Scheme of O_2/CO_2 Combustion with Partial CO_2 Removal from Recycled Gas. Part 1: Superlow NO Emission

摘要

A new scheme of O_2/CO_2 combustion with partial CO_2 removal from recycled gas is proposed. Through experiments and theoretical analysis of the system, the reduction of NO to N_2 and emission of NO were investigated for this new scheme. When CO_2 is partially removed from the recycled gas, a high gas recirculation ratio is needed to maintain the O_2 concentration at the furnace entrance and the stoichiometric O_2 amount necessary for the bum-out of coat It was found that this gas recirculation ratio increased with the CO_2 removal ratio from the recycled gas. The gas recirculation ratio could be as high as 98.9%; i.e., only 1.1% of the flue gas was exhausted. The CO_2 concentration in the flue gas was above 95%, which made its capture much easier and more economicaL The global conversion ratio from fuel N to erhausted NO decreased as the CO_2 removal ratio from die recycled gas increased. At a CO_2 removal ratio of 15%, die global conversion ratio from me! N to exhausted NO became as low as 3.95 × 10~(-3) Le., down to only 1/85, of that of conventional combustion in air. These results suggested that, with the new scheme of O_2/CO_2 combustion proposed in this work, superlow NO emission and easy CO_2 capture could be realized simultaneously.