STATE OF STUDY OF THE PROCESSES OF OBTAINING MONOCALCIUM AND MONOPOTASIUM PHOSPHATE.

Аннотация

The need to provide food and drinking water to the world's population is developing urgently due to the planet's rapidly expanding population and the loss of arable and irrigated land. At the start of the twenty-first century, this issue is still unsolved despite the tremendous advancements in agriculture and cattle farming. Increasing the productivity of livestock, poultry, and fish farming as well as the production of agricultural products is one of the best strategies to address this issue. The production and variety of potassium and NPK fertilizers without chlorine, as well as feed calcium phosphates, are on the rise in practically all industrialized nations worldwide. Keywords: Central Kyzylkum, monocalcium, monopotasium phosphate, NPK fertilizers. Analysis of existing methods for the production of potassium phosphates The main methods for producing potassium dihydrogen phosphate are the interaction of phosphoric acid with calcium-containing compounds, ion exchange and conversion methods. When phosphoric acid reacts with salts and potassium hydroxide, the following reactions occur: H PO + K CO = 2KH PO + CO + H O 3 4 2 3 2 4 2 2 H PO + KCl = KH PO + HCl 3 4 2 4 H PO + KOH = KH PO + H O 3 4 2 4 2 Modern production of phosphorus salts, as a rule, is based on multi-stage processes, including the production of phosphoric acid, its neutralization to the corresponding hydrogen phosphates, their isolation, drying and dehydration [59]. Commonly used are potash or potassium hydroxide and phosphoric acid. As a result, the fertilizer is expensive 271 and the scale of its production is small. Even the agricultural need for fertilizers for greenhouses is not met[60]. Currently, the production of feed, food and reactive salts of phosphoric acid is based on the use of thermal phosphoric acid, obtained by electrothermal method at a temperature of 1600-1800°C [61]. These industries are energy-intensive, which, in light of the continuous rise in energy prices, leads to an increasing decrease in their profitability. To obtain pure salts of potassium dihydrogen phosphate, thermal phosphorus, purified EPA is used or the process is carried out in an environment of organic reagents [62]. There is a known method for producing potassium dihydrogen phosphate by reacting TPA with potassium hydroxide, in which potassium hydroxide is preliminarily purified from insoluble impurities, poured into a crystallizer and, with stirring, TPA is introduced to pH 5.8-6, the solution is cooled to a temperature of 15-20°C and dihydrogen phosphate crystals are separated potassium [63]. Purification of EPA from accompanying impurities is a complex and relatively expensive method for producing acid. Purification of EPA can be carried out by evaporation and stripping with superheated steam, precipitation in the form of poorly soluble compounds, ion exchange, sorption methods, using organic solvents [64]. Therefore, the most promising methods for producing potassium dihydrogen phosphate are methods based on the use of EPA without preliminary purification. A method has been developed for the production of potassium dihydrogen phosphate by the interaction of EPA with potassium chloride in an aqueous-alcoholic medium [65]. A method for producing potassium dihydrogen phosphate is described, including the interaction of EPA and potassium chloride in a molar ratio of 2:1 at a temperature of 70- 145°C, grinding the resulting mass, extraction of excess acid with a boiling organic solvent and subsequent drying at a temperature of 80-100°C. Aminol, acetone, and N- butanol are used as organic solvents. There are methods for producing potassium dihydrogen phosphate using crude EPA [66]. The essence of the method is the neutralization of EPA with potassium carbonate (potash) at a stoichiometric rate to pH 3.5-4.5 at a temperature of 80-90°C, separation of the resulting mixture at a temperature of 70-80°C and crystallization of potassium dihydrogen phosphate from a solution at a temperature of 15 -20°C. A method has been developed in which EPA is used together with TPA, which involves mixing 52-54% phosphoric acid with potassium chloride at a mass ratio of 2:1 and heating to 265°C [67]. The resulting mixture is dissolved in water until a saturated solution is 272 obtained, water-insoluble impurities are separated by filtration and potassium dihydrogen phosphate is crystallized. There is a known method for producing chlorine-free monopotassium phosphate, which includes neutralization of EPA with a solution of potassium carbonate to pH 3.8-4.5 at a temperature of 70-78°C, separation of the resulting mixture by filtration, subsequent crystallization and separation of the finished product upon cooling [68]. The mother liquor is returned to the potassium carbonate dissolution stage. The ion exchange method for producing potassium dihydrogen phosphate consists of a heterogeneous reaction between a solid phase cation and a liquid phase cation exchanger in columns fille