Process for refining phosphoric acid
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This post was last edited by Chemical Gas Purification on 2011-12-7 at 11:56. Refined phosphoric acid products are widely used in metal surface treatment, the feed industry, and the food industry; their refining processes have always been kept as core secrets, with little information being disclosed to competitors. Currently, there are mainly two processing methods: 1. The thermal process, which is relatively traditional and requires high energy consumption; it is gradually being phased out ； 2. Wet extraction for the purification of phosphoric acid has been widely adopted due to its low energy consumption and low production costs. Let’s now discuss the future of the refined phosphoric acid products market and the development trends in related manufacturing processes Could you introduce it in relation to your company’s production process? Be sensitive only to the extent necessary. Hehe
We specialize in providing wet-process phosphoric acid extraction technologies and equipment; we have collaborated with numerous process suppliers abroad to carry out process optimization and equipment supply for large-scale phosphoric acid manufacturers. Basically, metal ions can reach around 1 PPM. It seems that the manufacturing processes vary from one manufacturer to another, but the main equipment is more or less the same. Abroad, the main companies are Albright & Wilson, Rhone-Poulenc, Prayon, Budenheim, FMC, and in Israel there is IMI; in China, it’s Sichuan University and Wuhan Institute of Technology.
2 Typical industrial processes for solvent extraction 2.1 The Albright & Wilson process in the UK Albright & Wilson in the UK developed a process of purifying wet phosphoric acid using solvents in the early 1970s. This process uses methyl isobutyl ketone (MIBK) as the extractant. The crude phosphoric acid feedstock is first concentrated to ω(P2O5) = 54%-57%, and after clarification it is fed into the extraction system, where washing and back-extraction are carried out to produce purified phosphoric acid. Since the extractant MIBK has a high flash point and good safety properties, it has very low solubility in aqueous phosphoric acid (1%-2%), and it can form azeotropes with water at low boiling points; therefore, the distillation and recovery of this solvent is relatively easy, without requiring large amounts of energy. In the early days, extractors used packing or mixed clarifiers; later, rotary disk towers were adopted, while the washing and purification equipment consisted of multi-stage mixed clarifiers or back-extraction towers. This purified phosphoric acid product can be used as industrial-grade phosphoric acid ； However, the sulfate content is high; to produce food-grade phosphoric acid, further treatment is required, such as using a crystallization process. 2.2 The process of the French company Rhone-Poulenc: The wet phosphoric acid purification process developed by Rhone-Poulenc in France uses tributyl phosphate (TBP) as an extractant. Wet phosphoric acid with ω(P2O5) of 40%-50% is fed into the extraction system after clarification and decolorization; through washing and back-extraction, purified phosphoric acid that meets the quality requirements for industrial use is obtained. After arsenic removal, concentration, and fluorine removal, food-grade purified phosphoric acid with ω(P2O5) of 60% can be produced. This process adds a certain amount of sulfuric acid during the extraction stage to improve the solvent’s efficiency in extracting phosphoric acid ； An appropriate amount of caustic soda is added during the washing stage to reduce the sulfate content in the extraction phase. This process can be used for purification with different extraction rates as needed. In the high extraction rate process, the sulfate content is almost twice that in the low extraction rate process; it is not possible to have both high extraction efficiency and high product quality. In cases where strict requirements are placed on sulfate content, a low extraction rate process is suitable, while the raffinate acid can be used to produce fertilizers. 2.3 Israel Mining Industries (IMI) process: Israel Mining Industries was one of the first companies to develop and industrialize the liquid-liquid extraction technique for phosphate purification. The extractant used in this process is 85% (by volume) isopropyl ether + 15% (by volume) n-butanol (or isopropyl ether). The extraction is carried out at 0–2°C; a large amount of phosphoric acid and minor amounts of impurities are extracted into the organic phase, while the vast majority of the impurities in the crude phosphoric acid remain in the raffinate phase (the aqueous phase). The organic phase containing loaded phosphoric acid is brought into convective contact with the leached product, dilute phosphoric acid, to wash away impurities from the organic phase. The aqueous phase obtained from the washing is returned to the extraction section. The washed organic phase is sent to the back-extraction section, where it comes into contact with deionized water; as a result, the phosphoric acid in the organic phase is back-extracted into the aqueous phase, yielding relatively pure dilute phosphoric acid. This dilute phosphoric acid is then concentrated and decolorized through solvent recovery, thereby producing highly pure refined phosphoric acid. The organic phase after back-extraction is returned to the extraction section for reuse. This purified acid has a high sulfate content, and therefore cannot be used directly as industrial phosphoric acid; it is only suitable for the production of industrial-grade and feed-grade phosphates. Now, this technical level has been further improved, enabling the production of industrial-grade and food-grade phosphoric acid. 2.4 The process of Prayon in Belgium: The wet phosphoric acid purification process developed by Prayon in Belgium uses isopropyl ether + TBP as extractants. Crude phosphoric acid with ω(P2O5) of 28%-30% must undergo a series of pretreatment steps and be concentrated to a mass fraction of 58%-60% before entering the extraction system. Pre-treatment includes adding phosphate powder to remove sulfate ions, aging, adding a flocculant for clarification and separation of solids, adding activated carbon to remove organic matter, and adding silicon during concentration to remove fluorine. The purified phosphoric acid produced by this process has a slightly high fluoride content, and post-treatment is required to produce phosphoric acid of food-grade and pharmaceutical-grade quality. 2.5 The process of Budenheim Company in Germany: The wet phosphoric acid purification process developed by Budenheim Company in Germany in the 1960s combines solvent extraction with ion exchange resin technology; isopropanol is used as the extractant, and H-type cation exchange resins are employed. The final product obtained is phosphoric acid with a quality concentration of 75%. The purified acid in this process has a high quality, as the use of H-type yellow cation exchange resin results in a very low level of cations.
Our company once tried on a small scale to extract wet phosphoric acid using organic solvents, and it caused quite severe corrosion to the equipment
The refinement of wet phosphoric acid is the direction of development, and at that time the price of yellow phosphorus will soar.
How many companies are there in China currently that produce phosphoric acid using the wet method?
By \"upstairs,\" do you mean the purification of phosphoric acid using wet phosphoric acid to produce refined phosphoric acid?
Moderators and experts, I mainly want to know which manufacturers use extraction processes? Please give me some guidance.
Reply to 1# fflei2002: I am familiar with the processes and technologies involved in the purification of wet phosphoric acid and the production of industrial monoammonium phosphate.