Vacuum, pressure reduction refining method and the vacuum, pressure reduction refining equipment

The present invention is to provide a vacuum, pressure reduction refining method and a vacuum, pressure reduction refining equipment, being able to use a cheap filter, to proceed dust collection by a vacuum, pressure reduction refining process without causing damage and burning of the filter. A vacuum reduced pressure refining vessel 1, a dry type dust collector 3 using a filter 2 and a reduced pressure exhauster 4 are connected with an upstream side duct 5 and a downstream side duct 6, in order, and a gate valve 7 is arranged in the upstream side duct 5. At the start of the vacuum reduced pressure refining treatment, a non-oxidizing gas is injected into the upstream side from the gate valve 7, and after substantially replacing oxygen at the upstream side, the upstream side is closed, and after completing the closed condition at the upstream side, the gate valve 7 is opened and the dust collector 3 is started to operate. At the end of vacuum reduced pressure refining treatment, the gate valve 7 is closed and only the non-oxidizing gas is injected into the upstream side to return the pressure and then the upstream duct is made open to the atmospheric air, and preferably an open port siding with dust collector 3 is closed in a waiting period from the end of vacuum reduced pressure refining treatment to the start of next vacuum reduced pressure refining treatment.