The Yunnan Bao Zipu Iron Concentrate Quality Technology Research

The genesis type of Baozipu iron ore in Dongchuan is sedimentary metamorphic ore deposit, of which the limonite ore has great reserves. The grade of iron and phosphorus in the limonite raw ore is 35% and 0.89% respectively.The process mineralogy shows that there is 74.2% of phosphorus scattering as isomorphismor or fine mechanical mixture in the limonite; 5.6% as isomorphism in the hematite; 20.2% existing as independent minerals of apatite. But based on the formation condition of isomorphism, phosphorus is hard to substitute as isomorphism form for ferrum, thus achievement of dephosphorization is possible. Because the reasons of low grade of iron concentrate and high grade of the phosphorus at the process of physical concentration, a further study of improving the quality of iron concentrate is necessary.The research methodology of the iron concentrate to improving its quality is consisted of three stages that are determining a preliminary program, researching and proving the preliminary program and optimizing the processing parameters of the selected program.In a preliminary program, reduction roasting for iron upgrading, immediate leaching with sulfuric acid, reduction roasting-sulfuric acid leaching, chloridizing roasting-sulfuric acid leaching for dephosphorizing are drafted.The test research of researching and proving the preliminary program indicates that leaching only with sulfuric acid,the result of dephosphorization to the iron ore is unsatisfactory; increasing the iron concentrate grade is feasible by reduction roasting and magnetic separation, but dephosphorization is unavailable. The aims to improving the grade of iron concentrate and decreasing that of the phosphorus are attained by the mean of reduction roasting and sulfuric acid leaching. The bulk ore of concentrate and middlings at the roasting and magnetic process is leached at the pickle test. The final concentrate of which the phosphorus grade decreases to 0.199% and the iron grade increases to 61.5% is acquired.In order to approach to the production, coke fines of which the cost is cheaper than activated carbon are used as the reductant at the test of optimizing the processing parameters of the selected program. The test shows that when the temperature of reduction is at 920°, the ratio of carbon to the raw ore is 8%, the constant time is for 40 minutes, the fineness of is 95% -0.074mm,the preferable results that is the grade and recovery of low intensity magnetic iron concentrate reaching to 59.03% and 87.7% respectively, are achieved by the magnetic operation;when the fineness of leaching ore is 95%-0.037mm, the ratio of liquid to solid is 3:1, the concentrate of sulfuric acid is 11% and the time is as long as 3 hours, the grade of phosphorus in final iron concentrate is decreased to 0.199%, and the iron grade and recovery in that is 61.5% and 83.5% respectively.In the paper, the aims of improving the grade of iron and decreasing the grade of phosphorus are accomplished by the reduction roasting-magnetic operation-acid leaching, on the basis of which the limonite is indentified as refractory ore with fine particle size and high phosphorus. The key technology consists of reduction roasting, shrend and acid leaching.