Phosphorus is widely used in industry, agriculture, medicine, ceramics and other industries. Although my country has abundant phosphate reserves, most of them are poor ores. They are not only complex in structure and have many impurities, but also have fine embedded particles and are difficult to separate. Especially for high-silicon phosphate ore, due to its high silicon content, desiliconization becomes a very critical step. In the process of desiliconization of high-silicon phosphate ore, the commonly used processes include direct flotation, single reverse flotation, direct and reverse flotation, reverse flotation and double reverse flotation, which are introduced below.
Positive flotation refers to directly floating out the target minerals and suppressing the gangue minerals. The positive flotation method of high-silicon phosphate ore first grinds the phosphate ore to dissociate the monomers, then adds a certain amount of water to adjust the concentration, and feeds a certain amount of collector to enrich the phosphorus on the foam. At the same time, inhibitors are added to the slurry to suppress gangue minerals such as sulfates and carbonates in the minerals. In this process, siliceous gangue is generally suppressed first, and then carbonates are suppressed.
The inhibitors that can be used in the process include sulfonated phenol tar series, F series, S series and L series inhibitors. Among them, phenol tar, F and S series inhibitors are suitable for fine-grained material sorting, with a grinding fineness of -200 mesh and a mass fraction of more than 90; the L series is suitable for coarse-grained sorting, and generally apatite and metamorphic apatite grinding fineness of -200 mesh and a mass fraction of 40 to 60 have a better effect.
Reverse flotation is often used to select phosphate ore containing dolomite. Usually, inorganic acid is used as an adjuster to adjust the pH value to weak acidity, and a collector is added to enrich dolomite in the foam, leaving phosphorus in the tank. The impurity removal rate of the reverse flotation process can reach 70-80%. Reverse flotation agents are mostly modified fatty acid collectors, which modify fatty acids by sulfation, or add additives during their saponification process to improve their water solubility, temperature resistance, capture and selectivity, and finally achieve flotation separation.
Direct and reverse flotation process refers to the process of first performing direct flotation and then reverse flotation in the selection process. This method is more effective for treating calcium-silicon phosphate ore.
The process flow of direct and reverse flotation is: first use inorganic alkali to adjust the pulp to weak alkalinity, add a quantitative collector to enrich the phosphate ore in the foam product, and the silicate gangue minerals are retained in the tank and discharged. The obtained foam product is the direct flotation concentrate, and then add inorganic acid to adjust the pulp to weak acidity, grind the direct flotation concentrate again (or not) and adjust the pulp, add collector to enrich carbonate impurities, and the useful phosphorus is retained in the tank to obtain reverse flotation phosphate concentrate.
Before flotation, the ore is first ground to achieve monomer dissociation (-200 mesh accounts for 70-80%), and then a collector is added under acidic medium conditions to enrich carbonate gangue to obtain reverse flotation concentrate, which is then re-grinded in the second stage, and then the phosphate concentrate is directly flotated under alkaline conditions. This flotation method has strong adaptability compared to the direct and reverse processes, ideal selection indicators, low acid consumption, but high alkali consumption, and it is difficult to recycle the return water of the ore dressing plant.
Double reverse flotation is mostly suitable for the separation of phosphate minerals from dolomite and quartz gangue minerals. Generally, inorganic acid is used to adjust the slurry to weak acidity, and fatty acid collectors are used to enrich dolomite gangue minerals in the foam, and then fatty amine collectors are used to enrich quartz gangue minerals. Finally, useful phosphate minerals are retained in the tank product to obtain reverse flotation phosphate concentrate.
The above are the five commonly used beneficiation methods for high-silicon phosphate ore. During the beneficiation process of high-silicon phosphate ore, attention should be paid to dephosphorization, and then the grade of phosphorus should be further improved to ensure the recovery rate of phosphorus.
