Control of inhalable particulate lead emission from incinerator using kaolin in two addition modes

Abstract

Particulate lead emission control by kaolin was performed in a fluidized bed incinerator at 850–1000°C. The inhalable particulate lead was sampled after a cyclone by a low pressureimpactor. The lead capture process is proposed as three steps: 1) after capture the kaolin particle reacts with lead vapor to form PbO·Al2O3·2SiO2, then 2) lead nanoparticles from homogeneous nucleation of lead vapor conglutinate onto the melting surface of kaolin, and 3) simultaneously, fine particles containing lead conglutinate onto coarse kaolin particles. The kaolin was added in two modes: 1) mixing with solid fuel, and 2) injecting with secondary air. Compared with mode one, kaolin injection caused a much higher concentration of kaolin in the flue gas which led to the capture characteristic difference between two modes. The optimum temperature for mode one to achieve the maximum capture efficiency of submicron lead was 950°C. The optimum kaolin addition proportion for mode two to achieve the maximum capture efficiency was 3%. Overall, kaolin injection is a more effective mode to control submicron lead emission over the temperature range from 850°C to 900°C, while kaolin mixed with the fuel is a simple mode and is more effective at 950°C.