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Float Glass Reduce The Amount Of Bubbles In The Glass

The main characteristic of Float Glass is Fe2O3 lower, below 0.015% (150 × 10-6), so the raw material type, chemical composition, particle composition, moisture content, weighing accuracy and so have strict requirements, and in the process On the strict control of the introduction of mechanical iron.

Development of raw material standards and control requirements

Each batch of feed before the sample inspection, the composition, size and moisture to detect, to ensure the use of qualified raw materials.

Strengthen control, reduce secondary pollution

As the Float Glass raw materials are highly susceptible to pollution, should strictly strengthen the feed and delivery system control, to prevent secondary pollution.

(1) try to use tons of bags of packaging, to achieve convenient handling, flexible purpose. Raw materials susceptible to pollution, sandstone powder larger, can be used in bulk, should be in the transport vehicle around the car and lining the bottom of the PE board or use stainless steel lining or regular painting to reduce pollution. Turn the sandstone powder forklift car dedicated, as far as possible to reduce the chance of exposure to iron equipment.

(2) in the process of conveying production lines, the powder library, silos, hoists, mixers and other equipment for the transformation of the inner wall and floor, lined with polymer polyethylene plate.

(3) broken glass system. The crushed glass silo and the feeder lined with a high molecular weight polyethylene plate and used as much as possible in the key parts of the mixture conveyor belt and the broken glass feeding system as high as possible with high strength iron remover or suspended AC electromagnetic disc , The effective removal of iron impurities.

Through the effective iron removal measures, the secondary pollution content of the batching process can be controlled at 0.0015% ~ 0.002%, and the content of Fe2O3 in the batch can be controlled within the range of 0.013%, which has satisfied the industrial production demand of ultra white float glass.

Production of ultra-white float glass, the main problem is the clarification of glass. Float Glass in the low iron content, high thermal conductivity, is 3 to 4 times the ordinary glass, which is ultra-white float glass melting brought great problems, glass clarification difficult, easy to discharge bubbles: ① because of low iron content , Resulting in ultra-white float glass heat permeability is good, high temperature glass, low viscosity, convection in the horizontal direction of strength, into a circular flow in the clear area to stay short time. ② Because the iron content is low, the vertical temperature gradient in the deep direction of the whole pool is obviously smaller than that of the ordinary float glass. The bottom temperature is about 6% higher than that of the ordinary float glass, and the upper and lower temperature difference of the molten glass is relatively small, Exhaust is more difficult than ordinary float glass. ③ the flow of molten glass below the annular flow in the process of increasing the temperature, making the glass has been absorbed by the micro-bubble in the role of thermochemistry was re-released into the glass, while low-iron glass viscosity Low, micro-bubbles easily rose to the surface flow, resulting in a significant increase in the bubble in the glass. ④ in the natural gas combustion of the whole oxygen furnace, the water vapor content is relatively large, accounting for the flame space gas components in the 1/3 ~ 2/3, and in the glass surface hot spot position the highest, reaching 1/2. Increased moisture content, glass is difficult to clarify, more micro-bubbles.

(1) adjust the heat load

Reduce the heat load of the melting circuit, take 6 pairs of small furnace as an example, reduce the heat load of 1 # ~ 3 # small furnace, improve the heat load of 4 # ~ 5 # small furnace, 6 # small furnace slightly improved, White float glass requirements. Ultra-white float glass liquid permeability is good, making the batch easier to melt, therefore, the melting circuit heat load is reduced. And it is difficult to clarify, in particular, the characteristics of micro-bubbles is not easy to absorb, making the clarification of the corresponding increase in heat load, but the end of the small furnace can not be too high, otherwise the flow of molten glass flow has been glass absorption of microbubbles easy to rise to the surface The formation of secondary bubbles in the stream.

(2) the use of auxiliary measures

Can be used to the bottom of the bubble technology to increase the composite compound in the clarifier, adding defoamers, but also combined with other advanced melt clarification technology to reduce the number of bubbles in the glass.

Ultra - white float glass is easy to mold

(1) the impact of high alkali

Glass mold is the result of the exchange of alkali metal ions R + with external ions. R + content more, the more serious the tendency to mold. Ultra-white float glass alkali metal oxide content of up to 15%, ordinary float glass in about 14%, so ultra-white float glass than ordinary float glass moldy.

(2) the impact of Float Glass divalent metal oxide

Float Glass divalent metal oxide RO reduced, weakened on the alkali metal ions R + suppression, resulting in easy moldy. According to the glass pressing effect theory, the diffusion coefficient of the alkali metal ion R + becomes smaller when a part of SiO in the R O-SiO binary glass is replaced with the divalent metal oxide RO, because the divalent metal ion R2 + is filled in the glass network structure Of the gap, which blocked the alkali metal ions R + diffusion movement, the monovalent alkali metal ions R + produced a repressive effect. In the ordinary float glass, the sum of CaO and MgO is 12% ~ 15% of the glass content, while the ratio of CaO to MgO is about 11% in the ultra white float glass composition. Oxide is reduced. In addition, Float Glass low iron content is also easy to cause mildew, because in the total iron content, about 30% of the iron is in the presence of divalent oxide state. All of these divalent metal oxide reduction of the role of weakening, making high levels of alkali metal ions are relatively active, Float Glass is naturally more moldy.

(3) the effect of thermal historical effects

Dense glass structure, in the face of climate weathering erosion has a strong role in retarding, and vice versa loose glass structure is easy to weather weathering erosion. The formation of a dense glass structure, determined by the thermal history of the glass, is mainly achieved by slow cooling of the forming process and a precise annealing process. As the current domestic float glass production line annealing furnace design is mainly for ordinary float glass, used in the production of Float Glass when the annealing is not accurate. So that the structure of Float Glass is not dense enough, leaving a hidden danger.

Float Glass cold stress value is higher than ordinary float glass 18%. Float Glass due to high radiation through the body, the body absorbs less heat, in the annealing furnace before the heating zone can not be the same as ordinary float glass absorption of heat, the vitreous relatively cold, so that the annealing process to shorten the cooling, resulting in more structural stress residue , Affecting the density of the glass structure.