US 4,102,659 A · Separation of H.sub.2, CO, and CH.sub.4 synthesis gas with methane wash

Abstract

A process for separation of a synthesis feed gas mixture containing hydrogen, carbon monoxide and methane. The feed gas mixture is countercurrently contacted with methane wash liquid in a first adsorption zone and the recovered absorber bottoms liquid is contacted with hydrogen rich vapor in a second adsorption zone to recover residual hydrogen gas as overhead. Hydrogen rich vapor is generated for the second absorption zone by vaporization of second absorption zone bottoms liquid, with the bottoms liquid recovered from the second absorption zone being fractionated to recover carbon monoxide overhead gas. The process achieves the rejection of hydrogen impurity in the second absorption and associated vaporization steps with minimum degradation of refrigeration temperature levels in the process and high recovery of carbon monoxide product.

Claims28

Dependent claims

A process for the separation of a feed gas mixture containing hydrogen, carbon monoxide and methane comprising the steps of:

(a) cooling the feed gas mixture;
(b) countercurrently contacting the cooled feed gas mixture with a methane wash liquid in a first absorption zone to recover hydrogen gas as overhead and bottoms liquid comprising methane, carbon monoxide and residual hydrogen;
(c) throttling the bottoms liquid from the first absorption zone to lower pressure;
(d) countercurrently contacting the throttled bottoms liquid with hydrogen rich vapor in a second absorption zone for absorption of carbon monoxide from the hydrogen rich vapor by the throttled bottoms liquid therein to recover residual hydrogen gas as overhead and bottoms liquid enriched in carbon monoxide, and warming second absorption zone bottoms liquid to vaporize a gaseous fraction therefrom containing hydrogen and carbon monoxide, as said hydrogen rich vapor for said second absorption zone;
(e) fractionating the bottoms liquid recovered from said second absorption zone in a fractionation zone to recover overhead gas comprising carbon monoxide and bottoms liquid comprising methane;
and
(f) recirculating at least part of the bottoms liquid recovered from the fractionation zone to the first absorption zone as the methane wash liquid therefor.

4 more elements

A process for the separation of a feed gas mixture containing hydrogen, carbon monoxide and methane comprising the steps of:

(a) cooling the feed gas mixture;
(b) countercurrently contacting the cooled feed gas mixture with a methane wash liquid in a first absorption zone to recover hydrogen gas as overhead product and bottoms liquid comprising methane, carbon monoxide and residual hydrogen;
(c) throttling the bottoms liquid from the first absorption zone to lower pressure;
(d) countercurrently contacting the throttled bottoms liquid with hydrogen rich vapor in a second absorption zone for absorption of carbon monoxide from the hydrogen rich vapor by the throttled bottoms liquid therein to recover residual hydrogen gas as overhead and bottoms liquid enriched in carbon monoxide;
(e) withdrawing bottoms liquid from the second absorption zone and warming same to vaporize a gaseous fraction therefrom containing hydrogen and carbon monoxide, separating the vaporized gaseous fraction from the warmed bottoms liquid, and passing the vaporized gaseous fraction to the second absorption zone as the hydrogen rich vapor therefor, the warming being conducted so as to maintain a temperature gradient in the fluid being warmed from the initial part of the warming to the final part thereof;
(f) fractionating the warmed bottoms liquid in a fractionation zone to recover overhead gas comprising carbon monoxide and bottoms liquid comprising methane;
(g) heat exchanging the bottoms liquid recovered from the fractionation zone with the bottoms liquid recovered from the second absorption zone for the vaporization warming of the latter in step (e) and cooling of the fractionation zone bottoms liquid;
(h) pumping the cooled fractionation zone bottoms liquid to higher pressure and subcooling a portion of same, passing the subcooled portion to the first absorption zone as the methane wash liquid therefor and warming the remaining portion of the cooled pumped fractionation zone bottoms liquid for vaporization thereof by heat exchange with the feed gas mixture as at least part of the cooling of step (a);
(i) dividing the overhead gas recovered from the fractionation zone in step (f) into two portions comprising a first portion and a second portion;
(j) heat exchanging the second portion of the overhead gas recovered from the fractionation zone for warming thereof with the feed gas mixture as at least part of the cooling of the latter in step (a);
(k) comprsssing the heat exchanged overhead gas second portion to higher pressure and withdrawing a part thereof as carbon monoxide product gas;
(l) cooling the remaining part of the compressed overhead gas portion and dividing same into a minor portion for isentropic expansion and a major heat pumping fluid portion;
(m) isentropically expanding the minor portion and joining the isentropically expanded minor portion with the first portion of the overhead gas recovered from the fractionation zone in step (f) to form a recycle minor part gas;
(n) warming the recycle minor part gas and joining same with the heat exchanged overhead gas second portion from step (j) for compression therewith in step (k);
(o) dividing the major heat pumping fluid portion into two parts, cooling one part for condensation thereof to form cooled liquid by heat exchange with fractionation zone bottoms liquid for vaporization of the latter to provide reboil vapor for the fractionation zone, subcooling the cooled liquid one part by heat exchange with the recycle minor part gas for the warming of the latter in step (n), throttling the other part of the major heat pumping fluid portion to low pressure and joining the subcooled liquid one part with the throttled other part to form a heat pumping gas-liquid mixture;
(p) throttling the heat pumping gas-liquid mixture to lower pressure and warming same to form a first gaseous fraction and a first liquid fraction therefrom by heat exchange with a portion of the bottoms liquid recovered from the fractionation zone being recirculated to the first absorption zone as the methane wash liquid therefor, for the subcooling of the latter in step (h);
(q) separating the first gaseous fraction of the heat pumping gas-liquid mixture from the first liquid fraction thereof;
(r) throttling the separated first liquid fraction of the heat pumping gas-liquid mixture to still lower pressure and warming same to form a second gaseous fraction and a second liquid fraction therefrom by heat exchange with the feed gas mixture as at least part of the cooling in step (a);
(s) separating the second gaseous fraction of the heat pumping gas-liquid mixture first liquid fraction from the second liquid fraction thereof;
(t) heat exchanging the separated second liquid fraction with fractionation zone overhead to provide reflux cooling for the fractionation zone;
and
(u) joining the second gaseous fraction and the first gaseous fraction with the recycle minor part gas.

19 more elements

A process for the separation of a feed gas mixture containing hydrogen, carbon monoxide and methane comprising the steps of:

(a) first partial cooling the feed gas mixture to condense a first feed liquid fraction therefrom;
(b) separating the first feed liquid fraction from the uncondensed first partial cooled feed gas mixture;
(c) throttling the separated first feed liquid fraction to a lower pressure level;
(d) second partial cooling the uncondensed first partial cooled feed gas mixture to condense a second feed liquid fraction from the uncondensed second partial cooled feed gas mixture;
(e) throttling the separated second feed liquid fraction to said lower pressure level of step (c);
(f) joining the throttled second feed liquid fraction with the throttled first feed liquid fraction to form a combined feed liquid;
(g) warming the combined feed liquid for partial vaporization thereof by heat exchange with the uncondensed first partial cooled feed gas mixture for the second partial cooling of the latter;
(h) separating the vapor portion of the partially vaporized combined feed liquid from the liquid portion thereof;
(i) joining the separated vapor portion of step (h) with the feed gas mixture for said first partial cooling of the feed gas mixture in step (a);
(j) countercurrently contacting the uncondensed second partial cooled feed gas mixture of step (d) with a methane wash liquid in a first absorption zone to recover hydrogen gas as overhead and bottoms liquid comprising methane, carbon monoxide and residual hydrogen;
(k) throttling the bottoms liquid from the first absorption zone to lower pressure;
(l) countercurrently contacting the throttled bottoms liquid of step (k) with hydrogen rich vapor in a second absorption zone for absorption of carbon monoxide from the hydrogen rich vapor by the throttled bottoms liquid therein to recover residual hydrogen gas as overhead and bottoms liquid enriched in carbon monoxide, and warming second absorption zone bottoms liquid to vaporize a gaseous fraction thereof containing hydrogen and carbon monoxide, as said hydrogen rich vapor for said second absorption zone;
(m) fractionating the bottoms liquid recovered from said second adsorption zone in a fractionation zone to recover overhead gas comprising carbon monoxide and bottoms liquid comprising methane;
(n) passing the liquid portion separated from the partially vaporized combined feed liquid in step (h), comprising substantially pure carbon monoxide, to the fractionation zone in step (m) for enhancement of the purity of carbon monoxide in the overhead gas recovered therefrom;
and
(o) recirculating at least part of the bottoms liquid recovered from the fractionation zone to the first absorption zone as the methane wash liquid therefor.

13 more elements

Dependencies are inferred from the claim text.

Separation of H.sub.2, CO, and CH.sub.4 synthesis gas with methane wash

Life of this patent

Separation of H.sub.2, CO, and CH.sub.4 synthesis gas with methane wash

Life of this patent

Abstract

Claims28