GB946644A - Steam generating unit - Google Patents

Abstract

946,644. Regulating steam temperature in water-tube steam boilers; automatic control of furnaces. RILEY STOKER CORPORATION. June 15, 1962 [July 27, 1961], No. 23112/62. Headings F4A and F4B. The temperature of superheated steam from a steam generator is regulated by a combination of waste gas recirculation with adjustment of the flame path within the steam generator. A vertical combustion chamber 18 has opposed projections 21, 23 at its lower end and has burners 22, 24 located on the underside of the projections, the direction of the combustion gases issuing from the burners and thus also their flow-path through the chamber 18 being controllable by angularly-adjustable vanes 83, 85, 88, 91. A projecting nose portion 122 in the upper part of the chamber 18 has an opening 124 in its underside through which recirculated flue gases may be introduced into the furnace. Upper and lower drums 25, 27 are connected by downcomer tubes 26 in the rearmost backpass 38 and further downcomer tubes 28 supply water to wall-lining steam generating tubes 31 which discharge into the steam and water drum 25. A radiant superheater 57 is disposed on the front wall 15 of the combustion chamber opposite a radiant reheater 69 on the rear wall 16. Further superheating surfaces 61, 62, 63 are disposed in the forward backpass 37, in the lateral pass 34 above the nose 122, and in the passage 33 between the nose portion and the front wall 15. A convection reheater 73 lies approximately above the outermost part of the nose portion 122. At low load the vanes of the burners are adjusted so that the flame passes up the front wall 15 and considerable quantities of recirculated gas are introduced through the opening 124 and flow down in a low pressure region at the rear of the combustion chamber 18 before mixing with the flame gases (Fig. 2, not shown). At high load, the flame passes up the rear wall (Fig. 3, not shown), so that the superheater surfaces 57, 63 receive less heat and the gases having a longer flow path are cooler on reaching the convection superheater 62. In addition less recirculated gas is introduced at high load. Temperature indicators 113 and 115 in the superheated steam and reheated steam headers respectively are coupled to an automatic control unit 101 associated with which are various hydraulic actuators controlling the positions of the vanes 83, 85, 88, 91 in addition to the air supply and recirculated gas dampers.