Capturing CO2 in coal-fired combustors using CaO-based sorbents

Carbonation/ calcination reactions of CaO sorbent, as a method for separation of CO2 from flue gases of coal-fired combustors, are investigated. CO2 can be absorbed by the sorbent through the carbonation reaction in the combustor system. The sorbent can then be regenerated in a calciner and the required heat can be obtained by burning pail of the fuel with pure O-2. A dual fluidized bed configuration has been proposed for the carbonation/calcination process, and efficiency approaching 40% for converting the fuel heat to power is expected based on the results of process simulation. Experimental work using a pilot-scale fluidized bed combustor shows that the reaction is sufficiently fast for the fluidized bed technology to apply. Activity decay of the sorbent with respect to CO2 capture is observed in both thermogravimetric studies and fluidized bed tests and the behavior of the decay is analyzed. The effect of adding fresh limestone to overcome the activity decay is discussed.