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Effect of freezing on drying and combustion characteristics of dewatered sludge |
MENG Qi1, YANG Tao2, YANG Cheng-jian1, AN Miao3, LI Zhi-hua1 |
1. Key Laboratory of Northwest Water Resource, Environment and Ecology, Ministry of Education, School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; 2. Shanghai Huanyun Renewable Energy Co., Ltd., Shanghai 201603; 3. Shanghai Environment Group Co., Ltd., Shanghai 200040, China |
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Abstract This work explored the effect of freezing operation on the drying and combustion characteristics of dewatered sludge and different freezing temperatures on the characteristics of the drying process for the sludge. In addition, the effect of different freezing temperatures and heating rates on the combustion characteristics of dewatered sludge were investigated by thermogravimetric analysis (TG-DTG). Then the dynamics analysis was carried out. The results indicated that compared with the original sludge, freezing turned the dewatered sludge into a hard structure that can be crushed, and when the temperature was dropped to –20℃, the drying rate of the crushed sludge was improved by 41.46%, and the drying time was shortened by 41.67%. Three degradation stages, dehydration, combustion of volatile and combustion of the fixed carbon were identified in the combustion process of the freezing dewatered sludge. As the temperature decreased, the ignition point, the volatile releasing index, the flammability index, the burnout index, and the general combustion index increased. According to the dynamics analysis, the reaction order of pre-peak was 0.9 and post-peak was 1.1. The apparent activation energy of the frozen sludge was higher than that of the original sludge, and as the temperature decreased, the apparent activation energy would decrease.
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Received: 14 May 2021
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