Effect of Pylorite-based Mullite on Performance of Ceramic Burner Brick
Mullite-andalusite-cordierite bricks have excellent thermal shock resistance and are widely used in hot blast stove ceramic burners. In this paper, a comparative test of mullite-andalusite brick and mullite-andalusite-cordierite brick is carried out to analyze the effect of mullite-mullite on the performance of ceramic burner brick.
Kyanite-based mullite is a synthetic mullite raw material, which is obtained by crushing, wet grinding, filter pressing, extruding mud molding and calcining at 1550 ℃-1600 ℃. The physical and chemical properties of bluestone-based mullite are shown in Table 1, and the X-ray diffraction analysis pattern is shown in Figure 1.
Table 1 Physical and chemical properties of mullite based on blue crystal
Fig.1 X-ray diffraction pattern of mullite based on bluestone
As can be seen from Table 1 and Figure 1, the bluestone-based mullite consists of 60% mullite phase, 30-40% glass phase, and 3-5% cristobalite phase.
The experimental design of two groups of process ratio, No. 1 process to bauxite-based mullite, andalusite, cordierite as the main raw material, No. 2 process for the blue crystal-based mullite, andalusite as the main raw material. It is mixed and milled by a 50kg mixer, molded by a 400 t press, and sintered in a tunnel kiln. The test sample is shown in Figure 2, and the physical and chemical performance test results are shown in Table 2.
Fig. 2 Test sample diagram
Table 2 Test results of physical and chemical properties
It can be seen from Table 2 that the chemical compositions of processes 1 and 2 are close. The pore rate, volume density, pressure strength and load softening temperature of No. 2 process are obviously better than that of No. 1 process. The load softening temperature of the No. 2 process is 68°C higher than that of the No. 1 sample, because the cordierite is completely decomposed into mullite and glass phase after the temperature reaches 1460°C . The raw material of synthetic cordierite for refractories contains many impurities (in order to expand the temperature range of cordierite formation and promote sintering), so the high temperature performance is general. Blue crystal-based mullite due to low impurity content, high main crystal phase content, good crystal type, high temperature performance (load softening temperature, creep rate) is much higher than other aluminum silicon raw materials with aluminum content.
The number of thermal shock resistance (1100 ℃ water cooling) of processes 1 and 2 is more than 100, which meets the requirement of thermal shock performance of ceramic burner bricks> 100 times. see fig. 3 for the test bricks after 100 thermal shocks. As can be seen from Figure 3, although both can complete 100 thermal shock tests without damage, the number, width and length of cracks in the No. 1 process are significantly smaller than those in the No. 2 process, which shows that the thermal shock resistance of the mullite-andalusite-cordierite brick is better.
The analysis suggests that the mullite-based mullite is a mullite-high silica glass composite material, and its well-developed mullite crystals, evenly distributed network structure and high-viscosity silica-rich glass phase all improve the thermal shock resistance of the material, especially the existence of its high-viscosity glass phase, which can not only reduce the slip between crystals at high temperatures, but also improve the thermal mechanical properties of the material, it also has the effect of inhibiting crack extension .
Fig. 3 Situation of test brick after thermal shock resistance test
Through the analysis of test data, the following conclusions are obtained:
1, blue crystal-based mullite-red pillar stone brick showed pore rate, volume density, load softening temperature, creep rate is better than mullite-red pillar stone-cordite brick.
2. The thermal shock of mullite-andalusite brick is more than 100 times, which can meet the most demanding thermal shock requirements of hot blast stove ceramic burner, but the thermal shock resistance of mullite-andalusite-cordierite brick is better.
3, blue crystal-based mullite-andalusite brick can replace mullite-andalusite-mullite-cordierite brick, applied to hot blast stove ceramic burner.
 Xie Guofeng. Study on preparation and properties of mullite-cordierite kiln furniture materials [D]. Zhengzhou: Zhengzhou University, 2016.