Summary of energy-saving methods for glass furnaces

Glass factories are big energy consumers. The main energy-consuming part of the glass factory is the glass furnace (which consumes more than 75% of the total energy). Therefore, it is imperative to pay close attention to the energy saving of glass furnaces. In the past few years, we have taken many energy-saving measures in the aspects of glass frit, feeding system, combustion system, furnace structure, kiln body insulation, waste heat utilization, and operation control, and achieved great results. The fuel consumption indicators of many plants have dropped significantly. Some factories have reached the level of first-class or special-class furnaces. But compared with foreign countries, there is still a big gap... So we have to work hard to further reduce energy consumption. Several energy saving approaches are proposed below:

 

First, increase the glass temperature without increasing the flame temperature


After the temperature of the molten glass is increased, the melting speed and the melting time can be shortened, which also increases the output and reduces the unit consumption. The specific method is:


(1) Increase the radiant heat of the flame space to the molten glass.


1. Liquid glass selectively absorbs radiant energy. Wavelengths less than 3 microns can pass through the liquid surface downward. It is the carbon particles in the flame and the inner wall surface of the kiln space that can emit radiant energy with a wavelength of less than 3 microns. Therefore, increase the blackness of the flame (by hypoxia heat medium or carbon increase measures) and maintain a high blackness value of the kiln masonry (related to the roughness and temperature of the masonry surface. The blackness of clay bricks and silica bricks at high temperatures Degree values are: 0.61-0.62 at 1000°C, 0.52-0.53 at 1200°C, 0.47-0.49 at 1400°C. The blackness value of fused refractory bricks at high temperatures is 0.4-0.5), which can increase the flame space’s resistance to molten glass Radiant heat.


2. Eliminate the "cold air" film near the liquid level. Pay attention to the height of the bottom of the small furnace from the liquid surface and the angle of flame spraying. It is also possible to consider the use of oxygen blowing to boost the flux (after blowing in oxygen at a speed of 195-500 m/s abroad, the heat transfer rate is accelerated, and the flame temperature near the liquid level is increased by about 100°C).


(2) Improve the temperature or temperature uniformity of the molten glass in the kiln.


The idea is to increase the heat transfer of the flame to the molten glass by reducing the liquid surface temperature. While the temperature of the liquid surface is lowered, the uniformity of the temperature of the glass in the depth of the pool is also improved. The measures taken to realize the above viewpoints are: 1. Bubbling at the bottom of the pool (pay attention to the purification of the bubbling medium and the erosion of the bubbling bricks). 2. Deepen the pool. The convection in the vertical direction can be intensified, and the uniformity of the temperature of the molten glass on the pool depth is improved. At the same time, it also adapts to the increase of melting rate. 3. Kiln body insulation. 4. Electric boosting.


Second, the shallow layer is clarified, the deep layer is taken, and the liquid flow is controlled to flow in a single channel direct current direction


This is from the viewpoint of increasing the temperature of the molten glass in the clarification zone, reducing backflow and selecting high-quality molten glass into the flow hole. In this way, the output and quality of molten glass can be improved and the loss of refluxing molten glass can be reduced. The measures taken to realize the above point of view are: set short and wide kiln ridges to reduce the sinking liquid cave below the clarification tank (the dark material may not sink when melting the dark material).


Third, strengthen homogenization


Most factories report that homogenization is a key process affecting product quality. At present, the homogenization process is basically in a state of "congenital deficiency and acquired disorder". It is difficult to maintain the uniformity of the batch after entering the kiln, resulting in uneven composition. The heat permeability of the molten glass and the heat dissipation from the kiln to the surroundings caused uneven temperature. Relying solely on natural diffusion for homogenization is obviously not enough. For this reason, mandatory homogenization measures must be taken. The current effective measures include: low bubbling in the pool (most obvious for dark materials), mixing in the material channel, discharge of the working material or the bottom of the material channel (with leakage holes) and electric heating of the material channel. When mixing measures are used, Pay attention to the insertion depth of the stirrer at the stirring point and the stirring process, otherwise the desired effect will not be obtained. The material of the domestic stirrer is an urgent problem to be solved. The surface liquid flow can not only strengthen the lateral flow and improve the temperature uniformity, but also pull away the liquid level. Dirty materials and crusts. The size of the ear delay should be appropriate, so as not to cause too much heat loss. The discharge can be continuous or intermittent. Electric heating can obviously improve the temperature uniformity in the depth direction of the forehearth pool, but the temperature distribution on the horizontal surface may not always be improved. The shape of the electrode, the determination of the resistance of the liquid glass between the electrical bases and the method of electrode adjustment, installation and maintenance are issues that need to be paid attention to when heating. While adopting compulsory homogenization measures, it is still necessary to give full play to the role of natural diffusion. Therefore, the size of the work section and the length of the feed channel should be carefully considered in the design.


Fourth, stable supply


The stability of the shape, size and temperature of the gob is the prerequisite to ensure the quality and output of the molding. The degree of separation between the forehearth and the working part, as well as the cross-section, size, heat preservation, heating system and cooling system of the forehearth are the main factors affecting the stable feeding. The full separation between the forehearth and the working parts enables the forehearth to maintain an independent operation system without interference. Some factories do not need to be completely separated, and the method of heating the forehearth by the heat of the melting part is questionable. The saddle-shaped cross section of the bottom of the forehearth can reduce the lateral temperature difference. Properly deepening the material bowl can increase the static pressure head and make the temperature of the material drop more stable. The length and width of the material channel should be determined according to the flow volume and output. A longer material channel is beneficial to temperature adjustment and can adapt to changes in flow volume in a larger range. The heat dissipation of the material channel is large, especially at the material bowl. Therefore, heat preservation must be strengthened. The heating and cooling system should be able to adjust the temperature of the molten glass flexibly and reliably, and maintain the uniformity of the temperature. The cooling system plays the role of coarse adjustment, and the heating system plays the role of fine adjustment. Most people think that a system that combines multi-nozzle gas heating and electric heating is ideal.


Fifth, reduce useless heat


(1) Reduce unusable heat, such as heat dissipation on the surface of the kiln body, radiant heat from the orifice, and heat carried away by the gas escaping from the orifice and brick joints. The measures taken are: 1. Kiln body insulation. my country has adopted kiln body insulation for several years and has achieved remarkable results. But it is only the initial stage, and the heat preservation effect can be further improved. The direction is to develop a multi-layer combined thermal insulation layer, use composite (such as sandwich type, filling type) thermal insulation materials, develop bulk concrete thermal insulation materials, and develop sealing materials matching various refractory materials. 2. The sealing of the orifice and the brick joint. Pay attention to the feeding port, temperature measuring hole, fire hole and so on. If conditions permit, use a fully enclosed feeder (such as screw type, wrap-in type), use corundum embedded tube to measure temperature, and use industrial TV to observe flame and chemical conditions. 3. Large-scale kiln. The larger the kiln scale, the lower the heat dissipation per unit output.


(2) Reduce the heat of repeated heating. The main purpose is to reduce the heat consumed by repeated heating of the refluxed molten glass (usually, this heat accounts for about one-tenth of the heat consumed by glass melting). The measures taken are: setting up kiln sills, sinking the flow hole, appropriately reducing the height of the flow hole and appropriately reducing the temperature of the molten glass in the flow hole.


Sixth, use available heat


(1) The fuel must be fully burned to release all the heat. For this reason, when burning oil, it is necessary to choose an oil nozzle with good atomization effect (such as domestic GNB internal mixing nozzle and imported machinery from Japan, the United States, and West Germany—medium atomization composite nozzle), and use enhanced mist The design of the small furnace structure and the height of the parapet wall matched with the nozzle. When burning gas, determine the appropriate momentum ratio between air and gas, and make air surround the gas.


(2) Improve heat exchange efficiency and increase the air preheating temperature as much as possible. For this reason, it is necessary to increase the heated surface area of checker bricks, adopt higher lattice bodies, and adopt novel checker bricks and their arrangements (such as cross-shaped and cylindrical bricks). , Arranged into basket weave or chimney). The material of checker bricks and the uniformity of airflow distribution in the grid should also be studied (the uniformity of airflow distribution is directly related to the utilization of checker bricks. The factors affecting the uniformity of the distribution are the construction coefficient of the grid body, the upper and lower channel volume of the grid body and the grid body Volume ratio, etc.).


(3) Utilization of flue gas waste heat. The heat carried by the flue gas discharged from the regenerator should be recovered as far as possible under allowable conditions. Many factories install waste heat boilers in the flue system. Individual factories have also installed heat pipes to recover heat. In addition, how to use the waste heat of flue gas to heat and even sinter batch materials should be studied.


Seventh, change the material side and batch spheroidization


(1) Incorporating a small amount of fluxing components in the material side, such as lepidolite, can lower the melting temperature of the glass and accelerate the melting of the glass. The output volume has increased significantly.


(2) Spheroidization of batch materials. Batch shaping treatment is a subject of concern to everyone. We advocate dry spheroidization. The batch material is pressed into small pellets without the addition of binder. It can eliminate the dust inside and outside the kiln, accelerate the solid phase reaction, and increase the contact area between the batch material and the molten glass. In this way, the melting time can be shortened and the furnace age can be extended, and the unit heat consumption is also reduced.


Eighth, the use of high-quality refractory materials and reasonable matching


It is currently recognized that various high-quality and durable refractory materials (such as fused refractories, zirconium, chromium, corundum, spinel and alkaline refractories, high-density, high-strength refractories, etc.) must be used and reasonable Matching, so that the overall service life of the kiln increases simultaneously. As we all know, the quality of furnace building materials has an important influence on kiln output, glass quality, fuel consumption and furnace age. Compared with foreign countries, there is still a considerable gap in the varieties, specifications and quality of refractory materials used in glass furnaces in my country. It is urgent to change this situation. We should also expand the use of high-quality refractory materials. From a long-term point of view, it is worthwhile to spend more on refractory materials. Energy-saving of glass kilns involves a wide range of areas and requires the cooperation and joint efforts of multiple parties to achieve results.