Oxyfuel technology: NO reduction during oxy-oil shale combustion

Abstract

Nitrogen oxides are one of the major environmental problems arising from fossil fuels combustion. Oxyfuel combustion is one of the most promising clean coal technologies for pulverized fuel-fired power plants to control and avoid CO2 emissions; with this technology NOx emissions are significantly reduced.Due to the importance of oil shale utilization in Jordan and all over the world, this study continues with our previous work on oil shale combustion. Unstaged and staged air-firing and oxyfuel combustion were carried out using Jordanian oil shale collected from El-Lajjun area. The reduction of simulated recycled NO has been investigated in a 20kW vertical reactor. The actual situation has been simulated by injecting NO in the reactor through the burner. It was found that the simulated recycled NO reduction efficiency is affected by the media and the mode of firing. The simulated recycled NO is reduced efficiently (60–70%) during unstaged oxyfuel combustion as well as air-firing of El-Lajjun oil shale. The reduction of the injected NO is more efficient with staging compared to unstaged combustion mode for both air-firing and oxyfuel combustion. The reduction of the injected NO for combustion in air ranges from 61% (without staging) to 100% (with staging) whereas for combustion in 27% O2/73% CO2, it ranges from 57% (without staging) to 100% (with staging). Moreover, El-Lajjun oil shale ashes are characterized as being high in CaO and SiO2, low in Al2O3, SO3, and P2O5 and with minor amounts of F2O3, MgO, Na2O, K2O, and TiO2.