System and method of recovering carbon dioxide from an exhaust gas stream

Abstract

A carbon dioxide capture system includes a first heat exchanger configured to exchange heat between an exhaust stream and a lean carbon dioxide effluent stream. The carbon dioxide capture system also includes a first turboexpander including a first compressor driven by a first turbine. The first compressor is coupled in flow communication with the first heat exchanger. The first turbine is coupled in flow communication with the first heat exchanger and configured to expand the lean carbon dioxide effluent stream. The carbon dioxide capture system further includes a carbon dioxide membrane unit coupled in flow communication with the first compressor. The carbon dioxide membrane unit is configured to separate the exhaust stream into the lean carbon dioxide effluent stream and a rich carbon dioxide effluent stream. The carbon dioxide membrane unit is further configured to channel the lean carbon dioxide effluent stream to the first heat exchanger.

What is claimed is: 
     
         1 . A carbon dioxide capture system comprising:
 a first heat exchanger configured to exchange heat between an exhaust stream and a lean carbon dioxide effluent stream;   at least one turboexpander comprising:
 a compressor coupled in flow communication with said first heat exchanger and configured to compress the exhaust stream; and 
 a turbine coupled in flow communication with said first heat exchanger, said compressor driven by said turbine, said turbine configured to expand the lean carbon dioxide effluent stream; and 
   a carbon dioxide membrane unit coupled in flow communication with said compressor, said carbon dioxide membrane unit configured to separate the exhaust stream into the lean carbon dioxide effluent stream and a rich carbon dioxide effluent stream, said carbon dioxide membrane unit further configured to channel the lean carbon dioxide effluent stream to said first heat exchanger.   
     
     
         2 . The carbon dioxide capture system in accordance with  claim 1  further comprising a cryogenic separation unit coupled in flow communication with said carbon dioxide membrane unit, said cryogenic separation unit configured to separate the rich carbon dioxide effluent stream into a carbon dioxide product stream and a recycle stream. 
     
     
         3 . The carbon dioxide capture system in accordance with  claim 1 , wherein said first heat exchanger is coupled to a power production unit, the power production unit configured to channel the exhaust stream to said first heat exchanger. 
     
     
         4 . The carbon dioxide capture system in accordance with  claim 1  further comprising a second heat exchanger configured to exchange heat between the exhaust stream and a cooling fluid stream. 
     
     
         5 . The carbon dioxide capture system in accordance with  claim 4 , wherein said cooling fluid stream comprises cooling water. 
     
     
         6 . The carbon dioxide capture system in accordance with  claim 1 , wherein said at least one turboexpander comprises two turboexpanders. 
     
     
         7 . The carbon dioxide capture system in accordance with  claim 2 , wherein said carbon dioxide membrane unit further comprises an inlet, the recycle stream channeled to said inlet of said carbon dioxide membrane unit. 
     
     
         8 . A method of reducing carbon dioxide in an exhaust stream, said method comprising:
 receiving an exhaust stream;   cooling the exhaust stream by exchanging heat with a lean carbon dioxide effluent stream with a first heat exchanger;   compressing the exhaust stream in a first compressor;   separating the exhaust stream into the lean carbon dioxide effluent stream and a rich carbon dioxide effluent stream in a carbon dioxide membrane; and   expanding the lean carbon dioxide stream in a first turbine, the first turbine configured to drive the first compressor.   
     
     
         9 . The method in accordance with  claim 8  further comprising separating the rich carbon dioxide effluent stream into a carbon dioxide product stream and a recycle stream in a cryogenic separation unit. 
     
     
         10 . The method in accordance with  claim 9  further comprising channeling the recycle stream to an inlet of the membrane separation unit. 
     
     
         11 . The method in accordance with  claim 8 , wherein receiving an exhaust stream comprises receiving an exhaust stream from a power production unit. 
     
     
         12 . The method in accordance with  claim 8  further comprising compressing the exhaust stream in a second compressor. 
     
     
         13 . The method in accordance with  claim 12  further comprising expanding the lean carbon dioxide stream in a second turbine, wherein the second turbine is configured to drive the second compressor. 
     
     
         14 . A mobile carbon dioxide capture system comprising:
 a transport apparatus;   a carbon dioxide capture system disposed on said transport apparatus, said carbon dioxide capture system comprising:
 a first heat exchanger configured to exchange heat between an exhaust stream and a lean carbon dioxide effluent stream; 
 at least one turboexpander comprising:
 a compressor coupled in flow communication with said first heat exchanger and configured to compress the exhaust stream; and 
 a turbine coupled in flow communication with said first heat exchanger, said compressor driven by said turbine, said turbine configured to expand the lean carbon dioxide effluent stream; and 
 
   a carbon dioxide membrane unit coupled in flow communication with said compressor, said carbon dioxide membrane unit configured to separate the exhaust stream into the lean carbon dioxide effluent stream and a rich carbon dioxide effluent stream, said carbon dioxide membrane unit further configured to channel the lean carbon dioxide effluent stream to said first heat exchanger.   
     
     
         15 . The mobile carbon dioxide capture system in accordance with  claim 14  further comprising a cryogenic separation unit coupled in flow communication with said carbon dioxide membrane unit, said cryogenic separation unit configured to separate the rich carbon dioxide effluent stream into a carbon dioxide product stream and a recycle stream. 
     
     
         16 . The mobile carbon dioxide capture system in accordance with  claim 14 , wherein said first heat exchanger is coupled to a power production unit, the power production unit configured to channel the exhaust stream to said first heat exchanger. 
     
     
         17 . The mobile carbon dioxide capture system in accordance with  claim 14  further comprising a second heat exchanger configured to exchange heat between the exhaust stream and a cooling fluid stream. 
     
     
         18 . The mobile carbon dioxide capture system in accordance with  claim 17 , wherein said cooling fluid stream comprises cooling water. 
     
     
         19 . The mobile carbon dioxide capture system in accordance with  claim 14 , wherein said at least one turboexpander comprises two turboexpanders. 
     
     
         20 . The mobile carbon dioxide capture system in accordance with  claim 15 , wherein said carbon dioxide membrane unit further comprises an inlet, the recycle stream channeled to said inlet of said carbon dioxide membrane unit.