Drying process solution for volume reduction of high-viscosity ETP sludge

ETP (Effluent Treatment Plant) sludge from chemical and textile printing/dyeing plants is highly viscous. During the drying process, it is prone to sticking to vessel walls and forming clumps, which often leads to clogging in conventional drying equipment and results in high operation and maintenance costs. Implementing a drying process specifically designed for high-viscosity materials can significantly reduce both the volume and weight of the sludge, thereby lowering costs for outsourced disposal while ensuring compliance with environmental emission standards.

Sludge Pretreatment: Following filter-press dewatering, the pasty ETP sludge undergoes conditioning—often through the addition of recycled dry sludge—to reduce its viscosity and break up large clumps. This ensures a continuous, uniform feed and minimizes the risk of material adhesion.

Equipment Selection: A hollow-paddle dryer is the preferred choice. It utilizes indirect heating combined with self-cleaning agitator paddles that continuously scrape sludge off the heat-exchange surfaces. This design is well-suited for high-viscosity, pasty sludge and offers superior thermal efficiency.

Moisture Content and Temperature Control: Raw sludge typically has a moisture content of 75%–85%. A multi-stage, low-temperature drying approach is employed to prevent the formation of a hard crust on the sludge surface. After drying, the moisture content can be reduced to below 30%, achieving significant volume reduction and facilitating subsequent off-site transport or co-disposal.

Exhaust Gas Treatment: Since the exhaust gas generated during drying often carries odors, the system must be equipped with dust removal and deodorization units to capture and treat the off-gases, ensuring that emissions remain within regulatory limits.

Operation and Maintenance: Key operational requirements include maintaining a stable feed rate and conducting regular inspections of the agitator paddles and the anti-corrosion lining of the dryer vessel. The primary focus of this process is to resolve issues related to wall adhesion and clogging, ensuring the long-term, stable operation of the sludge drying line at the wastewater treatment facility.