Reduction of NO_X by Char under Condition for Carbonator of Calcium Looping CO₂ Capture Process

Abstract

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 NO_X 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 NO_X 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.