VACUUM AND REDUCED PRESSURE REFINING METHOD AND VACUUM AND REDUCED PRESSURE REFINING EQUIPMENT

PROBLEM TO BE SOLVED: To resolve such problem that the filtrating function of a filter is deteriorated with remaining dust caused by entering the air into a dry type dust collector, during waiting time after executing vacuum treatment of a vac uum, reduced pressure refining equipment. SOLUTION: The vacuum, reduced pressure refining equipment constituted with a vacuum, reduced pressure refining vessel 1, dry type dust collector 8 using a filter reduced pressure exhaust device 6 and ducts 3, 5 for connecting these devices in order, is used. Then, during waiting time after completing the pressure recovery by closing both of gate valves 4, 17 freely opening/closing, arranged in the upstream side duct 3 for connecting the vacuum, reduced pressure refining vessel 1 with the dry type dust collector 8 and in the downstream side duct 5 for connecting the dry type dust collector 8 with the reduced pressure exhaust device 6, non-oxidizing gas is flowed into the dry type dust collector 8 so as to hold the inner part in the dry type dust collector 8 to the atmospheric pressure or higher.