The Liberation Effect Of Rare Earth Ore By Microwave Treatment On Grinding System

The crushing of the beneficiation process is recognized as a high energy consumption and low energy efficiency.It is extremely important for crushing process to how to improve the energy efficiency.The grade of rare earth ore from the Oka area of Quebec,Canada reaches the value for industrial exploitation,however,a huge challenge is brought into traditional grinding process on account of the complex mineral composition and structural characteristics.Moreover,it is difficult to quantitatively analyze the occurrence and particle size distribution of rare earth ore in the traditional way of grinding process and detection method.Therefore,it is of great research value to find new grinding technology and detection methods to study rare earth mineral technology,thus reduce the energy consumption of grinding process and improve the quality of grinding products.The rare earth ore was pretreated with microwave heating technology in accordance with the mineral composition and structural characteristics of Canada and the current situation of storage and resource utilization through reviewing the relevant papers in the domestic and overseas,which investigates the effect of grinding efficiency and the liberation of the main minerals in rare earth ore,discusses the mechanism of ore ground with microwave,and explores the main factors of the effect of affecting microwave assisted grinding.This processing method is to provide an effective technology for the comprehensive exploitation and utilization of rare earth ore.The rare earth ore selected was analyzed in this paper using mineral liberation analyser?MLA?,X-ray diffraction?XRD?,X-ray fluorescene?XRF?,scanning electron microscope?SEM?and thermogravimetric analysis?TGA?,which determined what the purpose minerals and the main minerals is,and what minerals existed a kind of well-abosorbing microwave ability.The experimental results shows that the optimum microwave power,microwave heating time and particle size are determined by the quality content of-7.4×10^-5 m in the grinding product as an evaluation of the grinding effect.These factors affects the effect of heating temperature and assisted grinding of ore,and then has a remarkable role on liberation and theory recovery of minerals.The study showed that the grade of REO 3.66%of the Canadian rare earth ore,with8.34%as bastnaesite and monazite of 0.01%as well as 1.77%as strontianite,22.91%goethite as the main mineral.The gangue minerals were mainly ankerite,biotite,ferrosilite and calcite.The embedded relationship was developed between bastnaesite and ankerite,goethite,strontianite,biotite and ferrosilite through mutual penetration,intergrowth and association.The minerals with Ce,La and Nd element-bearing in the rare earth ore were mainly present in the bastnaesite,and Fe element was mainly present in the goethite?Fe₂O₃?,accounting for 57.76%,the rest were in the gangue minerals of ankerite,accounting for 40.08%.In the rare earth ore,goethite was the best,bastnaenite was on second place,strontianite was poor and monazite was the worst in the liberation.The experiment showed strontianite,goethite and the main gangue mineral ankerite in the rare earth ore samples could be a good absorption to microwave energy and was quickly heated.The ore samples could be heated rapidly to above 250?after heated for a short period of time,meantime,the temperature heating rate was raising with the increase of microwave power and the microwave heating time.However,the rare earth ore could reach highest heating temperature with microwave power of 1.5 kW,the microwave heating time of 2.0 min and particle size of 1-2 mm.The higher temperature difference between the minerals could be formed with microwave pretreatment to the formation of thermal stress,generating the fractures bewteen the useful minerals and gangue grain boundary.These fractures could significantly improve grinding efficiency of the ore.The mineral composition and mineral phase did not change in the ore before and after microwave pretreatment by XRD and MLA.This study found the optimum microwave power selected must be on the basis of the liberation of the minerals in the ore as the microwave power was higher and the effect of assisted grinding was better.The microwave heating time extended could improve the temperature of the ore,but the grinding efficiency of the ore could not be improved with the increase of the microwave heating time,and the grinding efficiency was decreasing after a certain period of time.The reason was that the extension of the heating time leads to an increase in the temperature of the minerals to perform internal sintering.The quantity of 100 g the ore with particle size 1-2 mm could attain the highest heating temperature and the best grinding effect in this experiment.The quality content of-200mesh reaching 93%with microwave pretreatment was 23%as higher as with conventional comminution when the weight of 100 g,particle size 1-2mm of ore were pretreated with the power of 1.5 kW and the microwave heating time of 2.0 min.It was beneficial for improving liberation that rare earth ore developed the fractures betweent the useful minerals and gangue grain boundary with microwave pretreatment.The results as generated by MLA showed the quality of 100 g,partle size 1-2 mm rare earth ore samples were pretreated at microwave power of 1.5 kW and microwave heating time of 2.0 min.The sequence of liberation in the ore was:goethite>strontianium>bastnaesite>monazite,and the liberation of bastnaesite,monazite,strontianium and goethite was better under microwave pretreatment than that of conventional treatment.The particle size distribution of the main minerals in the rare earth ore was narrower than that of the conventional treatment,and the proportion of particles with particle size of-7.4×10^-5 m was the largest.The average particle size d₅₀ of the mineral was smaller than with conventional treatment.The liberation and theoretic recovery of the bastnaesite were best when the particle size of rare earth is 106-150?m.In summary,the pretreatment of the rare earth ore from the Oka area of Quebec,Canada with microwave heating technology can significantly improve the grinding efficiency of the ore.The parameter of mineralogy which lays some theoretic basis for flotation in the benefiation.