Method and system for capturing carbon dioxide in an oxyfiring process where oxygen is supplied by steam enhanced oxygen release from regenerable metal oxide sorbents

Abstract

An oxyfiring system and method for capturing carbon dioxide in a combustion process is disclosed. The oxyfiring system comprises (a) an oxidation reactor for oxidizing a reduced metal oxide; (b) a decomposition reactor wherein oxidized metal oxide sorbents are reduced with oxygen being released and a flue gas with an oxygen enriched carbon dioxide stream is produced; (c) a fuel combustion reactor for combusting a primary fuel and the oxygen enriched carbon dioxide stream into a primary flue gas; and (d) separation apparatus for separating a portion of the primary flue gas so that a carbon dioxide enriched stream can be sent to the decomposition reactor. Steam may be added to assist in controlling the partial pressure of oxygen during decomposition of the metal oxide and a condenser may be used to remove water from the oxygen enriched flue gas.

What is claimed is: 
     
         1 . A method of capturing carbon dioxide in a combustion process comprising the steps of:
 (a) providing a primary fuel and an oxygen enriched carbon dioxide stream to a primary fuel combustion reactor where the primary fuel and the oxygen enriched carbon dioxide stream are combusted to produce heat and a primary flue gas stream including water and a carbon dioxide stream;   (b) splitting the primary flue gas stream into a first flue gas portion and a second flue gas portion;   (c) supplying the second flue gas portion, a decomposition fuel, a predetermined amount of steam and a metal oxide sorbent to a decomposition reactor where the oxidized metal oxide sorbent is decomposed to a reduced metal oxide sorbent and oxygen, and the decomposition fuel is combusted with a portion of the oxygen to produce a secondary flue gas stream of which at least a portion serves as the oxygen enriched carbon dioxide stream used in step (a);   (d) transferring the reduced metal oxide sorbent to an oxidation reactor where, in the presence of air, the reduced metal oxide sorbent is re-oxidized into the oxidized metal oxide sorbent to be used in step (c); and   (e) capturing carbon dioxide from the first flue gas portion.   
     
     
         2 . The method of  claim 1  wherein:
 water is removed from the secondary flue gas stream thereby increasing the molar percentage of oxygen in the oxygen enriched carbon dioxide stream supplied to the primary fuel combustion reactor. 
 
     
     
         3 . The method of  claim 2  wherein:
 water is removed using a flash column. 
 
     
     
         4 . The method of  claim 2  wherein:
 water is removed using a centrifugal water-gas separator. 
 
     
     
         5 . The method of  claim 2  wherein:
 sufficient water is removed from the secondary flue gas stream such that the molar percentage of oxygen in the oxygen enriched carbon dioxide stream introduced into combustion reactor is in the range of 10-50%. 
 
     
     
         6 . The method of  claim 2  wherein:,
 sufficient water is removed from the secondary flue gas stream that the molar percentage of oxygen in the oxygen enriched carbon dioxide stream introduced into combustion reactor is in the range of 15-30% 
 
     
     
         7 . The method of  claim 2  wherein:
 sufficient water is removed from the secondary flue gas stream that the molar percentage of oxygen in the oxygen enriched carbon dioxide stream introduced into combustion reactor is in the range of 20-25%. 
 
     
     
         8 . The method of  claim 1  wherein:
 the metal oxide is CuO; and 
 the ratio of total molar flow rate of steam to the molar flow rate of CuO entering the decomposition reactor is preferably in the range 0.025 to 1. 
 
     
     
         9 . The method of  claim 1  wherein:
 the metal oxide is CuO; and 
 the ratio of total molar flow rate of steam to the molar flow rate of CuO entering the decomposition reactor is preferably in the range of 0.05 to 0.5. 
 
     
     
         10 . The method of  claim 1  wherein:
 the metal oxide is CuO; and 
 the ratio of total molar flow rate of steam to the molar flow rate of CuO entering the decomposition reactor is the range of 0.075 to 0.25. 
 
     
     
         11 . The method of  claim 1  wherein:
 heat from the secondary flue gas stream is transferred to at least one of the second flue gas portion, the decomposition fuel and steam to increase the temperature of fluids being introduced into the decomposition reactor. 
 
     
     
         12 . The method of  claim 1  wherein:
 the oxidized metal oxide sorbent is selected from the group consisting of one or more of a copper oxide (CuO), manganese oxide (Mn 2 O 3 ) or cobalt oxide (Co 3 O 4 ) carried on a substrate. 
 
     
     
         13 . The method of  claim 1  wherein:
 the decomposition reactor is maintained at a temperature between 600-1100° C. 
 
     
     
         14 . An oxyfiring system for capturing carbon dioxide in a combustion process, the oxyfiring system comprising:
 (a) a combustion reactor for combusting a primary fuel with an oxygen enriched carbon dioxide stream to create a primary flue gas stream including carbon dioxide and water vapor;   (b) an oxidation reactor utilizing air to re-oxidize a reduced metal oxide sorbent to an oxidized metal oxide sorbent;   (c) a decomposition reactor in communication with the oxidation reactor to receive oxidized metal oxide sorbents and to return to the oxidation reactor reduced metal oxide sorbents and in communication with the combustion reactor to receive a portion of the primary flue gas there from and to deliver an oxygen enhanced carbon dioxide stream to the primary combustion reactor;   (d) a separation apparatus for separating carbon dioxide from a portion of the primary flue gas stream received from the combustion reactor;   (e) a water removal apparatus for removing water disposed upstream of the combustion reactor to dehydrate an oxygen enriched carbon dioxide stream; and   (f) a source of steam in fluid communication with the decomposition reactor;   (g) where in the decomposition reactor the oxidized metal oxide sorbent may release oxygen in the presence of steam from the source of steam to produce a reduced metal oxide sorbent with the oxygen partially combusting with a decomposition fuel and partially enriching the portion of the primary flue gas stream received from the combustion reactor to produce an oxygen enriched carbon dioxide stream which is delivered to the combustion reactor to provide a source of oxygen for combustion.   
     
     
         15 . The oxyfiring system of  claim 14  wherein:
 the combustion reactor is one of a fluid catalyst cracker catalyst regenerator, a boiler, a fired heater, a power plant steam generator, biomass pyrolysis char combustor and a gas-fired turbine.