| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability and maintenance of a flue. SOLUTION: There are provided a purge air piping 18, a purge valve 19, and a nozzle 20 which purge primary air taken out from an air flow passage 3 located on the rear flow side of a primary air ventilating machine 2 installed usually in a furnace 6 in an inclined flue 8 located on the upstream side of an electrical dust collector 9 provided on a combustion waste gas flue discharged from the furnace 6 of a pulverized coal-fired boiler and the like. A gas flow speed in the inclined flue 8 is reduced upon low loading of the furnace 6 and purging for prevention of ash deposition is required, so that primary air used for fuel combustion in the furnace 6 is employed as purging gas. Upon high load each purge valve 19 is kept to a specified fine opening, whereby the primary air is supplied into the inclined flue by a small amount to prevent ash from being deposited in the flue 8.
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