Bubbles are common defects in glass, which are caused by many reasons, such as insufficient melting capacity, insufficient temperature, undesirable clarification, refractory material, and improper feeding operation. According to the theory that the solubility of gas in the glass liquid is inversely proportional to the temperature, the influence of the kiln structure and process conditions on the elimination of bubbles is discussed, and the equilibrium relationship between the melting temperature and the amount of material and the number of bubbles in the kiln is found.
The bubble elimination center in the glass melting process is a complex physical and chemical reaction process, including the silicate formation stage, the glass formation stage and the clarification homogenization stage, in which the clarification stage is the process of bubble removal. In this process, the viscosity of the glass liquid is reduced with the temperature rising, gas in the bubble, gas in the kiln and the glass in the process of the process. The balance between the physical dissolving and chemical combination of the gas in the liquid glass is established, and then the visible bubbles are floated on the glass surface to be removed. In the clarification process, the elimination of bubbles is carried out in the following two ways:
1 the volume of bubbles increases and accelerates to rise.
2 the gas components in the small bubble are dissolved in the glass liquid and the bubbles are absorbed and disappear. The size of the bubbles and the viscosity of the glass liquid are the determinants of the floating of the bubbles. According to Stokes's law, the rising velocity of the bubble is proportional to the square of the radius of the bubble, and is inversely proportional to the viscosity of the glass liquid. The viscosity of the glass liquid at different temperatures is compared with the glass formula in our company. To clarify the temperature of the glass liquid and the floating distance of the bubble, the floating time of the bubbles of different diameters is calculated. The increasing melting temperature can increase the floating speed of the bubbles above 0.2mm diameter, and reduce the time required for the floating. But the bubbles under the diameter of less than 0.2mm can be reduced. It is difficult to eliminate by floating up. It must be eliminated by adjusting the temperature to make the small bubbles absorbed in the glass liquid. In the process of cooling the glass liquid, the bubbles will become smaller because of the cooling of the gas and the constant pressure of the gas. The internal pressure of the bubble increases because of the decrease of the radius because of the surface tension of the glass. The saturation pressure of the gas is lower than the pressure of the gas in the bubble. The gas in the bubble is released into the glass liquid. Because of the release of the gas, the radius of the bubble is reduced, the surface tension of the glass liquid increases the pressure in the bubble, until the final bubble is completely absorbed by the glass liquid. During the clarification process, the large bubble is discharged from the small bubble absorption. These two stages are essential, the former requires the necessary temperature and duration, the latter requires a certain temperature gradient, and if these conditions are not reached, the products will be brought on the bubbles.
The influence of the furnace structure and the technological conditions on the elimination of bubbles
The structure of the 1. kiln structure has two characteristics: one is a small furnace structure with large inclination and small momentum ratio, and two is the sinking deep clarifier structure. This structure makes the flame have a high speed and rigidity, the flame is close to the glass surface, and the pile has a forward thrust. According to the measurement, when the melting temperature is insufficient and the amount of the material is large, the material heap moves after the material is moved. The mixture has not completely melted to the clarification section, taking up the clarification time, making the clarification not sufficient. The bubbles that should have been discharged in the glass liquid enter the cooling stage. The bubbles above 0.2mm in diameter are formed. The floating velocity of different diameter bubbles is different from the time required. Yao Changfang clarifies the distance short, the clarification time is relatively inadequate and the discharge of the large bubbles is sometimes inadequate. From the clarification pool structure analysis, the so-called deep clarifier sink is also limited. Compared with the previous sinking deep pool, the distance of the downward cooling of the glass liquid in the vertical direction is shortened, the time is reduced, and the temperature decrease is small. When the glass liquid is clarified downward, the glass liquid is clarified downward. The small bubbles can not be completely dissolved in the glass liquid, and the glass liquid entering the rising channel has both bubbles above 0.2mm diameter and the ash bubble below the diameter of 0.2mm. The glass liquid has a cooling process near the bottom of the rising path to the top and near the material basin. At the top, the temperature of the glass liquid is high. In order to make the molding temperature appropriate, the cooling air is increased. The glass liquid is rapidly forced to cool, and the glass in the epidermis affects the absorption of the small bubbles. This appears the phenomenon of the small bubble distribution on the products. In use, we reduce the heat preservation strength of the rising material and dismantle the insulation bricks. The measurement results show that the temperature of the glass liquid at the top of the rising road is reduced and the speed of the temperature regulating fan drops. The result of this treatment is that the bubble diameter on the product becomes smaller and the number of bubbles decreases.
The 2. feeding machine is reformed, the feeding machine equipped with the discharge quantity control can not realize the coating layer material, the proportion of broken glass is only%7, the height of the mixture floating on the glass level is large, which increases the area of the flame and increases the speed of the drifting speed. As material), the height of the material pile floating on the liquid surface is small. The phenomenon of the blanking in the front of the material pile is not obvious. The improved feeding machine reduces the spitting port, and the feeding machine is moved down to the glass liquid, the thickness of the pile is reduced, the force area is reduced, the distance of the blanking in the front of the material is reduced, which is beneficial to prevent the running material and increase the time of clarification.
3. the melting temperature is generally speaking, improving melting temperature is the most direct measure to solve the bubble. It is by speeding up the melting speed of the mixture, improving the temperature of the glass liquid, reducing the viscosity, and thus beneficial to the discharge of the bubbles. In this case, the melting temperature increases with the following direct effects. (1) increase the velocity and fire of the flame. Flame length. Flame speed