GB794893A - Improvements in or relating to steam generators of the steam transformer type - Google Patents

Abstract

794.893. Heating steam boilers by steam; return tube steam boilers. THOMPSON WATER TUBE BOILERS, Ltd., J. May 17, 1954 [May 15, 1953, Jan. 18, 1954], Nos. 13740/53 and 1504/54. Class 123(2) In a low pressure steam generator especially for marine use, water contained in a drum 1 is evaporated under normal conditions by high pressure steam, for example from the main boilers of the vessel, the steam flowing through a nest of tubes 8 immersed in the water When high pressure steam is not available, alternative heating means are provided for steam generation the means comprising two drums 21, 22 disposed below the main drum 1 and connected thereto by downcomers 23 and steam and water risers 24 which open into drum 1 just below the water level 11 therein. Each drum 21, 22 has a longitudinally disposed gas cooling tube 28 therein, the tubes leading to respective smoke boxes 25 whence return tubes lead back through the drums to gas uptakes 31, 32. From the front end plates of drums 21, 22 each of the tubes 28 is' extended forwardly to form short combustion chambers 29, 30 each of which is fired by a gas or oil burner producing combustion gases which are non-luminous, combustion being substantially completed within the chambers. With this arrangement the heat transfer in tubes 28 is predominantly by convection allowing a reduction in diameter of the tubes to much below that required for the same steam output with firing means producing luminous, highly radiant gases. In a modification, a return-tube, dry-back boiler has a flue tube of small diameter provided with an external combustion chamber, and a high pressure steam coil is disposed between two banks of return tubes to provide alternative heating for the boiler.