GB597530A - Methods of and apparatus for direct reduction of iron ores - Google Patents

Abstract

597,530. Reducing ores. DEHN, F. B. (Coast Reduction, Inc.). June 26, 1945, No. 16294. [Classes 51' (ii) and 55 (ii)] In the reduction of iron ore in a multiplehearth furnace in which the reducing gas is introduced at different hearth levels and moves upwardly through the descending ore, the reducing gas is heated to such a temperature that the sensible heat thereof is sufficient to supply the heat necessary not only for the reduction of the ore but also for compensating for radiation losses. As shown, the ore passes from a bin 33 through a rotary feeder 35 on to the top hearth and is rabbled inwardly and outwardly on successive hearths from the lower of which it is discharged through a conduit 40 into a waterjacketed cooler 41. The reducing-gas is supplied from the generators 37, a number of which, e.g., three, are spaced around the reduction-chamber. The generators are supplied with a fuel gas, e.g., natural gas, heated to a temperature of about 1,000‹F. and with air at a temperature of about 2,000‹F., the gases being decomposed by heating in the generators to produce a mixture principally of carbon-monoxide and hydrogen at a temperature in excess of 2,000‹F. The hot reducing gases are admitted to the three lower hearths, although it may be found desirable to hold intermediate hearths at higher temperatures than the lower ones. The spent reducing-gas passes through a duct 50 to a stack 51, having a pressure-relief 52, and is then taken to the burners of the air and gas preheaters. The rabble arms 12 are cooled by air supplied by a blower 15 through a control valve 18 and meter 19, an air-pressure relief 22 being provided. A tube 9, within the tube 8 carrying the arms 12, is connected to the air-return passages of the arms so that the heated air passes downwardly through the tube 9 and is taken by a pipe 44 to the airpre-heater 45 for supply to the generators 37. An induced air system may be used instead of a forced system, or natural gas or coke oven gas may be used for cooling the rabble arms. Some arms, e.g., the upper arms may be cooled by air and some by gas, and jets of air may be introduced into the upper hearths to ignite the reducing-gases and preheat the ore. The rabble arms 12 may have dove-tailed recesses for detachably holding the rabbles, and spacers may be inserted between some rabbles to prevent ridges from forming in the ore bed. One or more rabble arms at each hearth level may be-provided with an end scraper to prevent the accumulation of ore on the inner wall of the furnace. Specifications 240,165 and 328,240, [both in Class 51 (ii)], are referred to.