Combustion method with integrated CO2 separation by means of carbonation

Abstract

The invention relates to a method for separating CO 2 from combustion gases, which can be used at areas with large emissions (thermal power stations using any carbonaceous fuel). The separated CO 2 stream can be used and/or contained in geological formations. The inventive method aims to reduce the high costs involved in CO 2 separation which prevent large-scale use of the CO 2 confinement options included in the UN's IPCC reports. Said method consists of bringing the combustion gases into contact with a calcareous sorbent (limestone, calcined dolomite) at 650-750° C., thereby producing the CO 2 capture reaction by means of the rapid carbonation of the sorbent. The sorbent is regenerated in another reactor (calciner) which operates in CO 2 or CO 2 /H 2 O atmospheres.

1 . Combustion method with integrated CO 2  separation by means of carbonation based on the use of part of the heat generated in the combustion chamber on the part of the calciner in order to maintain the endothermic reaction of calcination and regenerate the sorbent, that comprises any type of combustion chamber, wherein any type of fuel is burnt with air, without the need to use the separating plant, in combination with a carbonator to treat the hot gases and in turn generate energy.  
     
     
         2 . Combustion method with integrated CO 2  separation by means of carbonation according to  claim 1 , characterized in that the heat exchange can be carried out directly through the metal walls that separate the combustion chamber (at temperatures higher than 1,000° C.) from the calciner (at temperatures lower than 900° C.).  
     
     
         3 . Combustion method with integrated CO 2  separation by means of carbonation according to  claim 1  characterized in that the heat exchange can be carried out indirectly by means of an inert solid (sand, alumina or others) circulating between the two chambers and, that is easily separable from the sorbent due to its different particle properties (density and/or size) in order to be able to operate continuously.  
     
     
         4 . Combustion method with integrated CO 2  separation by means of carbonation according to  claim 1  characterized in that the use of a calciner operating at partial CO 2  pressures below atmospheric pressure, producing a stream of pure CO 2  or CO 2  that can be easily purified, the low partial pressure of CO 2  permitting rapid calcination at moderate temperatures (equal to or lower than 900° C.), with the subsequent improvement of the activity of the sorbent and increase of the impelling force (ΔT) of heat exchange towards the calciner, the partial pressures of CO 2  below atmospheric pressure are achieved by introducing steam (easily separable from the CO 2 generated in the calcination) and/or applying a vacuum to the calciner.  
     
     
         5 . Combustion method with integrated CO 2  separation by means of carbonation according to  claim 1 , characterized in that the use of a powdered CaO and CO 2  carbonator, that may be a circulating fluidized bed, a drawn bed, or a cyclone reactor (depending on the size of the CaO particle and on the reaction rate) where there CaO carbonation reaction or the CO 2  capture is produced between 600-750° C.