Study On Preparation Of Lightweight Refractories From Low-grade Bauxite And Magnesite

The comprehensive utilization of low-grade minerals as well as the energy savingand environmental protection are urgently required recently. To respond the situationssuch as the large consumption of bauxite, the large production of fly ash solid waste,and the pursue of new lining refractory for industrial furnace, the study proposes theidea to use low-grade bauxite, the magnesite, and fly ash to prepare aluminosilicatecomposites. The effects of adding amount of magnesite, the sintering temperature andholding time on the phase composition, the morphology of the fibers and the physicalproperties of the composites are investigated. The lightweight aggregate refractorywere prepared from low-grade bauxite, the magnesite, fly ash, and a proper amount ofpore-forming agent, and the effect of the adding content of the pore-forming agent onthe properties of the lightweight aggregate refractory was studied. Furthermore, theas-synthesized lightweight aggregates and powder refractorys were used as rawmaterials to prepare the smear type lightweight refractory. The influences of theaggregate/powder ratio, the type and the amount of the binding agent, the content ofthe cyanite, andalusite and fly ash powders on the properties of the lightweightrefractory were studied.The results show that the main phases of the sintered products starting from thelow-grade bauxite, and the magnesite were mullite and corundum; when the addingamount of magnesite was higher than6.2wt%, the spinel phase appeared in the finalproducts; with an adding amount of8.95wt%of magnesite, the bending strength ofthe samples sintered at1450°C for4h was163.05MPa. Partial substitution ofbauxite by fly ash in the starting materials would benefit for the sintering of thesamples. When sintered at1350°C for4h with the magnesite added as5.84wt%, thebending strength of the sample reached159.10MPa. When using the low-gradebauxite as the main material with the magnesite added as8.95wt%, the sawdustadded as5wt%and the polystyrene spheres added as2.5wt%, lightweight aggregateswith the lowest bulk density of0.98g/cm3and the compressive strength of12.47MPawere obtained. The properties of the samples were also influenced by the particle size gradation. When the lightweight aggregate was added as40wt%, the sample sinteredat1300°C for2h got the highest compressive strength. The samples with12wt%aluminum dihydrogen phosphate and sintered at1300°C for2h got the bulk densityof1.50g/cm3and the compressive strength of10.63MPa. The samples with10wt%aluminate cement and sintered at1300°C for2h got the bulk density of1.40g/cm3and the compressive strength of4.85MPa. The as-prepared lightweight refractorywith partial substitution of cyanite and andalusite by the industrial alumina andlightweight aggregate got improved compressive strength after drying andhigh-temperature sintering. The samples with25wt%andalusite and sintered at1300°C for2h got the bulk density of1.46g/cm3and the compressive strength of10.23MPa.