Updated: July 2002

1. Combustion of Sludge

Recently, with the spread of organic polymer dewatering process, fluidized bed incineration (FBI) system has been widely applied in the sewage sludge treatment field. And large scale furnace such as 300 t/d tends to be installed for the more efficient treatment in the large city.
On the other hand, the decreasing of sludge moisture content is one of the important points. In the drying-incineration process, under which the sludge is dried in advance by the heat recovered from exhaust gas, the dewatered sludge, even if high moisture or low calorific value, can be burned with no auxiliary fuel.

2. Features

1) The large heat capacity of the fluidized sand makes stable operation even if the volume or the properties of the sludge may change.
2) The volatile matters in ash accounts for less than 1%. Screenings of the sewage can be burned by FBI.
3) Operation can be easily stopped and restarted.
Furthermore, the drying-incineration system has the following features:
4) By the pre-drying, sludge can be self-burned. It is an energy-saving system with low consumption of auxiliary fuel.
5) The volume of exhaust gas is less with the dryer than without the dryer.

3. Configuration

The sludge continuously fed into the furnace is preheated, dried, and crushed into the fine particles by the fluidized sand at a high temperature in the sand bed part.
The feature of the fluidized bed furnace is that sludge is continuously mixed with air by the fluidized effect, and uniform combustion is preformed in a short-time. The organic matters in the sludge burn completely as they pass through the free-board part and are exhausted from the top of the furnace. Normally, air ratio for combustion is approx. 1.3.