Method for purifying, cooling and separating a gaseous mixture and associated apparatus

Abstract

The invention relates to a method for cooling, purifying and separating a gaseous mixture containing at least one impurity, in which the gaseous mixture is cooled to a temperature no higher than the temperature at which the at least one impurity solidifies in a heat exchanger having cooling passages, the cooling passages being at least partially covered with a coating and/or physically treated and/or chemically treated, the coating and/or the treatment serving to limit or even prevent the solidified impurity from forming and/or adhering to a surface of the passages; at least one portion of the solidified impurity exiting the cooling passages of the heat exchanger is collected; and the gaseous mixture is withdrawn from the heat exchanger.

1 - 16 . (canceled) 
     
     
         17 . A process for cooling, purifying and separating a gas mixture ( 1 ) containing at least one impurity of a gas mixture, the process comprising the steps of:
 cooling the gas mixture containing at least one impurity to a temperature below or equal to that at which the at least one impurity solidifies in a heat exchanger, the heat exchanger comprising at least one exchange body having cooling passages configured to reduce the adhesion of the solidified impurity on a surface of the passages;   collecting at least one portion of the solidified impurity leaving the cooling passages of the heat exchanger and/or at an intermediate level of the heat exchanger;   withdrawing the gas mixture from the heat exchanger;   sending the gas mixture to a system of columns under conditions effective for separating the gas mixture by cryogenic distillation to produce at least a first fluid and a second fluid, wherein each of the first fluid and the second fluid are enriched in one component of the gas mixture,   wherein the cooling passages are at least partially covered by a coating and/or physically treated and/or chemically treated, the coating and/or the treatment serving to at least limit the formation and/or the adhesion of the solidified impurity on a surface of the cooling passages, and   wherein:   i) during substantially the entire time that the separation by distillation is carried out, the gas mixture is cooled in each exchange body having cooling passages configured to reduce the adhesion of the solidified impurity on a surface of the passages, and/or   ii) the first fluid and the second fluid are reheated in each exchange body having cooling passages designed to reduce the adhesion of the solidified impurity on a surface of the passages.   
     
     
         18 . The process as claimed in  claim 17 , wherein the gas mixture is purified to remove at least one fraction of the at least one impurity upstream of the heat exchanger, said one fraction representing between 20% and 95% of the impurity contained in the gas mixture upstream of the process. 
     
     
         19 . The process as claimed in  claim 17 , wherein at least one portion of the solidified impurity is collected downstream of the heat exchanger, by means of a phase separator and/or an endless screw. 
     
     
         20 . The process as claimed in  claim 17 , wherein the cooled gas mixture is treated downstream of the heat exchanger and/or at at least one intermediate level of the heat exchanger in order to eliminate the impurity in gaseous and/or liquid and/or solid form. 
     
     
         21 . The process as claimed in  claim 20 , wherein the gas mixture is cooled in the heat exchanger firstly to a temperature below or equal to the liquefaction temperature of the at least one impurity but above its solidification temperature, at least one portion of the gas mixture is taken out of the exchanger in order to eliminate a portion of the impurity in liquid form and at least one portion of the gas mixture containing some impurity is sent back to the heat exchanger in order to cool the at least one portion of the gas mixture containing some impurity to the solidification temperature of said impurity. 
     
     
         22 . The process as claimed in  claim 20 , wherein at least 50% of the impurity present at the inlet of the heat exchanger, referred to as the hot end, is eliminated by collecting the impurity downstream of the heat exchanger after cooling up to the outlet of the exchanger at the cold end. 
     
     
         23 . The process as claimed in  claim 22 , wherein the hot end of the heat exchanger is placed at a higher level than that of the cold end. 
     
     
         24 . The process as claimed in  claim 17 , wherein the hot end of the heat exchanger is placed at a lower level than that of the cold end or than that of an intermediate level of the exchanger in the case of an inverted U-shaped exchanger and at least 50% of the impurity present in the gas mixture to be cooled is eliminated at the inlet of the heat exchanger, referred to as the hot end, by collecting the impurity in solid or liquid form at the hot end of the exchanger where the impurity drops by gravity after cooling in the heat exchanger. 
     
     
         25 . The process as claimed in  claim 17 , wherein the gas mixture is:
 air with the at least one impurity being selected from the group consisting of water, carbon dioxide, and combinations thereof, or   a mixture of gases, having a main component selected from the group consisting of hydrogen, carbon monoxide, methane, and combinations thereof, with the at least one impurity being selected from the group consisting of water, carbon dioxide, and combinations thereof, or   a mixture of gases, having the main component of carbon dioxide and at least a second component selected from the group consisting of hydrogen, carbon monoxide, methane, oxygen, nitrogen, argon, and combinations thereof, with the at least one impurity being water.   
     
     
         26 . The process as claimed in  claim 17 , further comprising the step of treating at least one surface of the cooling passages thereby producing a surface that is hydrophobic and/or superhydrophobic and/or that has hydrophobic and hydrophilic, and/or hygroscopic zones, in order to at least limit the formation and/or the adhesion of solidified impurities. 
     
     
         27 . The process as claimed in  claim 17 , wherein the heat exchanger comprises at least one passage for reheating a fluid, the at least one reheating passage not having been treated or coated in order to at least limit the formation and/or the adhesion of solidified impurities. 
     
     
         28 . The process as claimed in  claim 17 , wherein at least one portion of the solidified impurity leaving the cooling passages of the heat exchanger is sent back to the heat exchanger to be reheated. 
     
     
         29 . The process as claimed in  claim 17 , wherein at least one portion of the solidified impurity leaving the cooling passages of the heat exchanger and/or at an intermediate level of the heat exchanger is collected and the gas mixture finds itself liquefied or is liquefied by a subsequent step downstream of the exchanger and/or is separated at a subambient temperature downstream of the exchanger, optionally after elimination, downstream of the exchanger, of remaining impurities that would be solidified at this subambient temperature. 
     
     
         30 . The process as claimed in  claim 17 , wherein frigories are supplied to the gas mixture which is cooled at at least one intermediate point of the heat exchanger downstream or upstream of a point for drawing off at least one portion of the solidified or liquefied impurity at an intermediate level of the heat exchanger. 
     
     
         31 . The process as claimed in  claim 17 , wherein the gas mixture is at least partially liquefied within the heat exchanger and is withdrawn from the cold end of the heat exchanger. 
     
     
         32 . The process as claimed in  claim 17 , wherein the gas mixture is cooled downstream and 
     
     
         33 . An apparatus for cooling and purifying a gas mixture containing at least one impurity comprising a heat exchanger comprising at least one, or even two, exchange bodies, each having cooling passages designed to reduce the adhesion of the solidified impurity on at at least one portion of the surface of the passages and reheating passages, means for sending the gas mixture containing at least one impurity to be cooled in the cooling passages of the exchange body or bodies to a temperature below or equal to that at which the at least one impurity solidifies and means for drawing off the, optionally at least partially liquefied, gas mixture from the exchange body or bodies, preferably at the cold end, means for sending a gas to be reheated in the reheating passages and means for collecting at least one portion of the solidified impurity leaving the cooling passages of the heat exchanger and/or at an intermediate level of the heat exchanger and means for taking the gas mixture of the at least one impurity out of the heat exchanger, wherein the cooling passages of each exchange body are at least partially covered by a coating and/or physically treated and/or chemically treated, the coating and/or the treatment serving to limit, or even prevent, the formation and/or the adhesion of the solidified impurity on a surface of the passages and in that reheating passages are connected to means for transporting a first gas to be reheated and other reheating passages are connected to means for transporting a second gas to be reheated. 
     
     
         34 . The apparatus as claimed in  claim 33 , wherein the number of cooling passages is not equal to the number of reheating passages connected to the means for transporting the first gas and the number of cooling passages is not equal to the number of reheating passages connected to the means for transporting the second gas.