US 4,609,388 A · Gas separation process

Abstract

A process for separating acid gases such as CO.sub.2, H.sub.2 S, and SO.sub.2, other sulfur-containing molecules such as COS, and other relatively high boiling point impurities from lower boiling point components of a gas stream comprises: dehydrating the gas stream and contacting it, at an elevated pressure and at substantially the dew point temperature of carbon dioxide therein, with a liquid carbon dioxide refrigerant-absorbent to absorb such impurities other than CO.sub.2, and separating the liquid carbon dioxide and absorbed impurities; condensing CO.sub.2, and separating the liquid carbon dioxide and absorbed impurities; and condensing CO.sub.2 from the residual gas stream at such pressure, preferably by indirect heat exchange. A crystallization process is also disclosed for separating the liquid carbon dioxide and absorbed impurities. The residual gas stream obtained following indirect heat exchange may be processed further by contact with a second refrigerant-absorbent which preferably comprises a liquid-solid slurry. Further, a crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase of the crystallizable material obtained upon freezing a liquid mixture of the materials. The solid phase is formed and melted at spaced locations in a liquid mixture of the materials and, within the liquid mixture, internal solid and liquid flows are maintained in opposite directions to effect separation of the materials. The solid phase is formed by evaporative cooling of the liquid mixture and melted by direct contact with a condensing vapor phase of the materials, each of these operations being performed substantially at the prevailing triple point locus conditions in the respective locations in the liquid mixture.

Claims44

Dependent claims

A process for the removal of contaminant gas molecules from a gas stream, comprising the steps of:

(1) contacting the gas stream in countercurrent flow with a liquid carbon dioxide absorbent to absorb and entrain the contaminant molecules;
(2) separating a substantially decontaminated residual gas stream from a mixture of the carbon dioxide absorbent and absorbed contaminant molecules;
(3) separating the carbon dioxide absorbent and concentrating the contaminant molecules of said mixture by crystallization;
and
(4) reusing at least part of the separated carbon dioxide absorbent as absorbent in step (1).

2 more elements

A process for treating a feed gas stream comprising relatively high boiling point gases including hydrogen sulfide, carbonyl sulfide, and carbon dioxide and relatively lower boiling point gas of primary value, comprising precluding the need to distill the feed gas stream by the steps of:

(a) providing a feed gas stream which is pressurized and cooled to a predetermined pressure and temperature;
(b) providing an absorption column and a supply of substantially pure liquid carbon dioxide absorbent at substantially said predetermined pressure and temperature;
(c) introducing absorbent from said supply thereof and said feed gas stream into said absorption column for separation of said hydrogen sulfide and carbonyl sulfide from said lower boiling point gas;
(d) contacting said feed gas stream in said absorption column with a countercurrent flow of absorbent in an amount sufficient, but not exceeding that required, to absorb and entrain substantially all of said hydrogen sulfide present in the gas stream and thereby also to absorb and entrain substantially all of said carbonyl sulfide in the gas stream while maintaining most of the absorbent in the liquid state at substantially said pressure and temperature, the balance of the absorbent being vaporized by the heat of condensation of the absorbed gas;
(e) withdrawing from said absorption column a substantially completely desulfurized residual gas stream containing said relatively lower boiling point gas and a mixture of the still liquid absorbent and gases absorbed or entrained therewith;
and
(f) recovering substantially pure carbon dioxide from the separated liquid mixture of said absorbent and gases absorbed or entrained therewith.

4 more elements

(a) providing a feed gas stream which is pressurized and cooled to a predetermined pressure and temperature;
(b) providing an absorption column and a supply of substantially pure liquid carbon dioxide absorbent at substantially said predetermined pressure and temperature;
(c) introducing absorbent from said supply thereof and feed gas stream into said absorption column for separating of said hydrogen sulfide and carbonyl sulfide from said lower boiling point gas;
(d) contacting said feed gas stream in said absorption column with a countercurrent flow of absorbent in an amount sufficient, but not exceeding that required, to absorb and entrain substantially all of said hydrogen sulfide present in the gas stream and thereby also to absorb and entrain substantially all of said carbonyl sulfide in the gas stream while maintaining most of the absorbent in the liquid state at substantially said pressure and temperature, the balance of the absorbent being vaporized by the heat of condensation of the absorbed gas;
(e) withdrawing from said absorption column a substantially completely desulfurized residual gas stream containing said relatively lower boiling point gas and a mixture of the still liquid absorbent and gases absorbed or entrained therewith;
and
(f) recovering substantially pure carbon dioxide from said desulfurized residual gas stream to concentrate further said relatively lower boiling point gas.

4 more elements

A process for treating a feed gas stream comprising relatively high boiling point gases including carbonyl sulfide and a relatively lower boiling point gas of primary value, comprising precluding the need to distill the feed gas stream by the steps of:

(a) providing a feed gas stream which is pressurized and cooled to a predetermined pressure and temperature;
(b) providing an absorption column and a supply of substantially pure liquid carbon dioxide absorbent at substantially said predetermined pressure and temperature;
(c) determining an effective flow range of absorbent equal to from about 70% to about 140% of the flow which would be required to absorb and entrain substantially all hydrogen sulfide in an otherwise indentical feed gas stream except for the substitution of hydrogen sulfide for carbonyl sulfide;
(d) introducing absorbent from said supply thereof and said feed gas stream into said absorber for separation of said carbonyl sulfide from the gas stream;
(e) countercurrently contacting said feed gas stream in said absorber with absorbent at a flow within said effective flow range to absorb and entrain substantially all carbonyl sulfide in the feed gas stream while maintaining most of the absorbent in the liquid state at substantially said pressure and temperature, the balance of the absorbent being vaporized by the heat of condensation;
and
(f) withdrawing from said absorption column a substantially completely desulfurized residual gas stream containing said relatively lower boilding point gas and a mixture of the still liquid absorbent and gases absorbed or entrained therewith.

4 more elements

Dependencies are inferred from the claim text.

Gas separation process

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Gas separation process

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Abstract

Claims44