GB688830A - Improvements in or relating to tubulous vapour generating and superheating units - Google Patents

Abstract

688,830. Water-tube steam boilers; superheaters. BABCOCK & WILCOX, Ltd. Nov. 28, 1950 [Nov. 29, 1949] No. 30559/49. Classes 123 (ii) and 123 (iii) A steam boiler comprises a first natural circulation section, including steam generating tubes 10 lining the front and side walls of the furnace 1, and a second forced-flow section, consisting of a circulating pump 13, economizer 14, steam generating tubes 15, steam separator 16 and a radiant superheater 22, the tubes of the latter and the tubes 15 lining the rear wall of said furnace. The economizer 14 is located in one, 5, of three parallel gas passes leading from the furnace, the other two, 3, 4, locating economizers 7, 8, the primary superheater 11 of the first boiler section 10 and a reheater 30, and in the gas passage 2 between the furnace and these passes is disposed the secondary superheater 12 of the said first section 10. The passes 3, 4, 5 are fitted with dampers 27, 28, 29, the damper 28 being controlled automatically in accordance with the steam temperature at the reheater outlet by means 31. Water is supplied to the boiler by a feed pump 6 which has direct connections with the economizers 7, 8 and circulating pump 13 through valves 40, 41 and 43 respectively and with the economizer 14 also through a valve 35, and the pump 13, which is controlled automatically by means 42 in dependence on the metal temperature of the radiant superheater 22, is directly connected to the steam-andwater drum 9 of the boiler by a pipe 32 with valve 33. The separator 16 has a water outlet pipe 21 which is fitted with a valve 20, automatically controlled by the water level in the separator, and a hand valve 23, and a two-way valve 24 is provided in the outlet pipe from the superheater 22, this valve 24 being, normally, automatically controlled by means 26 in dependence upon the outlet steam temperature of the secondary superheater 12 and having outlets leading respectively to nozzles 25 below the water-level in the drum 9 and to the inlet of the said superheater 12. At the beginning of firing, with the valves 23, 40, 41, 43 shut, valves 33, 35 open, and the valves 24 open only to the drum 9, the pump 13 is operated to withdraw water from the drum 9 and discharge it back to the drum through the economizers 7, 8 and also through the complete forced-flow section 14, 15, 16, 22, but as soon as an adequate supply of steam has been generated the valve 23 is opened so that steam only passes to the radiant superheater 22. The feed pump 6 is then started with the valves 40, 41, 43 open, valves 33, 35 closed, and the valve 24 set for automatic functioning. Alternatively the valve 43 may be closed and the valve 33 opened, in which case the pump 13 will continue to supply water from the drum 9 to the forced-flow section, and at high loads the valve 35 may be opened and the pump 13 dispensed with; the separator 16 may also be omitted. In a modification the boiler furnace is divided by a tube wall into two separately fired side-by-side chambers; the said tube wall may be constituted by the steam generating and radiant superheater tubes of the forced-flow section, but preferably the steam tubes are disposed in the firstfired chamber and the super-heater tubes in the second chamber which is fired when sufficient steam is flowing through the superheater to protect it.