Study On The Gasification Characteristics Of Sewage Sludge

With the development of the society, the output of sludge is increasing year after year. The treatment and sewage sludge tends to be a big problem of the society. Sludge treatment technology that can achieve decrement, detoxification and reclamation is studied all over the world. Because of some disadvantages, the utilization and promotion of the main current treatment technologies become more and more difficult.Compared to other technologies, sludge gasification technology has many particular advantages. This technology has significant effect on decrement. The pathogenic bacteria are killed completely and the most of the heavy metal can be fixed in the residue. The fuel gas produced by gasification can be directly used for power or heat generation, which leads to a higher energy utilization efficiency.Sludge was sampled from the municipal sewage plant and investigations were done on the gasification characteristics of sludge by process analysis, model setup, thermo-gravimetric analysis and tests in the fluidized bed and tube furnace.The gasification process could be divided into pyrolysis phase and gasifying reaction phase. The main reactions during gasification are analyzed. Gasification model and equations were set up based on these selected reactions.It was found through thermo-gravimetric analysis that both pyrolysis and burning process can be divided into three stages. The gases produced during pyrolysis were H2O, CO2, CO and hydrocarbon. Hydrocarbon was mainly released at lower temperature stage while CO was evidently released at high temperature stage. As the oxygen concentration rose, the ignition temperature decreased and the weight loss speeded upSludge gasification experiments were performed in fluidized bed. The components of the fuel gas and the effect of temperature on the gas components were studied. The results showed that the combustible gases in the fuel gas were mainly H2, CO and CH4. As the temperature rose, the concentrations of the combustible gases and the heat value of the fuel gas got a remarkable increase. The experiments revealed the feasibility of sewage sludge gasification and that higher temperature resulted in better gas quality.Sludge gasification experiments using water vapor as the gasification agent were performed in the tube furnace. The influence of the existence of water vapor and temperature on the gas products of gasification was studied. The results showed that when water vapor was added, the concentration of H2 increased obviously, while the concentration of CO and CH4 decreased. As the temperature rose, the concentration of H2, CO and CH4 increased. High temperature had a significant effect on the improvement of gas products of gasification.