During the operation of the glass melting furnace, due to the extremely harsh working environment of the internal kiln lining, the refractory materials are severely damaged. Common damage modes are as follows:
1 Burning
The burning of refractory materials in glass furnaces refers to the damage of refractory materials by melting (also known as burning flow) or softening and deformation under long-term high temperature. The refractory materials are melted when some parts of the kiln are locally overheated or the refractoriness of the refractory materials is not enough. Sometimes, the refractoriness is qualified, but the load softening temperature is low. In long-term use, the refractory materials will also soften and deform, affecting the stability and service life of the entire masonry. The severity of the burning depends on the temperature and the nature of the refractory materials. The small furnace ignition port crown, small furnace neck, tongue, heat storage chamber crown, melting part kiln crown and breast wall are parts that are easily burned.
2 Crack and wear
The crack of refractory materials in glass furnaces refers to the crack damage caused by stress and strain. The crack of refractory materials mainly occurs in the kiln baking stage. When the kiln is baked, a certain temperature difference occurs inside the refractory bricks, generating corresponding mechanical stress. If the heating speed is too fast and exceeds the limit strength allowed by the refractory material, cracks will appear until it breaks into pieces. Electric melting, highly sintered dense refractory materials are most susceptible to damage. In addition to stress caused by temperature difference, the expansion or contraction caused by the change of refractory crystal form will also generate stress. When the temperature rises too fast, the crystal form changes quickly, the volume changes drastically, and the stress is too large, causing the refractory material to crack. Therefore, when baking the kiln, the temperature must be raised according to the pre-established kiln baking curve. After the kiln is baked, the refractory material is under high temperature for a long time. The mechanical strength of the refractory material at this operating temperature is much lower than that at room temperature. If the mechanical load acting on the refractory material is too large, the refractory material will produce inelastic deformation (similar to extremely viscous flowing liquid), resulting in material damage.
The wear of refractory materials in glass kilns mainly refers to the effect of dripping water through stone when the glass liquid flows along the refractory material,
grinding grooves in the refractory material, which is the mechanical wear effect. The main wear parts are at the glass liquid surface. In addition, it is also clearly visible at the circulating liquid flow (especially at the turbulent liquid flow). When the liquid surface fluctuates and the liquid flow changes (such as affected by temperature fluctuations), the material wear is aggravated.
3 Upward drilling
Upward drilling When the glass liquid and the metal liquid melt the brick joint material and penetrate into the cushion layer under the paving bricks, the cushion layer is corroded and damaged. The glass liquid and the metal liquid erode the paving bricks vertically upward in a pit-like shape, that is, upward drilling. Attack from top to bottom, so that the paving bricks are melted through.
Therefore, in addition to wear resistance, the bottom bricks of the glass kiln pool must have good integrity. The paving bricks are in direct contact with the glass liquid, which can well protect the ramming pool bottom. Use cast AZS bricks with good corrosion resistance and wear resistance (high-quality sintered AZS bricks can also be used, but the disadvantage is that the size is small and there are many brick joints). The use of a composite pool bottom structure can reduce heat dissipation loss, extend the life of the pool bottom, and help improve the quality of the glass liquid.
4 Downward drilling
Downward drilling: Metal impurities (mainly iron, the order of metal corrosion intensity is Sn, Pb, Cu, Al, Zn) brought in by the batch (mainly broken glass) and the molten metal obtained by glass reduction sink to the bottom of the pool, forming a spherical or flat ring-shaped melt. Due to their large surface tension, they form a wedge-shaped mouth between the glass liquid and the pool bottom bricks, resulting in downward drilling erosion, especially drilling into the pool bottom brick seams. While drilling, erosion, and expansion to the non-corrosion-resistant pool bottom bricks (such as clay bricks, which are lightweight insulation bricks). In severe cases, most of the pool bottom bricks (under the paving bricks) can be hollowed out.
Only by understanding the damage mode of the kiln lining can we better configure the refractory materials in the early stage of the new kiln construction or maintenance, so as to prevent it as early as possible, slow down the loss of the kiln lining, and extend the life of the furnace.
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