GB918263A - Improvements in and relating to vapour generators - Google Patents

Abstract

918,263. Water tube steam boilers. FOSTER WHEELER Ltd. Oct. 25, 1961 [Oct. 27, 1960], No. 36993/60. Class 123 (2). A steam boiler installation comprises a main boiler in the flue gas exit of which is arranged the heating surfaces of an auxiliary boiler operating at a constant low pressure, e.g. 52 p.s.i., such that the heating surfaces are maintained at a temperature above the dew-point of the flue gases irrespective of load variations on the main boiler. In the form shown in Fig. 1 the main boiler is of a standard type and incorporates oil burners C and a superheater B. The auxiliary boiler comprises heating surfaces M, a lower water drum L, an upper steam drum K, and external downcomers N. The drum K contains a heat-exchanger R which is supplied with a controlled amount of boiler feed water through the line T, a pressure controller F sensitive to the steam drum pressure controlling the supply via valves G and H.. Make-up water for the drum K is supplied through the valve J. Feed to the main boiler A comprises a mixture of water flowing through the heat-exchanger R and that by-passing it through the valve H and the amount is controlled by a water level controller D and valve E. In a modification a controlled amount of feed water is sprayed into the drum K in order to maintain a constant pressure therein, an equivalent amount of water being blown down into the deaerator from which it is drawn by an extraction pump. In another modification the pressure within the auxiliary boiler is controlled by controlling the discharge of steam therefrom.