GB1036332A - A forced-flow once-through boiler - Google Patents

Abstract

1,036,332. Forced-flow boilers; tubes, mounting. SIEMENS-SCHUCKERTWERKE A.G. March 8, 1963 [March 8, 1962], No. 9420/63. Heading F4A. A forced-flow once-through boiler having an upright combustion chamber includes vertical tubes, carrying a downwardly-flowing working fluid at below boiling temperature during normal boiler operation, and arranged in pairs distributed at intervals around the walls of the combustion chamber, intermediate members rigidly connecting the two tubes of each tube pair, e.g. by being welded to them, and evaporator tubes, coiled about the combustion chamber being suspended from the vertical tubes or the intermediate members. In Fig. 1, the working fluid passes in turn from an economizer 1 to a non-heated tube system 3, thence tubes 4 which form contact heating surfaces, and then to a non-heated tube system 5 arranged with tubes in pairs at 1À5 to 2À0 metre intervals. The tubes of the system 5 support the combustion chamber walls and lead to distribution headers 6, whence the working fluid passes to the evaporator 7 coiled at a constant pitch angle about the combustion chamber. Above the region 8, vertical evaporator outlet tubes 9 lead to a header 10. From this header, the fluid passes in succession to an injection point 11, to a superheater 12 comprising sinuously coiled tubing which can be suspended on the evaporator tubes or the tube system 5, to a second injection point 17, and finally to a superheater 15. The boiler which can be fired under positive or negative pressure is covered with metal plates surrounded by insulation which itself is surrounded by a pressure-tight sheet metal casing. Horizontal tie beams holding the combustion walls together are provided with fastenings at the corners allowing thermal movements. In Fig. 3, two tubes 32, 33 of the system 5 are welded to an intermediate member 34 which contains apertures for the retaining pins 35 welded to the evaporator tubes 36 and secured by split pins 37 and washers 38. Welded-on plate 39 provides a seal on the rear side and horizontal members 40, 41 of U-section interconnect the pairs of tubes. Members 48 interconnect the members 40, 41 and are connected to horizontal tie beams by members 42. The members 48 are rigidly connected to one, and slidably mounted on the other of the members 40, 41. The tubes 32, 33 of the system 5 which extend up the rear wall of the combustion chamber across the region of the horizontal pass are welded directly to one another and are surrounded by vertical evaporator tubes capable of thermal movement, the spaces between the latter being pinned and covered with rammed material. The walls of the boiler flue next in the gas path are constructed analogously. In a modification the evaporator tubes may be connected directly to the tubes of the tube system 5.