GB674583A - Improvements in and relating to vapour generators - Google Patents

Abstract

674,583. Feedwater heating systems and installations ; heating air and gases. FOSTER WHEELER, Ltd. July 28, 1950 [April 22, 1950 ; April 22, 1950], No. 18971/50. Classes 64(i) and 64(iii). The economiser of a steam-boiler is arranged in sections one beyond the other in the path of the furnace gases, the sections being provided with inlets for separate streams of feedwater, a heat-exchanger serving to raise or lower the temperature of one stream so that two streams reach the economiser at different temperatures, the stream of lower temperature being fed to a section of the economiser more remote from the furnace than the section to which the stream of higher temperature is fed. The boiler has a furnace 10 fired by burners 12, a steam and water drum 14, a water drum 16, steam generating tubes 18 and a superheater 20. The economiser is in two sections 24, 26 in the flue 22, the remote section 24 being fed by a pipe 28 and the section 26 by a pipe 30 into which is led an outlet pipe 32 from the section 24. The section 26 has an outlet pipe 34 leading to the steam and water drum 14. Steam from the superheater 20 is fed through a pipe 38 to a turbine 36, whence condensate passes through a pipe 40 and a spray head 42 to a feedwater heater 44. Steam bled from the turbine passes through a pipe 46 to the heater 44 and make-up feedwater enters the pipe 40 through a pipe 48. The feedwater leaves the heater 44 through a pipe 50 and is split into two streams by a valve 52, one stream passing through the pipe 28 to the economiser section 24 and the other stream passing to a second heater 54 and thence to the economiser section 26. Steam is fed from the turbine through a pipe 58 into the feedwater heater 54 and after passing through the heater is exhausted through a pipe 60. The steam supply pipe 58 has a branch connection through a valve 64 to an airheater 66 supplying pre-heated combustion air to the furnace. Temperatures of feedwater, furnace gases, steam and air are tabulated. The heated feedwater leaving the heater 54 may be used to pre-heat the combustion air, the water after giving up its heat passing to the cooler section of the economiser. In an alternative arrangement the superheater is omitted from the boiler and the feedwater is not heated after it is split into two streams. One stream passes through the air-heater, where it is cooled before passing to the cooler section of the economiser.