China has rich reserves of high-bauxite bauxite resources, but due to disorderly mining in recent years, the reserves of high-grade bauxite raw materials have fallen sharply, and the overall utilization rate is low, and the level of utilization technology is limited. In recent years, some enterprises have started to prepare high-quality refractories with low- and medium-grade high-bauxite as the main raw material to improve resource utilization. Among them, the use of homogenization purification process to prepare bauxite homogenization material is a practical way. In this work, the physical and chemical properties of the same grade high alumina bauxite clinker and the bauxite homogenizing material prepared by the homogenization purification synthesis process are studied, and the two are used as aggregates to be prepared with the aid of a basic formula. The properties of high alumina castables provide a basis for the industrial application of two bauxite raw materials.
experiment
1.1 Performance measurement of two bauxite raw materials
The bauxite clinker and bauxite homogenizer used in the test were block samples from the same batch of the two manufacturers. The research process of its physical and chemical properties is as follows: 1) Before crushing and grading, extract two representative blocks of bauxite-based refractory materials (in the same batch), 5 blocks each, and measure the SiO2 according to GB/T 6900-2006 , Al2O3 and Fe2O3 content, measure its bulk density and apparent porosity according to GB/T 2999-2002; 2) After crushing and grading the two bauxite blocks, press 8～5, 5～3, 3～1 and For sampling with particle size ≤1 mm, refer to GB/T 17617-1998 for sampling method, and then detect the chemical composition of two raw materials with different particle sizes in accordance with GB/T 6900-2006.
1.2 Application of two bauxite raw materials in high-alumina castables
Two kinds of bauxite raw materials are used as aggregates (8～5, 5～3, 3～1 and ≤1 mm) respectively, and special grade bauxite powder, SiO2 powder, scorch gem powder and high alumina cement are used as matrix materials (the main The chemical composition is shown in Table 1), according to the basic formula of high alumina castable for cement kiln, two high alumina castables are made respectively. After weighing the raw materials, add appropriate amount of water and stir evenly, vibrate casting to form samples of 40 mm × 40 mm × 160 mm and 100 mm × 100 mm × 30 mm, and demould after natural curing for 24 hours at room temperature, constant temperature and humidity After curing for 24 h, dry it at 110 ℃ for 24 h. Then, one part measures the bulk density and apparent porosity according to YB/T 5200-1993, the normal temperature flexural strength according to GB/T 3001-2007, and the normal temperature compressive strength according to GB/T 5072-2008; the other part is tested at 1 200 ℃ After heat treatment for 3 h, test the bulk density, apparent porosity, normal temperature pressure resistance and flexural strength according to the above standards. At the same time, measure the permanent heating line change according to GB/T 5988-2007, and measure the temperature at 1 200 ℃ according to GB/T 3002-2004. Hot flexural strength, measured at room temperature abrasion resistance according to GB/T 18301-2001.
Results and discussion
2.1 The properties of two bauxite raw materials
From the five samples taken separately, whether it is Al2O3 content or Fe2O3 content, the fluctuation of bauxite clinker is much higher than that of bauxite homogenization material. In terms of extreme difference, the former is more than 7 times that of the latter. At the same time The content of Fe2O3 impurities in the latter is also significantly reduced. This shows that because the bauxite clinker has not been strictly selected before firing, the composition fluctuations between the blocks are inevitable, and even large differences; and after the homogenization process, bauxite blocks with large differences in composition can be removed. Homogenization can significantly improve the fluctuation of the chemical composition of alum, and control the fluctuation of the chemical composition within a reasonable range. At the same time, because some impurities can also be effectively removed during the homogenization process, thereby reducing the impurity content of the raw material to a certain extent , Improve the quality of raw materials.
The differences in the bulk density and apparent porosity of the bauxite clinker samples are also relatively large, while the differences between the bauxite clinker samples are basically negligible. This is because its chemical composition fluctuates greatly, and when various mixed-level raw materials are fired together, it will inevitably cause the lower sintering temperature to be completely fired, and the higher sintering temperature will cause underfire or overfire. As a result, the apparent porosity fluctuates greatly; and the bauxite homogenizer has undergone multi-stage homogenization before firing, and the chemical composition is relatively stable. If the process control is strict, the bulk density can obviously be avoided under a suitable firing system. And the fluctuation problem of apparent porosity, to achieve uniform and stable product performance.
In the two raw materials of different particles, as the particle size decreases, the content of Al2O3 gradually decreases, and the content of SiO2 and Fe2O3 gradually increases. Moreover, the change trend of bauxite clinker blocks is more obvious than that of bauxite homogenized materials. , Especially for those ≤1 mm, there is a big change. Analysis shows that both bauxite clinker and bauxite homogenizing material are burnt in bulk, the former is not homogenized, and the phenomenon of component enrichment is obvious, especially the enrichment of impurities, resulting in liquid phase enrichment during the firing process , Due to the low strength of the glass phase formed by the liquid phase during crushing, particles with smaller particle sizes are formed. Therefore, the content of Al2O3 in particles ≤1 mm is generally low, while the content of impurities such as SiO2 and Fe2O3 is generally higher; the latter Because after the homogenization and purification process, the sintering effect is better, and the liquid phase is effectively dispersed, the chemical composition difference between the particles of each particle size is eliminated to a certain extent. By comparing the physical and chemical properties of the two bauxite raw materials, it can be seen that the bauxite homogenizing material after homogenization and purification treatment, no matter its block material or the particles of each particle size, shows better uniform stability than bauxite clinker.
in conclusion
In terms of physical and chemical properties, whether it is block material or granular material of various sizes, the bauxite homogenizing material prepared by the homogenization purification process is more uniform and stable than bauxite clinker; moreover, the bauxite homogenizing material is used as the aggregate. Aluminum castables have better performance indicators than bauxite clinker as aggregates, especially in terms of high-temperature mechanical properties and wear resistance, and can be used as a higher level of refractory applications.
