For the treatment of sewage sludge, incineration is now the major process and the fuel cost has been reduced greatly by Mitsubishi Indirect Heat Dryer. Now Mitsubishi Heavy Industries Ltd. has developed new technology of drying system for better energy saving or even creating energy.

2. Characteristics

This new drying system shall utilize the waste heat from the indirect heat dryer, for more energy saving.
Steam consumption rate can be saved down to about 1/5, which means the effective utilization if such steam energy for power generation and/or other heat recovery.

3. Principle

This new drying system is an indirect heat pump system which reuses the evaporated and exhausted steam vapor.
The heat of evaporated vapor can be recovered into the recirculating steam at condenser, which is then boosted the heat losses by steam compressor to get the heat energy for sludge drying. This means all it needs to the sludge drying is the power of compressor only.
Therefore, all the recovered heat can be utilized for power generation and/or other heating, etc.

4. Flow Diagram

Simplified flow diagram of new drying system is shown below.

HIGH EFFICIENCY DRYING SYSTEM

Fig. DRYING ENERGY BALANCE