Process and apparatus for production of carbon monoxide by partial condensation

Abstract

A process for separating a mixture of hydrogen, methane and carbon monoxide by cryogenic distillation. The mixture is cooled in a first heat exchanger and is partially condensed in at least one second heat exchanger which is a bottom reboiler of a first or second column of the column system and at least one portion of the liquid produced by the partial condensation is sent to an intermediate level of the first column.

What is claimed is: 
     
         1 . A process for separating a mixture of hydrogen, methane and carbon monoxide by cryogenic distillation in a column system comprising a first column and a second column, comprising:
 i. cooling the mixture in a first heat exchanger and partially condensing at least one portion thereof in at least one second heat exchanger which is a bottom reboiler of the second column of the column system and at least one portion of the liquid produced by the partial condensation, or a liquid derived therefrom, by at least one step of partial condensation is sent to an intermediate level of the first column, only the at least one portion of the mixture and bottom liquid from the second column exchanging heat in the second heat exchanger, the vaporized bottom liquid being sent back to the column from which it originates,   ii. withdrawing a hydrogen-enriched overhead gas from the first column and reheating the hydrogen-enriched overhead gas in the first heat exchanger,   iii. withdrawing a liquid enriched in carbon monoxide and in methane from the bottom of the first column and sending it to at least one intermediate level of the second column,   iv. withdrawing a methane-rich liquid from the bottom of the second column and withdrawing a fluid rich in carbon monoxide from the top of the second column, and   v. producing refrigeration to keep the process cold by means of a refrigeration cycle.   
     
     
         2 . The process according to  claim 1 , in which a portion of the cooled mixture is sent to the second heat exchanger which is a reboiler of the first column. 
     
     
         3 . The process according to  claim 1 , in which at least one portion of the cooled mixture is sent to be cooled to the second exchanger which is a reboiler of the second column and then the at least one portion of the cooled mixture is sent to a third exchanger which is a reboiler of the first column. 
     
     
         4 . The process according to  claim 1 , in which at least one portion of the cooled mixture is sent to be partially condensed in the second exchanger which is a reboiler of the second column to produce a gas and a liquid, then the gas is sent to a third exchanger which is a reboiler of the first column and at least one portion of the liquid produced by at least partial condensation of the gas in the third exchanger is sent to the intermediate point of the first column. 
     
     
         5 . The process according to  claim 1 , in which a condensed portion produced following at least one step of partial condensation of the mixture, is sent to the top of the first column of the column system. 
     
     
         6 . The process according to  claim 1 , in which the first column has a bottom reboiler and has no overhead condenser. 
     
     
         7 . The process according to  claim 1 , in which the mixture is cooled in the first heat exchanger to an intermediate temperature thereof and then leaves the first heat exchanger before being sent to the reboiler. 
     
     
         8 . The process according to  claim 1 , in which the fluid rich in carbon monoxide from the top of the second column and/or the hydrogen-enriched overhead gas from the first column is (are) cooled in the first heat exchanger from the cold end of the first heat exchanger. 
     
     
         9 . An apparatus for separating a mixture of hydrogen, methane and carbon monoxide by cryogenic distillation, said apparatus comprising a column system comprising a first column and a second column, a first heat exchanger, a second heat exchanger, a means for sending the mixture to be cooled to the first heat exchanger, a means for sending the cooled mixture to be partially condensed to at least the second heat exchanger which is a bottom reboiler of the second column, a means for sending to an intermediate level of the first column at least one portion of the liquid produced by the partial condensation or a liquid derived from this liquid by at least one step of partial condensation, only the mixture and bottom liquid from the second column exchanging heat in the second heat exchanger, a means for sending the vaporized bottom liquid back to the second column, a means for withdrawing a hydrogen-enriched overhead gas from the first column, a means for sending the overhead gas to be reheated to the first heat exchanger, a means for withdrawing a liquid enriched in carbon monoxide and in methane from the bottom of the first column, a means for sending the liquid enriched in carbon monoxide and in methane to at least one intermediate level of the second column, a means for withdrawing a methane-rich liquid from the bottom of the second column, a means for withdrawing a fluid rich in carbon monoxide from the top of the second column and a refrigeration cycle to produce refrigeration to keep the process cold.