For waste water treatment plants looking for waste management solution, we offer an ecological technology for drying sewage sludge in hybrid dryers, using renewable energy sources. This technology allows for environmental-friendly processing of sewage sludge and reduces its amount over than 3 times. Unlike the traditional dryers using fossil fuel, it is possible to dry sludge using low-cost alternative energy sources such as heat from biogas combustion, waste heat utilization from treated sewage, waste heat from cogenerator cooling and solar energy. This allows for drying of the sludge regardless of weather conditions and increasing of process efficiency.
The hybrid sewage sludge drying installations consist of drying halls similar to green houses with steel structure covered with polycarbonate or glasses plates. The main principles of drying operation is the solar effect and heating floor exploitation to water evaporation from sewage sludge. Inside the drying hall sludge is transported, aerated and granulated by a mechanical turning sledge device. The automatic ventilation system ensures humidity removal outside the drying hall. The drying technology causes wet sewage sludge to granulate during processing. As a result the mass and volume of sludge becomes more than three times smaller. This technology is one of the cheapest solutions for water evaporation. The evaporation of 1 tonne of water uses only 20-30 kWh electrical energy. The final product dried sludge takes the form of a granulate and could be agriculturally or energetically used. The calorific value is similar to brown coal 12 MJ/ kg.
Avantages of the solution:
- Ecological technology allows for drying of the sludge regardless of traditional sources of energy – fossil fuel. No emissions of pollutants into the environment
- The dryer could be an independent installation without providing conventional sources of energy
- Cheap running costs and simple operation of the dryer
- Full process automation, which does not require constant service
- Over threefold mass and volume reduction of dried sludge
The hybrid sewage sludge drying technology using alternative energy sources is successfully used in Kłodzko (Poland), where it is applied in the Centralna Słoneczna Suszarnia Osadów. The process of drying is conducted in a drying hall using solar energy, and under-floor heating delivered by a hybrid heat generating using renewable energy, created by heating-pumps which recover energy from the treated sewage. The dryer enables an annual yield of 1300 t of sewage sludge processed into granules with an average dry substance content of 80%. Hybrid dryers also function at the waste water treatment plants in Iława and Łomianki (Poland).