| The high-phosphorus oolitic hematite in western Hubei is an iron-rich acidic oolitic hematite.Its embedded grain size is very fine.The grain sizes are mostly between 5 and 25?m,and some are even smaller than 2?m At present,for the ore,reduction roasting-fine grinding and magnetic separation process is one of the effective methods to improve the grade of iron ore.But the finer the size of the mineral,the weaker the magnetic properties,and even lower than the lower separation limit of the magnetic separator,which will lead to a lower recovery rate of the concentrate.Therefore,the experiment adopts a magnetic,coarser,coarse-grained natural magnetic species as a carrier for the adsorption of fine-grained artificial magnetite,combined with selective flocculation to enhance the adsorption efficiency of the magnetic species,and finally effectively improves the magnetic separation efficiency by the selective flocculation-magnetic seed method.The total iron grade of oolitic hematite used in the experiment is 47.56%,and the content of phosphorus is 0.93%.The magnetization roasting-stage grinding-magnetic separation test was carried out.After determining the optimum technological parameters,the fine grinding of the artificial magnetite was carried out for the continued lifting index..The degree of disintegration of the coarse concentrate under different granularity was analyzed,and the content of the grinding fineness below 0.022 mm was determined to be 79.6%.At this time,the degree of monomer dissociation was 84.63%.A selective flocculation-magnetic seed method was used to optimize the iron extraction process after fine grinding of coarse concentrate,and the optimum optimization process and process parameters were determined.With the help of Zeta potential analysis,vibrating sample magnetometer analysis,SEM image and EDS spectrum analysis,laser particle size analysis and infrared spectrum analysis,the mechanism of selective flocculation magnetic seed method is studied..The specific research content and results of this paper are as follows:The magnetization roasting conditions test showed that the optimal conditions were roasting temperature of 800°C,roasting time of 90 minutes and reducing agent dosage of 12%.Under this condition,the roasted ore was subjected to two-stage grinding magnetic separation,and the obtained crude iron concentrate grade was 57.73%.,phosphorus content 0.70%,iron recovery rate of 90.41%.The desliming-magnetic separation test was conducted after the coarse ore was finely ground to a content of 79.6% below 0.022 mm,and finally the “generalized magnetization-stage grinding and magnetic separation-fine grinding and desliming-magnetic separation” procedure was determined to be a superior routine.Under the optimal conditions,the comprehensive iron recovery rate is 62.41%,iron concentrate with 61.32% iron grade and 0.43% phosphorus content.The overall iron recovery rate is low.The selective flocculation-magnetic seed method was applied to the fine grinding of the concentrate concentrate magnetic separation process and determined by the condition test: the amount of sodium hexametaphosphate 650g/t,the pH value of the mineral pulp 11,the magnetic seed dosage 5%,and the magnetic seed particle size range-38?m~+30.8?m,CMS dosage 800g/t,flocculation speed 450r/min,slurry concentration 15%.Under this condition,iron ore concentrate with an iron grade of 60.95% and a working recovery rate of 83.18% can be obtained,which is about 11% higher than that of direct magnetic separation.The selective-magnetic seed method is applied to a conventional full flow,which is a magnetization roasting-stage grinding magnetic separation-fine grinding and desliming-selective flocculation-magnetic seed-magnetic separation process.The process can finally obtain iron ore concentrate with a total iron grade of 60.87%,a phosphorus grade of 0.41%,and a comprehensive iron recovery of 71.96%.Compared with the conventional whole process,the comprehensive recovery rate increased by 9.55%,and the yield of tailings II fell from 21.7% to 13.76%,iron grade decreased from 53.12% to 49.89%.The experiment examined the change of surface charge of minerals before and after the dispersant was added,revealing the dispersion mechanism of sodium hexametaphosphate.The magnetization characteristics of artificial magnetite(rough concentrate)and natural magnetite(magnetic species)with different particle sizes were analyzed and it was found that the specific magnetic susceptibility of the natural magnetic species(-38.5?m~+30.8?m)used was an artificial magnetite 2.4 times of(-22 ?m)at a magnetic field strength of 70 kA/m.The test of the particle size before and after flocculation found that the average grain size of the finely ground coarse concentrate can be increased by 9.58 ?m,but the change of the grain size of the quartz is very small.By FTIR analysis,it was found that the CMS functional group absorption peaks appeared after the addition of CMS,which further proved that CMS produced effective adsorption on the surface of artificial magnetite particles. |
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