| Microwave pyrolysis of sewage sludge possess the characteristics of heavy metal solidification and products utilization. The sewage sludge pyrolysis residues （SSPR） was landfilled or used as absorbant which was cheap but not efficient, and the former didn’t realize the reutilization of waste and the later wasn’t the final disposal. Response surface methodology was used to obtain the sludge microwave pyrolysis conditions which were best fit for the material utilization of SSPR and the conversion rate of sludge organic matter was the highest. SSPR was used to produce glass-ceramics using microwave energy, which realized the high ratio utilization of SSPR. The efficiency and mechanism of glass-ceramics produced from SSPR was investigated through comparing with the glass-ceramics produced by conventional energy and the promoting mechanism of microwave radiation on the properties and crystallization of the glass was revealed.The effect of microwave power, sludge moisture content and microwave absorbing material content on the sludge pyrolysis process and SSPR was investigated. The results indicated that the microwave power, sludge moisture content and microwave absorbing material content had great influence on the final pyrolysis temperature and the conversion rate of sludge organic matter. The organic matter in SSPR increased with the increase of the final pyrolysis temperature. In order to obtain SSPR which was fit for material utilization, response surface methodology was used to optimize the sewage sludge pyrolysis condition with the microwave power, sewage sludge moisture content and microwave absorbing material content as influence factors, and the conversion rate of organic content in sewage sludge and the fixed carbon content in SSPR as the response value. The conversion rate of organic content was 77.38% and the fixed carbon content in SSPR was 12.68% when the sewage sludge moisture content was 79.28%, microwave absorbing material content was 0.12 g/g dry sewage sludge and the microwave power was 1909 W. And the SSPR was fit for material utilization after microwave oxidation.Four CaO/SiO2 ratio glass raw materials were prepared with the introduction of different amount of CaO and SiO2.Because the glass raw materials cannot achieve the melting temperature under microwave radiation, the microwave reactor was designed to produce glass-ceramics successfully. The reactor was composed of three layers of alundum crucible and a double layer structure, which was filled with SiC:Al2O3=1:1 in the outer layer and SiC:Al2O3=9:1 in the inlayer.The effect of CaO/SiO2 on crystallization behavior and properties of glass-ceramics was investigated in the process of glass-ceramics production. The main crystalline phase of the glass-ceramics was anorthite and diopside, the grain size was uniform and closely packed, the density and mechanical properties were superior to the glass-ceramics of other CaO/SiO2 ratio when the utilization of SSPR was 80% and CaO/SiO2=0.33. The study of glass-ceramics with CaO/SiO2=0.33 indicated that the production of glass-ceramics using microwave energy decreased the temperature and reduced time of heat treatment and saved the energy consumption. The properties of microwave glass-ceramics were superior to those of the conventional glass-ceramics.In order to explore the promoted mechanism of microwave radiation on the crystallization and properties of the glass-ceramics, the crystallization behavior and crystallization mechanism of the glass-ceramics were investigated. The kinetics study of the glass indicated that microwave radiation decreased Ea about 76 kJ/mol. And it was calculated that k（Tp） of microwave glass and conventional glass was 0.29 and 0.24, respectively, the glass with smaller k（Tp） was more stable, which confirmed that microwave glass was easy to crystallize. The n values of microwave glass and conventional glass were in the range of 3.03-3.43 and 1.73-1.95, respectively, which indicated that the crystallization mechanism was altered from surface nucleation to bulk nucleation under microwave radiation. Microwave radiation promoted the movement of Mg2+, replacement of Si4+ by Al3+, rearrangement of [AlO4]Ca[AlO4] and the combine of [AlO4]Ca[AlO4] and [SiO4], so the main crystalline phase anorthite in microwave glass-ceramics was higher and there was diopside in microwave glass-ceramics. The microwave glass-ceramics possessed excellent properties because of the higher crystallinity and the compact microstructure. The solidification effect of heavy metals was better and the heavy metals mainly existed in residual state in the microwave glass-ceramics.SSPR was used to produce glass-ceramics which realized the high ratio resource utilization of SSPR. Microwave was used to produce glass-ceramics and the energy consumption was decreased. The glass-ceramics produced by microwave possessed better properties and the solidification effect of heavy metals was better, the study possess important value of research and application. |
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