GB922019A - Iron ore magnetic roast process - Google Patents

Abstract

<PICT:0922019/III/1> Magnetic particles containing Fe3O4 are formed from non-magnetic iron ore particles, e.g. haematite, Fe2O3, by contacting the ore in a preheating zone with p gases from a reducing zone which have been passed via a combustion zone to raise their temperature to, e.g. 1500 DEG -1700 DEG F., contacting the preheated ore in a reducing zone with a reducing gas, at preferably 1100 DEG -1500 DEG F., which contains a major proportion of steam mixed with H2 and CO2 and contacting the reduced ore in a cooling zone, at preferably 750 DEG -1500 DEG F., with a gas at lower temperature than the reducing zone, containing steam, CO, CO2 and hydrocarbon, which is then used as the reducing gas. Crushed haematite ore (e.g. containing 30-35% Fe) is fed through 19 to fluidized fines drier 3 and thence through 4 and hopper 2 to a refractory lined steel rotary kiln 1. The ore passes by gravity through the three zones of kiln 1 in countercurrent to the gases. Steam, at 212 DEG -400 DEG F., entering at 14 and hydrocarbon vapours, natural gas or liquid hydrocarbons, e.g. naphtha, kerosene or heating oil, entering at 15, pass through the cooling zone where part of the hydrocarbons and CO2 react with the steam to form H2 and CO2. Other reducing gas, e.g. producer or water gas, may be added through 16. The resulting reducing gases pass through the reducing zone and the remaining reducing constituents are burnt with air injected at 11 before entering the preheating zone. Fuel may be added at 11 to increase the temperature. A portion of the gases from kiln 1 may pass through 18 to drier 3 and thence through cyclone 21, the remainder of the gas passes through 23 to waste at 25 through waste heat boiler 24 forming steam which is fed to the kiln at 14. In an alternative apparatus (Fig. 2 not shown), the preheating is carried out in a separate kiln from the reducing and cooling. Fe3O4 is withdrawn at 13 for further cooling and processing, e.g. grinding, magnetic separation, briquetting or pelletizing. Fixed vertical kilns and fluidized beds may be used in place of a rotary kiln.