Vacuum distn. column for refining metals - using graphite heating electrodes connected to three phase electricity supply

摘要

Appts. for the continuous refining of metals, using a hermetically sealed, cooled and evacuated container for a distn. column fitted with multiple evapn. stages, the molten raw malt. being fed continuously into the top stage and flowing downwards to the outlet; electric heaters extend through the stages which are surrounded by perforated condensn. screens and a cooled condenser box. The novelty is the use of graphite rods in a three phase circuit for electric heating, the rods extending downwards through the evapn. stages whereas the melt flows downwards through the stages in a thin film. In the pref. appts., the evpn. stages consist of a vertical stack of baskets. For example, in refining tin to remove Pb and Bi, or the removal of Zn when refining lead. The graphite electrodes can be 75-710 mm dia. and by changing from a single phase supply to a three phase supply the power used in a protopyte plant could be raised from 250 kVA to 750 kVA without incurring any technical problems.