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Do you know why potassium salt wastewater is produced in the potash production process?

by:BOQU     2023-03-21
Do you know why potassium salt wastewater is so different from sodium salt? Although there are many double-membrane application cases on the market, you will find that there are very few double-membrane systems for potassium salts. What are the reasons for this? The double membrane has water inlet requirements (details), so the system is basically applied to the salt system corresponding to the monovalent cation. According to the periodic table of elements, combined with the daily application system, there are mainly four types: lithium, sodium, potassium, and ammonium. Among them, sodium salt is common, and lithium salt has added value. For the application of double membranes, in addition to solving the environmental protection problems of wastewater, the added value of acid and alkali generated by the double membrane system is particularly important. The hydroxides corresponding to the four types of monovalent cations, the added value of lithium hydroxide, followed by potassium hydroxide, third by sodium hydroxide, and ammonia monohydrate. Lithium salt and sodium salt are currently used in many double-membrane applications. Why is the potassium salt between the two so slow? The technical feasibility analysis is combined with the specific system composition, and in terms of economy, potassium salt has very high economic feasibility. Taking sodium sulfate and potassium sulfate as an example, the investment of converting 1T potassium sulfate (calculated as solid) by double membrane is about 80% of that of 1T sodium sulfate. Moreover, the lye corresponding to 1T is also generated (100 percent), and the operating energy consumption of the double-membrane system corresponding to potassium hydroxide is only 70-80% of that of sodium hydroxide. Potassium hydroxide is much more expensive than sodium hydroxide and ammonia water. Therefore, in the general direction, potassium salt is more suitable for double-membrane conversion than sodium salt, and the core lies in the particularity of potassium salt double-membrane conversion. What is the general situation of potassium salt and potassium hydroxide in China? Potassium salts are mostly in the form of potassium chloride and potassium sulfate. Potassium resources in my country are actually scarce, and most of them are imported, especially high-quality potassium salts. Domestic potassium chloride is mainly sourced from salt lakes, and the price of 60% crystal and powder products is about 2100-2200 yuan/t. Potassium sulfate is mainly synthesized from potassium chloride as the main raw material, and the 50% powder product is about 2600-3100 yuan/t. Domestic potassium hydroxide products are mainly in the following product forms: 45/48 industrial lye, 90/95 industrial caustic soda. The synthesis process of potassium hydroxide mainly includes ion membrane method, diaphragm method and mercury method. Domestic potash prices are relatively low, which makes the profits of potash companies without resources very limited, and it is also difficult for companies to process and purify potash at present, but the demand for potassium hydroxide is increasing year by year, and it can bring better Profit margins. In this case, the double membrane is very easy to cut into. Using potassium salt as raw material, double-membrane technology is used to prepare dilute potassium hydroxide solution, and then other thermal concentration processes are assisted to prepare potassium hydroxide solution products corresponding to concentration requirements. Based on current market feedback. For enterprises, he prefers to use lower-cost potassium chloride as raw material; and from the perspective of process and product requirements, potassium sulfate is more suitable. In this type of system, the dual-membrane technology is mainly compared with the ion-exchange membrane process, and the dual-membrane technology has very high advantages in terms of the pretreatment requirements for the original salt solution, the operating energy consumption, and the process requirements. In addition to the preparation of KOH products, the double membrane is also suitable for the resource treatment of potassium salt wastewater. Potassium salts are basically produced by the neutralization of acids and alkalis in the process, and where sodium hydroxide, sodium carbonate, ammonia water, etc. can be used conventionally, KOH is rarely used normally. Potassium salt wastewater is basically produced from organic chemical process systems at present. For example, potassium salt wastewater is produced in the production process of tebuconazole pesticide products and o-hydroxybenzoic acid, and it is basically potassium sulfate. The salt of potassium sulfate has a very characteristic solubility, 110g/L (20°C), and is easily soluble in water. In this type of system, potassium sulfate is often prepared and sold as a by-product of potassium sulfate. For the impurities in the system, it is mainly controlled through the pretreatment process. As for the concentration of potassium sulfate, when the influent concentration is low, membrane concentration technology can be used for concentration. For potassium sulfate high-salt wastewater, sulfuric acid and potassium hydroxide are prepared by double-membrane electrodialysis, in which the concentration of sulfuric acid is 7-10%, the concentration of potassium hydroxide is 7-12%, and both HCl and KOH can be directly reused. The double-membrane system of potassium sulfate converts 1kg of potassium sulfate, and the processing energy consumption is only 2.3-3.0kwh, and the processing energy consumption of producing 1kg of potassium hydroxide is only 1.5-2.0kwh. In addition to potassium sulfate, the same is true for potassium chloride wastewater generated during the process or wastewater treatment, such as potassium chloride wastewater from sargassum production of iodine potassium chloride, potassium chloride wastewater from dihydrate phloroglucinol process, and wastewater from certain pharmaceutical intermediates, etc. . For potassium chloride high-salt wastewater, double-membrane electrodialysis is used to prepare hydrochloric acid and potassium hydroxide. The concentration of hydrochloric acid is 5-8%, and the concentration of potassium hydroxide is 7-12%. Both HCl and KOH can be directly reused. The double-membrane system of potassium chloride converts 1kg of potassium chloride, and the processing energy consumption is only 1.4-2.0kwh, and the processing energy consumption of producing 1kg of potassium hydroxide is only 1.1-1.5kwh. all in all. At the source, enterprises routinely choose less potassium additives; at the end of wastewater treatment, potassium salts are easy to dispose of. Potassium salt system is special, and the double membrane has a good match. The double membrane can be used not only as a KOH production equipment, but also as a terminal potassium salt wastewater recycling equipment.
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