| Pulse combustion is an advance technology which has advantages in high energy efficiency, low emission and mass transfer intensity and high temperature (600-1200℃), high-frequency (30-300Hz) and high-speed oscillating flow can be generated by pulse combustor. Pulse combustor has advantages in simple structure, low cost. Compared with traditional spray drying, the pulse combustion spray drying materiel by its oscillating flow has many advantages. Municipal sewage sludge is the solid-liquid mixture which generated in the process of wastewater treatment and its moisture content is approximate80%. As the city’s economic and population develop rapidly, the environmental problems increasing seriously caused by the amount of municipal sewage sludge increase rapidly. Thermal drying sludge is an effective method of the ways of sludge treatment which can dispose sludge harmless, stability and reduction and it is widely used in sludge treatment in the current. This research project is atomizing and drying sludge using pulse combustion technology in order to explore a new sludge thermal treatment method. The thesis’s main contents are as following:(1) Study on drying characteristics of sewage sludge:Experiment research on different thin-layers sludge by hot-air and microwave, the results show that in the process of convective drying, the surface of sludge is easy to "form crust" which hindered the water migrate to out and the drying rate decreased. Microwave drying sludge has the advantages in shorter time, high drying rate and fewer energy consumption.(2) Energy consumption analysis of hot convective drying process of the sewage sludge:Hot air convective drying process of sewage sludge was conducted under various drying temperature by TGA. Energy consumption and drying characteristics was obtained. Some energy-saving methods are proposed and discussed in details based on the experimental results.(3) Pyrolysis and combustion kinetics characteristics of municipal sewage sludge: Experiment study on the pyrolysis and combustion characteristics of sewage sludge using TGA under nitrogen and air atmosphere. The results show that whole combustion process of sewage sludge could be divided into four stages and ignition temperature of the sludge samples was observed to be277.5℃and burning completely temperature was540℃, respectively. The apparent activation energy Ea and pre-exponential factor A was determined in the above main stages by using the continuity equation fitting method.(4) Study on the operation characteristics of Helmholtz pulse combustor:The influence of different tail pipe lengths and flow rates of LPG on the pulse frequency and amplitude of Helmholtz pulse combustor were analyzed. The excess air coefficient of the self-priming air was calculated. (5)Study on the atomizing and drying of sewage sludge using pulse combustion:The sewage sludge was drying and atomizing indirectly by the high temperature, high-frequency and high-speed oscillating flow generated by the pulse combustor. The effect of the frequency, different drying pipes, feed orifice diameters on atomizing and drying sludge were analyzed. The results show that the sludge can be atomized to small particles in0.5s by oscillating flow and the moisture content decreased to54%from80%with high drying rate. |
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