Study Of Alumina Ceramic And Its Acid Corrosion Resistance

Alumina ceramic was widely applied in sulfuric acid production area due to its high mechanical strength and strong chemical inertia property. However, its mechanical strength gradually decreases in the acid, which greatly reduces alumina ceramic's lifetime and acid production efficiency. If the mechanical strength and chemical inertia property would be improved, the alumina ceramic inside sulfuric acid suction tower will achieve longer lifetime. In order to improve the mechanical strength and chemical inertia property, the following research activities are investigated.First of all, alumina ceramic formula design principle is investigated. Thanks to high mechanical strength and strong chemical inertia properties which are required for the alumina ceramic inside sulfuric acid suction tower, alumina ceramic formula design will focus on the following three aspects:high Al2O3 content within the raw materials, excellent plastic clays and sintering aids. Calcined alumina and bauxites with highα-Al2O3 content are suitable candidates. That is becauseα-Al2O3 will directly transform into corundum phase and corundum phase content within the ceramics would increase. On the other hand, ChaYuan clay with 37% Al2O3 mass ratio is better than the others, which exhibits advantages such small particle diameter, excellent plasticity. Due to its flake crystal, the ceramic would be easily sintered into densification state. Based on the above analysis, six alumina ceramic formulas with 50～73%Al2O3 mass ratio are promoted in this dissertation.Secondly, novel alumina ceramic slurry preparation route is presented. In order to enhance intrinsic reactivity of calcined alumina, make particles distribute uniformly, and reach low temperature sintering, the ceramic slurry preparation with basket sand mill is promoted. The author studies the relationship among the particle size, grinding time, grinding bead diameter and stirrer speed experimentally and theoretically in the ceramic slurry (α-Al2O3) preparation process. The most dramastic decrease ofα-Al2O3 particle size is produced by the combination of ZrO2 grinding beadφ2.2mm with stirrer speed 2500±10rpm, and D50 reaches 1μm after the particles are grinded for 1h.Thirdly, influencing parameters related to the alumina ceramic sintering are investigated. Sintering aids such as Spodumenes and Witherites contribute to low temperature sintering and high ceramic densification. If the sintering temperature increases properly, the bulk density would increase and the crystal grows into better shape. However, if the sintering temperature is too high, the bulk density would decrease. Furthermore, if the holding time is prolonged, the ceramic would become higher densification state.Lastly, acid corrosioin resistance properties of the ceramic are investigated. Microstructure determined by both sintering temperature and high temperature holding time would influence acid corrosion resistance. The ceramic corrosion resistance would be improved if the ceramic is in the state of higher densification, less gasholes and larger corundum content. As the ceramics operate in 98%wt H2SO4 solution, the weight loss is less at the beginning time, but the weight loss increases dramatically after corrosion for 24h, and after that the weight loss would maintain at a fixed level. Moreover, the corrosion degree is quite different as the ceramic operates under acid with different temperature.