Silicon dioxide content affects the quality of iron ore concentrate, so its content should be reduced during the beneficiation process. So what are the methods for desiliconization of iron ore? This article introduces the main methods and typical process flows.
(1) Process characteristics
Reverse flotation is usually used after the grinding process, on the premise of ensuring that the ore is fully dissociated. The effect of reverse flotation may be different for iron ores of different hardness. Therefore, when processing iron ores with higher hardness, it is necessary to increase the grinding fineness. Finer particle size can enhance the application effect of reverse flotation.
(2) Actual application cases
An iron ore beneficiation plant in Anshan adopts the "stage grinding - weak magnetic - fine screening" process. The coarse concentrate is further reduced to below 7.8% by reverse flotation (such as anion reverse flotation). In actual production, the concentrator has achieved a significant improvement in the grade of iron ore concentrate by optimizing the reagent system and process flow, while reducing production costs and achieving good economic benefits.
(1) Wet/dry magnetic separation
Wet magnetic separation and dry magnetic separation have their own advantages and disadvantages in removing high-silicon gangue minerals. Wet magnetic separation has advantages when processing wet ores, which can effectively avoid ore adhesion and clogging, and has a good magnetic separation effect. Dry magnetic separation is suitable for dry ores and has the advantages of simple operation and low cost. Under different ore types and process conditions, it is necessary to select the appropriate magnetic separation method according to the actual situation.
(2) Actual application case
An iron ore concentrator adopts weak magnetic separation to discard tailings, discarding low-silicon tailings with a yield of 17%-25%, effectively reducing the silicon content entering the subsequent process. Through magnetic separation and tailings pre-selection, the concentrator reduces the processing volume of subsequent flotation and grinding, reduces production costs, and improves the grade of iron ore concentrate.
(1) High-pressure roller mill + stage grinding
High-pressure roller mill can effectively improve the dissociation degree of ore, and fully dissociate the iron minerals and silicate minerals in the ore through fine crushing. Combined with stage grinding, better grinding effect can be achieved. In actual production, it is necessary to adjust the process parameters of high-pressure roller mill, such as roller pressure, speed, etc., according to the properties of the ore and process requirements to ensure the full dissociation of the ore.
(2) Screening equipment and process
Cyclone classification and fine screen screening (such as high-frequency vibration fine screen) are commonly used screening equipment. Cyclone classification can effectively separate slurries of different particle sizes, and high-frequency vibration fine screen can accurately screen out coarse-grained conglomerates (gangue with high silicon content). During use, it is necessary to select appropriate screen hole size and screen surface material according to the properties of the ore and process requirements to improve screening efficiency.
(3) Practical application cases
Bengang Waitoushan Iron Mine reduced the SiO₂ content of the concentrate from 7.85% to 5.67% through fine screening and classification. In actual production, the beneficiation plant achieved a significant reduction in the SiO₂ content in the iron concentrate by optimizing the fine grinding and screening process, improved the grade of the iron concentrate, and achieved good economic benefits.
(1) Chemical leaching
In the chemical leaching process, process parameters such as the concentration of hydrochloric acid or sulfuric acid, temperature, and leaching time have an important influence on the leaching effect of silicate minerals. By optimizing these parameters, efficient leaching of silicate minerals can be achieved. In actual production, it is necessary to pay attention to the side reactions and environmental protection issues that may occur during the chemical leaching process, and take corresponding measures to deal with them.
(2) Bio-desiliconization
Biological desiliconization is an emerging desiliconization method that uses silicate strains to selectively decompose silicon minerals. At present, this method is still in the laboratory stage and has certain advantages and limitations. In the future, with the deepening of research and the maturity of technology, biological desiliconization is expected to be applied in actual production.
Take Anshan-type lean hematite ore as an example, its typical process flow is as follows:
Coarse crushing: The iron ore is coarsely crushed, and the crushing particle size is generally controlled at 20-30mm. The coarsely crushed ore is pre-selected by dry magnetic separation, and some waste rock is discarded to reduce the subsequent processing volume.
Dry magnetic separation: The magnetic field strength of dry magnetic separation is generally between 100-150mT. Iron minerals with strong magnetism are selected through magnetic separation, and low-silicon tailings with a yield of 20%-30% are discarded.
One-stage grinding: The pre-selected ore is subjected to one-stage grinding, and the grinding particle size is generally controlled at about -200 mesh 60%. After grinding, the coarse concentrate is selected by weak magnetic separation, and the magnetic field strength of weak magnetic separation is generally between 150-200mT.
Secondary grinding: The coarse concentrate is subjected to secondary grinding, and the grinding particle size is generally controlled at more than 90% of -200 mesh. After grinding, the grade of the iron concentrate is further improved by high gradient magnetic separation or reverse flotation. The magnetic field strength of high gradient magnetic separation is generally between 1000-1500mT.
Agent addition: During the reverse flotation process, reagents such as water glass and dodecylamine are added. The addition amount of water glass is generally 0.5-1.0kg/t, and the addition amount of dodecylamine is generally 0.1-0.3kg/t.
Flotation time: The flotation time is generally controlled at about 10-15 minutes. By optimizing the flotation time, it can ensure that the silicate minerals are fully floated and the grade of the iron concentrate is improved.
By comprehensively applying strategies such as reverse flotation desiliconization, magnetic separation tailings pre-selection, fine grinding and screening optimization, and chemical and biological methods, the SiO2 content in iron ore concentrate can be effectively reduced to below 5%, meeting the requirements of high-grade iron ore concentrate. In actual production, it is necessary to select appropriate desiliconization processes and strategies based on ore properties and economic benefits.
