At present, the refractory bricks used for small furnace tongues mainly use fused AZS bricks. The fused bricks have good strength, high temperature resistance and corrosion resistance, but their thermal shock resistance is poor and they are prone to cracks. This is because the zirconia in AZS bricks is at 1200 There is a phase change around ℃ to cause shrinkage. In addition, the structure is dense and there is little buffering phase.
Due to the alternation of hot and cold between gas, combustion air and exhaust gas, the temperature of the tongue hood will change rapidly between 1000 and 1600°C, causing the AZS tongue hood to have different cracking and peeling phenomena. In addition, Fused bricks are dense and require a strong steel structure for weight support, otherwise they are prone to collapse.
In addition, the small furnace tongue is also made of sintered mullite bricks, corundum, ordinary silica bricks and other materials. Although the thermal shock resistance is improved, the erosion resistance and erosion resistance are not ideal. In many actual kiln operations, The erosion and peeling of tongue ballast often occur. On the one hand, it is the erosion of high-temperature airflow. On the other hand, it is the erosion of fly material dust, especially the erosion of alkaline substances in the fly material. The following reactions occur:
1.NaOH erosion of sillimanite, clay bricks, mullite and AZS
AxSx+ NaOH→Nepheline+A1203(ΔV=6-36%)
2.NaOH corrosion of alumina corundum:
Al203 (a-alumina)+ NaOH-B-alumina (ΔV=28%)
3.NaO erosion of ordinary silica bricks:
CaO-Si02 (binding phase in silica bricks) + NaOH → Na20-Ca0-Si02-phase glass phase
After the above-mentioned erosion situation occurs, due to the formation of nepheline and glass at high temperatures, volume deformation and high-temperature softening occur, which also causes various problems in the tongue ballast. Therefore, higher requirements are required for the selection of materials for the small furnace tongue ballast parts. It is a refractory brick that is very economical at the same time.
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