Why Is Sodium Hexametaphosphate Used in Refractory Castables?

Anyone familiar with refractory castables knows that the fluidity of castables is largely determined by the fluidity of the matrix, which mainly depends on the interaction between raw materials and their distribution in water. 

The castable slurry needs to have good dispersion. With the sodium hexametaphosphate dispersant and coagulant, the construction performance and strength at normal and low temperatures are basically obtained.

Sodium Hexametaphosphate 

SHMP 68% Min

In clay-bonded refractory castables, the clay particles are fully dispersed through dispersants to reduce the bleeding of clay particles, while sodium hexametaphosphate can play a good dispersing role in clay-bonded refractory castables, making clay-bonded refractory castables The material has good fluidity and workability, thus ensuring its good high-temperature performance.

Generally, high alumina cement or pure calcium aluminate cement is used as the hardening accelerator, and the dosage is 0.2~3.0%. In the clay colloid dispersion system, adding alkali metal ions as an agent can form alkali ion clay, because the positive charge of alkali ions It has strong properties, large potential difference, and large repulsion between clay particles. Clay has more cations, and the increased spacing between particles allows the clay colloid to decompose and release free water, which enhances the fluidity of the castable and facilitates mixing and molding.

When sodium hexametaphosphate is used as a binding agent, it hydrolyzes into sodium dihydrogen phosphate (NaH2PO4) when exposed to water. NaH2PO4 and alkaline earth metal oxides such as magnesia can react at mixing temperature to form Mg(H2PO4) 2. Mg (H2PO4)2 quickly forms MgHPO4 after drying, which has high cohesiveness and can be used to make mixtures. Mg(H2PO4) 2 and MgHPO4 are condensed into polymagnesium phosphate [Mg(PO3) 2 and [Mg2P207)]n respectively after heating at about 500°C, which further improves the combination and reaches a considerable temperature range before the liquid phase appears ( 800℃) have quite high strength.

Therefore, compared with aluminate cement refractory castables, ordinary clay refractory castables have the characteristics of high strength, no decrease in medium temperature strength, and good spalling resistance; compared with aluminate cement refractory castables, they have the characteristics of convenient construction and easy storage. Its operating temperature is generally 1400-1500℃. Sodium hexametaphosphate is widely used as a binder in ordinary clay refractory castables: heating furnaces and other flame furnaces.

Henan Zhenglin New Material is a professional production factory. Our factory introduces advanced technology from Domestic and abroad, The company produces phosphate and water treatment products, mainly producing polyacrylamide,EDTA 4 Na,EDTA 2 Na,sodium tripolyphosphate, sodium hexametaphosphate, sodium dihydrogen phosphate, sodium gluconate ,citric acid,soda ash.HEDP,AA.AMPS and other phosphate and water treatment agents.

Our products are widely used in urban water supply, clean,drainage, power, steel, chemical, oil, paper, medicine, food and many other fields.

Any requirements ,please contact our email admin@cnzlnm.com or our whatsapp 86185956704222.