Abstract: Iron concentrate with TFe grade of only about 65% and SiO2 content of 4% ~ 5% was obtained using original production process in Yuanjiacun Iron Ore concentrator,which is difficult to meet the market demand for high-quality iron concentrate. Therefore, based on the detailed analysis of the properties of the mixed magnetic concentrate in the production process,a process of fine grinding,low-intensity and high-intensity magnetic separation and reverse flotation was used to carry out an experimental study on iron extraction and silicon reduction. For a mixed-magnetic concentrate with TFe grade of 42. 44% and SiO 2 content of 35. 42%,high quality iron concentrate with yield of 53. 87%,TFe grade of 67. 87%,SiO2 content of 1. 96% and TFe recovery rate of 86. 15% could be obtained under the condition of grinding fineness of -0. 045 mm accounting for 97%. When the fineness of grinding is -0. 045 mm accounting for 94% and the amount of RA collector is appropriately increased,high quality iron concentrate with yield of 54. 76%,TFe grade of 67. 14%,SiO2 content of 2. 09% and TFe recovery rate of 86. 63% could be obtained. The research results could be used as the process optimization decision basis for iron extraction and silicon reduction in concentrator,and have reference value for the development and utilization of refractory iron ore with similar properties.

Key words: horizontal stirring mill,combined high-intensity magnetic separator,silicon reduction and iron increasing,reverse flotation,high quality iron concentrate