抄録
This paper focuses on the emission behaviors of Pb, Cd and Cr during the sewage sludge combustion using a 2 m tall, 40 mm inner diameter electrically heated drop tube furnace. Equilibrium calculations were carried out before to predict the tendency of these trace metal emissions as the same conditions of experiments. The potential use of sorbent to manage emissions of Pb, Cd and Cr for the sewage sludge combustion was also tested. Experimental procedures involved baseline runs of sludge alone and a number of runs with the kaolin addition at 1073, 1148 and 1223K. The sample was collected by the aerosol size fractionation system composed of a water-cooled sampling probe with rapid N2 quenching and a Low Pressure Impactor (LPI). Particle size distributions (PSDs) indicate that most of Pb and Cd are contained in the fine particles (less than 1µm). However, Cr compounds are not enriched in the fine particulates. Since the equilibrium calculations predict that Pb and Cd vaporize at above 973K, these results are due to Pb and Cd vaporization and subsequent reaction in the furnace and/or nucleation in the probe. The addition of 5 % dispersed kaolin power causes an approximate 51 % of Pb and 40 % Cd reduction in the fine particles at the temperature of 1223K during sewage sludge combustion. Pb compound in coarse particles becomes insoluble because of the reaction with kaolin in the furnace.
