GB1349757A - Fuel burning heaters - Google Patents

Abstract

1349757 Water heater TECHNICAL DEVELOPMENT CAPITAL Ltd 3 May 1972 [8 May 1971] 13869/71 Headings F4A and F4B A heater, of the kind in which heat produced by combustion of fuel is transferred at least in part directly to a surface of a heat exchanger or other body to be heated, includes a bed 22 of refractory particles, and means for supplying air and fuel to the bed so as to fluidize the bed and to throw up some of the particles so that they impinge on the surface to be heated which is positioned above the bed. When the heater is switched on the fuel/air mixture is fed by means of a fan 25 through a porous plate 21 and, after a delay to allow the fan to reach full speed, fuel supply valve 30 is opened and the mixture is ignited by an ignition device 44 which is switched off when a flame is sensed in the combustion chamber 18. The initial gas velocity is sufficient to fluidize the bed but the particles do not rise above retaining ring 23; however when the gas temperature rises the gas velocity increases and causes particles to be thrown upwardly and to impinge on a cylindrical water jacket 11, having integral fins 20, surrounding the chamber 18. As the gases pass to outlet 19 they pass through a second bed of particles 45 and fluidize it, transferring further heat to the jacket 11, which may have integral fins 47 projecting into the bed. The particles of the second bed may be supported by a pierced metal plate 46 covered by a fine metal gauze which prevents the particles falling into the combustion chamber. Alternatively, Fig. 3, plate 46 and fins 47 may be replaced by parallel bars 152 having water passages 154, there being V-shaped channels 153 with narrow lower openings between the bars; particles from the bed 22 are thrown up between the bars and gas velocity is sufficient to maintain a fluidized bed thereon, the particles falling back to the bed 22 when the heater is switched off. Instead of the bars 152 there may be a plate, Figs. 4, 5 (not shown), having rows of downwardly tapering holes (155). The water jacket may have fins (148), Fig. 2 (not shown), having internal water passages. The plate 21 may be of porous ceramic material, with or without an upper layer of pierced aluminium, or of sintered inert metal; the refractory particles may be silica sand, with or without limestone. The water jacket may be omitted and supports above the bed 22 provided for objects such as metal billets, possibly with means for conveying them through the combustion chamber.