GB744797A - Improvements in forced flow, once-through tubulous vapour generating and vapour heating units and to a method of operation thereof - Google Patents

Abstract

744,797. Furnaces. BEUTHNER, F. Sept. 29, 1954 [Sept. 30, 1953], No. 26848/53. Class 51 (1). [Also in Group XIII] A forced flow, once through steam boiler comprises two cyclone furnaces 1 and 2 (not shown) which discharge through the front wall 3 of the unit into a secondary furnace chamber 4 when combustion gases pass through a tube screen 28 into a radiation chamber 5 from the top of which they flow through a lateral pass 6 locating a secondary, superheater 65 and a secondary reheater 76. The gases then flow downwardly in a pass 7, the upper part of which is divided into three parallel passes, the side passes 9 each locating the horizontal limb of a primary superheater 69 having vertical limbs extending across the outlet from pass 6 and banks of tubes 68 in which the transition zone is located, whilst the central pass 8 locates primary reheater tube banks 72, 74. Dampers 10, 11 are provided at the pass outlets for the control of gas flow therethrough. Below the dampers the gases pass through high temperature air heaters 84 and economizers 85 into a turning space 13 when they flow upwardly and downwardly in passes 14, 15 locating a low temperature economizer 86 and air heater sections 87. Cooled flue gas is withdrawn from a channel 89 between economizer sections 85 by a fan 88 which delivers the gases to the lower part of chamber 5 through an aperture 90 in the rear wall 42 thereof. The quantity of gases recirculated is controlled by dampers and/or by fan speed regulation. The cyclone furnaces and the walls, floor and roof of the secondary furnace, the radiation chamber and lateral pass are lined with steam generating and superheating tubes, which with the economisers, transition section tubes 68 and primary and secondary superheaters 69, 65 are connected to provide two parallel throughflow circuits for the working medium, the heating surfaces being so arranged, Fig. 7 (not shown), that should the cyclone furnaces be unequally operated, the two circuits will still receive equal amounts of heat. In each circuit, on the downstream side of the transition tubes 68, are disposed cyclone separators 103, for example as described on Specification 746,495, [Group II], the separators, which are dry in normal operation, being provided to remove salts-contaminated water when tubes 68 are being flushed. Spray type attemperators are provided in each circuit on the upstream side of superheaters 69, 65 to provide, a quick acting control of superheat on change of load, &c. The superheated steam pressure and temperature are regulated automatically by adjusting, the flow of water through the circuits and the rate of firing, while the reheated steam temperature is controlled by regulation of dampers 10, 11 and by regulating the quantity of gas recirculated these latter controls also being used to ensure that the transition zone remains within the tube banks 68 where suitable temperature conditions prevail irrespective of load variations on the unit.