- Time:Nov 23, 2022
The preparation principle of low cement refractory castable is the reasonable selection of granular gradation, ultrafine powder and admixture varieties and their dosage.
Refractory aggregates and powders are made from falsely burned clay clinker and high-alumina vanadite clinker. The maximum particle size of refractory aggregate, depending on the thickness of the engineering lining, is generally 10mm. Its particle gradation: 10~5mm, 30%~40%; 5～3mm，20%～30%； 3～0.15mm，30%～40%。 Generally speaking, when formulating low cement refractory castables, less general materials are used, but three or four grades are used to achieve the maximum bulk density. The dosage of refractory aggregate is 68%~72%.
Refractory powder generally uses secondary, primary or special grade high bauxite clinker as raw material, and should be treated with iron removal after grinding, and its fineness < 0.09mm or <0.044mm should be ≥ 90%. When formulated, it can be used alone or proportionally. High-grade materials such as alumina powder, white corundum powder or brown corundum powder of the same fineness are sometimes added to improve the matrix performance of low cement refractory castables. The amount of refractory powder is 18%~25%. Among them, if mixed with high-grade materials, the dosage is 5%~10%.
There are many varieties of refractory ultrafine powder, and active SiO₂ powder (that is, silica powder) is widely used at home and abroad, and α-Al₂O₃ powder, Cr₂O₃ powder and SiC powder are also used. Its dosage is 2%~12%.
The total dosage of refractory powder and ultrafine powder is 28%~32%. It should be pointed out that the varieties of low cement refractory castables are different, and the amount of ultrafine powder is also different, and there is a corresponding optimal dosage, which needs to be determined by testing. The optimal dosage for experience is 4%~10%.
In the low cement refractory castables, the admixtures used are mainly high-efficiency water reducing agents and dispersants, and their varieties are NNO, MF, JN, SM, humic acid, citric acid and tartaric acid and their salts, sodium tripolyphosphate, sodium hexametaphosphate and boric acid, etc., the dosage is generally 0.03% ~ 1.0%. When selecting admixtures, it should be combined with ultrafine powder, and the source of the material, ease of use and its cost should be considered. In general, the water-reducing and dispersing effect of organic admixtures is better than that of inorganic admixtures. In addition, expansion agents such as kyanite and sillimanite are also added to make the low cement refractory castables expand at high temperatures.
The high-alumina castables produced by ZHENJIN REFRACTORIES adopt modern ultrafine powder and low-CA cement addition technology to improve the medium temperature strength and high temperature stability. The dense microstructure ensures stability in the overall lining. The service life of high aluminum castables is 2-3 times that of traditional castables, with the characteristics of high density, high strength and low wear, and is a commonly used refractory castables for cement kilns, kiln hoods, grate coolers, preheaters, decomposition furnaces and tertiary air ducts.
