| In order to make high efficient utilization of dolomite which contains much calcium and magnesium elements(MgO,CaO), MgAl2O4-CaO·X(Al2O3) composites were synthesized by solid phase reaction using dolomite ore and aluminium sources in this essay, in addition, the gelling properties and service performance in refractory castable based on brown fused alumina were tested and coMPared. In the experiment, in order to determine temperature schedule in prior period of solid phase reaction, the phase transformation during the heat decomposition of dolomite ore yielded from Linshou, Hebei Province was analyzed by TG-DTA and XRD techniques at first. Subsequently, MgAl2O4-CaO·X(Al2O3) composites with the theoretical phase content were synthesized by usingα-Al2O3, Al(OH)3 andγ-Al2O3 as aluminium sources reacted with dolomite respectively. And the composites were characterized by XRD, SEM and EDS techniques. Fineness, water requirement of normal consistency, initial setting time, final setting time, flexural strength and compressive strength of MgAl2O4-CaO·X(Al2O3) composites with three different phase compositions were tested and analyzed respectively. Eventually, refractory castable based on brown fused alumina were fabricated by using these composites and one pure aluminate cement as cementing agent respectively, and then the linear change rate, flexural strength, compressive strength and slag resistance property of the samples, which were thermal treated at different temperature , were compared systematically and analyzed in detail.The following results were concluded: dolomite was decomposed in form of mixed salt during calcination, only MgO phase and CaxMg(2-x)(CO3)2 were generated before 700℃, then the CaO and MgO phases existed simultaneously between 700℃and 800℃, and dolomite were decomposed totally at 900℃. All ofα-Al2O3, Al(OH)3 andγ- Al2O3 can react with dolomite as aluminium sources respectively, for synthesising MgAl2O4-CaO·X(Al2O3) composite with theoretical content of phases at 1500℃; Properties including Fineness, water requirement of normal consistency, initial setting time, final setting time, flexural strength and compressive strength of the three MgAl2O4-CaO·X(Al2O3) composites synthesised in this study were agree with national standards(GB/T 205-2000). Time of setting and variation of maintenance strength were affected by the percentage of CA and CA2 phases directly. Due to existence of CA6 phase, linear change rate of refractory castable was rising before 1300℃(0.6%3.2%)and then reduced between 1300℃ 1500℃(-0.5%0.4%). flexural strength and compressive strength of refractory castable increased quickly with rising of temperature, and changed regularly with phase composition of composites; The slag resistance property of refractory castable based on brown fused alumina by using MgAl2O4-CaO·X(Al2O3) composites as cementing agent were better than using pure calcium aluminate cement as cementing agent, due to separation of MA synthesized in situ during process of iron slag corrosion. |
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