Co-pyrolysis of coal-derived sludge and low-rank coal: Thermal behaviour and char yield prediction

Abstract

Coal-derived sludge, a solid waste produced by the coal industry, offers potential opportunities for resource recovery due to its high organic matter. However, its products face challenges related to low utilization efficiency and economic value. Effective and clean treatment of coal-derived sludge is essential for sustainable development. Herein, we studied the co-pyrolysis treatment of coal-derived sludge and low-rank coal at different temperatures (500 °C−900 °C) and pretreatment methods (mechanical mixing and hydrothermal co-treatment). The co-pyrolysis of sludge and coal could increase the pyrolysis char yield and H₂ yield, as well as reduce CO₂ emissions. The hydrothermal co-treatment significantly improved the cleanliness of the co-pyrolysis treatment. Then we conducted a comprehensive analysis of the properties of the pyrolysis char using different characterization techniques. In order to better evaluate the distribution of co-pyrolysis product yield, six machine learning models were developed to predice co-pyrolysis char yield. The best model-predicted values showed excellent predictive performance when compared to the experimental values at high pyrolysis temperatures (≥700 °C). This study provided a new perspective on the resource utilization of coal-derived sludge and low-rank coal.