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The Classification of Bubbles

Through production practice, float glass bubbles can be roughly divided into two categories: melted clarified bubbles and non-melted clarified bubbles

(l) Melting and clarifying bubbles: bubbles caused by the instability of raw materials, melting, fuel, and combustion systems;

(2) Non-melting clarified bubbles are bubbles caused by brick material quality, nitrate condensate, and cooling equipment.

The float glass bubbles 1

The float glass bubbles 1

The causes and solutions of float glass bubbles

1. Raw Material Bubble

The air brought by the batch material forms bubbles-raw material masses (chips) or ultra-fine powder masses (chips), large mirabilite particles, and broken glass entrain the air into the people; carbon dioxide-the decomposition products of carbonate when the batch materials are melted; Water vapor—water added to the batch; nitrogen—air is entrained into the batch and fed into the furnace. The solubility of oxygen in the molten glass is relatively large, and most of the remaining gas is nitrogen. The gas is soluble and insoluble Dissolved gases Insoluble gases include nitrogen, carbon dioxide, and hydrogen. Soluble gases include oxygen, sulfur dioxide, and water.

The glauber's salt 1

The glauber's salt 1

2. Melting Bubble

The liquid level line around the melting furnace outside the bubble boundary: small bubbles come from the high-temperature area of the melting furnace; because the process of bubbles being absorbed or dissolved by the glass is related to time, the higher the temperature of the glass, the more gas is absorbed by the glass, causing the gasThe bubble becomes smaller. Bubbles below the diameter generally come from the melting part. Bubbles of diameter are generally produced in the neck areaRaw. Larger bubbles come from the cooling part or runner. 

Reason: 

There is a glass phase precipitated by refractory materials around the surface line of the glass, and it stays around the surface line of the refractory for a long time. The outside of this part is the pool wall cooling

The wind and cooling wind make the temperature inside the brick joints of the pool wall lower. It is easy to accumulate Glauber's salt. Under the changes of temperature, furnace pressure, and liquid level, the accumulated Glauber's salt enters the molten glass and produces bubbles. The heavy-duty insulation of the pool wall and the gaps between the pool wall bricks make the glass liquid seep out and enter the insulation layer of the pool wall, causing the gas to enter the glass liquid in the kiln along with the gaps in the pool wall, resulting in air entrapment.

Solution: 

Stabilize the pressure of the furnace, stabilize the convection of the molten glass, block the gaps in the tank wall, and stabilize the flame of the small furnace.


3. Clarification Bubble

Microbubbles generally refer to bubbles with a smaller diameter. Micro-bubbles are mainly produced in the clarification section. The clarification temperature is too low, and the flame of the small furnace is too strong or too weak. Reducibility of the flame atmosphere in the clarification zone, poor fuel atomization, the oil containsWith more particulate carbon, the bubble boundary is unstable and the flame is unstable. Sudden changes in convection.In addition to the influence of the clarification temperature, it is also affected by the unstable bubble boundary, the large change in the feeder speed, the large change in the liquid level, and the large change in the atmosphere in the furnace. The fuel oil contains particulate carbon, which is scattered on the surface of the liquid glass. It is caused by poor oil atomization. Sudden changes in the amount of melting can also cause clear bubbles.


4. Intermediate Bubble 

The air bubbles are generated by the neck cooling equipment and the partition wall. The cooling equipment here has two kinds of large water pipes and agitators. Water leakage in the cooling equipment will cause bubbles. The cold glass liquid at the stirrer will have fallen Glauber's salt, and the Glauber's salt that has condensed in the exposed space of the large water pipe will fall into the glass liquid due to changes in the pressure of the cooling part and cause bubbles. This kind of bubbles are generally in the upper-middle or lower part of the glass plate, and there is no obvious law. Observed under a microscope, there are generally heavy or light traces of Glauber's salt. The re-dissolution of crystallized glass will produce bubbles.

Solution: 

① Check if the cooling equipment is leaking. 

② Check if there are any around the liquid level line of the cooling equipmentTraces of foreign objects of fallen Glauber's salt. 

③ Strictly control the pressure of the cooling part, the pressure of the cooling part is generally controlled at 8 a 15 Pa. 

④ In the design, reduce the space exposed part of the large water pipe. 

⑤ The exposed space of the large water pipe is covered with glass liquid. 

⑥ Stabilize the glass level. 

⑦ Stable cooling water pressure.


5. Cooling Part Bubble

One is the bubbles generated from the upper space and the liquid level. The other is the bubbles generated from the bottom. Upper space The bubbles generated between the liquid level and the liquid level generally exist on the upper surface of the glass and are closed. When observed under a microscope, the bubbles caused by the falling Glauber's salt from the upper space generally contain traces of Glauber's salt with varying degrees of severity. Air bubbles generated near the liquid level are generally caused by the quality of the bricks, the gaps between the bricks on the pool wall, or the adhesion of foreign objects along the pool wall. The air bubbles generated at the bottom of the cooling part are generally caused by the quality of bricks, or foreign objects and welding slag iron remaining in the installation stage, and the diameter is generally larger or larger.

Solution: 

Aiming at the bubbles generated in the upper space and the liquid level line: 

① Stabilize the pressure of the cooling part. 

② Keep Maintain the purity of cooling air. 

③ Separate the melting part and the cooling part as much as possible to reduce the pollution of the cooling part by the exhaust gas from the melting part. 

④ Reduce the influence of the external environment on the cooling part. 

⑤ Check if there is any foreign matter on the liquid level line of the pool wall. 

For the bubbles generated at the bottom of the cooling part: 

① Check the glass liquid level of the cooling part and see if there are any bubbles discharged from the bottom.

② Remove the heat preservation at the bottom of the cooling part and reduce the bottom temperature of the cooling part. 

③ Cooling the bottom of the cooling pool can be used, and care must be taken to prevent crystallization. 

④ Increase the iron content in the glass composition and reduce the heat permeability of the glass. 

⑤ Deepen the size of the large water pipe as much as possible to reduce the return of glass liquid.


6. Runner Bubble

There are two types of runner bubbles, one is generated at the bottom of the runner, and the other is the awn falling from the upper space of the runner.Nitrate may be produced by the runner gate. Bubbles generated from the bottom of the flow channel: Generally, they are on the lower surface of the glass plate. The bubbles are closed. Even if it is an opening, there are signs of rupture on the edge. The diameter is generally the same, and sometimes the bubble diameter varies depending on the reason.

Reasons: 

① The bottom brick contains more and concentrated metallic iron elements. 

②The brick gap is large and the glass liquid leaks.

③The welding slag scattered during installation is not cleaned up. 

④ Metal or bricks are bonded to the surface of the bottom brick. 

Solution :

① Reduce the temperature of the runner. 

② Remove foreign matter. Glauber's salt falling from the upper space of the runner or bubbles generated by the runner gate: The bubbles caused by falling mirabilite from the upper space are usually accompanied by impurities on the upper surface of the glass, which are striped on the surface of the glass plate. 

Generally, it can disappear in a short time; the gate bubble of the runner generally exists on the upper surface of the glass, in a dot-dash line shape, and regularly spaced. Generally caused by cracks at the lower edge of the gate.

Another Solution: 

① Reduce the temperature of the runner. 

② Stabilize the pressure of the cooling part and control it at a pressure lower than the tin bath pressure. 

③ Increase the amount of protective gas for tin bath zero shells. 

④ Seal the gap of the runner. 

⑤ Replace the runner gate. 

⑥ Strictly control the SO2 in the glass composition.


7. Tin Bath Bubble

The bubbles generated by the bricks at the bottom of the bath generally occur in the high-temperature area of the tin bath of the newly put into production float line. The position of the bubbles can be observed through the observation window of the tin bath. The air-saturation presents an opening on the lower surface of the original glass plate, the opening is larger, the depth is shallow, and the macroscopic deformation is obvious.

Reasons: 

① The bricks at the bottom of the tank are wet and have high moisture content. 

② The porosity of the bricks at the bottom of the groove is too high. 

③ Tin bath kiln heating stageSection, the water in the bottom brick is not drained. 

④ Exhaust gas in the brick joints or bottom brick bolt holes. 

⑤ When installing, the remaining metal and tin co-dissolve to produce gas.

Solution: 

Drill a hole with a diameter of 10 mm on the bottom shell steel plate where the bottom bubble is generated. Generally, a hole with a depth of 30 mm and a tapered wire is required to drill the bottom brick. And use copper pipe to lead out and connect with the vacuum pump. The number of holes depends on the number of bubble sources.

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