| Dagushan preparation Plant of Anshan Mining Co., Ansteel Group, was set up and began to produce in 1955, sole magnetic beneficiation has been adopted during handling iron ore of Dagushan.The Third Separation Workshop was set up and began to produce in February 1958,beneficiation process of two-stage continuous grinding, fine regrinding has been adopted during handling iron ore of Dagushan, It deals with 2,500,000 tons, one third of the total factory,every year. Since 2000, its concentrate grade has increased from 63.5% to 67.17% in 2006 though three technical reforms. With the same iron ore, tail grade and working procedure, it also has a gap in concentrate grade of the secondary Workshop,67.2%. The particle size of crushing output is up to 95%-12mm in the reform at Dagushan preparation Plant in 2004. So the capacity of the first ball was made an increase of 10t/h after the reform.And the size before beneficiation was also turn to bigger which caused the whole flow in disorder and made the final concentrate grade low.So the technical department made an examination of production technology in grinding and classification operation which is different from the secondary Workshop. We found problems such as:size of overflow in primary classification and discharged Material was bigger than that of the secondary workshop's. The second overflow particle size didn't reach 85%(-0.074mm),The size before beneficiation was so coarse that it made the working procedure insufficient to increase the final grade. Some steps were adopted, for example, adjusting the working parameter of grinding, selecting the best dia. of medium in first grinding to increase the content of primary classification; confirming the parameter in order to minish the size of overflow in secondary classification though experiment.By these means, the size of overflow in secondary classification is up to 86.5% from 84%(-0.074mm).The concentrate grade in third workshop is also increased from 67.17% to 67.21%.
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