Drying Process

Dewatered sludge is conveyed into the push floor container of the dryer, controlled by the process controller and monitored by sensors, the push floor doses the sludge into a front facing screw feeder. This transports the sludge into a mixing trough, which leads to the dryer. The dried sludge is conveyed in the mixing screw from the dryer return line. Dry and wet are then mixed homogeneously to approximately 45% dry matter and conveyed into the first drying chamber.

Using the quickly rotating scoop blades that are fitted to the base of the dryer, the sludge is kept in a constant cloud of material in the air. Using the involvement of exhaust gas, air at 572°F is conveyed directly into the cloud of material in each chamber.

The impact of the high temperature combined with a high difference between the partial pressure and steam saturation pressure causes a turbo drying process. Moisture immediately becomes gaseous and is absorbed by the surrounding air. Throughout the entire drying time of approximately 5 minutes, the sludge remains in each chamber for the relevant portion of time.

At the end of the chamber time, a pneumatic cylinder opens the valve to the next chamber, and the sludge is simultaneously conveyed through it. In the last chamber, the fully dried sludge is thrown into a holding chamber, via a closed screw feeder to the dryer return line and transported for pelletization. The entire process is closed and operated at low pressure, meaning absolutely no emissions can escape into the surroundings of the dryer.

The exhaust gas is conveyed through the integrated fine filter chamber. External fans draw the exhaust gas through the filter bags. The dust is deposited in the filters, which are independently shaken at defined intervals. There is a screw feeder on the floor of the filter chamber, which conveys the filter dust to the holding chamber and adds it back into the dried sludge. There is no maintenance involved in removing the filter dust.