Method and system for separating co2 from synthesis gas or flue gas

Abstract

The present invention provides a method and system for separating CO2 from a gas stream containing CO2. A gas stream having an initial pressure is compressed and subsequently cooled. The compressed and cooled gas stream has an increased pressure and reduced temperature at which the CO2 in the gas stream is at least partially converted to the liquid phase. The liquid phase is separated from the compressed and cooled gas stream, to provide a liquid phase stream and a gas phase stream, wherein the output pressure of the liquid phase stream is higher than the initial pressure of the gas stream.

1 . A method for separating CO 2  from a synthesis gas stream or flue gas stream, the method comprising the steps of:
 providing a gas stream at a initial pressure and initial temperature;   compressing the gas stream;   cooling the compressed gas stream, wherein the compressed and cooled gas stream has an increased pressure and reduced temperature at which the CO 2  in the gas stream is at least partially converted to the liquid phase; and   separating the liquid phase from the compressed and cooled gas stream, to provide a liquid phase stream and a gas phase stream at an output pressure,   wherein the output pressure of the liquid phase stream is higher than the initial pressure of the gas stream.   
     
     
         2 . The method of  claim 1 , wherein the initial pressure is in the range of 20 to 65 bar. 
     
     
         3 . The method of  claim 2 , wherein the output pressure of the liquid phase stream is above 75 bar. 
     
     
         4 . The method of  claim 2 , wherein the output pressure of the liquid phase stream is in the range of 100 to 200 bar. 
     
     
         5 . The method of  claim 4 , wherein the output pressure is in the range of about 140 to 160 bar. 
     
     
         6 . The method of  claim 5 , further comprising the steps of:
 directing the liquid phase stream and the gas phase stream to one or more heat exchangers for cooling the compressed gas stream.   
     
     
         7 . The method of  claim 6 ,
 wherein the step of providing the gas stream includes:
 providing a synthesis gas stream; and 
 subjecting the synthesis gas stream to a water shift reaction, to provide a treated synthesis gas stream having an increased H 2  and/or CO 2  content. 
   
     
     
         8 . The method of  claim 7 , wherein the output pressure of the gaseous phase is substantially equal to the output pressure of the liquid phase. 
     
     
         9 . The method of  claim 8 , wherein the cooling of the compressed gas stream is at least partially performed in a multi-stream heat exchanger. 
     
     
         10 . The method of  claim 8 , wherein the compressed gas stream is split into at least two streams and the cooling of each of the split compressed gas streams is at least partially performed in separate heat exchangers arranged in parallel. 
     
     
         11 . A system for separating CO 2  from a gas stream containing CO 2 , the system comprising:
 a compressor for compressing the gas stream having an initial pressure and an initial temperature;   at least one cooling device for cooling the compressed gas stream, wherein the compressed and cooled gas stream has a pressure and temperature at which the CO 2  in the gas stream is at least partially converted to the liquid phase; and   a separator for separating the compressed and cooled synthesis gas stream in a liquid phase stream and a gas phase stream at an output pressure,   wherein the output pressure of the liquid phase stream is higher than the initial pressure of the gas stream.   
     
     
         12 . The system of  claim 11 , further comprising:
 a first heat exchanger, wherein the liquid phase stream is directed to the first heat exchanger for cooling the compressed gas stream.   
     
     
         13 . The system of  claim 12 , further comprising:
 a second heat exchanger, wherein the gas phase stream is directed to the second heat exchanger for cooling the compressed gas stream.   
     
     
         14 . The system of  claim 13 , wherein the separator comprises a cyclone, a swirl tube, and/or a demister mat.