GB794692A - Improvements in tubulous vapour generators - Google Patents

Abstract

794,692. Combustion apparatus. BABCOCK & WILCOX, Ltd. Aug. 16, 1956 [Aug. 18, 1955], No. 25109/56. Class 51 (1). [Also in Group XIII] In a water-tube boiler comprising a furnace lined with steam generating tubes extending from lower headers 20, 22 to a steam and water drum 24 and fired by three horizontal rows of pulverized coal burners 86, the combustion gases flowing upwardly past an arch 36 and then laterally in a pass lined with superheater tubes and in which is disposed the pendent tube banks of a secondary superheater 140, a reheater 180 and a primary superheater 160, 161, 162 to an outlet 218, the furnace is provided with a hopper bottom formed by walls 80, 82 converging downwardly to a throat 84 and is divided into three sections 90, 91, 92 by division walls 94, 96 including closely-arranged or contiguous steam generating tubes connected between lower and upper headers 98, 100 and 106, 108, respectively. Downcomers 102, 104 convey water from the drum 24 to the headers 98, 100 whilst steam-water mixture is delivered to the drum from headers 106, 108 through circulators 109, 110, the drum preferably containing separators of the form described in Specification 526,825, [Group XIII]. The tubes of each division wall 94, 96 are arranged to form a front section 120 and a rear section 122 separated by a gap 124 aligned with the throat 84 of the furnace hopper bottom, the gap providing for pressure equalization between the furnace sections which are each fired by an equal number of burners. Above the arch 36 some of the division wall tubes of each rear section 122 are offset to provide spaces for soot blowers 128, 132. To maintain the steam temperatures constant over a wide range of loads cooled flue gas is withdrawn from the outlet ducting 218 by a fan 192 which delivers it to the throat 84 of the furnace hopper bottom, the quantity of gas recirculated being controlled according to variations in load and steam temperature, for example by systems as described in Specifications 738,021 or 758,374, [Group XIII]. In a modification, the lateral pass is divided into superheater and reheater passes the gas flows through which are controlled to regulate superheat or reheat temperature.