Process for Removing Carbon Dioxide From a Gas Stream using Desublimation

Abstract

A process for removing carbon dioxide from a carbon dioxide containing gas stream is obtained through de-sublimation, vaporization, and liquefaction of various carbon dioxide-containing streams with little or no external refrigeration.

1 . A process for removing carbon dioxide from a carbon dioxide containing gas stream, said process comprising the steps of:
 a. compressing the carbon dioxide containing gas stream to a pressure that ranges from about 1.1 bar absolute to about 20.0 bar absolute to produce a compressed gas stream;   b. routing the compressed gas stream through a main heat exchange system comprising one or more main heat exchangers where the temperature of the compressed gas stream is reduced to a point that a portion of the carbon dioxide in the compressed gas stream is transformed into solid carbon dioxide with the remainder of the carbon dioxide remaining in gaseous form;   c. separating the solid carbon dioxide from the compressed cooled gas stream to form a stream of solid carbon dioxide and a cooled partially carbon dioxide depleted gas stream;   d. introducing the cooled partially carbon dioxide depleted gas stream into an expansion turbine in order to transform additional carbon dioxide within the gas stream into additional solid carbon dioxide;   e. separating the additional solid carbon dioxide from the cooled partially carbon dioxide depleted gas stream to form an additional stream of solid carbon dioxide and an expanded carbon dioxide depleted gas stream;   f. routing the expanded carbon dioxide depleted gas stream back through the main heat exchange system where the expanded carbon dioxide depleted gas stream is heated to a temperature that ranges from about −20° C. to about 50° C. to recover sensible heat and then venting the carbon dioxide depleted gas stream that is withdrawn from the heat exchanger;   g. using the streams of solid carbon dioxide produced to reduce the temperature of the compressed gas stream in step b) by: i) subjecting a portion of the solid carbon dioxide to a pressure that is equal to or greater than the triple point pressure of carbon dioxide in a first vessel in communication with the main heat exchange system to produce a carbon dioxide liquid stream and recovering fusion heat and sensible heat; ii) vaporizing a portion of the solid carbon dioxide in a second vessel in communication with the main heat exchange system at sub-atmospheric pressure to produce a sub-atmospheric pressure carbon dioxide gas and recovering at least sublimation heat; and iii) compressing the sub-atmospheric pressure carbon dioxide gas obtained to produce a compressed carbon dioxide stream.   
     
     
         2 . The process of  claim 1 , wherein the portion of solid carbon dioxide subjected to a pressure that is equal to or greater than the triple point pressure of carbon dioxide to produce a carbon dioxide liquid stream is obtained from step b). 
     
     
         3 . The process of  claim 1 , wherein at least a portion of the solid carbon dioxide vaporized at sub-atmospheric pressure to recover at least the sublimation heat and produce a sub-atmospheric pressure carbon dioxide gas is obtained from step d). 
     
     
         4 . The process of  claim 1 , wherein prior to step g), the solid carbon dioxide of step b) and step d) is combined for use in step g). 
     
     
         5 . The process of any  claim 1 , wherein the carbon dioxide containing gas stream is a flue gas stream. 
     
     
         6 . The process of  claim 1 , wherein in step e), the vaporization of the solid carbon dioxide is carried out with at least two different sub-atmospheric pressures. 
     
     
         7 . The process of  claim 6 , wherein the vaporization of the solid carbon dioxide with at least two different sub-atmospheric pressures is performed in at least two independent vessels with each independent vessel corresponding to a different sub-atmospheric pressure. 
     
     
         8 . The process of  claim 7 , wherein the vessels are in thermal communication with the main heat exchange system through a series of pipes that run through the main heat exchange system and the various vessels. 
     
     
         9 . The process of  claim 8 , wherein the recovery of the sublimation heat is carried out by circulating one or more fluids between the main heat exchange system and the vessels to recover cold from the phase changes in the vessels and release this cold in the main heat exchange system. 
     
     
         10 . The process of  claim 9 , where the one or more fluids are circulated by pumping the one or more fluids or by thermo-siphoning. 
     
     
         11 . The process of  claim 10 , wherein the one or more fluids are selected from CF 4 , NF 3 , C 2 H 6    
     
     
         12 . The process of  claim 1 , wherein the compressed carbon dioxide stream is further treated to obtain the desired carbon dioxide product. 
     
     
         13 . The process of  claim 1 , wherein the carbon dioxide liquid stream is further treated to obtain the desired carbon dioxide product. 
     
     
         14 . The process of  claim 1 , wherein from 90 to 99% of the carbon dioxide in the carbon dioxide containing gas stream is separated by de-sublimination with no external refrigeration cycle. 
     
     
         15 . The process of  claim 1 , wherein the latent heat of fusion for the liquefaction of the solid carbon dioxide in step g i is obtained from condensation of gaseous carbon dioxide in the stream of compressed carbon dioxide stream obtained from step g iii. 
     
     
         16 . The process of  claim 1 , wherein no external source of refrigeration is utilized. 
     
     
         17 . A process for removing carbon dioxide from a carbon dioxide containing gas stream, said process comprising the steps of:
 a. routing the carbon dioxide containing gas stream through a main heat exchange system comprising one or more heat exchangers where the temperature of the gas stream is reduced to a point that a portion of the carbon dioxide in the gas stream is transformed into solid carbon dioxide with the remainder of the carbon dioxide remaining in gaseous form, the carbon dioxide containing gas stream having a pressure from about 0.8 to 3.0 bar absolute;   b. separating the solid carbon dioxide from the cooled carbon dioxide containing gas stream to form a stream of solid carbon dioxide and a cooled partially carbon dioxide depleted gas stream;   c. routing the cooled partially carbon dioxide depleted gas stream back through the main heat exchange system where the cooled partially carbon dioxide depleted gas stream is heated to a temperature that ranges from about −20° C. to about 50° C. to recover sensible heat and then venting the carbon dioxide depleted gas stream that is withdrawn from the heat exchanger; and   d. using the stream of solid carbon dioxide produced to reduce the temperature of the carbon dioxide containing gas stream in step b) by: i) subjecting a portion of the solid carbon dioxide to a pressure that is equal to or greater than the triple point pressure of carbon dioxide in a first vessel in communication with the main heat exchange system to produce a carbon dioxide liquid stream and recovering fusion heat and sensible heat; ii) vaporizing a portion of the solid carbon dioxide in a second vessel in communication with the main heat exchange system at sub-atmospheric pressure to produce a sub-atmospheric pressure carbon dioxide gas and recovering at least sublimation heat; and iii) compressing the sub-atmospheric pressure carbon dioxide gas obtained to produce a compressed carbon dioxide stream.   
     
     
         18 . The process of  claim 17 , wherein the carbon dioxide containing stream is compressed prior to being routed into the main heat exchanger in order to have a pressure from about 1.1 to 3.0 bar absolute. 
     
     
         19 . The process of  claim 17 , wherein the carbon dioxide containing gas stream is a flue gas stream. 
     
     
         20 . The process of  claim 17 , wherein in step d), the vaporization of the solid carbon dioxide is carried out with at least two different sub-atmospheric pressures. 
     
     
         21 . The process of  claim 20 , wherein the vaporization of the solid carbon dioxide with at least two different sub-atmospheric pressures is performed in at least two independent vessels with each independent vessel corresponding to a different sub-atmospheric pressure. 
     
     
         22 . The process of  claim 21 , wherein the vessels are in communication with the main heat exchanger through a series of pipes that run through the main heat exchange system and the various vessels. 
     
     
         23 . The process of  claim 22 , wherein the recovery of the sublimation heat is carried out by circulating one or more fluids between the main heat exchange system and the vessels to recover cold from the phase changes in the vessels and release this cold in the main heat exchange system. 
     
     
         24 . The process of  claim 23 , where the one or more fluids are circulated by pumping the one or more fluids or by thermo-siphoning. 
     
     
         25 . The process of  claim 24 , wherein the one or more fluids are selected from CF 4 , NF 3 , C 2 H 6    
     
     
         26 . The process of  claim 17 , wherein the compressed carbon dioxide stream is further treated to obtain the desired carbon dioxide product. 
     
     
         27 . The process of  claim 17 , wherein the carbon dioxide liquid stream is further treated to obtain the desired carbon dioxide product. 
     
     
         28 . The process of  claim 17 , wherein the latent heat of fusion for the liquefaction of the solid carbon dioxide in step D i is obtained from condensation of gaseous carbon dioxide in the stream of compressed carbon dioxide stream obtained from step D iii.