GB747219A - Improvements in or relating to tubulous vapour generating and vapour heating units - Google Patents

Abstract

747,219. Water-tube steam boilers; steam superheaters. BABCOCK & WILCOX, Ltd. March 9, 1954 [March 9, 1953], No. 6825/54. Classes 123(2) and 123(3). [Also in Group XXIX] A water-tube boiler has twin combustion chambers 10, 12, separated by a division wall 20 formed of steam generating tubes which are offset at 206 to allow gas to pass from one chamber to the other, the chambers being lined with steam generating tubes which, together with the division wall tubes, extend from lower headers 18, 18<SP>1</SP> to an upper steam and water drum 14. Chambers 12, 10 are fired respectively by pulverized coal burners 22, 24 and 26, 28, the gases flowing from the top of chamber 10 laterally through a pass locating a secondary superheater 68 and then downwardly through a pass in which is disposed a primary superheater 80 and which is provided at its lower end with flow-controlling dampers 173. Similarly, the gases from the top of chamber 12 flow through a lateral pass locating a reheater 118 and a downpass controlled by dampers 175 and locating a second primary superheater 92. Steam from drum 14 divides into two streams, one flowing serially through a header 82, downpass lining tubes 86, 90, the superheater 80 and an interstage attemperator 116 to the inlet header 70 of superheater 68 wherein it is joined by the other stream which has flowed through header 94, downpass lining tubes, superheater 92 and interstage attemperator 108. The united streams pass through superheater 68 to the final outlet header 72. Each chamber 10, 12 has its own flue gas recirculation system, gas being withdrawn from the bottom of the respective downpasses by fans 174, 142 which supply it to ducts 178, 148 whence it enters the respective chambers through ports 156. The operation of the boiler is controlled automatically by a fluid pressure servomotor system (see Group XXIX), which controls the firing rate of the burners in accordance with the demand for steam and, over a wide range of load, holds the temperatures of superheat and reheat at the desired value by simultaneously controlling the distribution of heating gas between the chambers 10, 12, by operation of dampers 173, 175, the flow of gas recirculated to each chamber and the supply of water to the attemperator sprays. Specification 461,389, [Group XXIX], is referred to.