Rough Mill Application Of Cast Iron Segment As Coarse Grinding Media Theory And Practice Of Research

The Lead-zinc ore resources are characteristiced by:lean ore more,rich ore less, associated ores abundant and most of refratory ores. Because of the mechanical properties of being soft and fragile,there is generally extremly sliming in the grinding, and which causes the products hard to be separated and also makes the separation indexes bad.Using the cast iron segments as grinding medium in rough grinding,compared with the steel ball,can achieve finely grounded products and reduce the overgrinding and sliming,increase the fineness of grinding and make the grinding product size uniform.Thus, using the cast iron segments as grinding medium in rough grinding has great practical value.The thesis expounds the importance of ore grinding in the mineral processing,summarises the development of rough grinding home and abroad from the grinding technology,grinding equipment and grinding medium,tells its research background and significance. It analyses the flaw of the steel ball when using as rough grinding medium from the factors of affecting the rough grinding effects, the roles of grinding medium and the grinding characteristic and equirement,illustrates the selective dissociation of ball grinding is bad and the overgring is serious.And then it argues the feasibility of wear resistant cast iron segment as rough grinding medium from the shape and quality and ore equirement with regard to the selective milling.Regarding to the shape,the cast iron segment has bigger surface area than steel ball by above 20%,so the grinding capacity of it is better.In addition,short line contact is presented when ore crushing using the cast iron segment,and which can protect the fine partical from overgrinding,this will effectively reduce the overgrinding size fraction of the fragile ores in polymetallic ore.So,the cast iron segment as medium has both mechanical properties of metallic ore including the fragility, roughness, hardness and so on,and which keep the selective grinding more specific.Regarding to the meterial,the cast iron segment is made by grey cast iron as basic meterial, added some factors to enhance the mechanical strengh in a small amount,processed by casting,and satisfy the requirement of different minerals in polymetallic ore.Furthermore,it will cost saving due to the low price,high abrasive resistance and low unit consumption and will be appropriate for widely use in grinding work. In this thesis, the lead-zinc mixed oxysulphide ore from dressing plant in Huize was to be researched.The ore is very rich and rare,the grade of lead and zinc adds up to about 30%. The mechanical properties are soft,fragile and easy to be grinding but extremly sliming,and which seriously affect the promotion of separation indexes. Since the new beneficiation system has been went into operation in Huize mining and dressing plant for several years, the plant has arrived at the full capacity,but the dressing indexes are not desired,the recovery rate of lead is 83-84% and zinc 92～93%.There are three reasons,the first is that multiple products had been output which bring about dispersing of metal;the second is that every products contains each other;The third is that the size property is not well,which enhance the bad separated.The general grinding process is not suit for the rich ore grinding,and a new processe should be adopted aiming at the special mechanical properties,concretely,that is new selectively grinding process of accurate medium size and strong selectively grinding.In this thesis,the accurate ball diameter of different levels has been calculated by Duan's semi-theory formula according to the mechanical properties of the ore,the cast iron segment has replaced the steel ball as new medium, the ball distribution scheme has been recommended in the guidance of the principle of crushing statistical mechanics and been further identified through the laboratory examination which proved that using cast iron segment in rough grinding as medium has good grinding effect, the specific initial ball-load scheme is 65×70:50x60:45x50:35x40:30×35=20:20:20:10:30.The new selectively grinding process of cast iron segment adopted in rough grinding has improved the grinding effect roundly.It can satisfy the production requirement,of which the grinding capacity is better than that of steel ball,the degree of fineness increased by 4.90% with uniform partical, the middle size which is between 200-500 meshes of being easy to dress increased by 4.66%,beneficial for dressing,the content of metal loss decreased and the consume of eletric energy and steel reduced,the saving of medium consume up to 696000yuan according to estimation.