Process and Apparatus for the Liquefaction of Carbon Dioxide

Abstract

Apparatus for carbon dioxide liquefaction comprising a flow channel for carbon dioxide passage from an inlet port to an outlet port. The channel comprises a plurality of compressors ( 2, 5, 8 ) and coolers ( 4, 7, 9, 10, 13 ) arranged in series with an expansion chamber ( 14, 15 ) in said flow channel downstream of the final compressor ( 8 ) and cooler ( 9, 10, 13 ). The apparatus also comprises a recirculation channel ( 16 ) arranged to return gaseous carbon dioxide from said expansion chamber ( 15 ) into said flow channel ( 3 ) upstream of said final compressor ( 8 ) and cooler ( 9, 10, 13 ).

1 . A process for the production from a feed gas which comprises carbon dioxide of liquid carbon dioxide at a desired temperature and pressure which temperature is below ambient, above the triple point temperature for carbon dioxide and below the critical point temperature for carbon dioxide and which pressure is above ambient, above the triple point pressure for carbon dioxide and below the critical point pressure for carbon dioxide, said process comprising: feeding said feed gas into the entry port of a liquefaction apparatus having a flow path from said entry port to an exit port connected to an expansion chamber; flowing said gas as a fluid along the flow path through said apparatus and subjecting said fluid to a plurality of compression and cooling cycles whereby to generate liquid or super-critical carbon dioxide having a temperature and pressure above said desired temperature and pressure; passing said liquid or super-critical carbon dioxide through said exit port into said expansion chamber whereby to generate in said chamber gaseous carbon dioxide and liquid carbon dioxide at said desired temperature and pressure; and recycling said gaseous carbon dioxide into fluid flowing through a said compression and cooling cycle; and optionally withdrawing said liquid carbon dioxide at said desired temperature and pressure from said expansion chamber. 
     
     
         2 . A process as claimed in  claim 1 , wherein one or more of the compression cycles additionally involves an expansion step. 
     
     
         3 . A process as claimed in  claim 1 , wherein the fluid flowing to each compression cycle is monophasic. 
     
     
         4 . A process as claimed in  claim 1 , wherein the expansion chamber is provided with a liquid removal port through which liquid carbon dioxide is withdrawn. 
     
     
         5 . A process as claimed in  claim 1 , wherein the recycled carbon dioxide passes through one or more heat exchangers. 
     
     
         6 . A process as claimed in  claim 1 , wherein the recycled carbon dioxide is returned to the fluid flow at an upstream point. 
     
     
         7 . A process as claimed in  claim 1 , comprising 4 compression cycles. 
     
     
         8 . A process as claimed in  claim 1 , wherein water is removed after at least one compression cycle and before the final compression cycle. 
     
     
         9 . Apparatus for carbon dioxide liquefaction comprising a flow channel for carbon dioxide passage from an inlet port to an outlet port, said channel comprising a plurality of compressors and coolers arranged in series, with an expansion chamber in said flow channel downstream of the final compressor and cooler and with a recirculation channel arranged to return gaseous carbon dioxide from said expansion chamber into said flow channel upstream of said final compressor and cooler. 
     
     
         10 . Apparatus as claimed in  claim 9 , wherein the expansion chamber is provided with a liquid removal port such that liquid carbon dioxide can be withdrawn.