion;
d. cooling said dried first vapor portion to a temperature in the range of -20°
to 5°
C. thereby forming a second condensed portion and a second vapor portion;
e. feeding said first and second condensed portions to a stripper tower wherein said condensed portions are separated into a stripper bottoms containing essentially all of said C6 and heavier hydrocarbons and a stripper overhead containing at least a portion of said C3 to C5 hydrocarbons;
f. combining said second vapor portion and said stripper overhead to produce a combined vapor stream containing hydrogen, methane and C3 to C5 hydrocarbons with essentially no C6 and heavier hydrocarbons;
g. cooling said combined vapor stream to a temperature range of -110°
to -72°
C. thereby forming a third condensed portion and a third vapor portion;
h. dividing said third condensed portion into at least two demethanizer feed portions;
i. feeding a first one of said demethanizer feed portions directly to a demethanizer at a selected feed location;
j. heating a second one of said demethanizer feed portions to a temperature higher than said first one of said demethanizer feed portions and feeding into said demethanizer at a feed location below said selected feed location;
k. cooling said third vapor portion to a temperature range of -145°
to -120°
C. thereby forming a fourth condensed portion and a fourth vapor portion containing essentially only hydrogen, methane and a quantity of C2 hydrocarbons;
l. feeding said fourth condensed portion to said demethanizer at a feed location above said selected feed location;
m. separating in said demethanizer an overhead containing essentially only hydrogen, methane and a quantity of C2 hydrocarbons and a bottoms containing C2 and heavier hydrocarbons;
n. compressing and thereby heating said demethanizer overhead and said fourth vapor portion to a pressure of 25 to 45 bars; and
o. cooling said compressed demethanizer overhead and fourth vapor portion to a temperature in the range of -140°
to -100°
C. thereby forming a condensed demethanizer reflux and a vapor containing essentially only hydrogen and methane.
2 Assignments
0 Petitions
Accused Products
Abstract
A method of processing a cracked gas feedstream containing hydrogen and C1 to C6 and heavier hydrocarbons is described using a relatively low pressure as compared to conventional cryogenic separation processes. At pressures below 27 bars, the feedstream is dried and cooled in a series of steps to initially separate out essentially all of the C6 and heavier hydrocarbons forming a vapor stream containing the hydrogen, the C1 to C3 hydrocarbons and at least some of the C4 and C5 hydrocarbons. The C4 and C5 components act as an absorption liquid to lower the light ends partial pressure permitting the condensation of C2 and C3 components at higher temperature levels and permitting the operation at lower pressures. The vapor stream is then further cooled and separated in another series of steps and processed in a demethanizer column in a manner to provide a high pressure hydrogen and methane overhead product and a high recovery of C2 and C3 components in the bottoms.
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Citations
8 Claims
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1. A method of processing, at a relatively low pressure, a cracked gas feedstream containing hydrogen, methane, C3 to C5 hydrocarbons and C6 and heavier hydrocarbons to separate hydrogen and methane and produce a hydrogen stream at a relatively high pressure comprising:
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a. compressing said feedstream to a pressure of less than 27 bars; b. cooling said compressed feedstream to a temperature in the range of 10°
to 25°
C. thereby forming a first condensed portion and a first vapor portion of said compressed feedstream and separating said first condensed portion and said first vapor portion;c. drying said first condensed portion and said first vapor portion; d. cooling said dried first vapor portion to a temperature in the range of -20°
to 5°
C. thereby forming a second condensed portion and a second vapor portion;e. feeding said first and second condensed portions to a stripper tower wherein said condensed portions are separated into a stripper bottoms containing essentially all of said C6 and heavier hydrocarbons and a stripper overhead containing at least a portion of said C3 to C5 hydrocarbons; f. combining said second vapor portion and said stripper overhead to produce a combined vapor stream containing hydrogen, methane and C3 to C5 hydrocarbons with essentially no C6 and heavier hydrocarbons; g. cooling said combined vapor stream to a temperature range of -110°
to -72°
C. thereby forming a third condensed portion and a third vapor portion;h. dividing said third condensed portion into at least two demethanizer feed portions; i. feeding a first one of said demethanizer feed portions directly to a demethanizer at a selected feed location; j. heating a second one of said demethanizer feed portions to a temperature higher than said first one of said demethanizer feed portions and feeding into said demethanizer at a feed location below said selected feed location; k. cooling said third vapor portion to a temperature range of -145°
to -120°
C. thereby forming a fourth condensed portion and a fourth vapor portion containing essentially only hydrogen, methane and a quantity of C2 hydrocarbons;l. feeding said fourth condensed portion to said demethanizer at a feed location above said selected feed location; m. separating in said demethanizer an overhead containing essentially only hydrogen, methane and a quantity of C2 hydrocarbons and a bottoms containing C2 and heavier hydrocarbons; n. compressing and thereby heating said demethanizer overhead and said fourth vapor portion to a pressure of 25 to 45 bars; and o. cooling said compressed demethanizer overhead and fourth vapor portion to a temperature in the range of -140°
to -100°
C. thereby forming a condensed demethanizer reflux and a vapor containing essentially only hydrogen and methane. - View Dependent Claims (2, 3, 4, 5)
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6. A method of processing, at a relatively low pressure, a cracked gas feedstream containing hydrogen, methane, C3 to C5 hydrocarbons and C6 and heavier hydrocarbons to separate hydrogen and methane and produce a hydrogen stream at a relatively high pressure comprising:
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a. compressing said feedstream to a pressure of less than 27 bars; b. cooling said compressed feedstream to a temperature in the range of 10°
to 25°
C. thereby forming a first condensed portion and a first vapor portion of said compressed feedstream and separating said first condensed portion and said first vapor portion;c. drying said first condensed portion and said first vapor portion; d. treating said dried first condensed portion and said dried first vapor portion to separate therefrom essentially all of said C6 and heavier hydrocarbons and form a vapor stream containing said hydrogen, methane and C5 and lighter hydrocarbons with essentially no C6 and heavier hydrocarbons; e. cooling said vapor stream thereby forming at least one condensed demethanizer feed portion and a further vapor portion; f. feeding said condensed demethanizer feed portion to at least one selected feed location of a demethanizer; g. separating in said demethanizer an overhead containing essentially only hydrogen and methane and a quantity of C2 hydrocarbons and a bottoms containing essentially C2 and heavier hydrocarbons; h. compressing said demethanizer overhead and said further vapor portion to a pressure of 25 to 45 bars; and i. cooling said compressed demethanizer overhead and further vapor portion to a temperature in the range of -140°
C. to -100°
C. thereby forming a condensed demethanizer reflux and a vapor containing essentially only hydrogen and methane. - View Dependent Claims (7, 8)
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Specification