Effects of particle size and additives on the formation of fine particulate matter during sludge incineration

With the development of urbanization and industrialization, vast plenty of sewage sludge was produced. Incineration has been becoming the mainstream disposal method due to its many advantages. However, the problem of fine particulate matter produced from the incineration process made a restriction on the development of this method. In this study, the effects of temperature, particle size, and calcium-based additives (CaO) on the generation characteristics and micrographs of fine particulate matter were investigated via a lab-scale fluidized bed. The results revealed that the fine particulate matter showed a bimodal distribution and the two peaks was located at around 0.5 μm and 5 μm, respectively. With the increasing of temperature from 750°C to 950°C, the mass concentration of PM0.5 increased by 12.88 mg/g, while PM5 increased by 57.79 mg/g, which indicated as the temperature increases, the crushing degree of minerals and coke particles is more intense, which further leads to an increase in the amount of fine particles. The number of fine particles increased when the feed size getting smaller, which showed an intense link to the feed size. That was because the smaller the particle size, the more severe the degree of crushing, and the greater the number of fine particles formed after crushing. Furthermore, the results also found that CaO can be used as a good binder between particles to promote the growth and agglomeration of fine particles and inhibit the generation of fine particles. When the additive ratio was 3%, 6%, and 9%, the mass concentration of PM0.3 decreased by 53.7%, 63.5%, and 86.1%, while the mass concentration of PM3 decreased by 43.9%, 74.7%, and 91.7%. Therefore, CaO can be used to reduce the production of fine particles in practical engineering applications.