Calcium or other alkaline earth metal production in a horizontal cylindrical furnace that is vertically movable and has a graphite crucible heated by single phase electric current

摘要

Alkaline earth metals are produced by rapidly heating tablets of their oxides in a horizontal cylindrical furnace under vacuum and having an external metal framework to 1350 deg C. The tablets are obtained by strong pressing, at around 10000 N/cm2, of a homogeneous mixture of CaO or alkaline earth metal oxides and below 3 mm Al or FeSi shot in amount 15-25 weight % of the mixture. A graphite crucible (1) containing the tablets is the heating element, only the volume of the tablets is heated, the surface of contact of the crucible (1) with the tablets is very high, and the thickness to be heated is low, i.e. 300-600 mm. The formed metal vapors are sucked up by a vacuum pump and then condensed in the solid state in the sealed hood of the furnace on a water-cooled condenser (10). The graphite crucible (1) is cut in the form of a helix to increase its ohmic resistance, except at its two ends where two graphite contacts (17) are attached to current inputs (16). Lightweight insulators (2, 4) surround the crucible (1) and dense insulators (3, 5, 15) ensure support of the assembly. The furnace pivots in the vertical plane around an axis (8), and this allows easy input and withdrawal of charge.