2015 Volume 94 Issue 8 Pages 841-850
A dual-fluidized bed system that comprised a fast fluidized bed regenerator and a bubbling bed carbonator was operated under a temperature condition of Calcium Looping process for CO2 capture. Three kinds of coal with different volatile matter content were burned in the regenerator in oxygen-enriched atmosphere. Gas mixture consisted of NO, O2, and N2 was fed to the carbonator to simulate the interaction between char and NO in the flue gas from an air-blown combustor. Inert quartz sand was used as the bed material. Formation of CO and CO2 in the carbonator from oxidation of char which was entrained from the regenerator was measured. With char combustion, small amount of NOX was formed in the carbonator when NO-free gas was fed. With NO feed to the carbonator, a part of the fed NO was reduced by char. Thus the char particles in the carbonator were effective for NOX reduction when NO concentration in the feed gas was high. Formation of N2O in the carbonator was less than 10 ppm. The increase in greenhouse effect due to N2O emissions was calculated to be far less than the decrease in greenhouse effect by capturing CO2.