GB890406A - Improvements in or relating to steam boilers - Google Patents

Abstract

890,406. Forced flow steam boilers; regulating superheat. PEARCE, A. P. Nov. 9, 1959 [June 24, 1959], No. 21596/59. Classes 123(2) and 123(3) In a steam generator having a steam and water drum 6, two circuits for the working medium are provided, the first including a circulating pump 14 which draws water from the drum and forces it through a convectively-heated coil 10 from which steam-water mixture returns to the drum for separation, whilst in the second circuit steam from the drum flows through a radiantly-heated coil 2 into the inlet of which 25 to 30% of the total feed-water supply to the boiler is injected through a valve 7, the water evaporating in the coil. The remainder of the feed-water is fed directly to the drum which has a blow-down connection 21. Superheated steam discharges from the coil 2 to the point of use through a line 4 provided with a stop valve 34. The amount of feed water injected is controlled to give the desired steam temperature at a point 35 in the line 4. In this two-circuit boiler only minor deposition of salts occurs in the coil 2, this coil being flushed when the boiler is started by closing the valve 34 and opening a valve 19 so that the pump 14 forces water through both coils to the drum. Fig. 1 shows a construction of the boiler. The radiantly-heated coil 2 encloses a combustion chamber 1 fired by a burner 3, hot gases flowing outwardly through the coil turns to heat the coil 10 which encircles the coil 2 before passing to a stack 13. In a modification Figs. 3 to 5, not shown, a second steam generating coil is connected in parallel with the coil 10, the second coil being either welded to the coil 2 on the side remote from the furnace or mounted coaxially therewithin, steam being generated in this coil by heat conduction from the medium flowing in the coil 2.