| Iron ore is one of the most important mineral resources supporting national economy development,whether we can make economical ues of it,which is in relation to the healthy development of steel industry and industry security.But with the mass exploiting of iron ore,the iron ore with the high grade and easy to separate have became scarcity,so the characteristics of iron ore trend to poor,fine-grain and miscellaneous,which become more difficulty to separate.However,due to complex components and metasomatism,close symbiotic relationship and fine dissemination of iron ore in Meishan,coupled with unreasonable grinding system,grinding production inhomogeneity is prominent,steel and power consumption,liner wear,grinding production cost are high,and the resource utilization become lower.Through the 4th series grinding-classification process of Meishan iron ore plant study,it showed that the rate of particles of the overflow fineness of-0.01 mm from the second stage of classification is as high as 15.39%,the grade of iron and metal loss are also respectively up to 30.26%,10.36%,and over crushing is serious,because of low classification efficiency and unreasonable grinding media system.In order to improve the work efficiency of grinding-classification and grinding quality,achieve saving energy and reducing consumption,the optimization process of grinding-classification is conducted in this paper.First,the influential factors experiments of grinding process are studied to get the best optimal parameters.Then the mechanical properties of iron ore is tested which can provide parameters.And the experiment study of the grinding system is made,with half-theory formula of ball size,crushing statistic mechanics principle and laws of steel ball attrition.With the best grinding system,the industry experiment is carried out.(1)The influential factors and orthogonal experiment of grinding process show that the grinding time is main influence factor,followed by grinding concentration.Under optimal parameters: grinding time is 3min,grinding concentration range is: 70%~85%,and steel ball filling rate range is: 35~45%,the fineness of first stage grinding product is 38~42%,and the over crushing is 8~10%.As for the second stage grinding,it can show a good effect when grinding time is 3~4min,ginding concentration range is: 70%~85%,and steel ball filling rate range is: 35~45%.(2)The Platts hardness coefficient f of regular ore block is 16,which is several times higher than the irregular',according to the mechanics test of iron ore block.Based on half-theory formula of ball size,crushing statistic mechanics principle and laws of steel ball attrition,we can get the best grinding media syetem: the initional installation ball diameter of first stage grinding is ?100: ?80: ?60= 30%: 30%: 40%,addition of milling balls is ?100: ?80= 60%: 40%.And the initional installation and addition ball diameter of second stage grinding are ?60: <?40= 20%:20%,?60 =100% respectively.(3)After optimization of grinding condition and ball size precision,the industrial application results show that it has improved the uniformity of grinding product and classification efficiency.The over crushing of overflow from second stage of classification reduces by 21.7%,grades of qualified grain fractions increases by 6.91%,and the productivity of 0.076~0.038 mm increased by 26.78%.The total classification efficiency has increased by 27.98%.And the over crushing of tailings of magnetic separation is rose by 21.16%.Meanwhile,power and steel ball consumption is decreased,and the lifespan of liner has increased,which are equivalent to a 1.7 RMB/t reducation in cost.In conclusion,the industry experiment which optimizes of grinding-classification effeets well and has a good economic benefits.The method is worthy of expansion as a new technique to the similar grinding system,metal or non-metalic dressing plant. |
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