Sometimes the production of float glass will be due to a variety of reasons for the float glass bubble, then the current topic we discuss how to deal with float glass bubble.
Float glass melting furnace and other flat glass melting furnace compared to the structure is not much difference, is a shallow pool of horizontal flame pool kiln, but the scale said that the size of float glass melting furnace is much larger, the current world Float glass melting furnace melting up to a maximum of 1100t or more (usually 1000t / d said). Float glass furnaces and other flat glass furnaces are different, but their structures are in common. Float glass furnace structure includes: feeding system, melting system, heat supply system, waste heat utilization system, exhaust gas supply system.
The main characteristic of ultra-white 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 ultra-white 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. Ultra-white 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, or the flow of molten glass below the flow of glass has been absorbed by the micro-bubbles rose 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.