The main characteristic of ultra-white Float Glass is that Fe2O3 is lower than 0.015% (150 × 10-6), so the raw material type, chemical composition, particle composition, moisture content, weighing accuracy and so on have strict requirements, On the strict control of the introduction of mechanical iron.
1.1 to develop 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.
1.2 to strengthen control, reduce secondary pollution
As the ultra-white Float Glass raw materials are highly susceptible to pollution, should strictly strengthen the feed and transport 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. Turnover 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 Float Glass system. The crushed Float 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 Float Glass feeding system as high as possible with high strength iron remover or suspended AC electromagnetic disc separator , 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 of ultra white float Float Glass.
Production of ultra-white float Float Glass, the main problem is the clarification of Float Glass. Ultra-white Float Glass in the low iron content, high thermal conductivity, is 3 to 4 times the ordinary Float Glass, which is ultra-white float Float Glass melting brought great problems, Float Glass clarification difficult, the bubble is not easy to discharge: ① because of low iron content , Resulting in ultra-white float Float Glass heat permeability is good, high temperature Float 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 whole depth of the pool is obviously smaller than that of the ordinary float Float Glass. The bottom temperature is about 6% higher than that of the ordinary float Float Glass, and the upper and lower temperature difference of the molten Float Glass is relatively small, Exhaust is more difficult than ordinary float Float Glass. ③ the flow of molten Float Glass below the annular flow in the process of increasing the temperature, making the Float Glass has been absorbed by the micro-bubble in the role of thermochemistry was re-released into the Float Glass, while low-iron Float Glass liquid viscosity Low, micro-bubbles easily rose to the surface flow, resulting in a significant increase in Float Glass bubbles. 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 Float Glass surface hot spot position the highest, to 1/2. Increased moisture content, Float 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 Float Glass requirements. Ultra-white float Float Glass liquid heat 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 downstream flow of molten Float Glass has been Float Glass absorption of micro-bubbles 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 compound in the compound clarifier, adding defoamers, but also combined with other advanced melt clarification technology to reduce the number of bubbles in the Float Glass.