Patent GB-694347-A (GB)
Title: Improvements in or relating to air heaters incorporated in tubulous fluid heaters
IPC: F28D7/08
Filed: 1951-08-31
Abstract: 694,347. Air heaters. BABCOCK & WILCOX, Ltd. Aug. 31, 1951 [Sept. 1, 1950], No. 20589/51. Class 64 (i) A tubular fluid heater, such as a water-tube boiler, has fluid circulation tubes forming a wall defining one side of heating-gas pass, and a tubular air heater having inlet and outlet headers supported from the wall outside the gas pass, the air heater tubes extending from the headers between the tubes of the wall and to and fro across the gas pass with the reverse bends supported against the opposite tube wall. The invention is shown applied to a steam generator having a furnace lining of water tubes between the steam drum 20, Fig. 1, and header 17. The furnace is fired by burners 11 using pulverized fuel from a mill 12, the air heater being designed to vary the supply of hot air to the fuel to suit its moisture content. The hot gases from the furnace pass downwardly and then upwardly between walls 14, 21 formed by the down-coming banked water tubes, the walls defining a hot gas pass 15 in which are situated economiser tubes 26, 32, superheater tubes 24, 25 and the air heater tubes 46. The wall 21 has refractory material between its tubes. The economiser tubes coming from header 31, Fig. 2, are supported from the walls by brackets 27, 30, 34, 35, links 28, 29 and an intermediate support 36. The boiler unit is supported at the upper end by hangers 40, Fig. 1, and straps 37 so that thermal expansion is downward. Tie bars 41 welded to water tubes 22 support the tubes against horizontal lateral heat expansion. The air heater comprises inlet header 45 and banked U-tubes 46 leading to outlet header 47, both headers being outside the gas pass 15. Primary air to header 45 is provided by fan 42, Fig. 1, with control damper 53, a by-pass tube 52 with control damper 54 joining the hot air supply pipe 50 leading to the fuel pulverizer 12. The U-tubes 46 of the air heater are in rows, Fig. 3, with alternate tubes bent horizontally in opposite directions to pass at 56 between the water tubes at the same level and the U-tubes are supported by a saddle 57, Fig. 2, from the economiser tube 32a. Supporting saddles 60, 61 maintain the tubes 46 in alignment. The horizontal differential expansion between headers and wall 21 is allowed for by making the headers in longitudinal sections connected by bellows expansion joints 38 and the header sections are anchored at mid point to one of the tubes 22 to move both horizontally and vertically with the tubes as shown in Fig. 4. Upper and lower projections 63A, 63B on the header plate 63 engage lugs 62 on the tube 22. Additional supports 70, Fig. 3, similar to lugs 62, but arranged at the ends of each header section, connect the headers with the tubes but allow for horizontal heat expansion. Refractory enclosures 71, 72, 76, Fig. 1, are provided around the superheater headers 73, 74, 75, the economiser headers 33, 31 and the air heater headers 45, 47. Seal plates 82, 83, 84, Fig. 2, are also provided for the vestibule of enclosure 76. the lower end of the seal plate 84 being in horizontal and vertical sliding contact with the header 47.