GB707174A - Improvements in or relating to tubulous vapour generating and superheating units - Google Patents

Abstract

707,174. Water-tube steam boiler; superheating and reheating. BABCOCK & WILCOX, Ltd. Nov. 1, 1951 [Nov. 3, 1950], No. 25548/51. Classes 123(2) and 123(3) A steam &c. boiler comprises vertically extending furnace chambers 160, 162 which are disposed side by side, are lined with steam-generating tubes, and are separately fired by pulverized fuel burners. 190, 192 and 212, 214 respectively. A lower gas pass 184 locating, say, a steam reheater 166 leads from the top of the furnace 162 to an intermediate zone 28 of the furnace 160, and an upper pass 186 locating a superheater 164 directs the mixed gases from both furnaces through an economizer 240 and air heater 250 to an exhaust flue or stack. The fuel supply from a pulverizer 196 to the burners 190, 192 may be regulated, through an operator 204, by control means 210 responsive to the pressure of steam in the superheated steam outlet pipe 197; the supply to the burners 212, 214 is similarly regulated, through an operator 230, by the control 210 together with, if desired, a control 320 responsive to the temperature of the steam in the reheater outlet pipe 228. Flue gases from a position downstream of the superheater, e.g. between the economizer 240 and air heater 250, may be directed by ducts 274, 276 and a fan 272 for recirculation through one or both of the furnaces 160, 162. In one construction the gases are recirculated only through the furnace 160, being led to the secondary air ducts of the burners thereof through an opening 282 and the flow being regulated by a damper 284 subjected to a control 307 responsive to the temperature in the steam pipe 197. In a modification, as shown, the damper 284 is regulated, through a relay 410, by the control 307 and, in addition, a second control 405 responsive to steam flow in the pipe 197; gases are also recirculated through the furnace 162, by way of a branch 280 of the duct 276, a damper 294 in said branch being regulated, through a relay 402, by the reheat temperature and superheated steam flow controls 320, 405 respectively. The superheater and reheater are both in two sections 30, 32 and 60, 62 with tubes of the superheater section 32 forming a screen across the outlet from the reheater pass 184.