GB877665A - Improvements in forced draught boilers - Google Patents

Abstract

877,665. Furnace walls. WALTHER & CIE A.G. March 26, 1959, No. 10565/59. Class 51 (1). [Also in Group XIII] A straight-through forced draught boiler of the vertical type comprises a furnace chamber 16 lined with several helically wound, or sinuous groups of tubes 15 which converge at 17 and extend, preferably with a square crosssectional shape, partially into an uptake 21 which, consisting of vertical flat walls of tubing 23, contains heat transfer surfaces 28 ... 31 and, with the chamber 16, is enclosed by an inner refractory layer 18, an intermediate gas-tight sealing metal shell 19 with expansion elements 27, and an outer heat-resistant layer of lagging material 20 which may be supported by a wire mesh. A small excess pressure supplied through a branch pipe 42 leading from the pressure side of a combustion air blower 40 is maintained in the space between the shell 19 and a surrounding cylindrical gas-tight metal shell 35. The upper end of the shell 35 supports a transistion member 50 which contains dampers 38, supports a chimney 51, and accommodates the vertical gas tubes 36 of an air preheater 41. The blower 40 forces fresh air into the preheater draught box, preheated air being delivered to a burner 12 in the floor of the furnace through a thermally insulated duct 43 having expansion elements 44a. The heat-exchange surfaces 28 ... 31 are suspended from cooled fall tubes 48, the upper headers 32 for the economizer 31 being removably suspended from a cross beam 33. Observation tubes 22 are provided at the zone 17, an additional tube 46 being mounted lower down in the furnace chamber 16. Gas-tight entry doors 44 are located in the shell 35 opposite corresponding gas-tight entry doors 45 in the gas uptake 21, the boiler being supported upon a ring 10 resting on a concrete foundation 11. In a modification, the walls of the uptake 21 are formed of two parallel helically-wound tubes 54, 55, Fig. 5. At the top of a first part of the uptake 21 the lower tube 55 is brought inwards to form a two tube annular coil 56, the tubes then being sinuously bent in an horizontal plane above the annular coil 56 before being formed into a further annular coil 56. Alternate formations of annular and sinuous coils are provided until the required heating surface has been formed and then the tubes are again disposed in the form of a cylindrical helix 59. Each of two tubes 61, 62 of the economizer are bent to cruciform shape and then spiralled outwardly to descend obliquely two tube diameters to be bent again to cruciform shape and so on until the required heating surface has been made up. The tubes 54, 55 are separated by spacers 67 the helix being adjusted by an adapter 68 and the inner coils being held by a supporting ledge 70.