GB1078932A - Improvements in vapour generators - Google Patents

Abstract

1,078,932. Once-through vapour generator. BABCOCK & WILCOX CO. Oct. 1, 1964 [Oct. 1, 1963], No. 39983/64. Heading F4A. In a forced flow once-through vapour generator that includes an upright furnace chamber (10), Fig. 1, of substantially rectangular cross-section divided into two compartments by a vertical tube wall (28), combustion gases from burners (43) pass out of the top of the furnace chamber through a gas outlet (16), adjacent to which is arranged a secondary superheater (30), and flow through a horizontal gas pass (17) which contains a secondary reheater (31). The gases then flow down an upright gas passage (19) which is divided into parallel gas passes (32 and (33) by a vertical baffle wall (34) and which contains a primary superheater (36), a primary reheater (37), and a secondary economizer (38) over which the gases pass before passing through dampers (33A) and (34) and over a primary economizer (41) on their way to an air heater and stack (not shown). The front, rear and side walls of the furnace chamber (10), are formed by groups of tubes connected for parallel flow of the cooling, fluid, the individual groups of tubes being connected in sets of series-connected parallel paths, as shown in Fig. 8, so that groups of tubes on the same horizontal level combine to form fluid heating passes A, B and C. The tube groups A1, B1 and C1 from the front part of the floor (15) and the front wall' (11) of the furnace chamber the tube groups A2, B2 and C2 form the rear part of the floor (15) and the rear wall (12), and the tube groups A3, B3 and C3 form the side walls. The outlets of each group of tubes is in the form of an upright cylindrical fluid mixing vessel 90 from which the fluid passes to the inlet of the next group of tubes. The uppermost group of tubes in the rear wall (12) are bent inwardly and upwardly to form a nose arch (80) and then rearwardly to form the floor of the gas pass (17) and tube screens (71) and (79) and consequently the lengths and bend resistances of the tubes are increased compared with the corresponding tubes in the side and front walls. In order to balance out this difference and to supply a greater quantity of fluid to the higher heat pickup zone the fluid flow from the group of tubes B3 in the side walls is transferred to the uppermost group of tubes C2 of the rear wall and correspondingly the fluid flow from the group of tubes B2 in the rear wall is transferred to the group of tubes C3 in the side walls.