Technique for preparing sodium pyrophosphate from wet method phosphoric acid

Abstract

The present invention discloses a sodium pyrophosphate 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 and the sodium hydroxid react, which produces a disodium phosphate. I. The disodium phosphate is converged, which produces the sodium pyrophosphate. The present invention has the advantages of low integrative energy consumption and low production cost.

Description

technical field [0001] The invention relates to a preparation process of sodium pyrophosphate, in particular to a process for preparing sodium pyrophosphate using wet-process phosphoric acid as a raw material. Background technique [0002] Sodium pyrophosphate 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 day by day. [0003] The traditional process of preparing sodium pyrophosphate at home and abroad uses thermal phosphoric acid as raw material. The steps are: first neutralize thermal phosphoric acid and sodium hydroxide to obtain sodium dihydrogen phosphate, and then mix sodium dihydrogen phosphate with sodium hydroxide Neutralize again to obtain disodium phosphate, and finally polymerize disodium phosphate to obtain the target product sodium pyrophosphate. The advantages of this process are that there are few impurities in the reac...

AI Technical Summary

Problems solved by technology

But its disadvantage is that thermal phosphoric acid is prepared from yellow phosphorus. Due to the high energy consumption and high price of yellow phosphorus, the price is more than 10,000 yuan / ton, so the product cost is extremely high, not only the manufacturer's profit is low, and the production enthusiasm is lacking. Moreover, downstream product manufacturers are unwilling to use a large amount of sodium hexametaphosphate, 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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