NOX ABATEMENT WITH CARBON ADSORBENTS AND MICROWAVE-ENERGY

Nitrogen oxides (NOx) are formed during the combustion of coal and other fuels. The Clean Air Act Amendments of 1990 require reductions in NOx emission by all industrial processes. In this NOx abatement process, NOx in flue gas are adsorbed by a carbon adsorbent and then reduced by carbon to nitrogen and carbon oxides with microwave energy. Six carbon adsorbents were tested in this study to investigate the effects of the microwave treatment on the NOx adsorption capacity and rate. The surface areas of FMC calcined char and FMC cake increased from about 100 m(2)/g to around 800 m(2)/g. This is due to the carbon consumption in the microwave-induced NOx reduction reactions. Through increasing the internal surface area and nitrogen content, the microwave treatment improved the NOx adsorption capacity and rate for all carbon adsorbents, except the commercial activated carbon. The FMC calcined char showed the best improvement in NOx adsorption capacity and rate by microwave regenerations and was thus studied further to obtain the mechanisms of NOx adsorption on char and their reduction in the microwave energy held. The experimental results show that in the presence of oxygen and moisture, NO is converted to NO2 and HNO3 on carbon surfaces. The NOx adsorbed on carbon adsorbents can be reduced using microwave energy with the product gas at room temperature. Nearly 90% of NOx adsorbed on FMC calcined char is reduced in this process.