| With the economic development, population increase, urbanization propulsion, improvement of the disposal rate of sewage, production of sewage sludge has been increasing rapidly. While treatment technology and equipment of municipal wastewater in China are generally behind production increase, and the protection of safe treatment and disposal of sludge is very low. Sludge will result in serious secondary pollution for human and environment if not be prompt handled properly. Therefore, the properly scientific treatment and disposal of sludge has become an attractive subject of environmental protection at home and abroad.Sludge drying can significantly reduce capacity, and its product is stable, odorless and non-pathogenic. Sludge product after drying is used as fertilizer, soil conditioner, alternate energy and so on. And the incineration of sludge disposal is the most thorough method. In this paper, sludge drying, pyrolysis and incineration are studied by theoretical analysis, experimental and numerical simulation.Paper sludge is carried out by isothermal drying experiment in the temperatures range of 80~160℃under the conditions of the different drying temperatures, different thicknesses and different initial sludge cake moisture content. The kinetic models of sludge drying are fitted to find the best sludge drying kinetic model. The results showes that the higher drying temperature is, the faster drying rate is, and the shorter drying time is. The thicker sludge cake is, the slower the drying rate is, and the longer drying time is. The smaller the initial moisture content is, the faster drying rate is, and the shorter drying time is. Among seven different kinds of drying model, Page and Modified page model are suitable for fitting sludge drying process. Tested by the Page model, the experimental and fitted values have a good consistency. The diffusion coefficient of dry sludge ranges from2.03×10-8 to 8.25×10-8 m2/s, with the average values of 24.364 kJ/mol and the pre-exponential factor of 7.603×10?5m 2 /s.The pyrolysis characteristics of sludge are studied by thermogravimetric analysis to explore variations of sludge pyrolysis characteristics under different conditions. This study is focused on pyrolysis characteristics in nitrogen atmosphere and carbon dioxide atmosphere, and it also studies catalytic pyrolysis of sludge. Finally, the apparent kinetic models and kinetic parameters of sludge pyrolysis are studied. The results showed that sewage sludge pyrolysis in nitrogen atmosphere has three distinct weight loss peaks: the first phase at temperature range of 200~490℃, the second phase at temperature range of 490~650℃, the first three stages at temperature range of 650~ 920℃. According to the activation energy, the catalytic importance sequence for sludge pyrolysis is described as: MnO2> Al2O3> MgO> Fe2O3> CuO> CaO. The activation energy is practically constant in the range of 0.2~0.9, with the average values of 102.4 kJ/mol and 88.7kJ/mol calculated by FWO and KAS methods, respectively.The co-combustion behaviour of sewage sludge with biomass and coal are carried out in a thermogravimetric analyzer under different conditions. The study is also focused on co-combustion characteristics of sewage sludge with coal, sludge with straw and sewage sludge with waste. The catalytic combustion characteristics and the influence of oxygen concentrations are also studied. Finally, sewage sludge and coal and biomass co-combustion kinetic model and parameters are studied. The results show that: Among four kinds of samples, namely, sludge, coal, straw and garbage, the integrated combustion properties and combustibility of straw are the best, and the combustibility of coal is worst and the integrated combustion properties of sludge is worst. According to combustible index, the sequence for catalytic combustion of sludge is described as: sludge +MgO>sludge +MnO2>sludge +Fe2O3>sludge>sludge +Al2O3>sludge +CuO. While according to integrated combustion index, the sequence is described as: sludge +MgO>sludge +MnO2>sludge +Fe2O3>sludge +Al2O3>sludge +CuO>sludge. When sludge combusts in O2/N2 with different oxygen concentrations, the combustible index and integrated combustion index reach maximum at 60vol%. When sludge combusts in O2/CO2 with different oxygen concentrations, the combustible index and integrated combustion index reach maximum at 80vol%. These results show that oxygen concentration have effect on the integrated combustion properties and combustibility.Drying of paper sludge is tested in the self-made fluidized bed drying tower to analyze the experimental process of empty tower, fountain and sludge drying. The results show that paper sludge is a kind of solid waste having features of high-moisture, low heat value. If not is dried, or add auxiliary combustion, sewage sludge can not maintain the self-ignition, due to its negative caloric value. After semi-dry, the low calorific value of sludge can reach up to 3000~5000kJ/kg, equivalent to that of lignite, so it can be used as fuel. Sludge fluidized bed drying experiment carried out unfavorably is caused by following reasons: Uniform sludge spraying has a bad effect on drying. Spray angle is too large making the sludge wall. Blower does not match making the air supply not enough. Grid plate does not work well.Commercial CFD software FLUENT6.2 was used to simulate drying and incineration process of sludge in fluidized bed. The results show that when the flue gas inlet temperature is 433.15 K, the predicted gas outlet temperature is about 420.94, the temperature various trend is good agree with experimental data. Three kinds of operational conditions was modeled by CFD, the temperature is 413.15, 423.15 and 433.15 respectively, the predictions indicate that the effect of drying was influenced by the flue gas inlet temperature, the high inlet temperature is, the more water was evaporated, the mass percent of H2O is 1.66%, 2.02% and 2.35%. The predicted results of CFB furnace show that the co-combustion of paper sludge/coal is initially intensively at the bottom of bed; the temperature reaches its maximum in the dense-phase zone, around 1400K. The predictions indicate that paper sludge spout into furnace from the recycle inlet can increase the furnace maximum temperature (1396.3K), area-weighted average temperature (1109.6K) and the furnace gas outlet area-weighted average temperature(996.8K). The mathematical modeling predicts that 15 mass% paper sludge co-combustion is the highest temperature at the flue gas outlet, it is 1000.8K.
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