| Oolitic ironstone is one of the minerals with a wider distribution in nature.Oolitic ironstone is composed of oolites which are cemented together closely and have concentric rings banded structure that is composed of a variety of minerals which useful mineral and gangue mineral are included. And that useful minerals embedded very fine granularity is one of the fundamental reasons of refractory. The levels of harmful impurities phosphorus in the form of collophanite are higher, so it increases the difficulty of ore beneficiation. Magnetic roasting technology which could change the nature of minerals is one of the effective ways to deal with oolitic ironstone.The process mineralogy of oolitic ironstone are studied and oolites with uniform distribution and thinner particle size are obtained. In addition to part joint vein has iron, all kinds of minerals in ores are distributed uniform, in general, and it has smaller differences between the mineral compositions and structures of the samples. Oolitic ironstone has 65-80% oolites contents, ovals are the mainly shapes and partly are round or prolate ovals. Oolites diameters are between 0.3mm and 0.9mm, and mostly of 0.5-0.8mm. Oolite nuclear are mostly of clay granules and some are sand scrapes with diameters 0.005-0.010mm. Oolitic layers are composed of dense shale laminae iron or mixtures of ferrosilicon. Single-layer thickness generally less than 0.005mm, and some oolitic circles have disseminated hematite particles below 0.005mm. Straight-line method for particle sizes of oolites statistics is used and medium-grained contents with more than 95% are extremely uniform. Hematite are composed of particles which sizes are less than 0.005mm. Parts of limonits and goethites are mixted together with silicon and filled in the middle of oolites in the form of agglutinant in oolitic layers. It is decided that the oolitic ironstone with very fine-grained and multi-layered belongs to refractory ore.One way to utilize the oolitic ironstone effectively is the magnetic roasting to change its natures. Magnetic roasting-low intensity magnetic separation principle flowsheet wasused in the tests. Factors that affect the qualities of magnetic roasting were studied in resistor furnace. A four-factor and three-level orthogonal test was designed, as well as direct analysis and variance analysis were used to calculate datas, and finally the best conditions were gained as follows:oolitic ironstone particle size for roasting is 0-3mm, 4% anthracite,850℃temperature,60 minutes,70% grinding fineness and 2.0A magnetizing current. Oolitic ironstone of 43.63% grade was separated by the optimum technics, and iron concentrate with rate of production of 65.64%, grade of 58.40%, and recovery of 87.86% was got, but the phosphorus of 0.71% in iron concentrate was not significantly lower. Phosphorus leaching tests with dilute sulfuric acid were made and the ultimate iron concentrate was got with 63.97% rate,59.35% iron grade and 86.65% recovery.And the phosphorus content in the iron concentrate was 0.18%, phosphorus removal rate was 75.41%.Theoretical basises of direct reduction iron oxide by carbon was showed inellingham figure. Chemical reactions of magnetic roasting oolitic ironstone is divided into three steps as follows:direct reduction, indirect reduction and carbon gasification, eventually the carbon is consumpted as reducing agent. |
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