Scheme of O₂/CO₂ Combustion with Partial CO₂ Removal from Recycled Gas. Part 1: Superlow NO Emission

Abstract

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 burn-out of coal. 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 exhausted NO decreased as the CO 2 removal ratio from the recycled gas increased. At a CO 2 removal ratio of 15%, the global conversion ratio from fuel N to exhausted NO became as low as 3.95 × 10 −3 , i.e., 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.

Comparison of Particle Size Evolution during Pulverized Coal Combustion in O2/CO2 and O2/N2 Atmospheres

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