The most energy-consuming part of glass production equipment is the glass kiln, which accounts for more than 75% of the total energy consumption of glass production. How to reduce the energy consumption of glass kilns has become the key to energy saving in glass production. The following are 8 methods that can help glass kilns save energy well.
Part 01: Increase the temperature of the glass liquid without increasing the flame temperature
When the temperature of the glass liquid is increased, the melting speed can be accelerated and the melting time can be shortened, which will increase the output and reduce the unit consumption. The specific methods are:
(1) Increase the radiant heat of the flame space to the glass liquid.
① The glass liquid selectively absorbs radiation energy, and the wavelength 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 eject radiation energy with a wavelength less than 3 microns. Therefore, increasing the blackness of the flame and maintaining a high blackness value of the kiln masonry can increase the radiant heat of the flame space to the glass liquid. The blackness value is related to the roughness and temperature of the masonry surface. The blackness of clay bricks and silica bricks at high temperatures is: 0.61-0.62 at 1000℃, 0.52-0.53 at 1200℃, and 0.47-0.49 at 1400℃. The blackness of fused refractory bricks at high temperatures is 0.4-0.5.
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, that is, blowing oxygen at a speed of 195-500 meters per second to speed up the heat transfer rate and increase the flame temperature near the liquid surface by about 100℃.
Part 02: 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 liquid surface temperature is lowered, the uniformity of the glass liquid temperature in the depth direction of the pool is also improved. The measures taken to achieve the above view 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.
②Deepen the pool. It can intensify the vertical convection, improve the uniformity of the glass liquid temperature on the pool depth, and also adapt to the increase of the melting rate.
③Kiln insulation. High-quality silica bricks must be used, and the insulation layer in contact with the silica bricks must be made of silica insulation bricks to avoid contact reaction at the high-temperature interface. At the same time, the tightness of the brick joints must be ensured. The silica refractory mud cannot contain clay or other debris.
④Electric melting. With the help of electrodes, electrical energy is directly sent into the glass pool kiln heated by fuel to supplement part of the heat required for melting and improve the melting rate and quality of the glass liquid.
Shallow clarification, deep material collection, control the liquid flow to flow in a single-channel direct current direction
This is based on increasing the temperature of the glass liquid in the clarification area, reducing reflux and selecting high-quality glass liquid inflow holes. This can increase the output and quality of glass liquid and reduce the loss of reflux glass liquid. To achieve the above-mentioned measures, the following are required: set up a low and wide kiln sill to reduce the sinking flow hole under the clarification tank, so that dark materials can be melted without sinking.
Part 03: Strengthen homogenization
Homogenization is a key process that affects 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 mixed materials 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, stirring of the material channel, discharge of the working material or the bottom of the material channel, and electric heating of the material channel. When using stirring measures, pay attention to the position of the stirring point, the insertion depth of the stirrer and the stirring process, otherwise the ideal effect will not be achieved.
The material of the 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 dirty materials and crust on the liquid surface. The size of the agitator should be appropriate and should not cause too much heat loss. The discharge can be continuous or intermittent. Electric heating can significantly improve the temperature uniformity in the depth direction of the channel pool, but the temperature distribution on the horizontal surface of the channel may not necessarily improve. The electrode shape, the determination of the glass liquid resistance between the electrode base and the method 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.
Part 04: Stable feeding
The stability of the shape, size and temperature of the feed channel is the premise 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 parts can keep the channel in an independent operating system without interference.
The cross-section of the bottom of the channel is saddle-shaped, which can reduce the lateral temperature difference. Properly deepening the material basin can increase the static pressure head and make the drop temperature more stable. The length and width of the material channel should be determined according to the flow rate and output. A longer material channel is beneficial for adjusting the temperature and can adapt to changes in the flow rate within a larger range. The heat dissipation of the material channel is large, especially at the material basin. Therefore, insulation should be strengthened. The heating and cooling systems should be able to flexibly and reliably adjust the temperature of the glass liquid and maintain temperature uniformity. The cooling system plays a coarse adjustment role, and the heating system plays a fine adjustment role. A system combining multi-nozzle gas heating and electric heating is ideal.
Part 05: Reducing useless heat
Reducing useless heat includes two aspects:
(1) Reducing unusable heat, such as heat dissipation on the kiln surface, heat radiated from the orifice, and heat carried away by gas escaping from the orifice and brick joints. The measures taken are:
① Kiln insulation. In order to continuously improve the insulation effect. The improvement direction of kiln insulation is to develop a multi-layer composite insulation layer, use composite 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 feeding machine should be selected, and a corundum embedded tube should be used to measure the temperature, and an 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.
(2) Reduce the heat of repeated heating. The main purpose is to reduce the heat consumed by repeated heating of the refluxed glass liquid, which usually accounts for about one-tenth of the heat consumed by glass melting. The measures taken include 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.
Part 06: Utilize available heat
1) The fuel should be fully burned to release all the heat. To this end, when burning oil, choose an oil nozzle with good atomization effect, adopt measures to enhance atomization, and design a small furnace structure and breast wall height that match the nozzle. When burning gas, determine the appropriate air-gas momentum ratio and make the air surround the gas.
(2) Improve 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 basket weaving or chimney styles. It is also necessary to study the uniformity of the checker brick material and the airflow distribution in the checker body.
(3) 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. A waste heat boiler can be set up in the flue system and heat pipes can be installed to recover heat. In addition, it should be studied how to use the flue gas waste heat to heat or even sinter the batch.
Part 07: Change the material formula and spheroidization of the batch
(1) Adding a small amount of fluxing ingredients such as lithium mica powder to the material formula can reduce the melting temperature of the glass, accelerate the melting of the glass, and significantly increase the output.
(2) Spheroidization of the batch. It is recommended to use dry spheroidization for batch shaping treatment. 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. This can shorten the melting time and extend the furnace life, and the unit heat consumption will also be reduced.
Part 08: Use high-quality refractory materials and reasonably match them
It is necessary to use various high-quality and durable refractory materials, such as capacitor refractory materials, or zirconium, chromium, corundum, spinel and alkaline refractory materials, high-density, high-strength refractory materials, etc. and give reasonable matching, so that the overall service life of the kiln will increase synchronously. The quality of the furnace materials is crucial to the kiln output, glass quality, fuel consumption and furnace life. The use of high-quality refractory materials should also be expanded. From a long-term point of view, it is worth spending more on refractory materials.
Energy saving of glass kilns involves a wide range of aspects, and it requires cooperation and joint efforts from all parties to be effective.
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