Research On Roasting-gravity-magnetic Combined Beneficiation Technology Of Mengkun Limonite In Lao

Increasing the iron grade of the concentrate and reducing the silicon content are the guidelines for ironmaking raw material policy.For every 1%increase in the iron grade of the iron concentrate,the utilization coefficient of the blast furnace can be increased by2%and the ironmaking coke ratio can be reduced by 3%.Every 1%reduction of Si O₂content in iron concentrate can reduce 1%of waste residue discharge in ironmaking process.Further increasing iron and reducing silicon in high-grade iron ore can improve the efficiency of iron mills and the comprehensive benefits of beneficiation and metallurgy.Laos Mengkun limonite ore grade is high（55.20%）,Si O₂ content is 8.18%,iron and silicon reduction has obvious significance.In order to achieve the index of iron concentrate grade higher than 60%and Si O₂ content lower than 7%,beneficiation research is imperative.Process mineralogy showed that the iron grade of the raw ore is 55.20%,the iron mainly exists in the form of limonite,and the main gangue mineral is quartz.The ore is mostly void block structure;the disseminated particle size of limonite is 0.04-5mm,and the disseminated particle size of quartz is 0.01-0.2mm;the limonite is mainly wrapped structure;the average iron content of pure limonite is 62.20%.Physical separation is expected to obtain concentrate with iron grade of 60%.The physical separation test showed that the iron grade of the concentrate obtained by gravity separation,magnetic separation and gravity-magnetic combined treatment was56%～58.86%.Direct physical separation of raw ore can not obtain qualified concentrate.The test of’reduction roasting-gravity separation-weak magnetic separation’showed that the roasting effect was good when the amount of carbon powder was 4%of the amount of raw ore,the roasting temperature was 900°C and the roasting time was 60min.The iron grade of gravity separation concentrate of reduction roasting product is high and the content of Si O₂ was low.The recovery and Si O₂ content of low intensity magnetic separation concentrate were high.The advantages of gravity separation and low intensity magnetic separation are complementary.When the grinding fineness of the reduction roasting product was 80%of-200 mesh,the concentrate yield was 68.16%,the iron grade was 66.14%,and the recovery was 71.91%,the Si O₂ content was 5.46%.The process of’reduction roasting-gravity separation-low intensity magnetic separation’could be used for the treatment of the ore.Thermodynamic analysis showed that the loss on ignition of raw ore was 11.73%.The iron grade of raw ore can reach 60%after removing free water and crystal water.The high temperature dehydration of raw ore can improve the iron grade.However,the content of Si O₂ in the raw ore was bound to increase to more than 9%after high temperature dehydration.In order to reduce the content of Si O₂,the separation test should be carried out.The results showed that the content of Si O₂ in gravity concentrate of high temperature dehydration product of raw ore was low,the recovery rate and Si O₂ content of high intensity magnetic separation concentrate are high,and the advantages of gravity separation and high intensity magnetic separation are complementary.When the grinding fineness of the high temperature dehydration product of the raw ore was 80%of-200mesh,the concentrate yield is 79.73%,the iron grade was 63.58%,and the recovery was81.98%,the Si O₂ content was 6.41%.’Raw ore high temperature dehydration-gravity separation-high intensity magnetic separation’could be used for the mine treatment;the process was characterized by no need for reducing agent.The reduction roasting product or high temperature dehydration product of raw ore first gravity and then magnetic separation can better reduce the Si O₂ content in the concentrate,which can ensure that the Si O₂ content in the concentrate is less than 7%.It was a characteristic process and should continue to be optimized to create conditions for application.