| 摘要 |
PROBLEM TO BE SOLVED: To heat a NOx removal system in a short time even in the cold start operation to lower NOx concentration by providing a high temperature water supply means for supplying external high temperature water to a high pressure drum and a steam supply means for supplying external steam to a high pressure evaporator. SOLUTION: This exhaust heat recovery boiler is provided with a high temperature water supply pipe 27 for supplying high temperature water to a high pressure drum 22. Further, the boiler is provided with a steam pipe 31 for supplying some of steam to the high temperature water supply pipe 27 and the remaining to a high pressure evaporator 23. When the internal pressure of the high pressure drum 22 and the high pressure evaporator 23 becomes predetermined pressure, the exhaust heat recovery boiler closes a communicating valve 29 so that the high temperature water is supplied to the high pressure drum 22 and the high pressure evaporator 23 to raise the temperature of the periphery of a high pressure superheater 21 and the NOx removal system 24. Subsequently, purge operation is performed, and at that time, the purge air takes heat from the high pressure superheater 21 and the high pressure evaporator 23 to become high temperature, and the temperature of the NOx removal system 24 is further elevated. Thus, during warming-up and purge operation, the temperature of the NOx removal system 24 is elevated so that from the start, NOx concentration is suppressed.
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