Optimized heat exchange in a co2 de-sublimation process

Abstract

The present invention is a process for removing carbon dioxide from a compressed gas stream including cooling the compressed gas in a first heat exchanger, introducing the cooled gas into a de-sublimating heat exchanger, thereby producing a first solid carbon dioxide stream and a first carbon dioxide poor gas stream, expanding the carbon dioxide poor gas stream, thereby producing a second solid carbon dioxide stream and a second carbon dioxide poor gas stream, combining the first solid carbon dioxide stream and the second solid carbon dioxide stream, thereby producing a combined solid carbon dioxide stream, and indirectly exchanging heat between the combined solid carbon dioxide stream and the compressed gas in the first heat exchanger.

What is claimed is: 
     
         1 . A process for removing carbon dioxide from a compressed gas stream comprising:
 a) cooling the compressed gas ( 101 ) in a first heat exchanger ( 102 ),   b) introducing the cooled gas ( 103 ) into a de-sublimating heat exchanger ( 104 ), thereby producing a first solid carbon dioxide stream ( 113 ) and a first carbon dioxide poor gas stream ( 105 ),   c) expanding the carbon dioxide poor gas stream, thereby producing a second solid carbon dioxide stream ( 109 ) and a second carbon dioxide poor gas stream ( 110 ),   d) combining the first solid carbon dioxide stream and the second solid carbon dioxide stream, thereby producing a combined solid carbon dioxide stream ( 114 ), and   e) indirectly exchanging heat between the combined solid carbon dioxide stream and the compressed gas in the first heat exchanger.   
     
     
         2 . The process of  claim 1 , wherein the compressed gas is flue gas. 
     
     
         3 . The process of  claim 1 , wherein the compressed gas is cooled to a temperature higher than the carbon dioxide de-sublimation temperature. 
     
     
         4 . The process of  claim 1 , wherein the second carbon dioxide poor gas stream ( 110 ) is introduced into the de-sublimating heat exchanger ( 104 ) to indirectly exchange heat with the cooled gas ( 103 ). 
     
     
         5 . The process of  claim 1 , wherein after the second carbon dioxide poor gas stream exits the de-sublimating heat exchanger, it ( 111 ) is introduced into the first heat exchanger ( 102 ) to indirectly exchange heat with the compressed gas ( 101 ). 
     
     
         6 . The process of  claim 1 , further comprising introducing the combined solid carbon dioxide stream ( 114 ) into a second heat exchanger ( 117 ), after step d) and before step e), wherein the combined solid carbon dioxide stream indirectly exchanges heat with an external refrigeration loop ( 123 ). 
     
     
         7 . The process of  claim 6 , wherein the external refrigeration loop comprises:
 vaporizing a compressed refrigeration stream ( 125 / 127 ) in the de-sublimating heat exchanger ( 104 ), thereby producing a warmed refrigeration stream ( 129 / 130 / 120 ),   compressing the warmed refrigeration fluid ( 120 ), thereby producing a compressed refrigeration stream ( 122 ), and   condensing the compressed refrigeration stream in a second heat exchanger ( 117 ) by indirectly transferring heat with the combined solid carbon dioxide stream ( 114 / 116 ), thereby producing a cooled refrigeration stream ( 124 ).   
     
     
         8 . The process of  claim 6 , wherein the compressed refrigeration stream ( 122 ) is further warmed ( 123 ) in the first heat exchanger ( 102 ) before indirectly transferring heat with the combined solid carbon dioxide stream. 
     
     
         9 . The process of  claim 6 , wherein the cooled refrigeration stream ( 124 ) is further cooled ( 125 ) in the first heat exchanger ( 102 ), before being compressed.