| 摘要 |
PROBLEM TO BE SOLVED: To protect a duct effectively against corrosion with exhaust gas or adhesion of dust by making a gas blowing hole in the inner surface of a tubular duct while inclining in the tangential direction of the duct and the advancing direction of exhaust gas. SOLUTION: The duct 2 comprises a tubular double duct formed by arranging inner and outer iron ducts 2a, 2b through air gap 5 and air is pressure fed into an air supply pipe 6 from a coupling opening. The gas (air) pressure fed into the air supply pipe 6 is passed through a vent 8, the air gap 5, a vent 14 and a ventilation path 10 and blown from a blowing hole 16 to the inner surface of the duct while being inclined in the tangential direction of the duct and the advancing direction of exhaust gas. Exhaust gas flowing through the duct 2 is separated from the inner surface of the duct by a blowing gas layer flowing spirally and prevented from touching it directly. Consequently, the inner surface of the duct can be protected against adhesion of dust in the exhaust gas or corrosion with corrosive gas in the exhaust gas.
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