Experimental investigation on pressurized coal combustion characteristics under O₂/CO₂ atmosphere

The pressurized O₂/CO₂ combustion is a potential technique, which makes CO₂ separation and recovery more efficient. However, it has a notably different mechanism from the air combustion and the O₂/CO₂ combustion under atmospheric pressure. The combustion characteristics of an American bituminous coal and a Huaibei anthracite coal under O₂/CO₂ atmosphere were studied employing the thermo-gravimetric analyzer at various pressures (p=0.1~1.5 MPa). The influences of pressure, oxygen concentration, atmosphere and particle size on the coal combustion characteristics were inspected, and the ignition temperature was obtained. Also, the combustion kinetic parameters were calculated. The results indicate that as the total pressure or oxygen concentration increases, DTG curves move to the low temperature zone and the overall combustion rate of coal samples is accelerated under pressurized O₂/CO₂ atmosphere. The ignition characteristics of pulverized coal could be improved through the pressure enhancement, the increase of oxygen concentration and the reduction of particle size. The pulverized coal combustion under atmospheric pressure is basically a first order reaction. For pressurized oxy-fuel combustion, the reaction order is 0.5 under the low temperature zone, while the reaction order becomes 1.5 under the high temperature zone.