SEPARATION OF CARBON DIOXIDE (CO2) FROM GAS MIXTURES BY CALCIUM BASED REACTION SEPARATION (CaRS-CO2) PROCESS

Abstract

A reaction-based process developed for the selective removal of CO2 from a multicomponent gas mixture to provide a gaseous stream depleted in CO2 compared to the inlet CO2 concentration. The proposed process effects the separation of CO2 from a mixture of gases by its reaction with metal oxides. The Calcium based Reaction Separation for CO2 (CaRS—CO2) process consists of contacting CO2 laden gas with CaO in a reactor such that CaO captures CO2 by the formation of CaCO3. CaCO3 is regenerated by calcination leading to the formation of fresh CaO sorbent and the evolution of a concentrated stream of CO2. The “regenerated” CaO is then recycled for the further capture of CO2. This carbonation-calcination cycle forms the basis of the CaRS—CO2 process. This process also may use a mesoporous CaCO3 structure that attains >90% conversion over multiple carbonation and calcination cycles.

What is claimed is: 
     
         1 . A method for separating carbon dioxide and sulfur dioxide from a flow of gas comprising carbon dioxide and sulfur dioxide, said method comprising the steps of:
 reacting said carbon dioxide and said sulfur dioxide with a metal oxide sorbent to convert at least a portion of said metal oxide sorbent to a metal carbonate and at least a portion of said sorbent to a metal sulfate;   calcining at least a portion of said metal carbonate to form a reformed metal oxide sorbent and carbon dioxide; and   replenishing said metal oxide sorbent with said reformed metal oxide sorbent formed during calcination.   
     
     
         2 . The method of  claim 1 , further comprising:
 separating said metal carbonate from said gas flow in a cyclone.   
     
     
         3 . The method of  claim 1 , wherein said conversion of said metal oxide sorbent to metal carbonate and metal sulfate occurs at a temperature in the range of about 600° to about 650° Celsius. 
     
     
         4 . The method of  claim 1 , further comprising:
 removing said carbon dioxide produced during calcination.   
     
     
         5 . The method of  claim 1 , wherein said metal oxide sorbent has a mesoporous pore size distribution. 
     
     
         6 . The method of  claim 1 , wherein said calcining is conducted under partial pressure. 
     
     
         7 . The method of  claim 1 , wherein said calcining is performed by steam. 
     
     
         8 . The method of  claim 1 , wherein said metal oxide sorbent is selected from a group consisting of: ZnO, MgO, MnO2, NiO, CuO, PbO, and CaO. 
     
     
         9 . The method of  claim 1 , wherein said reformed metal oxide sorbent has substantially the same sorption as said metal oxide sorbent. 
     
     
         10 . A facility practicing the method according to  claim 1 . 
     
     
         11 . A method for separating carbon dioxide and sulfur dioxide from a flow of gas comprising carbon dioxide and sulfur dioxide, comprising:
 reacting said carbon dioxide and said sulfur dioxide with a sorbent in a gas-solid reactor to convert at least a portion of said sorbent to a metal carbonate and a portion of said sorbent to a metal sulfate;   calcining said metal carbonate so as to form a regenerated sorbent; and   directing said regenerated sorbent to said gas-solid reactor.   
     
     
         12 . The method of  claim 1 , wherein said sorbent is a metal oxide. 
     
     
         13 . The method of  claim 1 , wherein said sorbent is selected from the group consisting of: ZnO, MgO, MnO2, NiO, CuO, PbO, and CaO. 
     
     
         14 . The method of  claim 1 , further comprising:
 separating said metal carbonate from said flow of gas in a cyclone.   
     
     
         15 . The method of  claim 1 , wherein said regenerated sorbent has the same sorption capacity as said sorbent prior to absorbing said carbon dioxide. 
     
     
         16 . The method of  claim 1 , further comprising:
 sequestering said carbon dioxide formed during calcination.