The Research About Low Temperature Pyrolysis Characteristics Of Municipal Sludge And The Developmemt Of Pyrolysis Device

Due to the increasing amount of municipal sewage sledge and the shortage of traditional treatment of sewage sludge, the low-temperature pyrolysis technology of sewage sludge has been considered to be a promising disposal method with the advantages of reclamation, environmental friendly, and etc.A series of experiments, such as thermogravimetric analysis and bench-scale pyrolysis tests were conducted in this work. On this basis, the main pyrolysis reaction parameters were determined for the development of an industrial scale pyrolysis reactor. An external heated rotary kiln was adopted and optimal designed, which was including the diameter, length, configuration, control system, etc. This industrial pyrolysis apparatus was can be used in a20t/d sewage sludge drying project. Furthermore, the thermal characteristics of this apparatus were studied. The heat transfer and the simulation of pyrolysis process of sludge in this rotary kiln apparatus were presented.Characteristics of pyrolysis process of sewage sludge were firstly investigated with the thermo-gravimetric analyzer (TGA) in nitrogen. The basic parameters were obtained, such as the initial and final pyrolysis temperature, the temperature at the maximum pyrolysis rate, weight loss, and so on. The results showed that the main pyrolysis reaction appeared in200℃-500℃. Increased heating rate resulted in the lower initial pyrolysis temperature and the higher max loss rate. However, the total loss ratio was not related to heating rate. The kinetic parameters were analyzed. The apparent activation energy was24-29kJ/mol under30-50K/min heating rate.The bench scale experimental research of low-temperature pyrolysis of sewage sludge under different temperature and time was conducted. Between220to460℃, the yield of pyrolysis oil and gas increased at higher temperature, which was opposite to the production of pyrolytic char. The preferable reaction time for low-temperature pyrolysis of sludge was about40min. Copper was used as catalyst in the research. It can significantly improve the pyrolysis of the sludge pyrolysis. The pyrolysis oil production increased from25.63% to30.74%, while the char reduced about13%.Through the experimental research in this work, the main parameters were determined to use for the design and development of industrial sludge pyrolysis apparatus. The pyrolysis temperature of350℃and the residence time of40min were adopted. The capacity of this external heated rotary kiln reactor was about5t/d for dry sludge. The optimal design was performed on the basis of movement analysis of sludge in rotary kiln. The optimized diameter and heating length of this rotary kiln were0.9m and5.4m respectively. The configuration, control system, feeding and discharging system were further developed。The thermal performance and the balance of rotary sludge pyrolysis apparatus were analyzed. The result based on the thermodynamic analysis of sludge was similar with that from the analysis of reactor thermal balance. Both the methods can be used in the design and development of this kind of pyrolysis equipment. The heat-transfer process coupling with the pyrolysis reaction in the external heated rotary kiln pyrolysis apparatus were simulated in this work. The calculated sludge bed temperature and the material conversion are basically consistent with experimental data.