In chemical industry, the treatment of waste liquid generated during the production and purification of phosphoric acid has always been an important environmental issue. Especially in the wet phosphoric acid process, due to the high impurity content in the raw material phosphate ore, the phosphoric acid obtained often contains a variety of impurities such as iron, aluminum, and magnesium, making it difficult to meet the requirements of high-quality phosphate production. Centrifugal extractor, as an efficient liquid-liquid extraction and separation equipment, have shown significant advantages in the phosphoric acid extraction process and have become a key tool to solve this problem.
The application process of centrifugal extractor in phosphoric acid extraction usually includes pretreatment, selection of extractants, mixed contact, phase separation, back extraction and post-treatment.
- In the pretreatment stage, the waste phosphoric acid is mainly filtered to remove large solid impurities and suspended matter, and the acidity is adjusted to meet the requirements of the subsequent extraction process.
- When selecting an extractant, it is necessary to select a suitable extractant, such as tributyl phosphate (TBP), organic amines, etc., according to the composition and properties of the waste phosphoric acid and the type of impurities to be removed. These extractants should have the characteristics of high selectivity for impurities, immiscibility with phosphoric acid, chemical stability and easy recovery.
- In the mixed contact stage, the pretreated waste phosphoric acid and the selected extractant are added to the centrifugal extractor in a certain proportion. Under the stirring action of the mixing impeller inside the machine, the two immiscible liquids can quickly and effectively complete the mixing and mass transfer process.
- Under the action of centrifugal force, the denser water phase (purified phosphoric acid phase) will be pushed to the outside, while the less dense organic phase (extractant phase containing impurities) is located inside, achieving effective separation of the two phases.
- In order to ensure product quality and recover as many valuable components as possible, it is usually necessary to perform multiple washing and back extraction operations on the organic phase rich in the target product. That is, fresh water or other media are used to elute non-target substances in the organic phase, and then another strong extractant is used to transfer the target substance from the organic phase to the new aqueous phase. Finally, the obtained product solution is further processed by concentration, crystallization, etc. for storage and transportation or direct use in industrial production.
The advantages of centrifugal extractors in phosphoric acid extraction are mainly reflected in efficient extraction, flexible extraction methods, economy, wide application range and easy maintenance. Compared with the traditional mixer settler or extraction column countercurrent series extraction, the centrifugal extractor can complete the extraction process in a shorter time and significantly improve the yield of phosphoric acid. At the same time, its flexible extraction method can adjust the flow ratio of the extractant according to actual needs, thereby optimizing the extraction effect. In addition, the centrifugal extractor also has the characteristics of simple structure, easy maintenance and overhaul, and reduces the equipment maintenance cost.
In practical applications, the centrifugal extractor not only improves the yield and product quality of phosphoric acid, but also reduces equipment investment and floor space, and reduces the overall operating cost. Especially when dealing with low-concentration phosphoric acid, the centrifugal extractor shows higher extraction efficiency and a wider range of applications.
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