GB1164196A - Improvements in the Smelting of Iron Ores - Google Patents

Abstract

1,164,196. Producing iron. W. DAVIES. May 27, 1968 [June 9, 1967], No.26778/67. Heading C7D. Iron is produced from iron ore in a shaft furnace by a process of complete direct reduction, wherein all ore is charged to the furnace in the form of pellets composed of fine particles of ore and low volatility carbonaceous fuel such as coke or anthracite, intimately mixed with or without added flux-forming constituents. No solid carbonaceous fuel is added to the furnace other than that present in the pellets, the ratio of carbon to ore being high enough for complete reduction of all oxidic iron compounds of the ore but not exceeding the stoichiometric amount required for reduction by more than 20% by weight. In practice 4% by weight of the final melt is carbon, also supplied by the pellets, and generally the weight of carbon in the pellets is 15-25% of that of the iron ore. Fluxing materials, if present, are used to form a basic slag, generally with CaO; SiO 2 in the range 1À15-1À40. The pellets are of such a size to produce a gas-permeable burden in the furnace i.e. generally#"- 2" diameter, and so bonded e.g. with sodium silicate, to retain their form until reducing and slag forming reactions occur. 85 per cent of materials used to produce pellets should be preferably below 1 mm diameter. Pellets incorporating fluxing limestone are strengthened by replacing some limestone by quicklime. At the reaction temperature the carbon of each pellet reduces the greater part of the oxidic iron compounds of the same pellet to iron, producing carbon monoxide, which is burnt in a blast of air or air/O 2 mixture to provide the heat necessary for the reducing and slagging reactions to proceed. Heat efficiency is improved by injecting a small amount of liquid or gaseous fuel at the tuyeres, and also by recirculating some gases from the upper part of the furnace to lower regions.