In addition to contacting the upper space furnace atmosphere, the glass liquid also contacts a large area of the refractory wall. The refractory material has limited erosion resistance and will slowly dissolve into the glass liquid and become streaks. Refractory materials at the surface of the glass tend to scour the most, and the interface has the most alumina in the glass.
Liquid flushing is the key part of the formation of stripes. Each fluctuation of the glass surface will drive the increase or decrease of the corrosive-rich glass liquid. This liquid level fluctuation may be caused by the feeder idling or the feeding being out of control, or it may be caused by the failure of the flame to reduce the amount of melting, but Therefore, the damage caused is not small. When the glass surface fluctuates, a large number of stripes will flow into the glass in varying degrees. An appropriate liquid level control device should be adopted to avoid fluctuations in the liquid level.
When the prominent small corners and edges of the refractory material are eroded by the glass solution and dissolved, only the droplet-sized alumina solution is present in the cavity, but the “alumina line” that is not easily eliminated is formed in the glass solution. Firebricks with a rough surface naturally have more chances to produce stripes than flat bricks.
Dissolved refractories are continuously carried away by the glass stream causing striations, but the hazards are far less than those of “dead ends” in the liquid stream, such as the back of the kiln wall protrusion, brick seams, or other depressions. In the "dead corners", the alumina in the glass solution accumulates more and more, the colors are also different (having yellow-green variegated colors), and it also appears turbid (because it contains a lot of stripes). The difference between it and normal glass is that the content of Al2O3 is particularly high. , can be 3.7% higher than the Al2O3 content. The cracked parts of the refractory material also have the same effect as the “dead corners.” Therefore, it can be understood that after the molten pool and the crucible are used for a certain period of time, the voids, cracks, or perforations on the surface of the refractory material are increasing, and the glass is not Uniform failures are also much more frequent than new ones.
The boundary between the alumina-containing glass layer and the surrounding normal glass is very clear. Because the glass flow is very slow, there is no turbulence, and there is little chance of real mixing.
The alumina formed by the eroded cavities in the refractory material or the droplets formed by the protrusions will seriously contaminate the glass when they enter the glass. The circular objects shown in Figure 1 appear in the glass and they will follow the glass solution. The stream moves or becomes a rib that floats in the glass. Figure 2 Nepheline has precipitated in the nodules containing alumina.
The increase of Al2O3 content in the glass is not only the dissolution of the refractory material in the glass liquid, but also related to an obvious material exchange process. A portion of the glass composition diffuses into the refractory material and the resulting slag (glassy mucilage) composition corresponds to that contained in the glass plus a similar material composition to nepheline.
The correct choice of refractories is a method to avoid partial defects. The necessary conditions are basic refractories for alkaline glass and acid refractories for acidic glass, but this is difficult to fully satisfy. The biggest advantage of melting glass with a round crucible is that there is no "dead corner" material, but the alumina accumulated in the bottom glass layer of the crucible will affect the uniformity of the glass. Therefore, after the glass frit is used in the crucible, the crucible bottom glass must be cleaned. Clean, otherwise it will produce defects in the next molten glass. The use of new crucibles should be checked, preheated, baked, installed and melted in accordance with the operating procedures.
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