CONTROL METHOD OF STEAM TEMPERATURE AND CONTROLLER

PURPOSE:To increase the temperature of main steam smoothly and steady in the start-up operation by forcibly increasing the spray flow rate in stages according to the predetermined patterns of the flow rate and period of time until the rated capacity is achieved after starting up. CONSTITUTION:Beside a spray valve lift instruction signal 22 that is output from an adder 21, a step spray valve lift setting device 41 is furnished to transmit a step spray valve lift instruction 45 at start-up, and a signal that represents the outlet temperature 12 of a temperature reducing device 4 is input to the step spray valve lift instruction device 41. A step open signal switching device 44 is provided to switch the two instruction signals and send them to a spray valve 8. The step open signal setting device 44 is provided with a step open time setting device 42 to which a signal representing the outlet temperature 12 of the temperature reducing device 4 is given, and a timer 43 for step open time is put into action at the same time to transmit the step open instruction to the spray valve 8. The temperature of main steam smoothly rises without pulsating by forcibly spraying liquid at a predetermined flow rate Q for a predetermined period of time tp simultaneously with start-up.