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The Technological Characteristics Of Three Different Transmission Rates Of Float Glass

As is known to all, normal white glass is mainly used in construction field, and many domestic float line's flagship product, the product features for the glass transmittance between 67% ~ 89% (its value changes over the thickness of the glass), iron content at about 1000 parts per million; The ultra-white glass is an ultra-transparent and low-iron glass, also known as low iron glass and high transparent glass. It is a high quality and versatile new glass, with a rate of more than 91.5 percent, the iron content is generally below 150ppm. Mentioned in this paper, high white glass is a kind of varieties between white and super white glass, transmittance general control between 89.5% ~ 91.5%, iron content control between 200 ~ 400 PPM, its utility is used for processing into arts and crafts glass, satisfy the requirement of market decoration.


1. The process characteristics of three different permeability glass

The process control of different through rate glass variety is determined by its technological characteristics. The following is the comparison of white glass, high white glass and ultra-white glass.

Three through rate is one of the biggest differences between different glass Fe2O3 content is different, and the difference is bigger, white glass's Fe2O3 content is about 8 times that of super white glass, high white glass for 2 ~ 3 times of super white glass. So in three different varieties of transmittance glass when switching to each other, mainly considering the change of Fe2O3 content affect the glass diathermancy, diathermancy different will affect the glass melting heat transfer in the process, can make whole glass melt stove temperature transverse gradient and vertical gradient changes, which will affect the entire pool in furnace glass fluid backflow, which have influence on glass quality. So from a switch to the high white glass, white glass from high white glass switch to the super white glass, according to the different glass through hot make suitable process system and process control process, and modify it in the process of implementation, to get glass melt quality comparison, meet the needs of users.

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2. Control the process of three different kinds of glass through rate glass

During the actual production process, the heat transfer of glass will gradually increase through the switching of the glass with a low rate of glass to the glass. According to the previous report, the thermal conductivity of high white glass and ultra-white glass will be higher, and the heat transfer of the glass solution in the vertical direction of the kiln will be fast, so the temperature of the bottom will rise. But due to the high white glass, ultra white glass transmittance is higher, the radiation coefficient of glass melting stove will reduce, which determines the fuel combustion after the release of heat is absorbed by the glass can have a certain degree of reduce the heat, heat radiation to the furnace body and increases the heat along with flue gas, which creates a diathermancy of the glass, the higher the melting will be more difficult, the unit will be the higher energy consumption of glass; In addition, the higher the transmittance of the glass heating will be better, production will appear at the bottom of glass liquid temperature is higher, leading to higher average temperature of the glass, but the surface of glass liquid temperature is low, glass in the horizontal direction on convection strength increase, processing circulation in the clarification section residence time is shorter, most likely there will be a bad glass clarification. For three different kinds of transmittance of glass at the same time, the vertical temperature gradient in the direction of the deep pool and viscosity of the size of the order for white glass, high white glass, ultra white glass, glass liquid temperature decreases from top to bottom, convection will also corresponding reduced, air bubble discharge ease have greatly different. 's white glass due to the temperature gradient is bigger, up and down, in contrast, bubble discharge is the most easy, super white glass because of diathermancy, upper and lower temperature gradient is small, the bubble discharge is difficult, high white glass bubble discharge between white and high white glass, thus high white glass, ultra white glass production must first solve the problem is clear.

Above we analyzed the essence of the difference between three different transmittance glass, therefore in the process of practical production, the above three different transmittance glass when switching between varieties, making reasonable based on its technological characteristics of process control system, the following is from the production of white products to switch to high or super white white products process control process: (1) the rate of broken glass: the current yield when the float line in the production of white glass is generally higher, so the back glass is less, the general white glass production line's broken glass rate is around 10%, but in the high white glass, ultra white glass when switching, and clarify the differences due to absorption of heat, in order to produce high quality glass, so will broken glass rate up to a certain degree, broken glass, generally up to 20 ~ 30%, is helpful to enhance the glass melting process and clarification. (2) the melting process of heat load adjustment: the production of high white, super white glass when the glass clarification is mainly to solve the problem, so to reduce 1 #, 2 #, 3 # small furnace heat load, increase clarify loop 4 #, 5 #, 6 # small furnace heat load, but for a small furnace heat load at the end of the don't add too much, otherwise the shape of flow back glass has been absorbed by glass micro air bubble is easy to cause secondary air bubbles rise to the surface flow, at the same time, it is likely to exacerbate the bottom refractory erosion, separation bubble produce refractory materials. (3) furnace related auxiliary equipment adjustment: one is from general white when switching to high white and super white products, need to add more CARDS neck deep water bag into the depth of the glass, strengthen the clarification of glass to the hot glass liquid to flow, to clarify the temperature ascension, is good for micro air bubble discharge; Second, try not to use the card neck agitator, which can effectively prevent the occurrence of secondary bubbles; Third, the bubbler can be adjusted appropriately to enhance the convection of glass fluid in the vertical direction of the furnace and accelerate the discharge of air bubbles. (4) optimization of furnace process: one is to optimize the flame, including the rigid and Angle of flame; The second is the adjustment of the ratio of the ratio of mirabilite and carbon powder. The third is to adjust the atmosphere of oxidation reduction of each furnace. Fourth, adaptive adjustment to the thermal expansion coefficient of glass; Adjustment of material thickness.


3. Three kinds of glass switch production cases with different rate

An ultra clear float line according to the needs of the market, domestic demand in a certain cycle in manufacturing high white, white, white three different varieties of transmittance glass, the following is from a refueling high white glass, white glass last switch changes of the super white glass tank furnace process:

From a white material gradually switch to a high white material, the switch to the ultra white material, and the bottom temperature of 30 ~ 50 ℃, this is due to the three kinds of glass formed through rate there is a difference; With the different thermal properties of the glass, the thermal load of each furnace was adjusted to improve the ability of the glass to clarify and reduce the incidence of bubbles. Can be seen from the figure 1, the production of high transmittance of the glass, when the species number of micro bubbles per unit area showed a trend of increase, this is because the temperature difference is relatively small, up and down of glass bubble discharge of float glass is more difficult than the ordinary. For forming into square backflow glass in advance in the process of temperature rising, making the already absorbed by glass micro bubbles in under the action of thermal chemical is released back into the glass, low iron glass liquid viscosity is lower at the same time, the micro bubbles to rise to the surface flow, thus forming bubbles. Therefore, to improve the production quality of high white and ultra-white glass, it is necessary to set reasonable process control parameters according to its technological characteristics.

's white, white and white three kinds of high transmittance of different glass production, the higher the transmittance of the glass in the melting furnace convection strength on the horizontal direction is larger, the smaller the vertical temperature gradient, viscosity, compared with the ordinary float glass production, molten loop heat load due to lower,, and clarify the circuit must be properly heat load increases, but at the end of small furnace can not too high, at the same time to ensure that its strong oxidizing atmosphere, so as to effectively control the bubble risk, to produce high-quality high-grade building glass products.