Research On Impact And Abrasion Resistance Of Pure Minerals Based On JK Drop Weight Test And Grinding Test

Most grinding operations are the process that the particle size of ore material is reduced continuously under the combined action of impact and grinding.In the process of grinding,the mechanism of impact and grinding influence on materials is not the same,and the ability of ore components to resist impact and grinding influence is different.Therefore,there is often a contradiction between over-grinding of some minerals in the same grinding system and under-grinding of other minerals in the same batch of materials.In order to study the independent action mechanism and interaction rule of impact and grinding in milling,this study extended the grinding research to the mineral level of ore composition.Taking natural pure minerals such as calcite,chalcopyrite and sphalerite as the research object,using JK drop weight test method and grinding test method,under the condition of single impact,single grinding and the coexistence of two functions,the change rules of grinding behavior characteristics,specific parameters,material crushing rate and product particle size distribution characteristic value of three pure minerals were studied respectively.The results are as follows:?1?According to the standard particle size range of-63.0+13.2mm that specified by the JK drop weight test and expanded the particle size to the range of-13.2+4.75mm,the drop weight test was carried out.The impact crushing parameters and the corresponding hardness levels of the three minerals were obtained and related to the particle size.The smaller the particle size of the material,the smaller the value of the material's impact crushing capacity parameter A×b.This shows that there was a"hardening effect"of particle size reduction between the impact crushing ability and hardness levels of minerals by the drop weight test method,and the smaller the hardness of the mineral,the greater the effect of particle size.Therefore,using the results of JK drop weight test,the comparison of impact crushing resistance of different minerals must be strictly limited to the same particle size.?2?Whether according to the standard particle size range or expanded to a finer particle size range,the impact crushing capacity of the three minerals obtained according to the JK drop weight test was consistent with the mineral Mohs hardness characterization results.Under the same particle size condition,the impact crushing parameter A×b values order of the three minerals was:calcite>sphalerite>chalcopyrite.Therefore,chalcopyrite had the strongest impact crushing resistance,followed by sphalerite and calcite.This shows that it was reasonable to characterize the hardness of the material by the impact crushing ability parameter A×b value of the JK drop weight test.?3?In the grinding process when the medium was in the state of falling,the grinding effect was characterized by the breakage rate of the material and the product particle size characteristic value t₁₀are to characterize the grinding effect.The breakage rate and the value t₁₀of the three minerals were positively correlated with the increase of grinding time,and were complicatedly related to the hardness and particle size of minerals.but there was no obvious consistency with the influence of mineral hardness.The first-order linear model could be used to better fit the grinding kinetics in the cascading state.The kinetic parameters were related to the hardness of mineral and the size of feed.?4?Based on the media throwing crushing energy E in the grinding media motion theory,the grinding data t₁₀in the cascading state,the grinding data t₁₀in the throwing state,and the relationship between the crushing specific energy E_csand t₁₀were obtained by the JK dropping weight test,thus a new method for calculating the actual impact crushing energy of the media on the minerals in the throwing state was established.On this basis,it was proved that the material was subjected to the impact crushing specific energy during the composite grinding process in the throwing state,which was related to the grinding feed particle size and material hardness,the greater mineral hardness,the smaller effect of particle size.Within the range of mill speeds tested,the ratio of the impact specific crushing energy to the throwing specific crushing energy of the three minerals was the range from 10.18%to 41.67%for calcite,the range from 8.12%to26.87%for chalcopyrite and the range from 10.53%to 31.83%for sphalerite.?5?In the grinding process when the medium was in the state of throwing state,the grinding effect was characterized by the breakage rate of the material and the product particle size characteristic value t₁₀.The breakage rate and the value t₁₀of the three minerals showed a positive correlation growth trend with the increase of the mill speed rate,which was fast first and then slow,and was closely related to the mineral hardness.The higher the hardness,the smaller the breakage rate of the mineral,the later the delay in increasing the breakage rate,which reflected that the effect of mineral hardness was consistent with the conclusion of JK droping weight test,and t₁₀was more suitable for characterizing the composite grinding effect in the throwing state,not suitable for characterizing the grinding effect in the cascading state.The paper provides a theoretical basis for the subsequent deepening analysis of grinding mechanism and optimal control of grinding.The research results of this paper have high practical significance and academic value.