Book - School of Science and Technology

Automatic stokersBoiler firing ± solid fuel 279Of the overall choice available, there are several specific types of automatic stoker whichare particularly appropriate for use with the size range of boiler which falls within thescope of this book. These include those which are most commonly used, namely thevarious patterns of underfeed stoker and also, as shown in Figure 10.16, sprinklers,coking types and moving beds.All modern types of stoker may be arranged for some form of semi- or fully automaticcontrol whether this be variable through speed control of the mechanism or merely `onoff '. In the latter case a `kindling' control is a necessary feature, the stoker operating for afew minutes in each and every hour in order to keep the fire alive. A recent development,for use when starting the fire, is a form of electric ignition.BoilerfrontHopperF.D. fanAsh shuteSprinklerrotorScrewPlenum(a)Fixed grate(b)IgnitionarchGrateRamGratemechanism(c)F.D. fan(d)Figure 10.16 Types of automatic stoker: (a) underfeed; (b) sprinkler; (c) coking; (d) moving bed