Method for Separating a Carbon Dioxide-rich Gas by Partial Condensation and Permeation

Abstract

A carbon dioxide-rich gas is cooled in a first heat exchanger; the carbon dioxide-rich gas cooled in the first heat exchanger enters a first phase separator at a first temperature between −50° C. and −53° C.; a carbon dioxide-enriched liquid is drawn from the first phase separator and acts as product; a carbon dioxide-depleted gas from the first separator is reheated in the first exchanger to a second temperature between −35° C. and −45° C., without having been expanded downstream from the first phase separator and enters a permeation unit at the second temperature; the reheated gas is subjected to at least one permeation step in the permeation unit in order to produce at least two fluids which are then reheated in the first exchanger, the fluid from the permeation unit, reheated in the exchanger, which exits the permeation unit at the lowest temperature, being at a temperature of more than −54° C.

1 - 9 . (canceled) 
     
     
         10 . A process for separating a gas rich in carbon dioxide by partial condensation and permeation, the process comprising the steps of:
 cooling the gas rich in carbon dioxide at least in a first heat exchanger;   sending the gas rich in carbon dioxide cooled in the first heat exchanger or a fluid derived from this gas into a first phase separator at a first temperature between −50° C. and −53° C.;   withdrawing a liquid enriched in carbon dioxide from the first phase separator to be used as product or further treating the liquid enriched in carbon dioxide in order to further enrich the liquid enriched in carbon dioxide;   withdrawing a gas depleted in carbon dioxide from the first phase separator and warming the gas in the first exchanger or a second exchanger to a second temperature between −35° C. and −45° C., without having been expanded downstream of the first phase separator; and   sending the gas depleted in carbon dioxide to a permeation unit at the second temperature, wherein the warmed gas undergoes at least one permeation step in the permeation unit in order to produce at least two fluids that are then warmed in the exchanger in which the depleted gas was warmed, the fluid resulting from the permeation unit, warmed in the exchanger, which leaves the permeation unit at the lowest temperature being at a temperature above −54° C.   
     
     
         11 . The process as claimed in  claim 10 , wherein the depleted gas is warmed in the second exchanger and the at least two fluids resulting from the permeation being warmed in the second exchanger, the second exchanger not being used to cool the gas rich in carbon dioxide. 
     
     
         12 . The process as claimed in  claim 11 , wherein a fluid originating from the treatment of the liquid enriched in carbon dioxide is sent to the second exchanger at a temperature below −40° C., in order to warm the depleted gas and the at least two fluids resulting from the permeation. 
     
     
         13 . The process as claimed in  claim 12 , wherein the fluid originating from the liquid treatment is a liquid that contains at least 90% carbon dioxide produced by distillation and expanded in a valve. 
     
     
         14 . The process as claimed in  claim 10 , wherein the depleted gas is warmed in the first exchanger just like the fluids resulting from the permeation. 
     
     
         15 . The process as claimed in  claim 10 , wherein the permeation unit makes it possible to carry out a single permeation step and the permeate and the residue of the permeation step are sent to be warmed in the first or second heat exchanger. 
     
     
         16 . The process as claimed in  claim 10 , wherein the permeation unit makes it possible to carry out a first permeation step, producing a permeate and a residue, at least one portion of the residue then being separated by a second permeation step with an inlet temperature between −40° C. and −45° C., at least two of the fluids chosen from the list at least one portion of a residue from the first step and/or at least one portion of a residue from the second step and/or at least one portion of a permeate from the second step and/or a portion of a permeate from the first step being warmed in the first or second exchanger. 
     
     
         17 . The process as claimed in  claim 10 , wherein the gas rich in carbon dioxide is sent from the first heat exchanger to the first phase separator without having been separated by permeation. 
     
     
         18 . The process as claimed in  claim 10 , wherein the gas rich in carbon dioxide is treated by a step of partial condensation and the gas formed is at least partially condensed in order to form the fluid derived from the gas rich in carbon dioxide which goes into the first phase separator.