| 摘要 |
PURPOSE:To prevent phenomena of corrosion in a heat transfer tube and evaporation inside a fuel economizer by providing a deaerating steam generator in the minimum gas temperature zone inside a box and systems for regulating the pressure for the purpose of adjusting the pressure inside a deaerator and for bypassing at least one part of the fuel economizer. CONSTITUTION:The pressure inside a deaerator 3 is detected by a detector 37 and this pressure is adjusted to a set pressure value by means of opening/closing control of pressure regulating valves 33, 34 actuated by a pressure control unit 36. The fluid temperature inside this deaerator 3 is maintained above the acid dew point to some extent and the external surface temperature of the heat transfer tube of a deaerating steam generator 10 connected to the deaerator 3 via a low pressure drum 26 is maintained above the acid dew point to some extent so as to prevent generation of low temperature corrosion on this heat transfer tube. Meanwhile, when the temperature of feed water supplied from the deaerator 3 to a fuel economizer 6 is remarkably increased, inlet and outlet stop valves 40, 41 are closed, and a bypass line stop valve 39 is opened so as to allow the feed water from the deaerator 3 to flow while bypassing the first fuel economizer 6a. Thus, the temperature rise of feed water at the outlet of a second economizer 6b is restricted to prevent generation of evaporation phenomenon. |
