Schmid - Model UTSW - Moving Step Grate Firing System

1. Fuel supply with stoker screw
2. Combustion chamber with water cooling
3. Water-cooled step grate
4. Burnout zone
5. Under-grate de-ashing – automatic or manual
6. Automatic grate ash discharge
7. Access door to under-grate
8. Radiation vault
9. Refractory concrete with defined heat passage
10. Secondary combustion chamber – in accordance with low NOx process by means of air stages
11. 3-pass steam boiler
12. Boiler door with automatic pulse-jet cleaning system of the boiler tubes
13. Flue gas cleaning by multi-cyclone with automatic fly ash discharge
14. Flue gas fan – can be positioned either on the right, left or at the rear
15. Grate door with safety lock

The UTSW boiler unit is equipped with a step moving grate and also suitable for fuel with a high ash content. The fuel is fed on to the sloping feed grate from the rear of the furnace. The grate consists of water-cooled grate girders; the rods overlap on both sides, so that the minimum fuel slips through the grate. Furthermore, the grate is designed to enable a clear, uniform distribution of the primary air supplied to the various zones, thereby creating a steady, undisturbed gasification zone. The grate carriage has a hydraulic drive, so that the movement intervals can be automatically adjusted to the capacity. The entire combustion chamber is water-cooled and lined with fireproof material, thereby ensuring the required cooling even in the case of fuel that generate a high temperature in the combustion chamber.