GB965180A - Method and apparatus for generating power in a vapor generator-turbine plant - Google Patents

Abstract

965,180. Regulating steam temperature in boilers. COMBUSTION ENGINEERING Inc. Dec. 4, 1962 [Dec. 27, 1961 (2)], No. 45753/62. Heading F4A. In a unit power plant operating with double reheat the high and low pressure reheaters are arranged serially with respect to the combustion gas flow and reheat temperatures are regulated over a wide load range by adjusting the location of the combustion zone in the furnace and by regulating the quantity of flue gas recirculated to the furnace whereby the increase in the percentage of total heat absorbed by one reheater relative to that absorbed by the other as the load decreases and vice versa is compensated. In the form shown the boiler, which supplies steam to a turbine 48, has an upright furnace 10 fired by tilting burners 72, gases flowing past a final superheater 44 to a lateral pass 14 locating the second section 58 of the high-pressure reheater and the low-pressure reheater 66 to a downpass 16 in which are disposed a primary superheater 38, the first section 54 of the highpressure reheater and an economizer 20. A fan 74 withdraws cooled flue gas from the bottom of the downpass and discharges it into the lower part of the furnace through a duct 78 controlled by a damper 88. The tilt of the burners and the setting of the damper 88 are respectively controlled in dependence on the temperatures of the low-pressure and high-pressure reheated steam. At maximum load the reheat temperatures are at the desired values. With a decrease in load, when the high pressure reheater requires a greater proportion of the total heat absorbed relative to the demand of the lowpressure reheater to maintain the desired values, the burners are automatically tilted downwards and the gas recirculation increased, the effect being to decrease the heat absorbed by the low-pressure reheater 66 and increase that absorbed by the high-pressure reheater section 54 which constitutes the major proportion of the heating surface of this reheater, so maintaining the steam temperatures at the desired values. In a modification, the high-pressure reheater is arranged upstream of the low-pressure reheater and the controls actuate burner tilt and recirculated gas damper setting in inverse manner.