CO2 capture from the calcination of CaCO3 using iron oxide as heat carrier

Abstract

This paper presents a novel CaCO3 calcination process that uses the chemical looping combustion concept to generate the energy needed for calcination. The process could drastically reduce the CO2 emissions from cement plants by generating a separate stream of CO2 suitable for geological storage before the CaO is fed to the clinker oven. In the proposed system, the CaCO3 precalciner is a fluidized bed reactor where a flow of very high temperature solids (mainly Fe2O3 resulting from the exothermic oxidation of Fe3O4 with air in a separate reactor) supplies the heat required for the calcination of the CaCO3. The calciner also acts as a fuel reactor, where Fe2O3 is reduced to Fe3O4 while a fuel gas is oxidized to CO2 and steam. The dense Fe-rich solids are subsequently separated from the calcination products by segregation, before entering back to the air reactor. A conceptual process design is presented, in which the calcination system is integrated in the flowsheet of a standard cement plant, using information from the literature to choose reasonable conversions and efficiencies in the key reaction and separation steps. The results of this analysis indicate that fuel consumptions will be around 4 GJ/t CaO, which translates into a total energy demand of 93 MWt for a calciner to produce the CaO required for 3000 t/d of cement. These preliminary results confirm the potential of the proposed process for a future development and pilot testing.