Document zdpJeVqGqX7zJ78q1N7w1qwpn

382 CHAPTER 15 1957 Guide Automatic Fuel Burning Equipment 383 Fig. 3. Underfeed Anthracite Stoker with Automatic Ash Removal, Bin Type laf Fig. 6. Underfeed Screw Stoker, Bin Type, Class 2, 3 or 4 Fig. 4. Stoker-Fired Winter Air Conditioning Unit XiZ' v;. COM. DISTRIBtmMa Mt Fig. 7. Underfeed Side Cleaning Stoker Fig. 5. Underfeed Screw Stoker, Hopper Type, Class 2, 3 or 4 A rapid evolution of the combustible volatile matter occurs during and directly after the plastic stage. The distillation of volatile matter con: tinues above the plastic zone where the coal is coked. The strength and porosity of the coke formed will vary according to the size and character-'! istics of the coal. While some of the ash fuses into particles on the surfa?S of the coke as it is released, most of it remains on the hearth or grates and, as this ash layer becomes thicker with time, that portion exposed to tn? higher temperatures surrounding the retort fuses into a clinker. , T&S temperature in the fuel bed, the chemical composition and homogeneity f the ash, and the time of heating govern the degree of fusion. Most bituminous coal stokers of Classes 1, 2, 3 and 4 require manual removal of the ash in clinker form.