GB568908A - Improvements in installations for generating and heating vapour - Google Patents

Abstract

568,908. Steam boilers. JOHNSON, J. Oct. 20, 1943, No. 17265. [Class 123 (ii)] In a steam boiler comprising, for example, an upper steam and water drum 4 and a lower water drum 5 with two banks 1, 2 of interconnecting tubes, one bank on each side of the combustion Chamber 6, and in which there are two parallel flue gas passes 15, 16 controlled by a damper 35 and locating a reheater 21 and superheater 24 respectively, a by-pass 26 having a damper 28 is provided in parallel with the passes 15, 16, the said two passes and by-pass all leading to a common flue 32 extending upwardly above the boiler casing. An economiser 33 is preferably located in the flue 32 and an air heater 34 in a continuation of the latter, with a second by-pass 58, controlled by a damper 59, leading from the by-pass 26 to the flue at a position above said economiser. The arrangement is such that the degrees of superheating and reheating may be raised or lowered simultaneously by operation of the damper 28, to permit the passage of more or less of the flue gases through the by-pass 26, and the degree of reheating may be raised or lowered relatively to the degree of superheating by operating the damper 35 which controls the relative gas flows through the two passes 15, 16 ; moreover, during starting-up the boiler, and with the dampers 28, 35 closed, the damper 59 may be opened to prevent overheating of the reheater and economiser. The gas passes 15, 16 are bounded by the inner side walls 7, 7 of the boiler and walls 17, 18 respectively above the steam drum, the reheater 21 extending from the front to the back of the boiler and the superheater 24 stopping short of the back with its tubes forming a partition wall 25 defining the inner side of the by-pass 26. Downcomer tubes (not shown) between the drums 4, 5 are disposed at the front and rear of the boiler between the inner and walls thereof ; at the sides, the inner and outer wall constitute air ducts 11 between the outlets 64, 65 of the air heater 34 and a wind box around the burners 14.