摘要 |
The present invention has an object to improve the efficiency of collection of solidification constituents and solids in exhaust gas and to prevent early blockage of the filter without damaging the vacuum pump. In an exhaust path 48a, a vacuum pump and exhaust gas filtration device are provided. This exhaust gas filtration device is constituted by a trap device, pre-filter and filter. The pre-filter reduces the exhaust gas flow rate flowing through the interior of the exhaust path by controlling the exhaust gas flow path in the vessel. The aforesaid exhaust path is constituted by connecting this vacuum pump, trap device, pre-filter and filter which are arranged in this order from the side of airtight vessel and connected through piping if required.
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