| Microwave-heating-based pyrolysis for sewage sludge can produce bio-oil, syngas and carbonaceous adsorbent, which is beneficial to resource recovery of wastes and emission mitigation of pollutants. In this study, a pilot-scale microwave heating equipment with the processing capacity of 5 kg solid waste was constructed. Using the equipment, the effects of important microwave-related processing parameters were investigated such as heating rate, final pyrolysis temperature and radiation time, as well as catalyst usage on the yield and quality of bio-oil, syngas and carbonaceous adsorbent. Moreover, the mechanisms and kinetics of resources recovery from sewage sludge pyrolysis using microwave heating was explored by analyzing the components and properties of resultant products.By analyzing the impacts of microwave heating conditions on sewage sludge pyrolysis, it was found that microwave power and final temperature are the crucial factors during the temperature rising process. The generation of bio-oil occurred mainly in the range of 150-400°C, and the maximum bio-oil generation rate was researched at the temperature between 250-300°C. The syngas generation rate occurred at the temperature between 250°C-320°C. However, it decreased when the temperature was higher than 320°C. During the process of carbonaceous adsorbent production, the optimum carbonization temperature was approximately 600°C. When the temperature reached 700°C, violent pyrolysis reactions took place, leading to the decrease of carbon quantity and quality. In general, an increase in the microwave power was beneficial to enhancement of the bio-oil and syngas quality.The impacts of catalysts on the pyrolysis process were further examined. Results showed that catalysts had significant impacts on the generation of bio-oil, syngas and carbonaceous adsorbent.The catalysts decreased the quantity of resultant products except that FeSO4 and ZnCl2 increased the quantity of syngas.KOH,H2SO4,H3BO3和FeSO4 significantly increased the quality of bio-oil, while ZnCl2 decreased. For the syngas, acidified sewage sludge added with H3PO4 or H3BO3 decreased CO and CO2 production rate, but increased the generation rate of H2.Regarding carbonaceous adsorbent, the catalysts can stimulate the formation of porous structure of SBAs. There is much complexity existing in the process of sewage sludge pyrolysis as well as its impact factors. This leads to the difficulty in investigating the mechanisms and kinetics of the pyrolysis process using traditional first-principle models. Therefore, three statistical inference methods were employed instead for modeling and forecasting of temperature-rise and bio-oil production processes. The results revealed that support vector machine achieved the best forecasting performance, with their R-square values higher than 0.8. Despite the first attempt, it was desired that further studies be undertaken to improve the accuracy of the statistical methods and extend them for modeling the kinetics of other processes such as gas synthesis and carbonaceous adsorption.Moreover, energy and mass balance analysis was conducted. The results showed that the mass of the carbonaceous adsorbent, bio-oil and syngas accounts for 65–68.9%,10.1–15.3%, and 11.8–13.4% of the sewage sludge mass, respectively. The heat values of the carbonaceous adsorbent, bio-oil and syngas produced from each kilogram sewage sludge were 5.21 MJ–6.71 MJ,3.70 MJ–5.34 MJ和1.35 MJ–1.60 MJ, respectively. In addition, it was found that the addition of catalyst increased energy storage capacity of the carbonaceous adsorbent, but lowered that of the bio-oil.
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