Special Treatment Of Raw Materials For Zircon Brick

Zircon brick is one kind of refractory whose main crystal phase is zirconite, and it is one important kind of refractory containing zirconium. The raw material of zircon brick is selected zirconium sand in which zirconite is about 90%. The grain size of zirconium sand is very fine and single which is generally 0.1-.02mm, and it is not suitable to be directly made into a refractory brick.

 

To have a pure zircon brick made of coarse particles, zirconium sand need be special treated. In order to adjust the grain size of zircon brick and reduce the sintering shrinkage, zirconium sand is generally pre-calcined or is melted to zircon clinker lumps at high temperature. Before calcining, part of zirconium sand need to be grind fine powder, then mixed with the other part of zirconium sand, then sinter to dense mass at the temperature of 1500-1700℃ which is below the decomposition temperature of zirconite. If alkali metal oxide like MgO, CaO is existed in raw material, raw material should be sintered at the temperature of 1050℃. During calcining, zirconium sand begins to shrink when temperature is at 900℃, after temperature rise to 1350℃, shrinkage is stop and expansion appears, however, sharp shrink is occurred when temperature rise to 1700℃. So zircon brick has dense structure after calcining, and its bulk density can reach 3.5g/cm3 or above.

 

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