Drying characteristics of sludge in a rotary drum for fast-drying application

High temperature metallurgical slag (temperature, >1450°C) and high moisture sludge (moisture content, >80 wt.%) are common wastes with huge outputs. Many problems, such as high cost, low level of harmlessness, and low efficiency, are encountered in current treatment methods. If these wastes can be recycled, they can be valuable secondary resources. Therefore, using the drum apparatuses to treat these two kinds of wastes is proposed. The process uses waste heat of slag to dry sludge with high moisture content and is a kind of alternative circulation treatment technology in which steel balls are used as ball milling media and intermediate heat carriers. Besides, this technology can break up slag or sludge in real time, thereby ensuring high heat or mass transfer rate. This study presents an experimental investigation of the dynamic drying process of wet sludge mixed with hot steel balls in a rotary drum. The relationship of operation parameters (including sludge moisture content, sludge treatment mass, steel ball diameter, and rotary speed of drum) and drying effect is obtained. There are three kinds of final drying results: completely dried to powder, few sludge agglomerations, and sludge-to-wall adhesion. If the operating parameters are set well, the sludge could be efficiently and completely dried and eventually in powder form