GB277396A - Improvements in and relating to furnaces - Google Patents

Abstract

277,396. Ljungstr÷m, B. March 16, 1926. Steam boiler &c. furnaces; grates; firebridges; fuel, feeding.-A method of burning fuel in furnaces consists in delivering the fuel at one or more points of a fuel supporting surface and conveying it through the furnace with, if desired, a portion of the fuel residues, in a closed circuit, unburnt fuel and fuel residues which are not discharged from the furnace serving to ignite the fresh fuel and protect the fuel-supporting surfaces. Incombustible substances such as sand may be delivered to the fuel supporting surfaces to supplement the fuel residues or ash. Figs. 1 and 2 show a furnace in which the fuel is burnt as stated above. It comprises a travelling grate, sections 3 of which are supplied with fuel from a hopper 5 and carry it towards the rear of the furnace where it is deflected by the inclined sur. face of a bridge 18 on to forwardly moving grate sections 6. Adjustable flaps 21 on a shaft 22 cause a part of the ash to be deflected from the sections on to the sections 3 and to be recirculated through the furnace. A portion of the ash passes beneath the flaps to the ash-pit from which it is removed by conveyers 27, 28. The shaft 22 also carries loosely mounted flaps 20 resting by gravity on the sections 6. The grate sections 3 and 6 are driven in opposite directions by toothed discs 23, 24 mounted on shafts 25, 26 and adapted to be driven by suitable gearing. Partitions 7, 8 between the grate sections extend upwardly above the flued surfaces and serve to separate the forwardly and rearwardly moving fuel. A free communication between the travelling beds of fuel is however provided at the ends of the partitions. The bridge 18 and the flaps 21 may be provided with wedge-shape deflecting surfaces to facilitate the passage of the fuel and ash from one grate section to the adjacent one. The bridge 18 may be reciprocated laterally. In the modification shown in Fig. 9, fuel and non- combustible material are supplied to the section 3 of the grate through separate pipes 4 and the fuel is returned on two lateral sections 6. Various modifications are described in which the circuitous paths of the fuel and fuel residues vary. In other modifications the grate sections 3 and 6 are arranged at different levels throughout their length or at or between their ends. Instead of the partitions 7, 8, air or water-cooled partitions 42, Fig. 22 or water-cooled refractory partitions 43, Fig. 24, may be employed dividing the furnace into separate combustion chambers having grates moving in opposite directions. A modification is shown in Fig. 7 in which the fuel is conveyed through the furnace by screw conveyers, the fuel being conveyed rearwardly by the intermediate pair of screws and returned by the two outer pairs.