Evaluation of the Feasibility and Utilizability of Pretreated Sewage Sludge in Cement Kiln Co-Processing

Wei Cheng, Xiaohu Lin (), Wei Liu, Haihua Cao and Jingcheng Xu ()
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Wei Cheng: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
Xiaohu Lin: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
Wei Liu: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
Haihua Cao: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
Jingcheng Xu: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China

Sustainability, 2024, vol. 16, issue 20, 1-15

Abstract: The treatment and resource utilization of sludge from municipal sewage treatment plants is an important environmental issue. Cement kiln co-processing offers a promising solution, but challenges remain, particularly regarding sludge properties and feasibility in kiln systems. This study analyzes the characteristics of three pretreated sludges: mechanically dewatered sludge, deeply dewatered sludge, and lime-dried sludge. Using techniques such as thermogravimetric analysis (TGA) and X-ray diffraction (XRD), this study investigates their calorific values and raw material utilizability in co-processing. As the sludge moisture content decreases from interstitial to bound water, energy consumption per ton of evaporated water rises, particularly below 30%. At 10 °C/min heating, energy consumption for mechanically dewatered sludge at 80%, 30%, and 10% moisture was 3573, 8220, and 34,751 kJ/kg, respectively; for deeply dewatered sludge at 60%, 30%, and 10%, the values were 4398, 7550, and 11,504 kJ/kg. Keeping moisture content above 30% before kiln entry reduces energy use and enhances calorific value. Sludge utilizability as a raw material depends on its pretreatment. The ash composition of deeply and mechanically dewatered sludge resembles iron-rich raw materials, while lime-dried sludge aligns more with limestone. The utilizable ash content was 23.3%, 8.1%, and 46.3%, respectively, with lime-dried sludge showing the highest potential. This study provides insights into sludge properties and their co-processing potential in cement kilns, offering scientific and technical support for practical applications.

Keywords: sludge; cement kiln; dewatered sludge; dried sludge; co-processing (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2024
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