Preparation Of Magnesium Aluminum Spinel Powders And Ultra-fine Aluminum Silicate From Blast Furnace Slag

In recent years, as China’s steel production capacity increasing, blast furnace slag as the main byproduct of blast furnace ironmaking production is also growing. At present, the industrial use of blast furnace slag is mainly concentrated in the field of building materials with low added value. Blast furnace slag containing silicon, magnesium, aluminum components, is the main ingredients of preparation of silicate aluminum and magnesium aluminium spinel. In this paper, in order to improve the added value of comprehensive utilization of blast furnace slag and prevent the environmental pollution, blast furnace slag is used as the main raw material preparation of silicate aluminium body, and the waste liquid(silicon liquid) in the above process is used to prepare magnesium aluminate spinel. The main research results are as follows:1、Blast furnace slag through the early stage of the acid solution, silicon, filtered, the filter cake is polymerization silicate and the filtrate is silicon liquid waste, which are respectively the raw materials of the preparation of ultra-fine aluminum silicate and magnesium aluminate spinel. In the experiment, we mainly explored three aspects of process parameters. The optimal pH value of high slag liquid acid solution is 1.5 ~ 2, the best ratio of water and slag in the acid solution of blast furnace slag is 7:1, and the best pH value of solution system is 3 in the process of generating polymerization silicate.2、By means of the XRF chemical composition analysis of the silicon liquid waste and polymerization silicate, we find that the content of SiO2 in waste liquid is only 0.85%, while the content of Al2O3 and MgO is respectively 3.79% and 1.03% in separated polymerization silicate solid. It can be seen that the pre experiment of the acid hydrolysis can effectively separate the chemical composition of blast furnace slag to prepare the raw material of the following experiments.3 、 The experimental preparation of ultra-fine aluminum silicate by polymerization silicate was divided into two steps. The first step is to prepare sodium silicate by alkali leaching polymerization aluminum silicate, in which two aspects of process parameters were discussed respectively: NaOH solution mass concentration was 10% and the optimum reaction time was 4 h. The second step is to prepare ultra-fine aluminum silicate by sodium silicate. The exploration of optimal process parameters is that the ratio of water glass and aluminium sulfate was n(SiO2) : n(Al2O3) = 10 ~ 12 and reaction temperature was 60 ℃. Note that the injection rate of aluminium sulfate solution is not too fast.4、The ultra-fine aluminum silicate we have prepared is analyzed by X ray diffraction analysis, infrared spectrum analysis and X-ray fluorescence spectrum analysis. The results show that the content of Si O2 and Al2O3 is respectively 80% ~ 82% and 11% ~ 13%, so the product is amorphous structure. The chemical composition conforms to the enterprise universal standard, but the whiteness is slightly lower than the enterprise general standards, which is because the product contains more Fe content.5、In the preparation experiment of magnesium aluminate spinel, silicon liquid as raw material, synthesis of precursor through the urea homogeneous precipitation, after high temperature calcination, the magnesium aluminum spinel powders is obtained. The precursor synthesis temperature, the amount of urea, the calcination temperature and the calcination holding time were studied, and we got the following conclusion: the precursor synthesis temperature 100 ℃, the amount of urea as the theoretical amount of 10 times, calcination temperature 1100 ℃, holding time 2 h, are the optimum process conditions of preparation of magnesium aluminate spinel.6、We explored three kinds of methods of removing Fe in this experiment. Low fatty acid extraction method can remove 63% of iron impurity, but can cause the loss of the aluminum in the process of extraction. Low sodium sulfite can remove Fe impurity from the precursor and iron removal rate was 71.2%. Potassium permanganate method of removing Fe works best with iron removal rate up to 95%. However the reaction increases manganese content in the solution, which will settle down in the late preparation of precursor as the solution pH value increases, thus affecting the performance of magnesium aluminate spinel. Considering the above, we choose low sodium sulfite to remove iron impurity from the precursor.In this paper, blast furnace slag is used to prepare ultra-fine aluminum silicate and magnesium aluminium spinel, which not only increases the additional value of comprehensive utilization of blast furnace slag, but also provides a new way for the preparation of ultra-fine aluminum silicate and magnesium aluminate spinel.