Technique for preparing sodium hexametaphosphate from wet method phosphoric acid

Abstract

The present invention discloses a sodium hexametaphosphate production technology, taking a wet-process phosphoric acid as the material. The steps are as following: A. Vitriol is added to a phosphorite to produce the wet-process phosphoric acid. B. A sodium hydroxid or a sodium salt is added to the wet-process phosphoric acid to produce a ground paste containing a sodium dihydrogen phosphate. C. The ground paste produced from the step B is filtrated and a clear liquid is collected. D. Ammonia is added to the clear liquid to produce the ground paste containing a composite NaH2PO4.NH3. E. The ground paste is cooled and concentrated to make the composite be crystal. F. The concentrated ground paste is filtrated to collect the composite crystal. G. The composite crystal is heated to make the NH3 in the composite volatilize. The sodium dihydrogen phosphate crystal is produced. H. the sodium dihydrogen phosphate crystal is converged, which produces the sodium hexametaphosphate. The advantage of invention is the low production cost.

Description

technical field [0001] The invention relates to a preparation process of sodium hexametaphosphate, in particular to a process for preparing sodium hexametaphosphate using wet-process phosphoric acid as a raw material. Background technique [0002] Sodium hexametaphosphate is an important chemical raw material, which is widely used in water treatment, oil drilling, mineral processing and chemical fiber. In recent years, the market demand has been increasing. [0003] The traditional process of preparing sodium hexametaphosphate at home and abroad is to use thermal phosphoric acid as raw material. The steps are: first neutralize thermal phosphoric acid and sodium hydroxide to obtain sodium dihydrogen phosphate, and then polymerize sodium dihydrogen phosphate to obtain The target product is sodium hexametaphosphate. The advantages of this process are that there are few impurities in the reactants, the process conditions are easy to meet, the reaction is sufficient, the product...

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Problems solved by technology

But its disadvantage is that thermal phosphoric acid is prepared from yellow phosphorus. Because yellow phosphorus is expensive, the price is more than 10,000 yuan / ton, so the product cost is extremely high. Manufacturers are also unwilling to use it in large quantities, which greatly limits the application range of sodium hexametaphosphate. So far, there are few downstream products of sodium hexametaphosphate, and the price is high, which cannot meet the growing market demand.

[0004] In addition, due to the high energy consumption and heavy pollution in the preparation of yellow phosphorus, which does not comply with current industrial and environmental protection policies, many yellow phosphorus factories have been closed, and the source of raw materials is difficult.

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