The glass melting furnace generally uses air as the combustion-supporting gas, and the oxygen content in the air is only 21%. The remaining 78% of the nitrogen is inefficiently heated during the glass melting process and discharged from the kiln at high temperature, resulting in a lot of energy waste. This part of the heat loss accounts for more than 20% of the energy consumption, and N2 reacts with O2 at high temperatures to generate NOx gas. The discharge of NOx gas into the atmosphere will cause serious environmental pollution. In order to solve these problems caused by air combustion, oxy-fuel combustion technology has gradually attracted the attention and attention of various countries. After years of theoretical research and actual production, it has been discovered that the oxyfuel combustion technology has many advantages, but there are also some disadvantages, such as glass is prone to mold, and deep processing is prone to tempered rainbow.
Aiming at the problem of tempered rainbow after the deep processing of the glass produced by the oxy-fuel production line, this article compares the change in the amount of tin infiltration on the lower surface of the glass produced by the air-combustion glass melting furnace and the glass produced by the oxygen-fired glass melting furnace and the distribution of tin infiltration on the lower surface with depth Analyze the characteristics of tin infiltration on the lower surface of the glass on the oxy-fuel production line to provide a theoretical basis for industrial production.
1. Experiment and discussion
1.1 The change of tin infiltration rate of oxy-fuel glass
X-ray fluorescence analyzer (XRF) is a universally applicable material component analysis instrument that can efficiently analyze the amount of tin in the glass. In this experiment, it is determined that the SnL line system is selected for the tin element, and the sample is analyzed with the ZSX Primus Ⅱ X-ray fluorescence spectrometer under the conditions of accelerating voltage of 50 kV and accelerating current of 50 mA. The sample preparation method is to directly cut the original glass sheet to be tested into the size of the sample box and place it on the instrument for measurement. The tin count measured by XRF and the tin penetration value measured by spectrophotometry are curve-fitted to obtain the tin penetration amount.
Choose two float production lines of a domestic company, one is ordinary float, the other is full oxy-combustion float, both production lines have the same tin bath protective gas, bath pressure, and molding temperature system. Five groups of glass samples with the same thickness and the same production parameters were selected from the two production lines, and the amount of tin penetration on the lower surface of the samples was tested with an X-ray fluorescence analyzer. For the same thickness of glass, the amount of tin infiltration on the lower surface produced by the oxy-combustion process is greater than that of ordinary float glass, and the difference between the two increases as the thickness of the glass increases.
1.2 The variation of tin penetration of oxy-fuel glass with depth distribution
The Electron Probe Microscope (EPMA) uses a finely focused electron beam to enter the sample surface for qualitative and quantitative analysis of the micro-area components on the sample surface. It can also analyze the surface, line and point distribution of elements on the sample surface. In this experiment, the JXA-8230 electronic probe is used to test the sample under the conditions of an accelerating voltage of 20 kV and a beam current of 2.005 A. In the smooth section of the sample, starting from the lower surface of the sample, go to the depth direction of the sample at intervals of 0.1 mm A pop scan was performed to analyze the intensity of tin elements until the scanning was stopped at 25 mm. The spectrum showed the curve of the distribution of tin elements on the lower surface of the sample with depth.
The characteristics of the distribution of tin penetration with depth on the lower surface of the two types of float glass are basically the same, but the amount of tin penetration on the lower surface of the all-oxygen combustion float glass is higher than that of ordinary float glass, and the tin penetration depth is greater than that of ordinary float glass. The above X-ray fluorescence analysis results are consistent.
1.3 Discussion
Oxygen combustion is a new technology for melting float glass. It replaces air with pure oxygen as the combustion-supporting medium, which greatly reduces the introduction of ineffective nitrogen in the air, and has significant energy-saving and emission reduction effects. At the same time, oxygen combustion is produced in the glass melting furnace. The water vapor partial pressure is as high as 50%～55%, which makes the water content of the glass produced by the oxy-fuel combustion process reach (450～650)×10-6, while the water content of ordinary air combustion process glass is (200～300)×10- 6. Dai Zhixiang, Duan Qiutong, etc. used infrared spectroscopy to test the water content of the glass. The test results showed that the water content of the all-oxygen combustion float glass was 475×10-6 while the water content of ordinary float glass was about 300×10-6. The effects of high water content in oxy-combustion float glass on tin infiltration include:
(1) During the forming process of oxy-fuel float glass, the glass will undergo dehydroxylation reaction. After the water vapor enters the tin bath, it will weaken the protective gas effect, increase the pollution of tin, and increase the penetration and diffusion depth of tin. .
(2) Oxygen-fired float glass contains more hydroxyl groups, the ionic spacing becomes larger, and the anionic group's force on the cations is reduced, resulting in an intensified ion exchange reaction between the glass and the tin liquid contact surface.
(3) The effect of water entering the glass melt on its structure is similar to the effect of network outer body oxides such as Na2O. Water breaks the Si-O-Si bond in the silicate glass, which is equivalent to depolymerization. As a result, the ratio of Si tetrahedral coordination groups in the glass mesh body and the asymmetry of the short-range structure have changed, the viscosity of the glass becomes smaller, and the diffusion resistance of tin becomes smaller, which leads to an increase in the penetration amount and diffusion depth of tin.
2 Conclusion
(1) The amount of tin penetration on the lower surface of oxy-fuel float glass is higher than that of ordinary float glass, and the thicker the glass, the higher the amount of tin penetration; the depth of tin penetration of oxy-fuel float glass is also greater than that of ordinary float glass .
(2) The reason for the high tin penetration rate and tin penetration depth on the lower surface of the oxy-fuel float glass is mainly due to the high water content in the oxy-fuel float glass. Therefore, when using the oxy-fuel melting technology, more attention must be paid to the tin bath For pollution problems, minimize the oxidation of tin in order to control the amount of tin infiltration of glass more effectively....
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