Flotation is a commonly used process for iron ore beneficiation, which can effectively improve the grade of iron ore concentrate. However, during the operation, attention should be paid to the optimization of process flow, optimization of reagent system, selection of equipment and other issues in order to better improve the grade of concentrate.
The reverse flotation process has unique advantages in iron ore beneficiation. For concentrates after magnetic separation or strong magnetic separation, using reverse flotation to remove silicon is an effective method. In this process, anionic collectors, such as dodecyl amine, are preferred.
The "weak magnetic - strong magnetic - reverse flotation" process is a typical combined process that has been widely used in actual production. The steps of this process are:
a.Through weak magnetic separation, a large amount of tailings can be discarded in advance, reducing the processing volume of subsequent flotation and improving the efficiency of the entire mineral processing process.
b.After strong magnetic separation, the iron minerals are further enriched, so that the iron content in the concentrate is initially increased.
c.The concentrate is re-grinded to more than 85% of -200 mesh and then reverse flotation is carried out. The re-grinding step is crucial. It can make the iron minerals and gangue minerals more fully dissociate and improve the effect of reverse flotation.
Under acidic conditions, water glass becomes the main inhibitor, with a dosage usually between 300-800g/t. Water glass can effectively disperse(mining mud), preventing the encapsulation of iron minerals by mining mud, and can also inhibit some gangue minerals, enhancing the selectivity of flotation.
Activators can enhance the interaction between collectors and mineral surfaces in flotation, improving the floatability of minerals. In a weakly acidic environment (pH 5-6), sulfuric acid is a commonly used activator, which can activate gangue minerals such as quartz. Combined with the use of CaO (700g/t), the floatability of gangue minerals can be further enhanced. CaO can adjust the pH value of the pulp, causing changes in the surface potential of gangue minerals, which is conducive to the adsorption of collectors, thereby improving the effect of reverse flotation.
The selection of collectors directly affects the flotation effect. In addition, new types of collectors, such as TAO and R-2, are gradually receiving attention. They have better selectivity and collection performance and can be given priority in actual production.
Correctly selecting the grinding fineness is an important part of achieving good flotation effect. Usually, grinding iron ore to -0.074 accounts for 80%~95%, which can achieve monomer dissociation, and can also play a good auxiliary role in subsequent flotation separation.
Pulp concentration has a significant impact on the flotation process. During the roughing stage, the pulp concentration is generally maintained at 30%-40%.
pH value is another key parameter in the flotation process. According to different flotation processes and ore properties, it is necessary to precisely control the pH value. In alkaline positive flotation, the pH value is usually controlled at 11-12. Within this pH range, the surface of iron minerals carries a negative charge, which is conducive to the adsorption of collectors and improves the floatability of iron minerals. In weakly acidic reverse flotation, the pH value is controlled at 5-6. The acidic environment is conducive to the activation and collection of gangue minerals, achieving effective flotation separation of gangue minerals.
Pulp temperature also has a certain impact on the performance of flotation reagents and the floatability of minerals. Generally speaking, the suitable temperature for flotation is 30-35℃. Within this temperature range, the dispersion of collectors such as oleic acid is better, allowing them to fully exert their collection effect. If the pulp temperature is too low, it can be adjusted by heating to improve the flotation effect. Appropriate temperature can also increase the movement speed of mineral particles, promote the collision and attachment of bubbles and mineral particles, and improve the flotation efficiency.
Traditional flotation machines often have the problem of low separation efficiency when dealing with fine-grained iron ore. As a new type of flotation equipment, flotation columns have many advantages.
Mining mud can bring many adverse effects during the flotation process, such as increasing reagent consumption and interfering with the selectivity of flotation. Therefore, it is very necessary to carry out desliming pre-treatment. Using equipment such as hydrocyclones or high-frequency screens can effectively remove -20μm mining mud, with a desliming rate of 30%-50%. Through desliming pre-treatment, the adsorption and interference of mining mud on reagents can be reduced, the utilization rate of reagents can be improved, and it is also conducive to improving the flotation environment, enhancing the flotation effect, and further increasing the grade of iron ore concentrate.
In conclusion, by adopting a combined magnetic separation - reverse flotation process, optimizing the reagent system, reasonably controlling the grinding fineness, adjusting key parameters, and combining equipment and technology upgrades, the grade of iron ore concentrate can be significantly improved to over 65%.
