Study On The Properties Of Homogenized Bauxite And Its Application On Alumina-magnesia Castables

The homogenisation process of bauxite has provided an effective way of rational exploitation of bauxite resource.First,the chemical composition,microstructure and physical properties of homogenized bauxite grogs and natural calcined bauxite were studied in this paper.Based on the above study,the effects of different bauxite aggregates and matrix composition on Al₂O₃-MgO castables were discussed.Meanwhile,a thermo-chemical model was developed for the corrosion mechanism of homogenized bauxite based Al₂O-3-MgO castables by molten slag at 1600? through FactSage?6.2 software,and was investigated through dynamic testing method via an induction furnace.The research results indicated that:?1?Main crystal phase of homogenized bauxite is corundum,and minor crystal phase is aluminium titanate.But rotary kiln bauxite and down-draft kiln bauxite also have a small amount of mullite phase.The average grain size of homogenized bauxite,rotary kiln bauxite and down-draft kiln bauxite are 26.7 ?m,17.3 ?m and 20.5 ?m respectively.The apparent porosity and water absorption are lower due to the existence of small closed pores.?2?For the cement bonded alumina magnesia castable,t he corrosion resistance of 86# homogenized bauxite based Al₂O₃-MgO castables shows little difference with the natural 88# calcined bauxite based castables,but the slag penetration resistance and thermal shock resistance of 86# homogenized bauxite based castables are worse.Cracks are formed at the aggregate-matrix interface of the castables with homogenized bauxite aggregates near the hot face after the corrosion test,which exhibit negative effects on slag resistance.?3?The corrosion resistance of MgO-SiO₂-H₂O bonded Al₂O₃-MgO castables with 86# homogenized bauxite is better than that of castables with the 88# rotary kiln bauxite aggregates in the short term,but the influence is little.The slag penetration resistance of 86# homogenized bauxite based castables is worse.For the MgO-SiO₂-H₂O bonded alumina-magnesia castable,the slag resistance of the specimens with the 88# homogenized bauxite as aggregates is better than the one of the specimens with the 88# rotary kiln bauxite aggregates addition.?4?For the reaction between slag and homogenized bauxite based Al₂O₃-MgO castables,corundum,CA₆,gehlenite?C₂AS?and anorthite?CAS₂?were exsited at the aggregate/slag interface;spinel,C₂ AS and C AS₂ were formed when the matrix reacted with the molten slag.The thermo-chemical simulation results indicate that a CA₆ interlayer are formed resulting in an indirect dissolution of aggregate into slag.But no CA₆ are formed,showing a direct dissolution of matrix into slag.