Recently, we found that everyone has studied and discussed a lot on the production process of sodium hexametaphosphate, such as thermal or wet production, and what are the advantages and disadvantages of each. Today, the manufacturer of sodium hexametaphosphate in China reveals the various production methods of it.

1. Sodium dihydrogen phosphate method

The soda ash solution is neutralized with phosphoric acid at 80-100°C. for 2 hours, and the resulting sodium dihydrogen phosphate solution is evaporated and concentrated, cooled and crystallized to obtain sodium dihydrogen phosphate dihydrate. Heat to 110-230°C to remove 2 crystal water, continue heating to remove structural water, and further heat to 620°C to dehydrate, the resulting sodium metaphosphate melt will be polymerized into sodium hexametaphosphate. Then it is discharged and quenched from 650°C to 60-80°C to form tablets, and then crushed to obtain a finished product of sodium hexametaphosphate.

2. Phosphorus pentoxide method

Phosphorus pentoxide obtained by burning, oxidizing and cooling yellow phosphorus in a dry air stream is mixed with soda ash in a certain proportion (Na₂O:P₂O₅=1~1.1). The mixed powder is indirectly heated in a graphite crucible to make it dehydrated and melted, and the produced sodium hexametaphosphate melt is quenched into tablets and pulverized to obtain an industrial sodium hexametaphosphate product.

3. Heat the reagent sodium dihydrogen phosphate to 700-900°C to melt. When the melt is completely transparent and the internal bubbles disappear, it is quenched to 60-80°C to obtain a thin glass product, namely sodium hexametaphosphate.

4. Heat the reagent sodium dihydrogen phosphate to 250°C and quench it to obtain the dimer of sodium metaphosphate. Heating to 650°C and quenching to obtain sodium hexametaphosphate.

5. Phosphorus anhydride method　

After the yellow phosphorus is heated and melted, it is sent to the oxidation combustion furnace, and the oxygen in the dry air is used for oxidation and combustion reaction to generate the intermediate product phosphorous anhydride. After mixing phosphoric anhydride and soda ash, high-temperature polymerization reaction, quenching the tablets to obtain flake sodium hexametaphosphate; powdered sodium hexametaphosphate can be obtained by crushing.

6. Neutralization polymerization method

The process flow is as follows: pass phosphoric acid and liquid sodium hydroxide through their respective batch controllers (control each batch of liquid caustic soda and acid input, automatic batching, and the feeding speed can be adjusted in the range of 0-20L/min), according to requirements The added amount is continuously and accurately added to the neutralization tank for neutralization reaction. After the reaction is completed, the pH value reaches 4 to 4.4, and disodium hydrogen phosphate is generated, which is sent to the high-level tank through the neutralization liquid pump.

A certain amount of disodium hydrogen phosphate is continuously and uniformly sent to the dryer for drying to obtain flake disodium hydrogen phosphate with a specified moisture content, and then continuously sent to the high temperature of diesel burning made of special corrosion-resistant materials (750-850°C) In a polymerization furnace, disodium hydrogen phosphate is melt-polymerized. The molten material flows out continuously from the polymerization furnace, is quenched and compressed to obtain flake sodium hexametaphosphate, which is crushed and sieved to obtain the product.

There are many methods for preparing sodium hexametaphosphate, but only by choosing a suitable product from a high-quality manufacturer can the subsequent production requirements be met, and the production must be based on environmental protection and safety.