Energy efficiency improvement and cost optimization of municipal sludge pyrolysis carbonization via residual heat utilization

Sludge pyrolysis carbonization technology has attracted significant attention in the field of sludge disposal due to its advantages in volume reduction and carbon sequestration. However, high energy consumption and high operating costs have limited its engineering application and widespread adoption. To address these challenges, this study analyzed the energy-saving potential and process optimization based on measured data from an existing municipal sludge pyrolysis carbonization project. The results demonstrate that by implementing waste heat reuse for drying tail gas and optimizing the allocation of pyrolysis oil and gas, external fuel consumption can be reduced by 64.40%. Furthermore, the study elucidated the influence of sludge water content on system energy efficiency and established an energy cost model encompassing the entire sludge disposal process, including mechanical dewatering and thermal treatment. The model determined that when the water content during mechanical dewatering is controlled at 62% before entering the drying stage, the system achieves its optimal economic point, with a minimum operating cost of 35.64 $/t . Compared with existing incineration and anaerobic digestion processes, this improved process effectively combines low-cost operation with reduced carbon emissions, providing a theoretical foundation and engineering guidance for the sustainable disposal of municipal sludge.