Postcombustion Capture of CO₂ with CaO in a Circulating Fluidized Bed Carbonator

There is an emerging postcombustion capture technology that uses CaO to capture CO2 from combustion flue gases in a circulating fluidized bed reactor. This paper summarizes recent work conducted at CSIC to understand and develop this technology. The paper includes experimental results at conditions close to those expected in the real system, carried out in continuous mode in a 30kW test facility made up of two interconnected circulating fluidized bed reactors. In one of the reactors, CO2 is captured from the gas phase by the CaO continuously circulating from a calciner. In the second reactor, the CaCO3 formed in the carbonator is regenerated to CaO and CO2 by calcination. Modeling of the system at process level, at reactor level (in particular the CFB carbonator), and at particle level (decay in capture capability of CaO) is also outlined. The work carried out so far confirms that the carbonator reactors can be designed to attain capture efficiencies between 70–90%, operating at fluid dynamic conditions close to those present in circulating fluidized bed combustors.