Updated: July 2002

1. Outline of system

In recent years, further purification of exhaust gas and improved combustion efficiency is required for sewage incineration. In addition, the needs for the incineration involving screenings and sediments have increased. Incinerators allowing to remove the incombustibles outside the system during operation are also required.
To meet these requirement, we have lined up high efficient fluidized bed incinerators consisting of incineration promoters combined with diffusing pipes.

2. Characteristics

(1) Principle:

1) Incineration promoters
The incineration promoters are in a structure formed zigzag with ceramic pipes, and installed in the freeboard section of the incinerator. When the exhaust gas pass through the incineration promoters, the heat is returned inside the incinerator as the radiant energy by the promoters. In addition, the combustion efficiency inside the incinerator is increased by the stirring effect of passing gas.
2) Diffusing pipes
Preheated high-temperature air fluidized the air when it jets out of a number of nozzles made through the diffusing pipes.
The incombustibles contained in screenings and sediments fall down through the gaps between adjacent diffusing pipes. It is possible to draw out the incombustibles from the bottom of the incinerator.

(2) Merits:

1) Cleaned exhaust gas
The incineration promoters enhance the combustion efficiency of the incinerator, and control the generation of harmful incomplete combustion gas containing dioxin.
2) Compacted incinerators
Complete incineration can be expected because of enlargement the high-temperature areas and equalization the temperature in the incinerator, and shortening of retention time in the freeboard section is also possible.
3) Stabilized incineration involving screenings and sediments
It is possible to continuously discharge the incombustibles contained in screenings and sediments by combining the incinerator with the diffusing pipe system. By this, the accumulation of the substances hindering the fluidization on sand layers in avoidable, and preferable state of incineration can be secured.

3. Performance

Table 1 Nature of exhaust gas at the outlet of incinerators
(oxygen dioxide converted at a rate of 12%)

Table 2 Effect of reducing fuel cost

4. Applicability and objectives

(1) Applicability: waste incinerators
(2) Objectives: sewage sludge, screenings and RDF

Figure 1 Mitsubishi highly efficient fluidized bed