Obtaining high-quality iron concentrate from magnetite quartzites using a two-stage grinding and fine screening scheme

The possibility of improving the quality of concentrate obtained from magnetite quartzites of the Kursk Magnetic Anomaly using a two-stage grinding scheme is considered. The studies of the fractional composition by size and iron of the middlings of the first stage wet magnetic separation showed that with a decrease in the grain-size class, the mass fraction of iron in it increases from 13.69 to 65.63 %. In laboratory conditions, studies were performed on experimental modeling of the industrial scheme for processing middlings of the first stage wet magnetic separation. The study scheme consisted of preliminary screening of the middlings on a 0.15 mm sieve and separate enrichment of the undersize (rich) and oversize (poor) products. The undersize product is enriched according to a scheme including wet magnetic separation and screening of the magnetic product with a sieve size of 0.071 mm to obtain the first concentrate. The oversize product after grinding in the second stage is subjected to magnetic enrichment with screening on a 0.071 mm sieve of the magnetic product to obtain the second concentrate. The mass fraction of iron in the total concentrate (in undersize products) was 69.3–69.4 %. Based on laboratory studies, a two-stage scheme recommended for industrial use was developed. Recommendations are given on the sizes of industrial polyurethane screens. The possibility of obtaining an iron concentrate with an iron mass fraction of at least 69 % using a two-stage grinding scheme with fine screening is shown.