| 摘要 |
PROBLEM TO BE SOLVED: To prevent overloading of a feed water pump by suppressing a sharp increase in the flow rate of feed water by causing a phenomenon of sudden drop in the water level of a steam drum or the like in a waste heat recovery boiler. SOLUTION: In case a heat source of a heat source generator such as gas turbine is shut out by a trouble or the like, a set value of a water level of a high pressure steam drum 11 is lowered to limit the flow rate of feed water to be supplied to the high pressure steam drum 11, whereby overloading of a high pressure feed water pump 7 for supplying the feed water is prevented to enable the stable operation of a waste heat recovery boiler. In case the heat source such as gas turbine is shut out, a set value of a stream drum level is switched over to a value lower than the actual drum level. As a result, a feed water flow control valve 9 of high pressure water to be supplied to the high pressure steam drum 11 will not be opened by a proportional and integration operation, and is controlled under the full closure unless the actual water level of the high pressure steam drum 11 is lowered below a level set value set lower. Thus, there is no increase in the flow rate of feed water free from any sudden drop in the steam drum level, thereby eliminating excessive flow rate in the discharge of the high pressure feed water pump.
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