US 4,270,937 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; condensing CO.sub.2 from the residual gas stream at such pressure, preferably by indirect heat exchange; contacting the residual gas stream at such pressure with a second refrigerant-absorbent below the triple point temperature of carbon dioxide, and separating additional carbon dioxide therewith. The second refrigerant-absorbent is preferably a liquid-solid slurry comprising an organic liquid vehicle and carbon dioxide in the solid phase to provide in situ refrigeration by melting of the solid phase. The final, residual gas stream is heat exchanged to recover its refrigeration potential. 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.

Claims45

Dependent claims

A process for separating one or more relatively high boiling point gases from a gas mixture also containing one or more lower boiling point gases, comprising the steps of contacting the gas mixture first with one and then with the other of the following two sorbents:

(a) liquid carbon dioxide, and
(b) particulate solids having a temperature below the triple point temperature of carbon dioxide, said particulate solids being caused to undergo a change of phase, in whole or in part, during contact with said gas mixture;
and, after each such contact, separating sorbent together with relatively high boiling point gas sorbed thereby from a residual portion of said gas mixture;
and, in each instance, separating sorbent from the sorbed gas for reuse of the sorbent in the process.

1 more element

A process for separating primarily acid gases from a pressurized gas mixture also containing lower boiling point components to be concentrated, comprising the steps of

(a) supplying the pressurized gas mixture to at least one separating zone in a substantially anhydrous condition and at a temperature that is substantially the dew point temperature of the gas mixture at its pressure in said separating zone;
(b) contacting the pressurized gas mixture in said zone or zones with liquid carbon dioxide to absorb sulfur-containing components of the pressurized gas mixture;
(c) separating liquid carbon dioxide and absorbed sulfur-containing gas from a first residual portion of said pressurized gas mixture;
(d) cooling said first residual gas mixture portion in a cooling zone to below its dew point temperature at its pressure in said cooling zone to condense carbon dioxide therefrom;
(e) separating from a second residual portion of said gas mixture the liquid carbon dioxide condensed from said first residual gas mixture portion;
(f) contacting said second residual gas mixture portion in at least one subsequent separating zone with a refrigerant-absorbent comprising a particulate solid having a temperature below the triple point temperature of carbon dioxide, said particulate solid being caused to undergo a change of phase, in whole or in part, to condense carbon dioxide from the second residual gas mixture portion;
and
(g) separating the refrigerant-absorbent and condensed or frozen carbon dioxide entrained therewith from a third residual portion of said gas mixture in which said lower boiling components have thus been concentrated.

5 more elements

A process for separating carbon dioxide and other relatively high boiling point gas from a gas mixture also containing at least one lower boiling point component to be concentrated, comprising the steps of

(a) supplying the gas mixture to at least one separating zone in a substantially anhydrous condition, at a pressure of at least 250 psia, and at a temperature that is substantially the dew point temperature of the gas mixture as said pressure;
(b) contacting the gas mixture in said zone or zones at said temperature and pressure with liquid carbon dioxide to absorb other relatively high boiling point gas from the gas mixture;
(c) separating liquid carbon dioxide and absorbed gas from a first residual portion of said gas mixture;
(d) while substantially maintaining said pressure, reducing the temperature of said first residual gas mixture portion in a cooling zone to below its dew point temperature at its pressure in the said cooling zone to condense carbon dioxide therefrom;
(e) separating from a second residual portion of said gas mixture the liquid carbon dioxide condensed from said first residual gas mixture portion;
(f) while continuing to substantially maintain said pressure, contacting said second residual gas mixture portion in at least one subsequent separating zone with a refrigerant-absorbent in the form of a slurry of a particulate solid in a liquid vehicle, said slurry having a temperature below the triple point temperature of carbon dioxide so as to condense carbon dioxide from the second residual gas mixture portion;
(g) separating a refrigerant-absorbent residue and condensed carbon dioxide entrained therewith from a third residual portion of said gas mixture in which said lower boiling components have thus been concentrated;
(h) lowering the pressure of the separated refrigerant-absorbent residue and condensed carbon dioxide entrained therewith to evolve carbon dioxide therefrom while cooling a residual mixture of liquid vehicle and carbon dioxide to regenerate refrigeration absorbent with an excess of said vehicle;
(i) separating the excess vehicle from the regenerated refrigerant absorbent;
(j) using the regenerated refrigerant-absorbent to contact more of said second residual gas mixture portion in said at least one subsequent separating zone;
(k) contacting said third residual gas mixture portion at said pressure with the excess refrigerant-absorbent vehicle separated in step (i) to absorb additional carbon dioxide from the third residual gas mixture portion;
and
(i) recovering a finally concentrated mixture of said lower boiling point components from said excess refrigerant-absorbent vehicle and absorbed carbon dioxide.

10 more elements

A process for separating carbon dioxide from a pressurized gaseous mixture thereof with other, lower boiling gas, comprising the steps of moving a stream of said gas mixture through a contact zone in countercurrent contact with a flow of a sorbent initially comprising a particulate solid suspended in a liquid vehicle and having a temperature substantially below the triple point temperature of carbon dioxide, said particulate solid being caused to undergo a change of phase, in whole or in part, during contact with said gas mixture, whereby carbon dioxide is condensed from said gas mixture and is entrained with said sorbent and particulate material is melted to a liquid in said change of phase and augments said liquid vehicle of said sorbent, separating a gas mixture stream largely depleted of carbon dioxide from the flow of sorbent entering said contact zone, separating the sorbent and entrained, condensed carbon dioxide from the gas mixture stream entering said contact zone, reducing the pressure on the sorbent and entrained, condensed carbon dioxide to evolve carbon dioxide gas while cooling the sorbent below the triple point temperature of carbon dioxide and regenerating the sorbent to its initial condition, separating the so-formed gaseous carbon dioxide from the thus-regenerated sorbent, and returning the regenerated sorbent to said contact zone for reuse therein.

Dependencies are inferred from the claim text.

Gas separation process

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Gas separation process

Life of this patent

Abstract

Claims45