Particulate Matter Emission Characteritics of a Brown Coal under Oxy-fuel Combustion

摘要

The present paper was addressed toward the possible impact of oxy-fuel combustion on mineral transformation and fine ash formation. A Chinese brown coal was burned with O_2/CO_2 or O_2/N_2 mixture in a flat flame supported entrained flow reactor at 1723K. The ash samples, collected using cyclone and 13-grade low pressure impactor (LPI) after properally diluting and quenching, were characterized in details by SEM and XRF to study the ash formation behaviors, and the comparison was made between oxy-fuel combustion and air combustion. It was proved that oxy-fuel combustion did not significantly affect the species of mineral phases formed in the PM10 mode but did affect the relative amounts of the phases, in comparison to air combustion. Oxy-fuel combustion can drastically decreased the vaporization of refractory oxides and thus the fraction of refractory oxides in submicron mode, as compared to air combustion with the same O_2 concentration, because of the decrease in the char combustion temperature. While increasing O_2 faction of oxy-fuel combustion to 30 percent, the yield and chemical component of submicron mode are comparable to those of air combustion. It suggested that significant diminish of submicron PM emission for oxy-fuel combustion can be reached, if flame stabilization and burn out problem at relatively low oxygen fraction, say 20 percent for example, be solved.