Process and apparatus for production of ammonia synthesis gas and pure methane by cryogenic separation

Abstract

A process for the production of ammonia synthesis gas and pure methane by cryogenic separation of a feed gas containing at least 75% hydrogen as well as methane and nitrogen, the feed gas is cooled in a heat exchanger and partially condensed, the partially condensed feed is sent to a phase separator, the gas from the phase separator is sent to a nitrogen wash column, liquid nitrogen is sent to the top of the nitrogen wash column and ammonia synthesis gas is removed from the top of the nitrogen wash column, the liquid from the phase separator is expanded and sent to a separation column, a nitrogen enriched gas stream is removed from the top of the column and a nitrogen depleted liquid stream rich in methane is removed from the bottom of the column and the nitrogen depleted liquid stream rich in methane is vaporized to form a pure methane product.

1 - 15 . (canceled) 
     
     
         16 . A process for the production of ammonia synthesis gas and pure methane by cryogenic separation of a feed gas containing at least 75% hydrogen as well as methane and nitrogen, the process comprising the steps of:
 cooling and partially condensing the feed gas in a heat exchanger to form a partially condensed feed;   introducing the partially condensed feed to a phase separator;   introducing gas from the phase separator to a nitrogen wash column;   introducing liquid nitrogen to the top of the nitrogen wash column;   withdrawing ammonia synthesis gas from the top of the nitrogen wash column;   withdrawing liquid from the phase separator and expanding the liquid before sending the liquid to a separation column;   withdrawing a nitrogen enriched gas stream from the top of the separation column;   withdrawing a nitrogen depleted liquid stream rich in methane from the bottom of the separation column; and   vaporizing the nitrogen depleted liquid stream rich in methane to form a pure methane product.   
     
     
         17 . The process according to  claim 16 , wherein the feed gas comprises at least 5% nitrogen. 
     
     
         18 . The process according to  claim 16 , wherein the separation column contains a bottom reboiler and at least a part of the feed gas and/or a gas derived from the feed gas is used to heat the bottom reboiler. 
     
     
         19 . The process according to  claim 16 , wherein feed gas is cooled and partially condensed to form a gas and a liquid and at least a part of the gas resulting from the partial condensation is used to reboil the separation column. 
     
     
         20 . The process according to  claim 16 , wherein liquid from the bottom of the nitrogen wash column is sent to the top of the separation column. 
     
     
         21 . The process according to  claim 16 , wherein the separation column has a top condenser and wherein liquid nitrogen is vaporised in the top condenser, the nitrogen enriched gas stream is partially condensed in the top condenser and the liquid from the phase separator is sent to an intermediate region of the separation column. 
     
     
         22 . The process according to any of  claim 16 , wherein the separation column has no top condenser and wherein liquid from the phase separator is sent to the top of the separation column. 
     
     
         23 . The process according to  claim 22 , wherein liquid from the bottom of the nitrogen wash column is vaporized in the heat exchanger. 
     
     
         24 . The process according to  claim 16 , wherein the liquid sent to the separation column from the phase separator contains at least 65% methane and at least 5% nitrogen. 
     
     
         25 . The process according to  claim 16 , wherein the liquid sent to the separation column from the phase separator contains at least 70% methane and at least 5% nitrogen. 
     
     
         26 . The process according to  claim 16 , wherein the liquid sent to the separation column from the phase separator contains at least 70% methane and at least 10% nitrogen. 
     
     
         27 . An apparatus for the production of ammonia synthesis gas and pure methane by cryogenic separation of a feed gas containing at least 75% hydrogen as well as methane and nitrogen, the apparatus comprising:
 a heat exchanger configured to cool and partially condense the feed gas;   a phase separator in fluid communication with the heat exchanger, the phase separator configured to receive a partially condensed feed from the heat exchange and separate the partially condensed feed into a liquid and a gas;   a nitrogen wash column in fluid communication with a gas outlet of the phase separator such that the nitrogen wash column is configured to receive gas from the phase separator;   a conduit for sending liquid nitrogen to the top of the nitrogen wash column;   a conduit for removing ammonia synthesis gas from the top of the nitrogen wash column;   a valve for expanding liquid from the phase separator connected to the separation column via a conduit;   a conduit for removing a nitrogen enriched gas stream from the top of the separation column;   a conduit for removing nitrogen depleted liquid stream rich in methane from the bottom of the separation column; and   a device configured to vaporize the nitrogen depleted liquid stream rich in methane to form a pure methane product.   
     
     
         28 . The apparatus according to  claim 27 , wherein the separation column has a bottom reboiler and comprising a conduit for sending at least a part of the feed gas and/or a gas derived from the feed gas to heat the bottom reboiler. 
     
     
         29 . The apparatus according to  claim 28 , further comprising means for cooling and partially condensing the feed gas to form a gas and a liquid and means for sending at least a part of the gas resulting from the partial condensation to the reboiler. 
     
     
         30 . The apparatus according to  claim 27 , further comprising a conduit for sending liquid from the bottom of the nitrogen wash column to the top of the separation column. 
     
     
         31 . The apparatus according to  claim 27 , wherein the separation column has a top condenser and comprising a conduit for sending liquid nitrogen to the top condenser, a conduit for sending the nitrogen enriched gas stream to the top condenser and a conduit for sending the liquid from the phase separator to an intermediate region of the separation column. 
     
     
         32 . The apparatus according to  claim 27 , wherein the separation column has no top condenser and comprising a conduit for sending liquid from the phase separator to the top of the separation column. 
     
     
         33 . The apparatus according to  claim 32 , further comprising a conduit for sending liquid from the bottom of the nitrogen wash column to be vaporised in the heat exchanger.