| 摘要 |
PURPOSE:To continuously change in available heat transfer area to improve the heat recovery ratio by controlling a liquid level within a condenser. CONSTITUTION:A liquid level control valve 19 is interposed in a condensate tube 8 between an outlet side header 18a of a condenser 6 and a liquid tank 16. With the lowering of the temperature of waste gas, when the temperature of a lower temperature side heat transfer tube 9a within an evaporator 3 or the temperature of steam is lowered to draw near to a dew point temperature, a valve opening contracting signal is generated from controller 20 to operate a liquid level control valve 19 to the closed side by an actuator. As a result, the flow quantity of a liquid heat medium is throttled to raise the liquid level of the heat transfer tube 9 within the condenser 6 and to reduce the available heat transfer area for steam condensation of the heat transfer tube 9. That is, when the height (h) of the liquid level becomes high, the available heat transfer area is reduced. As a result, the condensation quantity of steam is reduced. Hence, the reduction of the load of the evaporator is prevented and the lowering of the surface temperature of the heat transfer tube within the evaporator 3 to a temperature less than the dew point is also prevented, and is maintained at a temperature more than the dew point of acid or the like. |
