【作者】 杜茂华；

【导师】 段希祥；

【作者基本信息】 昆明理工大学 ， 矿物加工工程， 2007， 博士

【摘要】 金属矿石的磨矿是以解离矿物为目的的解离性磨矿。球磨作业中,磨机内所装钢球的尺寸大小和各种钢球的配比和补加钢球方法,不仅决定着磨矿产品质量的好坏,而且关系到磨矿效率和生产能力高低,决定和影响着选别指标的高低,同时还影响到磨矿的电耗和钢耗。因此,装补球方法的研究对于磨矿至关重要。论文首先综述了磨矿的发展趋势、影响球磨机磨矿效果的因素和改善球磨机磨矿效果的途径、国内外装补球现状及钢球介质的尺寸偏大的原因和论文研究的背景和意义。在此基础上,从岩矿的宏观力学性质包括硬度、韧性、解理和结构缺陷,以及岩矿宏观力学性质与微观结晶的关系阐述了矿石的力学性质对破碎效果的影响,并分析了不同力学特性矿物的磨碎行为的差异。针对本论文所研究的矿石,测定了标准试件矿块与自然矿块的抗破坏特性的力学性能差异,其结果是:不规则矿块的抗压强度仅为规则试件抗压强度的42.88%。由测定结果可知,按规则试件的抗压强度值确定磨矿介质钢球的尺寸是可靠的。论文论述了岩矿的变形与破坏类型特点、球磨机中钢球的运动状态以及钢球尺寸与磨碎作用的关系,说明了在球磨机中使用适宜大小的钢球尺寸进行磨矿,才能使被破碎矿物呈现消耗能量最小的破坏形式即脆性破坏,也才能取得好的磨碎效果。通过对影响球径确定的因素的分析以及对球径的精确计算公式即段氏球径半理论公式的推导过程的详细介绍,说明球径的精确计算公式是在破碎力学原理的基础上用系统而严密的思想推导出来的,较全面地包含了影响球径确定的各因素,所以可以作为实际磨矿过程中计算所需适宜钢球直径的理论指导。同时,得出了结论:1)钢球尺寸大小精确或适宜,可保证破碎能即钢球做抛落运动时落到筒体衬板上的法向冲击动能大小精确或适宜,因而保证破碎力的大小精确或适宜。2)破碎力太大,能量将被无谓地消耗掉。破碎力太小,一次作用又不会使矿粒产生破碎,需要反反复复地作用在矿粒上使其产生疲劳破碎,这种情况也严重浪费了能量。这两者均是应该避免的。3)理想的磨矿过程是使用精确球径,使破碎能或破碎力精确。基于以上理论基础和分析,针对长期以来我国粗磨作业的球径过大、生产中装补球方法普遍不合理但国内外却未提出行之有效的解决办法的状况,结合云南大红山φ3.6m×4.5m磨机中采用原装补球方法磨矿效果不佳的状况,本论文在吸取现有装补球方法优点的基础上,比较系统地研究了一种精确化装球新方法。该新方法是:针对矿石力学特性及磨机工作条件,利用段氏球径半理论公式计算精确球径,依据全给矿粒度特性用破碎统计力学原理为指导,经计算配出初装球方案,作为初装球的精确化推荐方案。在与精确化推荐方案同等的磨矿条件下,进行了实验室扩大试验,配出偏大(大球比例偏高)、偏小(小球比例偏高)方案,再加上现场方案作磨碎效果研究。通过对比推荐方案、偏大方案、偏小方案及现场方案四种装球方案的磨碎结果,证明了精确化推荐初装球方案是最佳的方案。采用破碎统计力学原理,对钢球精确化配比、偏大配比、偏小配比及现场配比这四种球径配比冲击作用下钢球一个破碎循环中可能产生的破碎概率进行了计算。计算结果的对比显示:钢球精确化配比方案(推荐方案)的总破碎概率最大,其中,粗细粒级的破碎概率均介于偏大和偏小这两种装球方案之间,但总的磨碎效果最好:现场配比总的磨碎效果最差;而偏大和偏小配比这两种装球方案破碎概率界于精确化配比和现场配比之间。其原因是:精确化配比装球方案下,各类球径的球均有适当比例,粗、中、细粒级均能较有效地被磨碎,产品中过粗及过细的均不太多,按合格粒级(扣除磨不细粒级及过粉碎粒级后剩的粒级)计的产率最高,所以磨碎效果最好。而且,在精确化配比下,大小球相间的情况类似于最紧密堆积,球荷之间的实际接触面积加大,研磨效果加强。所以,其磨矿效果比偏大配比或偏小配比都要好。至于现场配比的装球方案,由于球径过大,故粗级别的破碎概率最高;另一方面由于装载量一定,所以现场方案球的个数最少,每一个钢球破碎循环中总的破碎概率数也最少,由于球的数量少,特别是适于破碎细粒级的球数少,因而细级别的破碎效果最差,总的磨碎效果也最差。除了对钢球精确化配比方案比其他三种方案的破碎概率最大的原因进行上述分析外,还进一步总结了装球新方法的磨碎机理和规律,得出了如下结论:1)针对实际矿石的力学特性,可通过确定精确的钢球直径来控制钢球的精确破碎力,在破碎力精确的情况下,使得矿石沿不同矿物的结合界面裂开,形成理想的矿物单体。因此,从矿石破碎所需的破碎力大小出发,即从实际矿石的力学特性所表现的抗破碎性能出发来精确确定破碎力,可提高磨矿单体解离度,同时可提高磨矿生产率。2)影响破碎概率的因素有:磨机中各粒级矿粒在矿浆中的固体体积百分含量γ_固(%)、适宜于破碎某级别矿粒的钢球个数m_b、各级别矿粒的选择破碎函数为S(小数)及其破裂函数B。影响规律可描述如下:当球径小于精确球径的计算(采用段氏半理论公式)结果的,破碎不能发生,球径大于计算结果的,均能破碎;破裂函数B对应于粗级别的值大些,而细级别的B值小些。在综合考虑生产中S和B对矿粒破碎的实际影响的同时,当装入磨机中用以破碎某级别矿粒的钢球个数m_b与该级别矿粒在矿浆中的固体体积百分含量Y_固(%)相适应时,磨碎效果最好。3)矿物破坏状况与破碎力的关系、破碎力选择、磨碎过程遵循的规律是:在精确确定各粒级矿粒所需钢球尺寸的前提下,再分别配以与粗、细矿粒百分率一致的各种钢球的适宜的个数,才能做到在合适的破碎力下破碎沿矿物晶界面之间发生,破碎才有好的选择性,这样才能使各级别有最高的磨碎概率。提出了简便、实用的作图补球新方法:以初装球正累积特性曲线为依据,作初装球曲线的平行线,使钢球经磨损而补加球后的球荷特性大体上能保持初装球的球荷特性,即得补加球的累积球荷曲线,从该曲线上便可方便地查出各种球的补加比例。经工业实践,证明了该补加球的方法是可行的,能反映钢球的磨损行为。将本论文上述装补球新方法用于φ3.6m×4.5m磨机中,全面改善了磨矿效果:在磨矿产品细度提高6.02个百分点的前提下磨机台时处理能力提高了18.50%;矿物单体解离度显著提高,其中铜矿物的单体解离度提高9.76个百分点,铁矿物的单体解离度提高10.83个百分点;过粉碎有所减轻;铜精矿和铁精矿的回收率分别提高了1.41个百分点和7.09个百分点,铜精矿和铁精矿品位分别提高了0.55个百分点和1.35个百分点;钢球消耗和磨矿能耗显著下降,其中球耗下降了16.67%,电耗下降了18.44%。更多还原

【Abstract】 The purpose of metalore grinding is to liberate minerals. In the ore grinding operation, the diameters of loaded media balls and their proportions in ball mill and the methods of adding balls not only determine the quality of the product, but also have a great deal to do with the grinding efficiency and productivity and, separation indices, the electricity and steel consumption. Thus studies on ball-load-addition methods in ore grinding are of key importance.The dissertation summarizes the developments and trends of ore grinding, the factors of affecting ore grinding effects in ball mill, the ways of improving ore grinding effects, status of ball-load-addition studies at home and abroad, the reason for oversize balls used in the ore dressing-works in China and its research background and significance. It expounds the influence of the mechanics properties of the ore on crushing effects from the macromechanics properties of the ore, including the hardness, roughness, cleavage and structure faults to relationship between the macromechanics properties of the ore and its micro crystallization. It analyses the difference of ground performance of the minerals with different mechanics properties. The differences of the destruction-resistant mechanics properties between standard and natural samples of ore blocks studied in the dissertation are tested. The test result shows that average compressive strength of the irregular block samples is merely that of 42.88 percent of the standard ones. It follows that it is reliable that the diameters of media balls for ore grinding are determined according to the average compressive strength of the regular standard ore block samples.The deformation and the characteristics of the destruction patterns of the ore, the movement states of balls in the ball mill and the relationship between the sizes of balls and the ground action are explicated, which illustrates that adopting fitted sizes of balls in ball mill can only make the destructed minerals present the destruction form of consuming least amount of energy, called brittle destruction. In turn, good ground effects can be achieved.The factors of affecting the determination of the diameters of the balls are analyzed and the deductive process of the formula of accurately calculating the diameters of the balls, Duan’s semi-theory formula, is presented in detail to show that the formula is deduced in systematic and unassailable thought based on the principle of crushing mechanics and it basically contains all-round factors affecting the determination of the diameters of the balls. Consequently, the formula can be used to theoretically instruct the calculation of the fitted ball diameters needed in practice. In the meantime, the conclusions are drawn as follows:1) the fitted or accurate ball sizes can make the crushing energy, the normal kinetic energy falling to the linings in the ball mill fitted or accurate, that is, the crushing forces fitted or accurate.2) too big crushing force will make the energy wasted, as the same in the case of too small force because the force is too small to break the particles in one impact action and make them fatigue and broken by repeated impacts. These two cases should be avoided.3) accurate ball diameters ought to be used to make ore grinding process ideal, which will make the crushing energy or crushing forces accurate. Based on the theories and analyses mentioned above, aiming to the problems of oversize balls used in the coarse ore grinding operation over a long period of time in China and of having no practical and effective way of solving it and combining with the worse results of ore grinding in 3.6m diameter by 4.5m long ball mill by using original ball-load scheme on the spot in Dahongshan in Yunnan province, the dissertation studies on a new accurate ball-load method systematically: taking the mechanics properties of the ore and operation circumstances of the mill into consideration and calculating accurate ball diameters by adopting Duan’s semi-theory formula, the ball-load scheme, which is rationed in accordance with the grain composition characteristics of the fed ore and in the guidance of the principle of crushing statistical mechanics, is used as accurate recommended initial ball-load scheme.Under the same ore grinding conditions as the accurate ball-load scheme, expanded experiment studies are conducted in the laboratory. The ball-load scheme of bigger balls prevailed, and of smaller balls prevailed, respectively, are designed, plus the scheme on the spot, their ground effects are contrasted. The ground results of four schemes show that the effect of the accurate ball-load scheme is the best.By using crushing statistical principle, the breakage probabilities of four ball-load schemes under the impact action in one crushing cycle of the balls are calculated. The contrast of the calculated results shows that the total breakage probability in the accurate scheme is the highest, that is, its total ground effect is the best, although among which, the numerical values of the breakage probabilities of the coarse and fine grains are between that of both the ball-load schemes of bigger balls prevailed and smaller balls prevailed. The total ground effect of the scheme on the spot is the worst. The reason why the ground effect of the accurate ball-load scheme is better than that of both bigger balls prevailed scheme and smaller balls prevailed scheme is that each kind of ball accounts for the proper percentage in the accurate ball-load scheme, all of the coarse, medium and fine grains can be ground effectively, both over-coarse and over-fine grains are not too much, the production rate of regular grains - remaining grains by deducting those unable to be ground fine and those over crushed - is the highest, that is, the total ground effect of this scheme is the best. Furthermore, in the accurate scheme, the case of the spaces between bigger and smaller balls is similar to the most compact pileup, so the actual contact areas between balls are increased, which in turn enhances the ground effect. As to the scheme on the spot, the oversize balls used cause that the breakage probabilities of the coarse grains are the highest. On the Other hand, since the total weight of the balls loaded in the ball mill is definite, the number of the balls of the scheme on the spot is the least, the total breakage probability of it is the least, and especially, the number of the balls fitted to crush the fine grains is the least, thus the crushed effect of the fine grains is the worst, which leads to the totally worst ground effects.In addition to the above mentioned reasons that the ground effect of the accurate ball-load scheme is the best compared to the other three schemes, the ground mechanism and laws of the accurate ball-load scheme are concluded as follows:1) Aiming at the mechanics properties of the specific mineral needed to be crushed, the accurate crushing force exerted by the ball can be controlled through determining the accurate ball diameter. Under the fitted crushing force, the ore may be split along the combining interface of different minerals and form ideal monomer minerals. Therefore, accurately determining the crushing force according to the need of the crushed ore, in other words, according to the crushability-resistance represented by the specific mineral can improve the liberation degrees and the productivity during ore grinding process.2)The factors of affecting the breakage probability are: the percentage of the solid volume of each grain size contained in the slurry in the mill(γ_solid,%), the number of the balls fitted to crush certain grain size（m_b）, the selective crushing function （S） of each grain size and its breakage function （B）. The law of their influences is that the breakages cannot occur if the actual ball diameters are less than the value of accurate ball diameter calculated in terms of Duan’s semi-theory, and they can if the actual ball diameters are greater than the latter; the value of B corresponding to the coarse grain is greater, it is relative smaller corresponding to the fine grain; under the condition of considering the comprehensive actual influence of both S and B in practice, the ground effect is the best if m_b is suitable toγsolid.3) The law of the relationship between the mineral destruction state and the crushing force, the choice of the crushing force and the ground process followed is that under the premises of accurately determining the ball diameter needed by each grain size, matching the percentage of the coarse and fine particles respectively with the suitable number of the balls can make the breakage occur along the combining interface of different minerals with the accurate crushing force, which make the breakage well selective and the ground probability of each grain size high.A new simple, convenient and practical ball addition method - diagraphy is put forward in the dissertation: based on the initial ball load positive accumulation characteristics curve, to which parallel line is drawn, the ball addition accumulation characteristics curve can obtained by making the ball charge characteristics after the balls are worn and added keep that of the initial ball load. From the ball addition accumulative characteristics curve, the percentage of each kind of balls can be consulted very conveniently. The industrial practice shows that the new method is practical and can reflect the ball wear action.By applying the new ball-load-addition method of the dissertation to the 3.6m diameter by 4.5m long mill, the ore grinding effects are entirely improved: the processing capacity of the grinding mill per hour has been improved by 18.50 percent on the basis of 6.02 percent improvement of the fineness （ - 200 mesh percent） of the grinding product; and the mineral liberation degree of copper has been improved notably by 9.76 percent, and of iron by 10.83 percent; over crushing of the mineral is somewhat mitigated; the grades of copper concentrate and iron concentrate have 0.55 percent and 1.35 percent improvement respectively, and their recovery 1.41 percent and 7.09 percent increase respectively; the ball wear and the energy consumption of handling unit amount of mine are decreased markedly by 16.67 percent and 18.44 percent respectively.更多还原