Glass kilns are the main energy-consuming part in glass factories (its energy consumption accounts for more than 75% of the total energy consumption). Therefore, energy saving in glass kilns is very important. In recent years, enterprises have taken many energy-saving measures in terms of glass material, feeding system, combustion system, kiln structure, kiln insulation, waste heat utilization, operation control, etc., and the effect is quite good. But compared with foreign countries, the gap is still not small. Hongtai Refractory Materials Company, as a well-known domestic glass kiln construction, glass refractory material production and supplier, has summarized some experiences on glass kiln energy saving, and shares the following with you:
First, increase the temperature of glass liquid without increasing the flame temperature
When the temperature of glass liquid is increased, the melting speed can be accelerated and the melting time can be shortened, which increases the output and reduces the unit consumption. The specific method is:
(I) Increase the radiant heat of the flame space to the glass liquid.
1. Glass liquid selectively absorbs radiation energy. Wavelengths less than 3 microns can be transmitted downward through the liquid surface. The carbon particles in the flame and the inner wall surface of the kiln space can spray radiation energy with a wavelength less than 3 microns. Therefore, increasing the flame blackness (by means of oxygen-deficient heat medium or carbon-increasing measures) and maintaining a high blackness value of the kiln masonry (related to the roughness and temperature of the masonry surface. The blackness values of clay bricks and silica bricks at high temperatures are: 0.61-0.62 at 1000°C, 0.52-0.53 at 1200°C, and 0.47-0.49 at 1400°C. The blackness value of fused refractory bricks at high temperatures is 0.4-0.5) can increase the radiation heat of the flame space to the glass liquid.
2. Eliminate the "cold air" film near the liquid surface. Pay attention to the height of the small furnace bottom plate from the liquid surface and the flame ejection angle. You can also consider using oxygen blowing to assist melting (after blowing oxygen at a speed of 195-500 m/s abroad, the heat transfer speed is accelerated, and the flame temperature near the liquid surface is increased by about 100°C).
(II) Increase the temperature or temperature uniformity of the glass liquid in the kiln pool.
The view is to increase the heat transfer of the flame to the glass liquid by lowering the liquid surface temperature. When the temperature of the liquid surface is reduced, the uniformity of the temperature of the glass liquid in the depth direction of the pool is also improved. The measures taken to achieve the above viewpoint are: 1. Bubble the pool bottom (pay attention to the purification of the bubbling medium and the erosion of the bubbling bricks). 2. Deepen the pool. It can intensify the vertical convection and improve the uniformity of the temperature of the glass liquid in the pool depth. At the same time, it also adapts to the increase in melting rate. 3. Insulate the kiln body. 4. Electric melting.
Second, shallow clarification, deep material collection, control the liquid flow to flow in a single-channel direct current direction
This is based on the viewpoint of increasing the temperature of the glass liquid in the clarification area, reducing reflux and selecting high-quality glass liquid to flow into the liquid hole. This can increase the output and quality of the glass liquid and reduce the loss of reflux glass liquid. The measures taken to achieve the above viewpoint are: set up a short and wide kiln sill to reduce the sinking liquid hole below the shallow clarification pool (it can not sink when melting dark materials).
Third, strengthen homogenization
Most factories reflect that homogenization is a key process affecting product quality. At present, the homogenization process is basically in a state of "congenital deficiency and acquired imbalance". It is difficult to maintain the uniformity of the mixture after entering the kiln, resulting in uneven composition. The thermal permeability of the glass liquid and the heat dissipation of the kiln to the surroundings cause uneven temperature. It is obviously not enough to rely solely on natural diffusion for homogenization. For this reason, forced homogenization measures must be taken. The current effective measures are: bubbling at the bottom of the pool (most obvious for dark materials), stirring of the material channel, discharge of working materials or the bottom of the material channel (with leakage holes) and electric heating of the material channel. When using stirring measures, attention should be paid to the insertion depth of the stirrer at the stirring point and the stirring process, otherwise the ideal effect will not be achieved. The material of domestic stirrers 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 dirty material and crust on the liquid surface. The size of the ear should be appropriate, not causing too much heat loss, and the discharge can be continuous or intermittent. Electric heating can significantly improve the temperature uniformity in the depth direction of the material channel pool, but the temperature distribution of the material to the horizontal surface may not necessarily improve. The electrode shape, the determination of the resistance of the glass liquid between the electrodes, and the methods of electrode adjustment, installation, and maintenance are issues that need to be paid attention to when heating. While taking forced homogenization measures, the role of natural diffusion should still be fully utilized. Therefore, the size of the working part and the length of the feed channel should be carefully considered in the design.
Fourth, stable feeding
The stability of the shape, size, and temperature of the droplet is the prerequisite for ensuring the molding quality and output. The degree of separation between the feed channel and the working part, as well as the cross-section, size, insulation, heating system, and cooling system of the feed channel are the main factors affecting stable feeding. The full separation between the feed channel and the working part can keep the feed channel in an independent operating system without interference. Some factories do not use full separation, and the practice of heating the feed channel with the heat of the melting part is questionable. The cross-section of the bottom of the feed channel is saddle-shaped, which can reduce the lateral temperature difference. Appropriately deepening the material basin can increase the static pressure head and make the droplet temperature more stable. The length and width of the feed channel should be determined according to the flow rate and output size. A longer feed channel is beneficial to adjusting the temperature and can adapt to changes in the flow rate within a larger range. The heat dissipation of the material channel is very large, especially in the material basin. Therefore, it is necessary to strengthen the insulation. The heating and cooling systems should be able to adjust the temperature of the glass liquid flexibly and reliably, and maintain the temperature uniformity. The cooling system plays a rough adjustment role, and the heating system plays a fine adjustment role. Most people believe that the system combining multi-nozzle gas heating and electric heating is ideal.
Fifth, reduce useless heat
(I) Reduce the heat that cannot be used, such as the heat dissipation of the kiln surface, the radiation heat of the orifice, and the heat taken away by the gas escaping from the orifice and brick joints. The measures taken are: 1. Kiln insulation. my country has adopted kiln insulation for several years with remarkable results. But it is only in the initial stage, and the insulation effect can be further improved. The direction is to develop a multi-layer combined insulation layer, use composite (such as sandwich type, filling type) insulation materials, develop bulk concrete insulation materials, and develop sealing materials that match various refractory materials. 2. Sealing of orifices and brick joints. Attention should be paid to the feeding port, temperature measuring hole, fire viewing hole, etc. If conditions permit, a fully enclosed feeder (such as spiral type, wrap-in type) should be selected, and a corundum embedded tube should be used to measure temperature, and industrial television should be used to observe the flame and the material. 3. Large-scale kiln. The larger the kiln scale, the lower the heat dissipation per unit output.
(ii) Reduce the heat of repeated heating. The main purpose is to reduce the heat consumed by repeated heating of the refluxed glass liquid (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 glass liquid entering the flow hole.
Sixth, use available heat
(i) The fuel should be fully burned to release all the heat. For this reason, when burning oil, choose an oil nozzle with good atomization effect (such as the domestic GNB type internal mixing nozzle and the imported mechanical-medium atomization composite nozzle from Japan, the United States, and West Germany), adopt measures to enhance atomization, and design a small furnace structure and breast wall height that match the nozzle. When burning coal gas, it is necessary to determine the appropriate momentum ratio of air and coal gas, and make the air surround the coal gas.
(ii) Improve the heat exchange efficiency and increase the air preheating temperature as much as possible. To this end, it is necessary to increase the heating surface area of the checker bricks, use higher checker bodies, and use novel checker bricks and their arrangement methods (such as cross-shaped and cylindrical bricks, arranged in a basket or chimney style). It is also necessary to study the checker brick material and the uniformity of the air flow distribution in the checker body (the uniformity of air flow distribution is directly related to the utilization rate of the checker bricks. Factors affecting the distribution uniformity include the construction coefficient of the checker body, the ratio of the upper and lower channel volumes of the checker body to the volume of the checker body, etc.).
(iii) Utilization of flue gas waste heat. The heat carried by the flue gas discharged from the heat storage chamber should be recovered as much as possible under permitted conditions. Many factories set up waste heat boilers in the flue system. Some factories also installed heat pipes to recover heat. In addition, it should be studied how to use the flue gas waste heat to heat or even sinter the batch materials.
Seventh, change the recipe and spheroidization of the batch
(i) Adding a small amount of fluxing components such as lithium mica to the recipe can reduce the melting temperature of the glass and accelerate the melting of the glass. The output is significantly increased.
(ii) Spheroidization of the batch. The shaping treatment of the batch is a topic of concern to everyone. We advocate the use of dry spheroidization. The batch is pressed into small pellets without adding a binder. It can eliminate dust inside and outside the kiln, accelerate solid-phase reaction, and increase the contact area between the batch and the glass liquid. In this way, the melting time can be shortened and the furnace life can be extended, and the unit heat consumption will also be reduced.
Eighth, use high-quality refractory materials and reasonably match them
It is currently recognized that various high-quality and durable refractory materials (such as capacitor refractory materials, zirconium, chromium, corundum, spinel and alkaline refractory materials, high-density, high-strength refractory materials, etc.) must be used and reasonably matched to increase the overall service life of the kiln. It is well known that the quality of the furnace materials is crucial to the impact of kiln output, glass quality, fuel consumption and furnace life. Compared with foreign countries, there is still a considerable gap in the variety, specifications and quality of refractory materials used in glass kilns 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 perspective, it is worth spending more on refractory materials. Energy saving in glass kilns involves a wide range of aspects and requires cooperation and joint efforts from multiple parties to achieve results.
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