Collaborative disposal of municipal sludge in metallurgical sintering process: a comprehensive analysis from fundamental research to industrial application

The collaborative disposal of urban solid waste using existing industrial kilns has become a trend. Municipal sludge is difficult and costly to dispose of owing to its high moisture content, strong odor, and high content of pollutants. This paper proposes a new process for collaborative disposal of municipal sludge using metallurgical sintering processes. Through fundamental research and industrial applications, the limiting factors of sludge disposal are comprehensively analyzed, and solutions and appropriate sludge ratios are proposed. The results showed that the sintering machine could directly dispose of high moisture content sludge without dewatering/drying pretreatment. The content of P and S in sludge, as well as the mixing of sludge with sintering materials, were limiting factors in disposal. Effective improvement could be achieved by adjusting material ratios, reducing fuel ratios, and adding an intensive mixing equipment. Taking the steel plant that had already implemented application as an example, when the ratio of sludge (with a moisture content of 86%) was 3.1%, the annual sludge disposal was 187900 tons. It could reduce the amount of water added to the sintering mixture by 79.14% and the fuel usage by 4%. It had little effect on the sintering indicators and sintered ore, and the flue gas emissions could meet the ultra-low emission standards. The use of sintering machines to dispose of sludge can achieve reduction, harmlessness, and resource utilization of sludge, improving the economic and social benefits of steel plants.