N₂O Reduction and NOx Adsorption in Carbonator of Calcium Looping CO₂ Capture Process

Abstract

A dual-fluidized bed solid circulating system that comprised a bubbling bed carbonator and a fast fluidized bed regenerator was operated under a condition of Calcium Looping (CaL) CO2 capture process. Calcined limestone (CaO) was employed as bed material. Gas mixture simulating flue gas from air-blown combustor consisted of CO 2, N2O, NO, O2, and N2 was fed to the carbonator. Most part of the fed CO2 was captured by the calcined limestone particles, then the partially carbonated particles were transported to the regenerator, in which thermal decomposition of CaCO 3 was carried out in air stream. The carbonator of CaL process was found to be effective for N2O reduction when the sorbent particles had activity to capture CO2. A part of NO in the feed gas was also adsorbed by CaO particles, then the adsorbed NO was transported to the regenerator, and released to the gas phase there, though the net decomposition of NOx was not observed. CaL process was revealed to be a multifunctional process of CO 2 capture, N2O decomposition, and removal of a part of NO in the flue gas fed to the carbonator.

NOx Emissions from Regenerator of Calcium Looping Process

“…Apart from oxy-fuel combustion and chemical looping combustion, the calcium looping (CaL) process has been developed as one of the promising postcombustion CO 2 capture technologies suitable for coal-fired combustors. − Calcium looping is a dry absorption and desorption route, carried out in two reactors, i.e., a carbonator (absorber) and regenerator (calcinator or calciner) where a reversible reaction of CO 2 absorption by solid CaO absorbent (eq ) and CaCO 3 decomposition (eq ) occur: The carbonation reaction (eq ) proceeds in the carbonator while the decomposition of CaCO 3 (eq ) happens in the regenerator. To recirculate the solid absorbent, solid transportation lines connect the calciner and the regenerator.…”