GB714517A - Improvements in tubulous vapour generators - Google Patents

Abstract

714,517. Water-tube steam boilers; steam superheaters. BABCOCK & WILCOX, Ltd. Dec. 6, 1951 [Dec. 6, 1950], No. 28635/ 51. Classes 123(2) and 123(3) A steam boiler is fired by a pair of cyclone furnaces 16, each arranged for example, as described in Specification 552,747, [Group XII], the hot gases from the furnaces passing through outlets 18 in a division wall 22 formed of refractory covered steam generating tubes into a secondary furnace 24 and then under a partition 30 and upwardly through a tubelined radiant heat absorption chamber 44 in the upper part of which are disposed platens formed of return bend radiant superheater tubes which divide the gas flow into a number of parallel paths, the tubes being connected in series by means of headers 168, 186, 198 and 212. The gases are deflected by the roof 42 of the chamber into a tube-lined downpass 46, which is divided by a vertical metallic wall into a pass locating a primary convection superheater and one locating a reheater, the gases from both passes finally discharging through a breeching 236, dust chamber 238 and air heater tubes 232. Control of superheat is obtained by proportioning the flow of gas through the downpasses by dampers 80 located at the outlet of the reheater pass and by recirculation of furnace gas which is withdrawn from chamber 238 by a fan 246 and passed into the bottom of chamber 44 through a duct 250. The steam generating tubes lining the furnaces, the chamber 44 and downpass 46 are connected between a water drum 36 and a steam and water drum 54, circulation being established through external downcomers 138. Where the tubes lining the front wall 40 of the chamber 44 cross the secondary furnace outlet they are bent to form spaced platens 34 whilst in the lower part of chamber 44, further tube platens 106 and 108 are provided to form a slag screen. A vigorous water circulation is provided through the tubes forming platens 106 and 108 and those forming the division wall 22, which are all exposed to gases at a very high temperature, by pairing tubes in the wall and in each platen and connecting each pair at the top to a single tube of larger diameter. Thus, as shown in Fig. 6, pairs of tubes 22 and pairs forming platens 106 and 108 are united by Y-connectors 412, 432 and 440 respectively and joined to larger diameter tubes 110 and 98 which continue upwards as lining tubes for the side and rear walls of chamber 44.