Method for producing industrial-grade potassium dihydrogen phosphate (KH2PO4) by wet method purified phosphoric acid and potassium sulfate

Abstract

The invention discloses a method for producing industrial-grade potassium dihydrogen phosphate (KH2PO4) by wet method purified phosphoric acid and potassium sulfate, belonging to the field of phosphorus chemical industry. The method comprises the following steps: a. adding potassium sulfate in wet method purified phosphoric acid and fully dissolving potassium sulfate, wherein the addition amount of potassium sulfate based on mole ratio is that p:K is 0.6-1.2:1; b, adding calcium carbonate slurry with solid content of 50-90% in the solution obtained from the step a, stirring for reaction, wherein the reaction temperature is controlled to 60-90 DEG C, the addition amount of the calcium carbonate slurry based on mole ratio is that Ca:S is 0.6-1.2; c. filtering a mixed material system which is obtained by the reaction in the step b; and d. adjusting the pH value of the filtrate obtained from the step c to 4-5, and then concentrating and crystallizing, thus obtaining the potassium dihydrogen phosphate product. The method is simple in process, easy to control and industrially apply, low in cost and high in yield; and the yield of P2O5 can be up to over 96% and the yield of K2O can be up to over 98%.

Description

technical field [0001] The invention belongs to the field of phosphorus chemical industry, and in particular relates to a method for producing industrial-grade potassium dihydrogen phosphate by purifying phosphoric acid and potassium sulfate by a wet method. Background technique [0002] The phosphate industry is a large branch of the chemical industry, KH 2 P0 4 It is an important product of the phosphate industry. Pure potassium dihydrogen phosphate containing potassium oxide (K 2 O) 34.6%, phosphorus pentoxide (P 2 o 5 )52.2%. Potassium dihydrogen phosphate (KH 2 PO 4 ) is a colorless or white lustrous orthorhombic crystal, soluble in water, acidic, insoluble in alcohol. Due to its special properties, potassium dihydrogen phosphate is an important chemical commodity, which is widely used in agriculture, industry, food, medicine and other industries. [0003] In 1821, potassium dihydrogen phosphate was prepared for the first time, which was obtained by first neutr...

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Problems solved by technology

[0005] 1. Neutralization method: In the existing potassium dihydrogen phosphate enterprises, most of them adopt the neutralization method process. This method has simple process flow, mature technology, less equipment investment, and stable and reliable product quality. However, thermal phosphoric acid and hydrogen Potassium oxide is a raw material, which is expensive and the production cost is too high, which limits its application range to a certain extent

[0006] 2. Potassium chloride high-temperature metathesis method: Since KCl is used as raw material, it has certain cost advantages, but the production process consumes a lot of heat, the equipment is severely corroded, and the product quality is poor due to side reactions

[0007] 3. The solvent extraction process is simple, the scale can be large or small, the reaction is low temperature, the equipment is less corroded, the cost is low, and there is no "three wastes" pollution. The disadvantage is that the organic solvent is expensive, and there are still problems of solvent loss and deactivation. can be well resolved

[0009] 5. Ion exchange method: use ion exchange resin to separate H 2 PO 4 - and K + Potassium dihydrogen phosphate is generated during the adsorption and regeneration process. The biggest disadvantage of this production method is that the amount of evaporated water is too large and the energy consumption is too high

The biggest problem with this method is that the phosphate rock powder has a high fluorine content, and insoluble potassium fluorosilicate is produced during the reaction process. In addition, a part of potassium gypsum is formed, and the loss of potassium reaches more than 20%, which is economically impossible to pass.

Also due to the many impurities in the phosphate rock powder, the quality of potassium dihydrogen phosphate is poor

[0011] Due to the drawbacks of the above methods, so far, there is no large-scale production line, resulting in a shortage of potassium dihydrogen phosphate in the market, and the product price has been high.

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