GB783765A - Improvements in tubulous vapour generating, superheating and reheating units - Google Patents

Abstract

783,765. Regulating steam temperature in boilers. BABCOCK & WILCOX, Ltd. May 9, 1956 [May 10, 1955], No. 14394/56. Classes 123(2) and 123(3) A water-tube steam boiler comprises an upright radiation chamber 10 lined with steam generating tubes extending between a water drum 18 and a steam and water drum 16 which is equipped with cyclone separators, for example as described in Specification 526,825. A cyclone furnace 22, for example of the form described in Specification 598,141, supplies hot gases to a secondary furnace chamber 28 disposed at the bottom of chamber 10 and separated therefrom by a tube wall 212 and slag screen 30, 32. The gases flow through the screen and upwardly in the chamber 10 to each side of wing walls 174 formed of .steam generating tubes and projecting into the chamber from its rear wall. Disposed across the upper part of the chamber 10 are widely spaced platens 96, 118 of tubes constituting respectively the radiantly-heated sections of a superheater and reheater. From the top of the chamber 10 the gases flow laterally through a pass locating a convection reheater 124, 126 and then through a turning space 42 and downpass 44 in which are disposed convection superheater sections 102 and 74...77 repectively. The proportioning of the heating surfaces of the superheater and reheater between the radiant and convection stages is such that constant steam temperatures are maintained over a substantial load range. A temperature control range on both the superheater and reheater is obtained by varying the excess air supply to the cyclone furnace, the temperature of superheat and reheat being reduced when required by the use of interstage attemperators, for example of the form described in Specification 656,551. To control the gas temperature in the chamber 10 to prevent overheating of the radiant steam heaters 96, 118, cooled flue gas is withdrawn from the boiler outlet flue by a fan 150 which discharges it through ducts 156, 160 into the chamber, the gas recirculation also being effective to increase the amount of heat available for convection steam heating.