Fundamental Study On Grindability Of Donganshan Refractory Iron Ore

Grinding technological process,as a important unit operation,is widely used for comminution of ores in mineral industries.In mineral processing,the primary goal of comminution is to liberate valuable components from gangue minerals,and the other important role is to obtain a desired particle sizes for all the downstream separation and/or extraction operations.Over-grinding or low liberation leads to a lower recovery of valuables.The Donganshan iron ore is classical refractory hematite in China.Especially in recent years,the content of siderite has increased with increasing of mining depth,and the phenomenon for non-uniform of product size distribution and sliming has been more and more concerned during grinding process.Because of a large number of non-conforming product size produced,it deteriorate seriously separation of the iron ores using floatation processing.In the paper,using a small laboratory-scale mill,experiments were first carried out on the wet grinding of mono fractions of quartz,hematite,siderite and chlorite on the base of the characteristics of the technological mineralogy of the Donganshan iron ore.In terms of the population balance grinding kinetics model,the breakage characteristic parameters(the first-order output characteristics,the breakage rate(selection)and cumulative breakage distribution functions)of the four single minerals were obtained.The results indicated that the four single minerals sizes conformed to the first-order breakage behavior in the feed size range investigated.The fine fraction output for-0.5+0.25mm size fractions of quartz,hematite,siderite and chlorite had a clear the zero-order output characteristics at a relatively short grinding time,respectively.The cumulative breakage distribution functions for-0.5+0.25mm size fractions of the four single mineral were obtained using G-H algorithm,B-II algorithm(back-calculation method)and empirical model.In addition,the simulated product size distribution data obtained,using the discrete-size,continuous-time Population Balance Model(PBM),were consistent with experimental data for-0.5+0.25mm size fractions of the four single mineral.Based on the breakage behaviors of the four single minerals,the breakage characteristics,the grinding product size distribution and interaction among minerals in their binary mix,their tenary mix and the artificial mixed minerals were investigated using laser particle analyzer,(X-ray diffraction analysis)XRD,Zeta potential analyzer,X-ray fluorescence spectrometry(XRF)and chemical titration analysis,etc.The ruslts show that all of the breakage behavior for their binary mix,their tenary mix and the artificial mixed minerals followed first-order grinding dynamic model,and the breakage characteristic parameters for each mineral in mix were abtained.The simulation results of the overall product size distribution for any the mix,using the population balance model,were in good agreement with the experimental data.The simulated data lines are very close to the experimental data points.The errors between the simulate results and experimental results are no more than 3%.From the research on the ball grinding of a binary minerals mix with various volume ratios,it could be concluded that there is an interaction between components in a binary mix when ground simultaneously.The similar results have been found when gound the tenary mix and the artificial mixed minerals.The essence and rule of the changes of breakage characteristics for each mineals and interaction behavior among minearals were revealed using the class DLVO theory and solution chemistry in wetting grinding process.The research and theory analyses indicated that Zeta potential of mineral surface,pH values and unavoidable metal cations(Ca2+ and Fe3+)had a direct impact on the interaction energy between the two minerals with different physical properties in aqueous solution.Two different grinding breakage mechanisms were presented based on the interaction energy between the two minerals in wetting grinding environment.One was that the higher hardness mineral particles were likely to receive more frequent and higher energy impact or abrasion during ball-ball collision due to coarse particles of the higher hardness mineral shielding mechanism against the fine particles of the lower hardness mineral when coagulation and adsorption behavior between two minerals particles have never occured.So the lower hardness mineral was prevented from being broken further due to the acting of shielding mechanism when ground in the presence of the higher hardness mineral.On the contrary,the orther was that the shielding mechanism of the higher hardness mineral had no any effect to breakage behavior for the lower hardness mineral when matual coagulation and adsorption behavior between two minerals particles occurred.In addition,the presence of the higher hardness minearal resulted in an increased breakage behavior for the lower hardness mineral.According to theoretical grinding study above,laboratory batch wet ball milling tests of Donganshan iron ore were also carried out for various feed size fractions.The breakage characteristic parameters of Donganshan iron ore and the parameters optimization of the ball grinding process were both obtained.The product size distributions for ball grinding natural particle size distribution of Donganshan iron ore sample were simulated and computed at any grinding time using PBM.The calculation results showed that the product size distributions for ball grinding natural particle size distribution of Donganshan iron ore sample could be reasonably simulated and predicted at right grinding time.The fundamental research on grinding characteristics of Donganshan iron ore has.been carried out,and the research results has identified its grinding characteristics.The results presented will not only provide theretical supports to technical innovation of ball milling for Donganshan beneficiation plant,but also have a significant guide for improving separation indexes.