GB1179441A - Improvements in Steam Generators - Google Patents

Abstract

1,179,441. Water tube boilers; preventing overheating of reheater tubes. FOSTER WHEELER CORP. 1 Feb., 1967 [2 Feb., 1966], No. 4833/67. Heading F4A. A marine water tube boiler 10 is fired by roof burners projecting into a front tube lined furnace combustion chamber (Fig. 1, not shown). The exhaust gases pass over a bank of steam generating tubes extending between upper and lower drums 26, 28 respectively, and into a rear upright convection pass 14 through lower opening 40. A fin tube wall 42 divides the pass 14 into main and by-pass passages 46, 44 respectively, the main passage containing the secondary part 52 of a two part superheater 48 through which steam flows in parallel to the exhaust gases, and a reheater 54 through which the steam flows in counterflow to the exhaust gases. The by-pass passage contains economizer section 64. The gases from both passages then pass over economizer section 81 in flue 74. An opening 58 extends through the partition wall 42 to allow gas to pass from below the main passage 46 to the by-pass passage 44 after passing over the primary part 51 of superheater 48. The primary superheater part 51 is itself by-passed by an additional by-pass passage containing a further economizer section 62 and control dampers 60. During normal operation, steam superheat and reheat temperature control is effected by regulation of dampers 60, 66 in the by-pass passages. On going astern, when vapour flow through reheater 54 is stopped, damper 66 is opened wide and shut off dampers 70 in main passage 46 closed to prevent gas flow therethrough. The combustion gases then pass through opening 58 to the by-pass passage 44. As damper 70 is closed, damper 79 linked to it by shaft 80 is simultaneously opened to allow cooling air or other gas from wind box 75 to pass over the reheater tubes 54. Variation of damper 60 continues to regulate the superheater steam temperature.