Vertical roller mill

The main components of iron ore are iron oxides, primarily including hematite (Fe₂O₃), magnetite (Fe₃O₄), and goethite (FeO(OH)). Hematite is known for its high iron content, approximately 70%, and is often regarded as a representative of high-grade iron ore; magnetite has an even higher iron content, around 72%, and possesses strong magnetic properties, making it suitable for magnetic separation processes; goethite has a relatively lower iron content, around 60%-62%, but is easy to reduce, making it suitable for specific smelting processes.

Iron ore also contains certain impurities, such as silica (SiO₂), alumina (Al₂O₃), and phosphorus, which can affect the smelting efficiency and the quality of steel products. For example, high phosphorus content in iron ore can lead to increased brittleness in steel products. Therefore, the quality evaluation of iron ore considers not only the iron content but also the assessment of impurity levels. The average iron content of high-grade iron ore globally ranges from 58% to 65%, with specific compositions varying by source.

The processing flow of iron ore primarily includes steps such as crushing, grinding, magnetic separation, flotation, and gravity separation. First, iron ore is mined from the mine and undergoes primary crushing to break large ore blocks into smaller particles. Next, the ore is ground into fine powder using a vertical mill to enhance the efficiency of subsequent beneficiation steps.

Magnetic separation is a commonly used process in iron ore processing, utilizing the magnetic differences between magnetite and hematite to separate iron minerals from gangue using magnetic separation equipment. For ores with lower iron content, flotation is another effective separation method that involves adding chemical agents to separate iron minerals from impurities. Gravity separation utilizes the density differences of the ores to separate iron minerals through gravity or centrifugal forces.

After these processes, the iron elements in the ore are extracted and concentrated, forming iron concentrate with an iron content of up to 65%-70%. These iron concentrates are typically sent to steel mills for use in the blast furnace ironmaking process. The average beneficiation recovery rate for iron ore globally is over 85%.

In the grinding process of iron ore, a vertical mill can achieve a fineness ranging from 80 to 325 mesh (equivalent to 180 to 45 microns), with specific fineness adjustable according to production requirements. Typically, 80 mesh (180 microns) is suitable for coarse grinding, while 325 mesh (45 microns) is suitable for fine grinding.

By adjusting the classification device of the vertical mill, the discharge particle size can be accurately controlled to ensure consistent product quality. The design of the grinding rollers and grinding table in the vertical mill is optimized to provide higher crushing force and grinding efficiency.

The iron ore vertical mill increases the specific surface area of the particles by grinding the iron ore into finer powder, thereby enhancing the efficiency of chemical reactions. When the grinding fineness reaches 200 mesh, the reduction rate of iron can be improved to over 90%, which is about 5% higher than that at a 100 mesh fineness.

The use of a vertical mill has increased smelting production efficiency by 15%-30%, reducing energy consumption per ton of ore by 20%-30%. One smelting plant increased its annual output by 100,000 tons and reduced production costs by approximately 50 yuan per ton, saving 5 million yuan annually through the use of the vertical mill. The use of the vertical mill also reduced dust emissions by 30% and decreased carbon dioxide emissions, positively impacting the environment.

Vertical mills can process a variety of iron ores, including hematite, magnetite, limonite, and siderite.
Hematite: Hematite (Fe2O3) is a common type of iron ore with a high iron content. A vertical mill can grind hematite into ultrafine powder. By using a vertical mill, 80% of the hematite can pass through a 325 mesh sieve, thereby increasing the iron recovery rate, usually by about 5%-10%.

Magnetite: Magnetite (Fe3O4) is suitable for enrichment by magnetic separation due to its natural magnetic properties. The efficient grinding performance of the vertical mill can refine the magnetite particles and make the magnetic iron minerals more dissociated from the gangue minerals. When using a vertical mill to process magnetite, an iron recovery rate of up to 95% can be achieved, which is about 15% higher than that of a traditional ball mill.

Limonite: Limonite (FeO(OH)·nH2O) has a relatively low iron content and is easy to absorb water. The vertical mill can effectively process limonite through its dry or wet grinding technology, reduce its moisture content, and improve the efficiency of subsequent smelting. The iron content of limonite concentrate ground by the vertical mill can be increased to 55%-60%, which significantly reduces the energy consumption and cost of subsequent processes.

Siderite: Siderite (FeCO3) usually contains more carbonate impurities, which affects the smelting efficiency. The vertical mill can grind siderite efficiently, making it easier to remove impurities such as carbonates through flotation and other processes. Actual production data shows that the iron grade of siderite concentrate treated by vertical mill grinding can be increased to more than 50%, while the impurity content is significantly reduced.