Sumitomo Heavy Industries, Ltd. is engaged in planning, design, procurement, fabrication, construction and start-up of the municipal solid waste incineration plants throughout the world. Its long and profound experience in the field of environment facilities allows an optimized approach to the clients' real needs and guarantees high operational reliability and efficiency while complying with strictest environmental regulations and standards.

[Incineration System]

Sumitomo municipal solid waste incineration plant has many features. Those are:

- The grate has no drops.
- The waste transport through the grate zones is fully controlled.
- A controlled, high-pressure drop over the grate lining ensures optimum  distribution
  of the air.
- The grate is self- cleaning.

Fig. 1 Processes of refuse disposal

[Characteristics]

The distribution of the waste on the grate is controlled by varying the cycle time, stroke length and feed rate of the hydraulically driven feeder ram below the waste chute. After regulation in the feeder, the waste passes through three grate zones: the drying zone, main combustion zone, and final combustion zone where the residues are burnt.

The forwards movement of the waste results from the superimposed arrangement of the grate bar rows moving in opposite directions. The moving and stationary bar rows lie in horizontally mounted supports, located in a solidly built grate support structure.

On the double- motion overthrust grate, ignition not only takes place from above by radiation and fluegas convection but also inside the waste layer. This is because the ignited material is constantly pushed downwards by intensive rotation and stirring of the waste layer causing ignition to also start from the bottom.

Fig. 2 Double- motion overthrust grate

The continuous poking and rotation repeatedly loosens and rearranges the waste layer. This helps the ignition and combustion by creating a larger surface area, which favours combustion air admission.

The service life of an incineration grate depends on, among other things, the grate temperature. The bars are therefore blower-cooled. Before the primary air reaches the waste layer, it flows through a labyrinth system beneath the bars, cooling them and heating itself in the process. The heated air exits at the front end of the grate bars and enters the waste layer.

The translational movement of the grate bar rows is a key factor in the air distribution, which has to be even. The air leaving the air slots is controlled to ensure an optimum air distribution in the waste layer. The slots are kept clean by the relative motion of the fixed and moving grate bars.

[Actual results]

This horizontal double- motion overthrust grate system has installed in many countries. In Japan, SHI is building new plants in Chikunan(375t/d) and in Akashi(480t/ d) now.