Pyrite is an important mineral raw material for extracting sulfur and making sulfuric acid. In the flotation of non-ferrous metal sulfide ores such as copper, lead and zinc, pyrite is often recycled as a by-product. The commonly used pyrite beneficiation methods include gravity separation, flotation, and gravity separation-flotation combined method. In the selection of beneficiation methods, it is necessary to conduct beneficiation tests on pyrite and select the appropriate method according to the properties of the ore.
(1)Jig gravity separation
Jig gravity separation has significant advantages in processing coarse and medium-sized pyrite. The process operation is relatively simple, the equipment processing capacity is large, and it can meet the needs of large-scale production. At the same time, jig gravity separation also has a certain separation accuracy and can effectively separate useful minerals and gangue minerals in pyrite.
Mineral particle size has a great influence on the effect of jigging and gravity separation. In order to select the appropriate particle size, mineral processing engineers usually conduct a series of tests. They will adjust the ore particle size according to different ore properties and production requirements to achieve better separation results. In actual operation, the process parameters of jigging and gravity separation can be optimized by changing factors such as the type, size, and shape of ore.
(2)Spiral chute gravity separation
Spiral chute gravity separation is mainly used to process fine-grained pyrite. This method has the advantages of large processing capacity, high feed concentration, small footprint and simple operation.
In the spiral chute gravity separation process, feed amount and feed concentration are important factors affecting the separation effect. When the feed amount is too large, the recovery rate of pyrite will decrease. For example, in the actual production of a certain ore dressing plant, when the feed amount exceeds a certain limit, the recovery rate of pyrite drops from the original 80% to about 60%. This is because excessive feed amount will shorten the residence time of minerals in the spiral chute, thus affecting the separation effect.
At the same time, when the feed concentration is too high, the grade of pyrite concentrate will decrease. Excessive feed concentration will increase the mutual interference between minerals, which is not conducive to the separation of useful minerals. Generally speaking, the feed concentration should be controlled within a certain range to ensure a higher concentrate grade and recovery rate.
In order to give full play to the advantages of spiral chute gravity separation, operators need to reasonably adjust the feed amount and feed concentration according to actual conditions. Through experiments and experience accumulation, better operating parameters can be determined to improve the beneficiation efficiency of pyrite.
(1)Collector function
Short-chain xanthate is a common collector for pyrite flotation. Its hydrophobic product is a double xanthate type, which can effectively enhance the floatability of pyrite. Short-chain xanthate undergoes chemical adsorption on the surface of pyrite, which enhances the hydrophobicity of the surface of pyrite, making it easier to adhere to bubbles and float. For example, in some ore dressing plants, the recovery rate of pyrite can be increased by 15% to 20% after using short-chain xanthate as a collector.
(2)Activator function
Sulfuric acid plays an important role as an activator for pyrite flotation. On the one hand, sulfuric acid can lower the pH value of the solution, so that Ca2+, Fe2+, Fe3+ and other ions form complexes or insoluble salts on the surface of pyrite, thereby restoring the fresh surface of pyrite. For example, when the pH value of the solution is reduced to a certain level, the oxide film on the surface of pyrite will be dissolved, exposing the fresh mineral surface, which is conducive to the adsorption of the collector. On the other hand, the presence of sulfuric acid can make the surface of pyrite less susceptible to oxidation, thereby activating the suppressed pyrite to float. When the surface of pyrite is deeply oxidized, it can be activated by Cu2+. After Cu2+ replaces Fe2+, a copper-containing sulfide film is formed in the pyrite lattice, thereby improving the adsorption capacity of xanthate.
(3)Effect of pH value on flotation performance
In the flotation process of pyrite, the pH value of the flotation medium is an important factor affecting the flotation effect of pyrite. In acidic media, pyrite tends to float when the pH value is less than 6 due to the effect of xanthate. As the pH value increases, the floatability of pyrite decreases under alkaline conditions. For example, when the pH value increases from 6 to 8, the recovery rate of pyrite may decrease by 20% to 30%. Therefore, in the flotation process of pyrite, the pH value of the flotation medium needs to be strictly controlled to obtain the best flotation effect.
The combined pyrite gravity separation and flotation method has significant advantages in dealing with situations where gangue minerals are prone to mud formation. When the gangue minerals contained in pyrite, such as serpentine, chlorite, kaolinite, etc., are prone to mudification, a large amount of slime will be produced to cover the surface of the pyrite during the flotation process, inhibiting its floatability. , at this time, it is an ideal choice to use the gravity separation-flotation combined method for mineral processing. Advantages of gravity-flotation combined method:
(1)Good process indicators
This method has good process indicators and can more effectively separate useful minerals and gangue minerals in pyrite compared to a single flotation process. For example, in the actual application of some concentrators, the grade of pyrite concentrate has increased by 10% to 15% and the recovery rate has also been significantly improved after the combined gravity separation and flotation process.
(2)Less consumption of medicine
Low reagent consumption is also a major advantage of the gravity-flotation combined method. Since gravity-separation is performed first to remove some impurities, the concentration of reagents used in the subsequent flotation process is greatly reduced. According to statistics, compared with the single flotation method, the reagent consumption of the gravity-flotation combined method can be reduced by 30% to 40%.
(3)Fast flotation speed
Fast flotation speed is also one of the characteristics of this method. The mineral particles after gravity-separation are purer, and the adhesion speed with bubbles is faster during the flotation process, thereby improving the flotation efficiency. In actual production, the flotation speed of the gravity-flotation combined method can be increased by 20% to 30% compared with the single flotation method.
