Study On Composite Magnesia-alumina Spinel Castable With Crust-resistance

Cement manufactory is the pillar industry of domestic economy and a typicalhigh energy consumption industry. The ultilization of precalciner, which replaced thebackwardness technologies, not only improved the qulity and quantity of cement, butalso reduced the energy consumption and pollutant emission. However, the heattransfer of accumulation in the precalciner brought about higher practical energyconsumption. Short process precementation technology can obviously enhance theheat transfer process and efficiency and reduce energy consumption by increase thetemperature of raw meal. The temperature of raw meal in short processprecementation kiln was increased from900℃to1200℃, which would cause thevariation of alkali-chlorine-sulfur environment, leading to such problems as crust andblock. Therefore, the refractories used in short process precementation kiln shouldhave excellent crust-resistance, thermal shock-resistance, and hightemperature-resistance.This dissertation is one important research of "kinetics study and process controlof clinker sectional burning", based on the "973" national projects “fundamentalresearch on cement production with low energy consumption and high efficientapplication”, aimed to develop anti-crust refractory castable and its optimal formula,which suit to the condition and requirement of the short process precementation kiln.The main contents include the following aspects:（1） According to the requirement of short process precementation kiln, theMagnesia-Alumina Spinel with excellent sulfur alkali corrosion-resistance andtemperature-resistance property was used as main crystal. The cordierite with highthermal shock-resistance was chosen as the secondary crystalline phase and theMgO-Al₂O₃-SiO₂-H₂O was selected as the combined phase. Based on theMgO-Al₂O₃-SiO₂three ternary phase diagram, the equilibrium composition can belocated at the connected line of the spinel （MA） and cordierite （M₂A₂S₅）.（2） In view of disadvantagement of the current anti-crust performance test standard,the split tensile strength method was designed for quantitative analysis ofcrust-resistance. Four Sandwich specimens was tested by this method. The resultsshowed the order of their crust-resistance performance, i.e. MA₂> MA₁>50S=13NL.Meanwhile, the single factor analysis of variance was carried out to compare the test results within groups and between groups. The results proved that the significantdifferences between the split tensile strength were caused by different species, andalso verified the rationality and accuracy verification of the method.（3） The optimum formula of the composite Magnesia-Alumina Spinel castable wasobtained through the black-box principle and four orthogonal experiments. The effectof the ingredient content on the performance of castable was also obtained.（4） The crust-resistance, thermal shock-resistance, and corrsion-resistanceperformance of optimum formula of the composite Magnesia-Alumina Spinel castablewere systemically studied, which was much higher than13NL and50S. The thermalstability, mineral composition, morphorgy, et. al of the combined phase werecharacterized by methods like TG/DTA, XRD, SEM. Moreover, the reasons for theimproved performance of optimal formula were also anylized.