Iron Ore Beneficiation Methods

For single magnetite ore, wet weak magnetic separation, followed by roughing, cleaning, or regrinding and cleaning, can generally meet the concentrate requirements. For ores containing both magnetite and hematite, a weak magnetic separation-strong magnetic separation-gravity separation or weak magnetic separation-strong magnetic separation-reverse flotation process can be used. For single hematite ore, strong magnetic separation-reverse flotation or strong magnetic separation-roasting-weak magnetic separation is generally used. However, due to the weak magnetism and fine grain size of hematite, conventional physical beneficiation often does not achieve good separation results. For iron ore with high sulfur content, the sulfur-containing minerals can be floated out first by flotation before magnetic separation. If sulfur exists in the form of barite, it can be treated by reverse flotation. If the phosphorus content is too high, dephosphorization of the magnetic concentrate is necessary, which can be done by leaching with dilute sulfuric acid. For iron ore reverse flotation, dodecylamine, sodium oleate, oxidized paraffin soap, and RA series collectors are used as collectors, and starch is used as an inhibitor. In cationic flotation, sodium carbonate is used to adjust the pH value for direct flotation. In anionic flotation, lime is generally added to activate quartz, NaOH is used to assist lime in adjusting the pH value, and then starch is used to inhibit iron ore, and anionic collectors are used to float silicate gangue minerals. Sometimes, when there is a significant difference in particle size between the valuable minerals and silicate gangue minerals in the strong magnetic separation concentrate, high-frequency fine screening or selective flocculation can be used.

Iron ore beneficiation equipment usually involves a combined gravity-magnetic-flotation process. Dry magnetic separation is used for tailings removal, and the tailings are then ground as feed for wet weak magnetic separation or strong magnetic separation, or even combined with gravity separation and flotation. For copper-lead-zinc polymetallic ores, for simple low-sulfur lead-zinc ores, galena is generally floated under weakly alkaline conditions using zinc sulfate or in combination with sodium sulfite to inhibit sphalerite. The concentrate from rough separation (using 25# black reagent as collector) is subjected to multiple cleaning steps to obtain the final lead concentrate. The tailings from rough separation are subjected to several scavenging steps, and then lime, copper sulfate, and xanthate are added to activate and float sphalerite. For high-sulfur lead-zinc ores, pyrite and sphalerite are generally inhibited under strongly alkaline conditions using lime and zinc sulfate. The concentrate obtained from rough flotation (using 25# black reagent as a collector) is the lead rough concentrate. The tailings from the rough flotation are subjected to several scavenging stages, with lime added to inhibit pyrite and copper sulfate added to activate sphalerite. For the zinc flotation tailings, copper sulfate is directly added to activate pyrite. If the activation effect is weak or the pulp pH is still relatively high, sulfuric acid can be added to neutralize the lime, followed by the addition of copper sulfate to activate the pyrite.