GB699139A - Improvements in or relating to hopper bottom pulverised fuel fired furnaces - Google Patents

Abstract

699,139. Pulverulent fuel fired furnaces. BABCOCK & WILCOX, Ltd. July 18, 1952 [July 21, 1951], No. 18194/52. Class 51(i) In a hopper bottom pulverized fuel fired furnace adapted to operate with evacuation of slag in molten form, a cyclone furnace is arranged to discharge gases through an opening at the bottom of the hopper bottom and through the hopper bottom into the pulverized fuel fired furnace. In the furnace shown, Fig. 1, the tube lined combustion chamber 1 arranged for corner firing in known manner by pulverized fuel and primary air nozzles 14 separated by a secondary air nozzle 15 located at each corner is closed below by a pyramid shaped hopper bottom 5 the walls 6 of which merge into the wall 7 of a tube lined cylindrical cyclone furnace chamber 8 suspended therefrom and coaxial with the chamber 1 and having a cone-shaped bottom 10 with slag outlet 11. If desired the chamber 8 may be shaped to widen upwardly in conical fashion. The outlet 11 leads to slag removal means having gas tight connection with the chamber 8 and including a trough 12 conveniently suspended either from the chamber 8 or directly from the bottom 5. The trough is partly filled with water in which a scraper conveyer 13 operates. The chamber 8 is provided with a primary air and fuel nozzle 16 and secondary air nozzle 17 all of which are so tangentially arranged as to produce a whirl in the same direction as that produced in chamber 1. When necessary the firing of chamber 1 may be discontinued the necessary combustion of fuel then being carried out by the cyclone furnace alone. When the latter is operating alone it may be used to light up the burners in chamber 1. The fly ash separated from the gases in the vapour generating unit to which this combustion apparatus is being applied may be mixed with the fuel supplied through the nozzle 16 or may be supplied with carrier air to the cyclone furnace chamber 8 through an additional nozzle. In a modification, Fig. 3, the hopper bottom 5 continues into the chamber'8 the primary air and fuel nozzle 16 and the secondary air nozzles 17 being provided at the upper end of the chamber such that during operation the flames within the chamber rotate spirally downwards and then upwards through the throat 19. As a result of the relatively high angular velocity in the throat fine dust is thrown on to the inner surface of the throat and burnt out,