GB512771A - Improvements in heat treatment processes employing fused solids as heat transfer media - Google Patents

Abstract

512,771. Heating systems and apparatus. SEAILLES, J. C., and SYLVANY, R. Dec. 4, 1937, No. 33642. Void. Convention date, Dec. 4, 1936. [Class 64 (ii)] Apparatus such as tunnel ovens are heated by. direct radiation from the surface of a fused solid. The heating medium may circulate by thermo-siphon, or by impulses derived from the induction of electric currents in it, or by injection of gases, or by the movements of a refractory body dipping into it. The medium, e.g., a metal, alloy, or a salt, may be fused by a burner or electric arc. If the furnace atmosphere is oxidising, the metal may be one whose oxide is easily reducible, and a reducing agent may be present in the metal-heating chamber. Cast iron may be used since the contained carbon is oxidised before the metal and it may be recarbonised in the heating zone. To avoid the presence of carbon gases, copper, tin or bismuth may be used. The combustion products of a single furnace may be used, at successively lower temperatures, to fuse cast iron, tin, and bismuth-lead-tin alloys. The metal 4 is fused by an electric arc employing electrodes 5, 6. The metal circulates through a heating chamber 1 in a stream 9, 10 around a refractory block 2. Leakage of metal is prevented by employing walls of sufficient thickness to ensure solidification of the metal before reaching the outer side, or by cooling passages 11. The surface of the molten metal may be protected by a layer of slag or a refractory slab, and a neutral gas may circulate between the metal and the slab.