两段磨矿精确化装补球方法的开发及应用研究

【作者】 肖庆飞；

【导师】 段希祥；

【作者基本信息】 昆明理工大学 ， 矿物加工工程， 2008， 博士

【摘要】 磨矿是选矿厂的领头作业,选矿厂的作业率和原矿的处理能力实际上取决于球磨机的生产率和处理能力。磨矿作业产品质量的高低也直接影响着选矿指标的高低。如提高有用矿物的单体解离度、降低有用矿物的过粉碎可以提高选别作业的精矿品位和有用矿物的回收率,减少有用矿物的金属流失,提高选矿厂的过滤效率等。众多选矿工作者长期以来,围绕着通过什么样的工艺或方法来全面改善磨矿效果,其中最有实际意义的是从磨矿介质这个因素入手,使磨矿效果全面改善,这是因为磨矿作业是通过磨矿介质实现的。然而,磨矿介质又受诸多因素如介质尺寸大小与形状、磨机装载量、介质配比、合理补加钢球制度和磨机转速等因素的制约。2003年～2005年课题组开发了一段磨矿中的精确化装补球方法,在若干厂矿应用后效果显著:①在给排矿粒度不变的情况下,提高磨机生产率10～20%;②在磨矿细度不变的情况下提高矿物单体解离度5～6个百分点;③在选矿条件不变下提高回收率1～3个百分点及精矿品位同时提高;④在钢球材质不变时,降低球耗10～20%;⑤在装球不变下降低磨矿单位电耗10～20%;⑥降低磨机噪音5分贝以上;⑦延长衬板寿命约30%。但是把此方法应用到两段磨矿中后,磨机处理能力却大幅降低。可见,一段磨中的精确化装补球方法在两段磨中根本不适应。为此,深化拓展并开发出适合于两段磨矿中的精确化装补球方法就是本论文的主要研究内容。本论文首先研究了磨矿对象岩矿的力学性质,包括硬度、韧性、解理及结构缺陷。硬度大、韧性大的矿石难磨,存在解理现象和结构缺陷的容易磨,因此,要针对矿石的力学特性来选择与之相适应的磨矿条件才会有好的磨矿效果。而矿石的力学性质依破碎力的不同而表现出不同的抗破碎性能,一般以“坚固性系数”f(即普氏系数)来表示岩石的相对坚固性。而测定岩矿的极限抗压强度又分为规则矿块及自然矿块的测定,在10mm以上矿块中要对标准力学试件抗压强度值进行修正,修正幅度以等体积换算受压面积方法计算。因此,矿石的抗破碎力学性质研究强化了磨碎的针对性,并为精确计算球径提供了必要的参数数据和力学依据。钢球既是磨矿作用的实施体,又是能量的传递体,它决定着矿石的破碎行为能否发生及怎样发生,也影响着磨机生产能力的大小、磨矿产品质量(包括磨矿产品的粒度特性、单体解离特性等)的好坏及磨矿过程中钢耗和能耗的高低等。但是影响钢球尺寸的因素很多,怎样精确计算钢球尺寸就是一个急待解决的问题。本论文着重介绍了段氏球径半理论公式,该公式在粗磨、中磨和细磨的广泛领域都能精确的计算特定条件下所需的球径。而两段磨矿又因为其粒度范围、所需破坏力、矿浆浓度、介质形状等特殊要求使得两段磨中的球径精确技术有其特定的要求。球径半理论公式只解决了计算单一窄级别球径的问题,对于给矿为多级别的混合矿料,磨机内的钢球就必须确定装球的级别尺寸及各尺寸之间的比例,这就靠初装球来解决。本论文根据破碎统计力学的研究方法,不去研究单个钢球的运动规律,而是通过研究单个钢球对矿粒的破碎作用来研究钢球的集合体的破碎行为,用破碎事件量的高低来衡量磨碎效果的好坏,对于单一球径的破碎统计力学,可以确定最佳球径并验证段氏球径半理论公式的最佳球径的准确性,而对于混合球组的破碎统计力学,则为磨机初装球的配比提供依据。初装球也只解决了磨机工作前的装球问题,磨机一经工作,钢球磨损随即产生,接着就是补加球的问题。传统的简单装补球方法和合理平衡装补球方法,由于其本身的缺陷使得这两种装补球方法难以在厂矿贯彻执行或执行的效果不好。目前还没有一个纯理论的磨球磨损规律的数学模型,所以钢球的补加在实际操作中不易执行。为此,本论文用作图法来实现钢球的合理补加,比合理平衡补加球计算少了两次清球,且初装球和补加球计算一次完成,节省了大量工作和时间。在两段磨矿的细磨阶段,本论文提出使用新型耐磨铸铁段来替代传统的钢球作为细磨介质,并经混合段组与混合球组的对比试验证明新型细磨介质的效果更好。在粗磨阶段,对粗磨机进行提高转速后精确化装补球方法的适应性研究,得出方法可用但要调整球量的结论。由以上研究,本论文深化拓展出两段磨矿中的精确化装补球方法:即针对矿石的力学性质确定精确的钢球尺寸,运用破碎统计力学原理确定钢球的种类及配比,根据作图法进行精确简易的补加钢球,粗磨段磨机采用较高转速,细磨段用短截头圆锥耐磨铸铁段作为细磨介质。2005年把此方法应用在狮子山铜矿,研究结果说明:①试验后磨机生产能力由76.46吨/时增至83.34吨/时,提高9%;②在提高生产能力的同时,磨矿产品细度由-200目76.41%提高至84.29%,提高7.88个百分点;③在原矿品位由0.72%降至0.67%,降低0.050个百分点(降低6.94%)及精矿品位提高0.66个百分点的情况下,回收率提高2.98个百分点;④选矿厂电耗降低10.81%;⑤磨矿介质单耗降低10.42%。由此可见,精确化装补球方法在两段磨矿流程中应用效果很好,使选矿厂处理能力由1850吨/日提高到2000吨/日,达到预期目标。2006年我们进行了粗磨阶段提高磨机转速的精确化装补球方法的适应性研究。结果显示:①二阶段磨机台时能力达91.84吨/时,比研究前的76.46吨/时提高了15.38吨/时,提高20.12%,幅度是相当大的,比前一阶段也提高10.20%;②一段磨电耗下降17.92%,选厂电耗则降低21.33%;③介质单耗则降低30.64%。由此得出结论,二段磨矿中适当提高粗磨机的转速率(转速率低于88%)后,精确化装补球方法仍然能使用,而且有很好的增产降耗效果,使狮子山铜矿的处理能力由2000吨/日提高到2200吨/日。但提高转速后要适当减少装球量,使装球量与转速率相适应。一个规模2200吨/日的中型选矿厂,因采用两段磨矿的精确化装补球后,30个月中增收节支的经济效益达7151.98万元,按完整的2007年计,年增收节支4298.11万元,经济效益是十分显著的。工业试验及应用的效果证实,开发出来的两段磨矿中的精确化装补球方法在厂矿中应用效果显著,是值得推广应用的新技术。更多还原

【Abstract】 Ore grinding is the leading operation in ore dressing plants.The capacity rate of processing original ore in workshops in the plants actually is decided by the productivity and processing ability of ore grinding.The quality of the grinding products gravely affects the targets of ore processing.For example increasing the mineral monomer separation degree and decresing the overcrushing of mineral can increase the grade of concentrates and recovery of useful mineral,reduce run off useful mineral of the metals and raise a percolation efficiency mineral separation plants etc.Among many processes or methods of improving grinding effect,the most actual meaningful one is to grasp grinding media factor to make grinding effect improved completely.This is because of grinding workshop section to lie grinding media.However, grinding media is lie many factors for the size and shape of media,capacity of mills, distribution ratio of media,reasonable add steel ball system and revolution speed of mills etc.The group development the method of accurate ball-load-addition in single stage grinding from 2003 to 2005 and show the effect after some plant apply:①The mill’s productivity has increased by 10～20%in the case of the same grain size distribution of the mill’s feeding and discharging.②The mineral unit separation degree has increased 5～6%on condition that the size distribution of the grinding products has not changed.③The recovery has increased 1～3%and the concentrate grade also risen on the same ore dressing condition.④The consumption of steel ball has decreased by 10～20%for the same quality ball.⑤The unit electricity consumption of grinding has decreased by 10～20%for the same ball loading system.⑥The mill’s noise has descended more than 5dB.⑦The life of grinder’s lining board has prolonged 30%.But apply this method to the two stage grinding,the capacity of ball mills significantly lower.Thus the method of accurate ball-load-addition in single stage grinding is unsuitable to the two stage grinding.For this,deeply expanding and developing suitable accurate ball-load-addition method for two stage grinding is the main research contents of this thesis.This thesis first studied the mechanics property of the grinded ores,including the hardness,roughness,cleavage and structure faults.Hard and rough ores are difficult to be grinded,the cleavage phenomenon and structure faults ore easy grinded.Therefore aiming at the mechanics characteristic of ore and fitting it with grinding condition will have a good ore grinding effect.The mechanics property of ore depend on crush dint of dissimilarity express an anti- crushing function,generally mean rocky opposite and hard with"hardly coefficient".The compressive strength limit of ore is divided into the regular ore and natural ore.The compressive strength limit of regular ore above 10mm must be revised and calculated by converting the volume of the ore to the compressed area method.Therefore, the anti-crushing mechanics property research of ore enhanced the aim of grinding,and provide for the necessary of parameter data and mechanics basis to precision computed ball diameter.Steel ball is the implement body which grinding function and the deliver of energy body.It decide the broken up behavior of ore can take place and how take place,influence produces ability of mills,the quality of the grinding quantity(include grain degree characteristic,monomer separation degree characteristic etc.)and steel consume and energy consume etc.But the factor of the influence steel ball size be a lot of,how the precision compute steel ball the size be the problem to resolve.The thesis emphasized on introducing Duan’s ball diameter semi-theory formula,which can give precise diameters of balls needed under the particular conditions at rough and fine ore grinding.The two stage ore grinding because of its grain,the destructive power,pulp concentrates,the shape of media etc,has a paticular request to the accurate medium ball diameters.Ball diameter semi-theory formula only solved the problem which calculation single narrow grain size diameter,for feed for hybrid grain size,the steel ball has to make sure the comparison of of the grain size and each size of pack the ball,this depend the loading ball to resolve.This thesis according to the research method of crushing statistics mechanics, don’t study the sport regulation of single steel ball,but the crushing behavior of the aggregation which passes to study single steel ballcrushing function of mineral grain.Use fall in pieces affairs’ quantity to measure quality of grate the effect.For single diameter of crushing statistics mechanics,can make sure the best diameter and identify the accuracy of ball diameter semi-theory formula.For mixture ball set of crushing statistics mechanics, can provide basis for loading balls in mills.The beginning loading balls only solved the pack a ball problem before mills working, as soon as mills work,the steel ball wears away to immediately produce,immediately be repair problem of adding ball.Traditionally and in brief pack to repair ball method and reasonable balance method,because of it of the blemish make these two kinds pack to repair a ball method hard carry through to performance or ineffective.So far not a mathematics model which purely and theoretically mill ball to wear away regulation,so the adding ball impose physically in operation don’t easily carry out.For this,this thesis useds to a diagram method to carry out steel ball of reasonable repair to add.Compare reasonable balance add a ball calculation without twice pure ball,and loading ball and adding ball to compute a completion,saved a great deal of work and time.In the two stage fine grinding,this thesis puts forward an new wearable iron sect medium as a substitute for traditional steel ball,and the contrast experiments show the new fine grinding media effect is better than that of the mixture ball set and of hybrid iron sect set.In rough stage,daptability research of the method of accurate ball-load-addition by increasing revolution speed of rough mill,can give a conclusion of the method can use and must adjust the amount of balls.From the above research,this thesis deeply expand the method of accurate ball-load-addition for two stage grinding.According to the mechanics property of ore determines accurate steel ball size.Using crushing statistics mechanics principle the category and ratio of balls.According to diagram method carrys on accurate simplely adding balls.Using higher revolution speed in rough mills in rough stage.Using short head cone iron sect acts as fine grinding media.The method is applied in Shizishan Copper Mill in 2005.The conclusions are:①The grinding’s productivity has increased by 9%from 76.46t/h to 83.34t/h for a grinder.②The fineness of grinding products(-200 mesh)has increased by 7.88 percentage points from 76.41%to 84.29%.③The ore grade decrease from 0.72%to 0.67%and concentrates grade has been increased 0.66 percentage points,the recovery increases by 2.98%.④The electricity consumption decreased by 10.81%.⑤The grinding media consumption decreased by 10.42%.So the method of accurate ball-load-addition for two stage grinding make mill’s production has increased from 1850t/d to 2200t/d and attain an expectation target.The adaptability research of the method of accurate ball-load-addition for two stage grinding in rough grinding by increasing revolution speed has been carried out.The conclusion show:①The grinding’s production has increased by 20.12%from 76.46t/h to 91.84t/h for a grinder,increased 10.20%as last year.②The first stage electricity consumption decreased by 17.92%and plant electricity consumption decreased by 21.33%.③The grinding media consumption decreased by 31.64%.From here get conclusion,the method of accurate ball-load-addition for two stage grinding can still keep use after increase revolution speed(low in 88%),make mill’s production has increased from 1850t/d to 2200t/d in Shizishan Copper Mill.But increase revolution speed must decrease the pack amount of ball and make pack amount of ball response to revolution speed.A scale 2200t/d of medium-sized mill after adopting the accurate ball-load-addition method,the economic performance reaches to 71,519,800 dollars in 30 months.In 2007, the yearly economic increases is 42,981,100 dollars and the economic performance shows very well.Industry experiment and applied effect confirmation show that the development of the method of accurate ball-load-addition for two stage grinding effects well and is worthy of expansion as a new technique.更多还原