Effects of acidic gases and operation parameters on denitrification in oxy-fuel CO_2 compression process

摘要

Oxy-fuel combustion technology has great potential as a technically feasible method to significantly reduce CO2 emissions from coal-fired power plants. In an oxy-fuel combustion system, gas impurities such as SO2 and NOx must be removed before CO 2 recovery because they can cause potential corrosion risk to CO2 compression and purification units (CPU). An attractive strategy is to simultaneously remove SO2 and NOx in the existing CO2 CPU system in place of traditional flue gas treatment device. Since NOx contains more than 90% of insoluble NO, the removal of NO has attracted much attention. In this study, NO removal efficiency in CO2 compression process were experimentally investigated on a pressurized reaction system. Effects of acidic gases (SO2, CO2) and operation parameters (pressure, temperature, initial O-2 concentration and residence time) were taken into consideration. NO removal was achieved in pressurized reaction system as a result of oxidation to NO2 in the presence of O-2 and the absorption of NO2 in water. NO conversion to NO2 was the key step for NO removal, which was strongly and positively dependent on the pressure and negatively dependent on the temperature. With the addition of 1000 ppm SO2 in simulated gases, NO removal efficiency was reduced by 8.1% at 2.0 MPa. The gas phase and liquid phase reactions between SO2 and NO2 suggested that partial NO2 was converted to insoluble NO when reacting with SO2. It was also found that NO removal efficiency in O-2/CO2 atmosphere was slightly higher than that in O-2/N-2 atmosphere. The dissolution of CO2 in water increased the residence time as well as the acidity of the aqueous solution, which could facilitate the oxidation of NO.