GB1006713A - Electric arc furnaces - Google Patents

Abstract

1,006,713. Electric arc shaft furnaces. PECHINEY COMPAGNIE DE PRODUITS CHIMIQUES ET ELECTROMETALLURGIGUES. April 26, 1962 [April 28, 1961; March 27, 1962], No. 15959/62. Heading H5H. An electric arc shaft furnace, suitable for the carbothermal reduction of alumina, includes about the or each electrode a structure having an electrically insulating upper portion which surrounds or contacts the electrode in a vapourtight manner in the upper portion of the shaft, and a lower portion extending outwards around and spaced from the electrode. Charge 6, Fig. 2, descends to be fused between soleplate 9 and arc electrode 1, the insulating ring 2 permitting movement of the electrode but preventing the escape of vapour, and the graphite structure 3 preventing the conductive crust 7 from contacting the electrode. Water cooling 4 promotes the formation of a condensed deposit 11 which shields the upper portion from direct radiation, the formation of small local arcs preventing complete bridging of the annular gap by the deposit. In further embodiments, an annular chamber surrounding the electrode is formed in the central portion of the structure, with provision for the introduction of a cleaning gas, e.g. nitrogen, hydrogen, carbon monoxide, or steam (Fig. 3, not shown); the electrode is surrounded by a sheath of aluminous cement, which meets as it nears the arc (Fig. 4, not shown); and the electrode is surrounded by a slowly flowing composition consisting of the oxide included in the furnace charge, together with a binder, e.g. alumina, sodium aluminate, and water (Fig. 5, not shown). Specifications 865,861 and 893,345 are referred to.