GB1044053A - Apparatus and method for starting a forced through flow vapour generator and associated power plant - Google Patents

Abstract

1,044,053. Forced flow steam boilers. COMBUSTION ENGINEERING Inc. March 5, 1964 [March 25, 1963 (3)], No. 9408/64. Heading F4A. A method of starting a forced flow once through steam generator and associated power plant operating at or above critical pressure including a feedwater heating system and a furnace lined with steam generating and superheating tubes consists of clean-up of preboiler equipment between the condenser and economizer, clean-up of economizer and furnace tube walls, clean-up of superheating section and warming, rolling and synchronizing the associated turbine plant. During this start up a major portion of the fluid input through the generating tubes is recirculated to provide protection against overheating. The working fluid is circulated by a turbine-driven feed pump 22 and a boost feed pump, Fig. 3 (not shown), through H.P. feedwater heater 24, steam operated feed valve 26, economizer 21, furnace tube walls 30a, 30b, boiler throttle and boiler throttle by-pass valves 32a, 32b, superheater 33, H.P. turbine 36, reheaters 38, 39, L.P. turbine 40 and condenser 10. Condensate is circulated by pump 12, through a filter and demineralizer 14, L.P. feedwater heater 18 and deaerator 16. Water of acceptable purity is supplied from a make-up tank 11 leading to the condenser 10 and the concentration of impurities such as copper and iron in the water is measured by chemical analysis equipment 33a, 33b, 33c, 33d. Fluid is recirculated by pump 28 through the furnace tubes 30a, 30b, via conduit 46. A flash tank 44 is connected, in parallel across valves 32a, 32b by conduits containing valves 42, 51, to the feedwater supply line by conduit 41 containing valve 37 and to the condenser by conduit 50. An auxiliary boiler 20 supplies steam for turbine seals, the deaerator 16 and for the initial operation of pump 22 and valve 26. The method of starting commences with preboiler clean-up comprising closing valves 26, 42, 51, filling the preboiler equipment with demineralized water and circulating it by pumps 12, 19 through the equipment and conduits 41, 45. Both feedwater heaters comprise two parallel heaters arranged so that the entire flow can be passed through each heater separately to increase the speed and efficiency of clean-up. When the impurities are reduced to an acceptable value, e.g. 20 p.p.b. boiler clean up is commenced by firing the boiler and circulating about 5% of maximum feed water flow through the economizer and tubes 30a, 30b, the flash tank 44 and the condenser, valve 42 controlling the pressure at which is gradually raised from 1000 to 3500 p.s.i.g. L.P. steam from tank 44 is passed through the superheaters for cooling and when it is sufficiently pure is passed from the tank through superheaters 38, 39 to the turbine to roll and synchronize it, the firing rate being gradually increased.