The commonly used methods for hematite beneficiation include magnetic separation, gravity separation, magnetic roasting magnetic separation combination, and magnetic separation flotation combination. For low-grade and high sulfur hematite, it is necessary to develop a suitable beneficiation process based on mineral composition analysis, phase analysis results, etc.
A certain hematite ore in Yunnan has a high sulfur content, low grade, fine particle size, and complex embedding relationship, belonging to low-grade, low phosphorus, and high sulfur hematite. The interplay of minerals is extremely complex, with barite appearing as fine vein like, scattered disseminated, and colloidal aggregates distributed between hematite particles. To produce hematite as a single unit, a grinding fineness of -0.074mm is required, accounting for over 95%.
The sample iron grade is 32.15%, with hematite accounting for 93.84% of the total iron content. In addition, there are also small amounts of siderite, goethite, magnetite, and limonite; The content of harmful elements sulfur and phosphorus is 0.91% and 0.07%, respectively.
The valuable minerals in this ore are mainly hematite, while the gangue minerals include quartz and barium sulfate. In order to effectively separate hematite from quartz and barium sulfate, a strong magnetic separation concentrate re grinding reverse flotation process is required, which is an effective means of achieving mineral separation.
The widely used SLon vertical ring pulsating high gradient magnetic separator can effectively recover hematite and create favorable separation conditions for flotation. To achieve relatively sufficient monomer dissociation of iron minerals, it is necessary to grind the ore very finely. Therefore, adopting stage grinding and stage selection processes can achieve good separation results.
During the grinding experiment, as the grinding fineness increases, the grade of the first stage of strong magnetic separation concentrate gradually increases, while the recovery rate gradually decreases. This is because during the grinding process, the ore continuously mud and the fine mud has a higher grade and is difficult to recover. The finer the ore is ground, the greater the loss of iron with the fine mud. In order to balance iron recovery rate and concentrate grade, a grinding fineness of -0.074mm was selected, accounting for 65%. At this time, the recovery rate of the concentrate is 74.32%, the grade is 51.21%, and the sulfur content of the iron concentrate is 0.60%.
Due to the low grade of the raw ore, high sulfur content (barite), fine particle size, and complex embedding, in order to dissociate mineral monomers, a grinding fineness of 0.074mm or more, accounting for 95%, is required. The necessary condition for ore sorting is the dissociation of mineral monomers. Based on previous experimental experience, sodium hydroxide was selected as the iron mineral inhibitor, active calcium oxide as the silicon mineral activator, and the collector QS was used for reverse flotation experiments on strong magnetic concentrates.
On the basis of the above experiments, a stage of grinding to -0.074 mm accounted for 65% of the strong magnetic separation tailings, and the strong magnetic separation concentrate was further ground to -0.074 mm accounted for 95%. After a full process experiment of one coarse and one sweep reverse flotation, an iron concentrate with a grade of 59.24%, an operational recovery rate of 79.56%, and a recovery rate of 59.13% from the original ore was obtained; The reverse flotation test reagents are NaOH 1200g/t, Qs 500g/t, and CaO 700g/t.
The low-grade and high sulfur hematite finally adopts the strong magnetic separation concentrate regrinding reverse flotation process. When the induction intensity of the Lon pulsating high gradient magnetic separator is 1.0T, the coarse iron concentrate with a grade of 51.21% and a recovery rate of 74.32% can be obtained by discarding the strong magnetic separation tailings. After grinding the crude iron concentrate to -0.074mm, accounting for 95%, sodium hydroxide is used as an inhibitor, calcium oxide is used as an activator, and QS is used as a collector. Through reverse flotation, an iron concentrate with a grade of 59.24%, a recovery rate of 59.13%, and a sulfur content of 0.11% can be obtained.
