Thermogravimetric Experiment and Dynamic Analysis on Municipal Sewage Sludge Combustion

Abstract

The drying and combustion characteristics of sludge may be obtained by the thermogravimetric experiment, then further analysis of their mechanism will provides the basis for the energy utilization of sludge. In this paper, the drying stage, the flammable stage and the nonflammable stage of municipal sludge were studied by the thermogravimetric experiment methodology. The results show the drying stage consists of five stages: preheating stage, rapid weight loss stage, constant-rate weight loss stage, decelerating weight loss stage I and decelerating weight loss stage II. The kinetic process for the drying and for the combustion of sewage sludge should be expressed by phase interface reaction mechanism function g(a)=1-(1-a)n and chemical reaction equation f(a)=(1-a)n respectively. Then kinetic parameter calculation for these three stages of municipal sludge were done. Kinetic parameters reveal that activation energy decreases in the sequence of non-flammable stage, flammable stage and drying stage, and when raising the heating rate, the activation energy increases significantly in flammable stage while nearly remains unchanged in non-flammable stage.