| 摘要 |
PROBLEM TO BE SOLVED: To prevent drastic variation of water level and stabilize the dryness of steam in an once-through boiler. SOLUTION: A boiler comprises a water level detector 8 for detecting the water level in the boiler 1, feedwater devices 6, 7 for feeding feedwater to the boiler and an operation control device 12 for controlling the feedwater devices on the basis of the water level detected by the water level detector. The water level detector detects a water level at a water level position E1 and a water level position E2 which is lower than the position E1. The feedwater devices can control feedwater feed velocity. When the water level goes down to the position E2 during the operation of the boiler, the operation control device conducts H% of water feed, and when the water level goes up to the position E1, the device conducts L% of water feed. The feedwater feed velocity of the H% water feed is larger than the set value of the water feed velocity of the L% water feed.
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