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In order to adapt to the development trend of blast furnace ironmaking and iron ore pre-reduction direct steelmaking industry, the ore dressing industry adopted the "fine grinding and deep selection" measures to improve the quality of iron concentrate. In addition to improving the efficiency of the selection process, the deep selection technology has been developed mainly from three directions. Namely: fine sieve regrind process, concentrate reverse flotation process and product deep deliming process.
Limited to the characteristics of the magnetic separation process and equipment, regardless of natural magnets or calcined magnetite, after several stages of weak magnetic separation, the concentrate grade generally only reaches 62 to 64% of TFe. After the fine screening and re-grinding technology, the final concentrate grade is increased to 66-68% TFe and SiO 2 is reduced to 7-9%, meeting the demand for concentrates in sintering, pellets and blast furnace ironmaking.
However, for magnetic separation concentrates with complex mineral composition, fine particle size composition, and special magnetic properties or particle surface characteristics, such as roasting magnetic separation concentrate or concentrates requiring further deep selection and purification, the reverse flotation process is more Easy to achieve satisfactory results.
Through long-term, extensive experimental research and production practices, it is more generally believed that deep selection of magnetic separation concentrates by reverse flotation process has the following favorable factors:
(1) The SiO 2 content of the magnetic separation concentrate is generally less than 15%, accounting for about 1/6 of the weight of the selected mineral. Compared with the original ore reverse flotation, the yield of the foam product is small and the selection process is simple.
(2) Magnetic separation concentrate is a product after multi-stage grinding of raw ore, generally containing tailings with a yield of about 60-70%, fully de-sludged, can be in neutral medium and no iron ore is added. Under the conditions of the substance inhibitor, reverse flotation is easy to obtain the best selection index.
(3) The particle size composition of the magnetic separation concentrate is relatively uniform. It is more suitable for processing by reverse flotation process. The roasting magnetic separation concentrate with more serious magnetic agglomeration phenomenon has no obvious influence on the anti-flotation index.
(4) Since the surface of the reverse flotation concentrate particles does not adsorb a large amount of chemicals, dehydration and filtration are relatively easy, and the requirements of the sintering or pellet process on the concentrate water can be satisfactorily satisfied.
The reverse flotation of magnetically selected concentrates is usually for the following purposes:
(1) Through reverse flotation to obtain a super concentrate with TFe>68% and SiO 2 <2%, which is processed into self-fluxing pellets to improve the smelting smelting index, and made sponge iron for direct steelmaking or for powder metallurgy, xerography and electronic, chemical and many other industries.
(2) The reverse flotation process is used to deepen the sorting process. Through reverse flotation, a part of the non-monomeric dissociated middle ore can be separated, and then re-grinded and re-selected to increase the sorting rate.
Characteristics and basis of reverse flotation of magnetic separation concentrate
60 years later, the world steel industry developed rapidly, increasing the large blast furnace, "concentrate, strong winds, high temperatures" become the iron making technology operations generally follow the guidelines of the demand for high-quality, low silicon material growing strongly.