| As one of the most important parts of mineral processing, ore grinding determines the efficiency of mineral processing operation to a great extent. Among a great deal of factors that affect grinding efficiency, grinding medium is of most importance .The size and shape of grinding medium play a decisive role on mineral liberation degree of the grinding products and the composition of particle sizes. Therefore, how to determine grinding medium's size accurately and choose grinding medium's shape that can suit mineral nature becomes important content in grinding studies. The ore is one kind material, whose structural mechanical property is non-uniformity, the interior binding force of mineral crystal is the strongest; the exterior binding force of mineral crystal is less than that of the interior. The binding force between the homogeneous mineral crystal's surface is more than that between non-homogeneous. Because the goal of dissociative grinding is to make the dissociation of non-homogeneous mineral crystal polymer, the breaking force should be precise to cause the dissociation of non-homogeneous mineral crystal . If the breaking force is overbig, the destruction of ore occurred along crystal's contact surface, even in the crystal lattice. The penetrative function lacks selectivity and its breaking behavior is not along the non-homogeneous mineral crystal's surface, but along the breaking force's principal stress direction. So the broke product is often not of the monomer dissociation of non-homogeneous mineral granule, but of the mechanically becoming finess of ore material granule. In addition, the overbig breaking force is often easy to cause seriously smashing phenomenon. Otherwise, too small breaking force couldn't achieve the breaking stress's request and couldn't produce the disposable breaking, and only produce fatigue break in low effiniency. So we know, the more precise of breaking force, the higher of the mineral dissociation selectivity. That means, how to precisely choose the breaking force is an important question in grinding.The analysis for the concentrate's mineral existence state showed that the above 55% mineral is the monomer that mixed in the concentrate. The -0.01mm rank's particle's nickel status is the lowest and its magnesium oxcide content is the highest: above the 90% mineral is monomer mineral in this grade. The magnesia mineral is mainly serpentine mineral in the concentrate. This showed that the content of magnesium oxcide is high in concentrate because the serpentine is massively mixed. The thick monomer serpentine is mixed in concentrate because of the flotation, the thin monomer serpentine is mixed in concentrate because of the surface energy. The agentia reducing the MgO's content is difficultyly functioned in these two kinds of situations. This indicated that reducing the magnesia's content is not only to be done in the floating and also the serpentine's pelitization should be reduced as far as possible in the grinding.For the nickel concentrate, if the MgO's content is excessively high that would be elevate the smelting furnace's temperature, increase the slag's viscosity, reduce the smelt's recycled-ratio. Using the fast stove would be caused the fast stove bunched because the slag's viscosity is oversized. When the content of magnesium is high in the nickel concentrate, the slag is not easy to discharge because it's viscosity. At present, the mined deposit of nickel sulfide magnesium's silicate mineral. The content of MgO is high in the nickel concentrate because the silicate mineral is easy to be mudded and its flotation is great. In the fast stove's smelting craft, there is a strict request for the concentrate quality. The request is that the nickel's content is above7%, the MgO's content is lower 7%, and the sulfur's content is above 25% in concentrate. Therefore, reducing the MgO's content and enhancing the nickel concentrate's content is extremely efficiency for increasing the smelting efficiency and reducing the unit cost. In addition, now the smelting slag of the nickel concentrate mainly is as the cement's raw material, and if the MgO's content is oversized would be influential to the cement quality. So the factory requested: when the MgO's content in concentrate is lower than 7%, the slag can be only used. Because the content of MgO is a important reasons for metallurgical, so we study the effect of properties of the ore for reducing the content of magnesia. Including: natural floatability of MgO,hardness of ore,mineralogy and so on. Considering those reasons, we introduce some traditional technology of reducing the content of magnesia. for example: reducing the content of magnesia from mixed concentrate,studying of process mineralogy,studying of new pharmacy for floating,the joint use of efficient flotation agent,quick flotation,program of two products,acid flotation,electrochemical flotation,pharmacy of reducing magnesia.Properties of the ore are the basis to determine the grinding and separation. The character of nickel sulfide and other brittle metallic minerals that is easy to break, which will result in preferential comminution and over-grinding by selection, and it is difficult to be covered in the flotation system because of the existence of fine particles. Being the special properties of the gangue in the said rich ore, the ore can convert to the gangue serpentine with low intension by erosion, which is easy to form the so-called sliminess upon the grinding. The slimy serpentine interferes the floating of nickel mineral and it is difficult to reduce the content of magnesia in the concentrate. The demand of the grinding of the floating of nickel ore is to reduce deficient-grinding, over-grinding and increase the liberation degree of minerals to a specific demand, which will satisfy the demands for choice the new-style medium that can protect the fine particles with the precise new grinding medium powerfully. According to results of many experiments in the lab, the application of this new technology in grinding shows that the recovery can get improved and the content of magnesia in the concentrate can get reduced effectively, which realize the specific demand for flotation operation.Because the grinding is a quite complex process, in general it included two stages: (1) ore aggregate's breaking and different ore particle's dissociation; (2) the further breaking of each kind of mineral granule. When mixed ore's particles suffered the grinding, each kind of mineral's grinding behavior presented the difference: the mineral of mechanical strength is high that it's breaking probability is low, it is difficulty to be broke and it's grinding speed is slow; the mineral of mechanical strength is low that it's breaking probability is high, it is easy to be broke and it's grinding speed is fast. In other words, the different mineral's mechanical strength caused the different grinding speed. The difference of each kind of mineral particles' grinding speed caused the difference of each kind of mineral particles' size in the final grinding product: the mineral particle of mechanical strength is high that it's size is big because it's grinding speed is slow, the mineral particle of mechanical strength is low that it's size is small because it's grinding speed is fast. Therefore, the grinding product of mixed mineral is the non-uniform grain system that the quantity distribution and the size distribution is to beyond comparison: the mineral particle of mechanical strength is high that it's distribution is much more in the thick rank, the mineral particle of mechanical strength is low that it's distribution is much more in the thin rank. We called the phenomenon is the selective grinding.This thesis sets out from Professor Duan Xixiang's half-theory formula to determine the size and shape of grinding medium through experiment. Using its conclusion on the grinding system of the concentrator of JinChuan Group Co., Ltd. Study in the whole procedure laboratory (including grinding, and separation etc.) indicates that: combining the half-theory formula with the law of experiment to determine medium size's is innovative and practical in theory and practice to some extend.With consideration of the characteristic of grinding and separation for the rich ore in the No.2 mining area in the company, following conclusions have been obtained by the study in laboratory and industrial application:According to the commercial experiment of No.4 system of the rich ore in the No.2 concentrator, results indicate that: the rate of recovery of nickel is raised by a percentage point of 1.341,the rate of recovery of copper by a percentage of 1.82;and the content of magnesia of concentrate decreases remarkably to 5.294%.And the new technology has been proved to be feasible in optimization of constitution of particle sizes in the ground products, making the rate of recovery for copper and nickel improved, and reducing the content of MgO of concentrate remarkablely.
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