GB739764A - Improvements in the control of the temperature of superheated steam in water-tube boilers - Google Patents

Abstract

739,764. Steam superheaters. FOSTER WHEELER, Ltd. April 13, 1954 [April 13, 1953], No. 10851/54. Class 123 (3). In a water-tube boiler comprising a steam and water drum 10 to which are connected steamgenerating tubes 12 and downcomers 14 and a superheater having three series connected sections 16, 18, 20 arranged in a lateral gas pass 22, the saturated steam from drum 10 passes through pipes 28 to a heat-exchanger 30 wherein it is brought into indirect heat-exchange contact with water drawn from drum 10 through a pipe 32. Part of the steam condenses and the steam-water mixture leaves the heatexchanger through a nozzle 36 arranged in an enlargement 38 of a pipe 40 which connects the upper part of the water space of the heatexchanger to the first superheater section 16. The suction created by nozzle 36 reduces the pressure in the water space of the heat-exchanger and thus reduces the temperature of the water therein to below saturation temperature, part of the water evaporating into steam which passes through pipe 40 to join the steamcondensate mixture flow to the superheater. The flow of steam from the water space of the heat-exchanger is controlled by a valve 46 which is actuated in response to temperature variations in the superheater outlet header 24 by a regulator 48. A constant water level is maintained in the heat-exchanger by adjustment of a valve 44 in pipe 32, the valve being actuated by a float-controlled regulator 42. The arrangement provides means for maintaining the final steam temperature constant over the load range of the boiler. If, for example, this temperature rises with increasing load, the opening of valve 46 is increased and more steam passes from the water space of the heatexchanger causing the pressure therein to fall. The temperature of the water is thus reduced and more steam condenses, the water content of the mixture fed to the superheater consequently increases and the final steam temperature decreases to the required value.