1,Clarify the reasons for difficulties
The main problem in producing ultra white float glass is the clarification of the glass liquid. Ultra white glass has a low iron content and a high thermal conductivity, which is 3-4 times that of ordinary glass. This poses great challenges for the melting of ultra white float glass, making it difficult for the glass liquid to clear and for bubbles to be easily expelled. ① Due to the low iron content, ultra white float glass has good thermal conductivity, high glass liquid temperature, low viscosity, strong horizontal convection intensity, and short residence time in the clarification zone as a circular flow. ② Due to the low iron content, the vertical temperature gradient in the entire depth direction of the pool is significantly smaller than that of ordinary float glass, and the bottom temperature of the pool is about 6% higher than that of ordinary float glass. The temperature difference between the upper and lower parts of the glass liquid is relatively small, reducing convection and making it more difficult to remove bubbles than ordinary float glass The temperature of the reflux glass liquid below the circular flow continues to rise during the forward process, causing the microbubbles that have already been absorbed by the glass liquid to be re released into the glass liquid under the action of thermochemistry. At the same time, the viscosity of low iron glass liquid is low, and microbubbles are easily lifted into the surface flow, leading to a significant increase in bubbles in the glass liquid In the all oxygen melting furnace of natural gas combustion, the water vapor content is relatively high, accounting for 1/3 to 2/3 of the gas composition in the flame space, and the content is high at the hot spot position of the glass liquid surface, reaching 1/2. As the moisture content increases, the glass liquid becomes difficult to clarify and there are more microbubbles.
2, Solution method
(1) Adjust heat load
Reduce the heat load of the melting circuit. Taking 6 pairs of small furnaces as an example, reduce the heat load of small furnaces 1 # to 3 #, increase the heat load of small furnaces 4 # to 5 #, and slightly increase the heat load of small furnace 6 #. This can meet the requirements of ultra white float glass. The ultra white floating glass liquid has good heat permeability, making the batch material more easily melted, thus reducing the heat load of the melting circuit. And its difficulty in clarification, especially the characteristic that microbubbles are not easily absorbed, increases the heat load of the clarification circuit accordingly. However, the increase cannot be too high for the small furnace, otherwise the microbubbles absorbed by the glass in the reflux glass liquid below the forming flow will easily rise to the surface flow and form secondary bubbles.
(2)Adopting auxiliary measures
Bottom bubbling technology can be used, composite clarifying agents can be added to the mix, defoamers can be added, and other advanced melting clarification technologies should also be combined to reduce the number of bubbles in the glass liquid.