Study On The Preparation Of Al-Si-Ti Oxide Of Fly Ash In Huainan By Activation And Impurity Removal

With the constant development of economy, the emissions of the coal fly ash in China is increasing day by day and has a great impact on environment and the high value use of fly ash is seriously insufficient. Fly ash contains aluminium and silicon, titanium and other elements and can be used as the raw material of alloy of aluminum, silicon and titanium. The iron in fly ash can reduce alloy performance and needs to be taken off. This paper studies the activation processe and removal miscellaneous process of fly ash. Silicon-titanium-aluminium oxide suitable for electrolysis can be prepared. The main research contents and conclusions are as follows.In this paper, fly ash emitted from power plant in Tian Jian’an of Huainan as main research object, using chemical analysis, SEM, XRD and other modern means of analysis on the physical and chemical properties of fly ash, mineral composition and microstructure. The experimental reuslts show that fly ash gives priority to glass phase materical.Crystalline substance has primarily quartz mullite and contains a small amount of silicon line stone and etc. the iron mainly exists in the form of hematite. Particle appearance is mainly in the form of the glass beads, carbon particles and so on.The mechanical grinding can physically activate fly ash, then produces chemical reaction with NaOH solution to improve the ratio of silicon and aluminium of fly ash. After physical activation, the particle diameter of fly ash reduced, and specific surface area increased. The fly ash of the large size was broken and the wrapped layer of glass phase was fratured. The technological conditions was analyzed to study the influence to improve the ratio of silicon and aluminium and the best technological conditions such as reaction temperature, the concentration of NaOH solution, the volume of NaOH solution and reaction time were optimized. When the concentration of NaOH solution was25%, the volum of NaOH solution was140mL, reaction temperature was90℃and reaction time was2.5h, the highest ratio of silicon and aluminium was1.49and the activated effect was best. After composite activation, in mineral composition of fly ash the content of glass phase is rare, and this can show chemical activation will take away the glass phase material of fly ash. From the microstructure of fly ash we can see:the smooth surface of glass phase layer was corroded off and other mineral phases wrapped in the glass phase were exposed.The mixed acid of sulfuric acid and oxalic acid was used in the research to take off the impurity(the main impurity is ferric oxide). The influence of the technological conditions on the rate of taking off iron in fly ash was analyzed and the optimal process parameters such as the concentration of oxalic acid and sulfuric acid, leaching time, leaching temperature and solution volum were optimized. On the condition of concentration of oxalic acid as65g/L, sulfuric acid as0.50mol/L, the volumes of mixed acid solution as respectively120mL, leaching temperature as80℃and leaching time as3h, the rate of deferrization can be high to69.57%. After physical activation and deferrization the mineral composition and microstructure of the fly ash had a little change and the impurities wrapped in the glass phase still cannot be removed and need further activation. The rate of deferrization of fly ash was raised9.74%to79.71after composite activtion compared to only physical activation. Its main mineral composition is quartz, mullite and silicon line stone, and mineral phase containing iron in it disappeared. By means of adding a small amount of alumina and titanium dioxide to the fly ash after activation and impurity taken off, the alloy of silicon, aluminum and titanium materials can be prepare—silicon-titanium-aluminium oxide. The electrolysis test and the performance test of the alloy show that the production conform to the national standard.