| The pyrolysis technology of sewage sludge has been greatly concerned in the fields of environmental protection, waste disposal and renewable energy, etc. Nowadays, practicable devices and product characteristics data of sewage sludge pyrolysis at wide temperature range are scarce. The pyrolysis mechanism of sewage sludge needs further research.In this thesis, a series of experiments were conducted in fluidized bed to explore the pyrolysis of sewage sludge with theoretic analysis. Thermogravimetric analysis was applied to investigate the effects of factors of reaction atmosphere, heating rate, and mixture of sewage sludge and coal on the pyrolysis reaction. The releasing characteristics of gases and apparent kinetics parameters were analyzed. The assumption condition and heat transfer model were established for numerical calculation of the heating process of sewage sludge particles in fluidized bed. A bubbling fluidized bed reactor was designed to study the products distribution and characteristics of sewage sludge pyrolysis at wide temperature range. The pyrolysis reaction mechanism of sewage sludge was discussed.The reaction characteristic parameters of sewage sludge are different in different atmospheres. The maximum weight loss rate increases with the increase in heating rate, which has little influence on the total weight loss rate. In different reaction stages, there are different reaction mechanisms and kinetics parameters for sewage sludge with apparent activation energy within the range of 60-100 kJ/mol. In the co-pyrolysis of coal and sewage sludge, sewage sludge and the inorganic matters in sewage sludge ash play a catalytic role in coal pyrolysis, and the interaction between sewage sludge and coal is related to the characteristics of samples and the mixing ratio.The pyrolysis product distribution at wide temperature range is obtained by the pyrolysis experiments of sewage sludge in fluidized bed. With the increase in pyrolysis temperature, liquid production rate increases and then decreases. At 550℃, liquid production rate reaches the maximum,50.35%. With the increase in pyrolysis temperature pyrolysis gas production rate increases and reaches 51.58% at 950℃. With the increase in pyrolysis temperature char production rate decreace which is 36.92% at 950℃. The pyrolysis products are analyzed to obtain product characteristics data of sewage sludge pyrolysis at low temperature and high temperature.The compositions and content change trends of pyrolysis gas at low temperature and high temperature are different. With the increase in pyrolysis temperature, CO2 content of low temperature pyrolysis gases decreases, and the contents of H2,CH4 and CO incerease. After 550℃, The relation of gas compositions is CO>H2>CH4>CO2. The heating values of high temperature pyrolysis gases are 15.36-16.35 MJ/m3 and the relation of gas compositions is H2>CO>CH4>CO2. Sludge pyrolysis gas is used for chemical industry as syngas or burning application.Many kinds of compounds are identified in pyrolysis tars and the composition and content are different with pyrolysis temperature variation. Analysis results of pyrolysis tar made at 550℃show that the toluene insoluble is 36%, the contents of asphaltene and components dissolved in heptane account for 37.04% and 26.96%, respectivey. In this tar sample, gasoline fraction is 2%, diesel distillate fraction is 18%, vacuum distillate fraction is 15% and residue fraction accounts for 65%. The contents and quantity of single ring aromatic, aliphatic compounds, oxygen compounds, nitrogen compounds, nitrogen and sulfur heterocyclic compounds, steroid compounds and polycyclic aromatic hydrocarbons are different with pyrolysis temperature changes. Low temperature pyrolysis tasr are less toxic and the main compositions are alkanes, alkanes, esters,carboxylic acid compounds, etc. Polycyclic aromatic hydrocarbons appear at 600℃witch are the majority of high temperature pyrolysis tar. The tars can be potentially used as liquid fuel, from which many chemical raw materials can be extracted.The compositions and structures of chars change during sewage sludge pyrolysis which have distinct orous characteristics. Pyrolysis temperature affects the compositions and structural characteristics of char samples. With the pyrolysis temperature increases, in char samples, the fixed carbon and water contents change a little, ash contents increase, volatile contents decrease. There are various hole structures in char mainly with 3-5 nm micro-porous. The specific surface area of char at 450℃is 35.872 m2/g. The pyrolysis char of sewage sludge can be burned, and cheap absorption material can be preparated by carbonization and activation.According to the pyrolysis experiments of sewage sludge in fluidized bed, the pyrolysis process and reaction mechanism are studied, and the plenty of data on product characteristics can provide great reference for the promotion and development of sewage sludge pyrolysis technology.
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