Patent GB-373298-A (GB)
Title: Improvements in or relating to processes for producing metal sponge
IPC: C21B13/14
Filed: 1931-02-28
Abstract: 373,298. Metals and alloys. GUSTAFSSON, E. G. T., 95, Birger Jarisgatan, Stockholm. Feb. 28, 1931, No. 6323. Convention date, March 6, 1930. [Classes 72 and 82 (i).] In a modification of the process described in Specification 343,954 for the production of metal sponge, e.g. iron, chromium, nickel, cobalt or iron chrome sponge, the charge of oxide-containing ore or material and excess reducing agent in a loose or briquetted form is first reduced incompletely but to a substantial extent by supplying to the mixture in a shaft or rotary furnace or a tunnel kiln the requisite heat wholly or in part by means of hot combustion gases of an oxidizing character which burn at least part of the excess reducing agent in contact with the charge, the charge being further reduced in another section of the furnace or in a separate furnace out of contact with the oxidizing gases and by the aid of heat stored up in the charge, or heat indirectly supplied, or both. The reducing agent may be carbonaceous material alone or in admixture with a thermic reducing agent e.g. ferro-silicon, ferro-aluminium, or ferro-silico-aluminium, and the charge may be briquetted with the aid of a calcareous binding agent e.g. lime white. After moulding, a layer of carbon may be applied to the surfaces by strewing or blowing the moist briquette with powdered coal. The shaft furnace 3, Fig. 1, is provided with an annular combustion chamber 7 for the fuel burnt in burners 8, whereby the final reduction zone 3c is heated for example by means of channels in the walls of the furnace or from pipes outside or inside the zone. The final reduction in this zone may be assisted by the introduction of strongly reducing gas preferably preheated, containing carbon monoxide or hydrogen or both. The gases produced pass through openings 9 into the reduction section 3b and travel upward through the charge enriched with carbon monoxide from the charge and from zone 3c. Air, preheated if desired, is supplied through openings 11, 12 from pipes 13, 14 and the thus enriched gases may preheat and reduce the charge in the zone 3a. Thereafter they may be used to dry moist briquettes or if they still contain combustible constituents they may supply additional fuel to the burners 8. The sponge is cooled in the section 3d by means of a double walled hopper 18 having air or water circulating between the walls the air being afterwards used in the burners 8. If strongly reducing gas is introduced into the section 3c it may be suitably heated by being first led through this cooling section. The sponge is discharged by screws 22, 23, cooled if necessary. In the rotary furnace, Fig. 3, the charge passes through the preheating zone 3a, the reduction zone 3b, and the final reduction zone 3c and the still incompletely reduced charge passes through an outlet 33 and a shaft 35 into an electric smelting furnace 36 where reduction is completed and the sponge melted. A charge of oxide ore and carbon is introduced through a feed 4a to increase the proportion of reducing gas. Gas developed in this furnace passes through a pipe 40 to a burner 8 with air for the combustion chamber 7 which heats the zone 3c and supplies the combustion gases for the zone 3b. Gas may also be led to the zone 3c through the shaft 35 or through a separate pipe. Air may be supplied through inlets 11, 12 and the gases passed eventually into a dust collector 42.