Document LK0wNQYa6vqRwbBz37V3R72Xd

American Society of Heating and Ventilating Engineers Guide, 1936 supplied under the moving grate to carry on combustion at a sufficient rate to complete the burning of the coal near the rear of the furnace. The ash is carried over the back end of the stoker into an ashpit beneath. This type of stoker is suitable for small sizes of anthracite or coke breeze and also for bituminous coals, the characteristics of which make it desirable to burn the fuel without disturbing it. This type of stoker requires an arch over the front of the stoker to maintain ignition of the incoming fuel. Frequently, a rear combustion arch is required to main tain ignition until the fuel is fully consumed. A typical traveling-grate stoker is illustrated in Fig. ,1. . . Another and distinct type of overfeed flat-grate stoker is the spreaderor sprinkler type in which coal is distributed either mechanically or by air over the entire grate surface. This type of stoker has a wide application Chapter 28--Automatic Fuel Burning Equipment stoker is suitable for all coking coals while in the smaller sizes it is suitable for small sizes of anthracites. In this type of stoker the fuel is delivered to a retort beneath the fire and is raised into the fire. During this process the volatile gas is released, is mixed with air, and passes through the fire on small sized fuels and on certain special fuels such as lignites, high-ash coals, and coke breeze. Overfeed Inclined Grate Stokers \ In general the combustion principle is similar to the flat grate stoker, but this stoker (Fig. 2) is .provided with rocking grates set on an incline to advance the fuel during combustion. Alsb this type is provided with an ash .plate where ash is accumulated and from which it is dumped perodically. This type of stoker is suitable for all types of coking fuels but preferably for those of low volatile content. Its grate action has the tendency to keep the fuel bed well broken up thereby, allowing for free passage of air. Because of its agitating effect on the fuel it is not so desirable for badly clinkering coals. Furthermore, it should usually be provided with a front arch to care for the volatile gas. Underfeed Side Cleaning Stokers In this type (Fig. 3), the fuel is fed in at tlie front of the furnace to one or more retorts, is advanced away from the retort sis combustion pro gresses, while finally the ash is disposed of at the sides. This type of 486 Fig. 2. Overfeed Inclined Grate Stoker Fig. 3. Underfeed Plunger Type Stoker where it is burned. The ash may be continuously discharged as in the small stoker or may be accumulated on a dump plate and periodically discharged. This stoker requires no arch as it automatically provides for the combustion of the volatile gas. Underfeed Rear Cleaning Stokers This type of stoker carries on combustion in much the same manner as the side cleaning type, but consists of several retorts placed side by side 487