Abstract: With the increase in mining depth at the Sijiaying Yanshan Iron Mine,the magnetite content in the ore gradually rises. In order to address issues such as poor separation efficiency in gravity concentration,low iron recovery rate,and high production costs in the current oxide ore beneficiation process,a series of process studies were conducted based on the analysis of raw ore properties. These included stage grinding combined with stage low-intensity magnetic separation + high-intensity magnetic separation,cleaning of low-intensity magnetic separation concentrate using a elltriation machine and the anionic reverse flotation of high-intensity magnetic separation concentrate. The results showed that the raw ore had an iron grade of 24. 24%,with iron minerals primarily composed of magnetite ( 71. 00% distribution rate) and hematite ( 20. 75% distribution rate). Under the conditions where the grinding fineness of the first and second stages was -0. 074 mm accounting for 60% and 90% respectively,the weak magnetic separation in the third stage yielded a weak magnetic separation concentrate with an iron grade of 67. 65% and an iron recovery rate of 70. 11%. The high-intensity magnetic separation concentrate was further processed through a one-roughing,one-cleaning,and one-scavenging reverse flotation circuit,yielding a reverse flotation concentrate with an iron grade of 53. 30% and a recovery rate of 5. 71%. The final combined iron concentrate achieved an iron grade of 66. 30% and a recovery rate of 75. 82%. This study achieved efficient recovery of low-grade mixed magnetite-hematite ore and provided a technical basis for optimizing the beneficiation process at the concentrator. 

Key words: mixed iron ore,stage grinding,stage magnetic separation,elutriation machine,reverse flotation