Combining with concrete example of a boiler feed-water control system in the start-up system with built - in boiler water circulatory pump for one 600 MW supercritical unit

and based on analysis of feed-water regulating process in the full load range

a typical four-loop feed-water control system and its working principle have been presented

the said system controls fuel/water ratio by using heat absorption and enthalpy increase of the evaporator

and corrects fuel/water ratio by using the enthalpy value at outlet of the separater

as well as correcting feed-water flow rate by using the temperature decrease of the first-stage desuperheater.