| 摘要 |
A vacuum/reduced pressure refining vessel (1) is connected, by an upstream duct (5) to a dry dust collector (3) that uses a filter (2). The dry dust collector (3) is connected to a reduced pressure evacuating apparatus (4) by a downstream duct (6), and a block valve (7) is provided in the upstream duct (5). At the start of a vacuum/reduced pressure refining treatment, a non-oxidizing gas is injected into the upstream duct at a position that is upstream of the block valve (7) to substantially replace the oxygen in the upstream duct and to hermetically close the upstream duct. After the hermetically closed state has been established in the upstream duct, the block valve (7) is opened and operation of the dry dust collector (3) is started. At the end of the vacuum/reduced pressure refining treatment, the block valve (7) is closed and only the non-oxidizing gas is injected into the upstream duct to return the pressure, and then the upstream duct is opened to atmospheric air, and preferably an open port on the side of the dry dust collector (3) is closed during a waiting period from the end of the vacuum/reduced pressure refining treatment until the start of the next vacuum/reduced pressure refining treatment.
|
