| 摘要 |
PROBLEM TO BE SOLVED: To maintain a boiler quickly by providing an air supply duct in a combustion furnace and supplying low temperature fluid through the air duct thereby shortening the cooling time in the furnace. SOLUTION: At the cooling time in a furnace, an inlet side fan 3 is operated to supply cooling air into a boiler 1 through an inlet side air duct 2 and an outlet side fan 5 is operated simultaneously to discharge heated air in the boiler 1 to the outside through an outlet side air duct 4. In this regard, liquid nitrogen is sprayed from a delivery nozzle 12 into the inlet side air duct 2 and vaporized to cool the cooling air being supplied thereto. Liquid nitrogen being sprayed is fed from a liquid nitrogen storage tank 9 to the delivery nozzle through a liquid nitrogen piping 13 and the flow rate is monitored by means of a flowmeter 14 so that the flow rate is regulated to a set level by means of the flowmeter 14 and a flow regulation valve 15.
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