GB861130A - An improved method of producing power utilising high pressure elastic fluid and an improved tubulous steam generating unit - Google Patents

Abstract

861,130. Regulating steam temperature in boilers. BABCOCK & WILCOX Ltd. June 11, 1957 [June 13, 1956], No. 18440/57. Class 123(3) A water-tube steam boiler has an upright, hopper-bottom furnace 24 lined with steam generating tubes extending from lower headers 28, 32 to an upper steam and water drum 38 and is fired by burners 116...118, the furnace gases flowing between widely spaced platens 106, 108 of reheater tubes in the upper part of the furnace into a lateral pass 26 in which are disposed more narrowly spaced reheater platens 110 and platens 92, 78 of secondary and primary superheater tubes respectively. The gases leaving the pass 26 flow downwardly in a pass 54 lined with superheater tubes and containing banks 160, 162 of economizer tubes to discharge from the unit through an outlet 168. Cooled flue gases are withdrawn from the bottom of the downpass by a fan 122 which delivers them into the throat 144 of the hopper bottom of the furnace through a duct 140, 142 controlled by dampers 146 and into a furnace region immediately below the reheater platens 106, 108 through a duct 126 controlled by dampers 136. In operation, to maintain the reheat temperature constant over a wide load range, the flow of gases through the duct 126 is increased from a minimum at a partial load corresponding to the lowest load at which the superheat temperature can be maintained to a maximum at full load, the effect of the introduction of cool gas immediately before the reheater being to reduce the radiant heat adsorption of the panels 106, 108. To maintain the superheat temperature constant over a wide load range, an increasing flow of cool flue gas is provided through the duct 140, 142 as the load decreases, the effect of introducing gas into the hopper bottom of the furnace being to decrease the proportion of available heat absorbed by the furnace wall tubes and thus to increase the heat input to the convectively heated superheaters 78, 92. The dampers 136, 146 may be controlled auto matically by means primarily responsive to representations of reheat and superheat temperatures respectively. Specifications 526,825 and 656,551 are referred to.