Study On Combustion And Pollution Emission Characteristics Of Sewage Sludge

The quantity of sewage sludge is being generated in an ever increasing amount due to development of economic, rapid urbanization and higer rate of sewage treatment. As the output of sludge is quite huge and the components in it are extremely complicated. How to treat this issue has become one of the most urgent studies for environmental protection. The source, harm, main handling methods and current treatment situation of sewage sludge are firstly introduced, and the research advance of sludge incineration technology both home and abroad is summarized in this paper. The main tasks of this dissertation are as follows.By means of thermogravimetric analysis, a series of sludge combustion experiments are performed on the big quantity material thermogravimetric analysis experimental device. The effects of water contene and sample particle diameter on the combustion characteristics are analyzed through experiment. Based on the thermogravimetric curves of sludge combustion derived from the device, the sludge combustion kinetic model is proposed. According to kinetic principle, the most optimum mechanism fuction which is used to describe sludge combustion process is obtained. And by using the obtained optimum mechanism function the kinetic parameters are solved. At the same time, the comparison experiments are done on the differential thermal balance. The thermogravimetric analysis curves of small amount sludge combustion are obtained. Comparison and analysis on weightloss curves obtained from both types of experiments are carried out.The main pollutants emission characteristics of sulfur dioxide and nitrogen oxides during combustion of sludge with different water content are studied. The results suggest that the sludge with higher water content showes lower emission of sulfur dioxide and nitrogen oxides, especially for sulfur dioxide. The emission of sulfur dioxide during wet sludge combustion is only 16.15% of which discharges during sludge with 50% water content combustion.On the basis of analysis on heavy metal content in incineration residue, the source, migration mechanism, distribution in different incineration products and various forms as well as the comprehensive toxity of heavy metals in incineration residue are discussed in this dissertation. A column of experiments are conducted in a fixed bed incinerator at temperatures of 500℃,700℃, 900℃and retained time of 20 minutes in order to investigate the temperature on the behaviour of heavy metals fractions (including heavy metals fractions distribution and retained characteristic in sludge residue) during dewatered sludge incineration. In addition the heavy metal comprehensive toxicity index used for quantitative analysis is proposed and applied to assess the toxicity of heavy metals in sludge and its residue after incineration, which provides the scientific basis for environmental safety evaluation of sludge disposal and residue resource utilization.