METHOD AND SYSTEM FOR CONTROLLING DRAIN WATER LEVEL OF FEED- WATER HEATER

摘要

Disclosed are improvements in a method of controlling the drain water level of a high pressure feed water heater for heating feed water with steam extracted from a turbine through the control of the opening of first and second water level control valves respectively provided in a first drain duct leading from the heater to a deaerator and a second drain duct leading from the heater to a low pressure feed water heater according to the detected drain water level and also a system for carrying out the control method. The state of drain in the neighborhood of the drain outlet of the high pressure feed water heater and the state of drain in the neighborhood of the drain inlet of the deaerator are detected, and the drain led to the high pressure feed water heater from a preceding stage or drain led out from the high pressure feed water heater is led to the deaerator prior to being subject to the effect of flashing according to the detected drain states, thus ensuring reliable control of the drain water level even at the time of the flashing in the neighborhood of the inlet of the first water level control valve and suppressing abnormal drain water level changes even in the case of a sudden change of the load or in the case of switching drain paths.