Study on the Co-Combustion Behavior of Municipal Sludge and Bagasse: Evaluation of Ultrasonic Pretreatment

Currently, the production of sludge in China is on the rise annually, and the co-combustion of sludge with biomass for power and heat generation represents a viable method for the bulk treatment of sludge. In this study, we examined the combustion characteristics of municipal sludge (MS), bagasse (BA), and their blends using thermogravimetric analysis. Orthogonal experiments were conducted to assess the impact of ultrasonic pretreatment on the co-combustion properties of MS and BA. Prior to ultrasonic pretreatment, the combustion of BA was characterized by three distinct stages, while MS exhibited two stages. At a 30% MS ratio, the promotional interaction between BA and MS was most pronounced. Following ultrasonic pretreatment, the combustion of BA was simplified to two stages. With a 10% MS mass ratio, ultrasonic pretreatment enhanced the comprehensive combustion characteristic index, thereby improving the combustion performance of the mixture. The activation energy increased post-pretreatment, particularly when the MS content was 50%. Under the conditions of 45 kHz frequency, 500 W power, 3 h duration, and a 10% MS blending ratio, the mixture displayed reduced mass residue, elevated reaction rates, and superior combustion efficiency. This research aims to introduce a novel approach to the harmless disposal, volume reduction, and resourceful utilization of sludge.