Updated: July 2002

1. Outline of system

In recent years, the realization of high calories in sewage sludge has been advancing. With this development, moves to reconsider sludge as resources for energy and utilize it have been on the increase. Our company, having noted the sludge incineration waste heat, has realized a sewage sludge incineration waste heat recovery and steam power generation facility which recovers waste heat and carries out steam power generation.
Fig.1 shows the outline of this equipment. In the recovery of incineration waste heat, incineration exhaust gas in subjected to recovery of heat 830ºC to 250ºC by the waste heat boiler which are arranged in parallel with catch other and the air preheater. Also, the conditions of steam to be recovered in the waste heat boiler are set at a pressure of 3.0 MPa and a temperature of 355ºC which have many track records. Furthermore, a condensing extraction turbine has been adopted as the steam turbine and the turbine steam conditions are set at an inlet pressure of 2.75MPa and an exhaust pressure of 14.7 kPa. Also, the turbine output is 2500 kW when three pieces of incineration equipment with a capacity of 300 t/d are operated.

Fig.1 Flow in the sludge incineration waste heat recovery and steam power generation facility

2. Characteristics

(1) Stable recovery of waste heat in the high temperature zone:
By further recovering in the waste heat boiler a surplus amount of waste heat resulting from the utilization of exhaust gas waste heat with the use of the conventional air preheater, it is possible to effectively utilize waste heat in a stable manner.
(2) Realization of high rate of self-supply of electric power equipment
By recovering all of the surplus amount of calorie in the waste heat boiler after self-combustion is started in the incinerator, a high rate of recovery of waste heat is attained. Thus, the realization of a high rate of self-supply of electric power equipment has been achieved.
(3) Restraint of the amount of CO2 discharged: Heat island restraint
By recovering waste heat from incineration exhaust gas, it is possible to recover energy, thus enabling power generation. Therefore, there is no generation of CO2 which originates from fuel and is consumed for generation of electricity, and thus, it is possible to reduce gas discharge which contributes to global warming and it is hence possible to restrain the heat island phenomenon.
(4) Utilization of a heat source in the form of steam is also possible.
By extracting a part of the steam from the steam turbine, it is also possible to supply steam to each device and use steam as a heat source for heating and cooling in the facility.

3. Performance

Table 1 shows equipment specification for this sludge incineration waste heat recovery and steam power generation facility. This facility has a power generation quantity of 2500 kW when three pieces of sludge incineration equipment with a capacity of 300 t/d are operated.

Table 1 Facility specification

4. Applicable fields and materials to be treated

(1) Applicability: Equipment for recovery and effective utilization of waste heat
(2) Objectives: Exhaust gas resulting from incineration of wastes

Fig. 2 Steam power generation equipment