Method And Device For Separating A Mixture Of Hydrogen, Methane And Carbon Monoxide By Cryogenic Distillation

Abstract

A method and to a device for separating a mixture of hydrogen, methane and carbon monoxide by cryogenic distillation is provided. In particular, the present invention relates to a method for producing a mixture of H 2 /CO with a low CH 4 content, possibly combined with the production of CH 4 in liquid form.

1 - 13 . (canceled) 
   
   
       14 . A method for separating a mixture of hydrogen, carbon monoxide and methane by cryogenic distillation, comprising:
 a) cooling the mixture in an exchange line and sending at least a portion of said cooled mixture to a liquid CO scrubbing column,   b) removing a gas at the top of the scrubbing column,   c) removing the bottom liquor from the scrubbing column, and sending said bottom liquor to a CO/CH 4  separation column,   d) removing a CO-rich liquid at the top of the CO/CH 4  separation column, at least partially pressurizing said CO-rich liquid, and at sending at least a portion of said pressurized CO-rich liquid to the top of the scrubbing column, and   e) removing a methane-rich liquid at the bottom of the CO/CH 4  separation column by way of end product, at least some of the separation energy being provided by a closed cycle using a cycle fluid selected from the group consisting of nitrogen, methane, oxygen, argon, helium and hydrogen.   
   
   
       15 . The method of  claim 14 , wherein step c) further comprises removing the bottom liquor from the scrubbing column, purifying said bottom liquor, and sending said bottom liquor to a CO/CH 4  separation column. 
   
   
       16 . The method of  claim 14 , in which the gas removed from the top of the scrubbing column comprises a mixture of H 2  and of CO, containing less than 1 mol % of CH 4 . 
   
   
       17 . The method of  claim 14 , wherein the closed cycle is used to condense the head liquors of the CO/CH 4  column. 
   
   
       18 . The method of  claim 14 , wherein the closed cycle is used for reboiling the bottom liquors of the CO/CH 4  column and/or of a stripping column. 
   
   
       19 . The method of  claim 14 , wherein the closed cycle provides at least some of the energy used to liquefy this CH 4 . 
   
   
       20 . The method of  claim 14 , wherein, at least two liquids of the closed cycle vaporize at least two different pressures in the exchange line. 
   
   
       21 . The method of  claim 14 , wherein at least two of the temperatures selected from the group consisting of the inlet temperature at which the mixture enters the scrubbing column; the temperature of the CO-rich liquid from the CO/CH 4  column; and the temperature of the supercooled liquid methane; differ at most by 5° C.: 
   
   
       22 . The method of  claim 14 , wherein the cycle fluid is methane. 
   
   
       23 . The method of  claim 14 , wherein the cycle fluid is nitrogen. 
   
   
       24 . A device for separating a mixture of hydrogen, carbon monoxide and methane by cryogenic distillation, the device comprising;
 a) a liquid CO scrubbing column,   b) a CO/CH 4  separation column,   c) an exchange line in which the mixture is cooled,   d) means for sending at least some of the cooled mixture to the scrubbing column,   e) means for tapping off a gas at the top of the scrubbing column,   f) means for sending the bottom liquor from the scrubbing column to the CO/CH 4  separation column,   g) means for drawing off a CO-rich liquid from the CO/CH 4  separation column,   h) means for pressurizing at least some of the drawn-off liquid,   i) means for sending at least some of the pressurized liquid to the top of the scrubbing column,   j) means for drawing off a methane-rich liquid at the bottom of the CO/CH 4  separation column by way of end product,   k) a closed cycle using a cycle fluid selected from the group consisting of nitrogen, methane, oxygen, argon, helium and hydrogen; to provide at least some of the separation energy.   
   
   
       25 . The device of  claim 24  further comprising a pump connected to the top of the CO/CH 4  column and to the top of the scrubbing column. 
   
   
       26 . The device of  claim 24 , wherein the closed cycle provides at least some of the energy used to liquefy this CH 4 . 
   
   
       27 . The device of  claim 24 , further comprising a stripping column for purifying the bottom liquor of the scrubbing column upstream of the CO/CH 4  separation column.