Ceramic factories are high-energy-consuming enterprises, such as high power consumption and high fuel consumption. These two costs together account for almost half or more than half of the cost of ceramic production. Facing the increasingly intensified market competition, how ceramic factories can stand out from the competition and how to effectively save energy consumption and reduce costs are topics they have always been concerned about. This article introduces several energy-saving measures for ceramic kilns.
11 energy-saving measures for ceramic kilns:
1. Increase the temperature of refractory insulation bricks and insulation layers in high temperature zones
According to data, the heat storage loss of the kiln masonry and the heat dissipation loss on the furnace surface account for more than 20% of the fuel consumption. It is meaningful to increase the thickness of refractory insulation bricks and insulation layers in high-temperature zones. The thickness of the kiln roof bricks and kiln wall insulation layer of the kilns currently designed in the high-temperature zone has been increased in different ways. In many companies, the thickness of the kiln roof bricks in the high-temperature zone has increased from 230 mm to 260 mm, and the thickness of the kiln wall insulation layer has increased from 140 mm to 200 mm. mm. At present, the insulation at the bottom of the kiln has not been improved accordingly. The common situation is to lay a layer of 20 mm cotton blanket and 5 layers of insulating bricks at the bottom of the high-temperature zone for insulation. The situation has not improved. In fact, based on the huge heat dissipation area at the bottom, the heat dissipation at the bottom is very considerable. It is necessary to increase the thickness of the appropriate bottom insulation layer, use insulation bricks with lower bulk density and increase the thickness of the insulation layer to improve the insulation at the bottom. Such investment is Necessary.
In addition, if a vault is used for the top part of the kiln in the high-temperature zone, it is very convenient to increase the thickness and sealing of the insulation layer to reduce heat dissipation. If a suspended ceiling is used, it is best to use ceramic parts for the suspended ceiling instead of heat-resistant steel plates, supplemented by heat-resistant steel hooks. This way, all the hanging parts can be buried and the thickness and sealing of the insulation layer can be increased. If heat-resistant steel is used as hanging panels for ceiling bricks, and if all the hanging panels are buried in the insulation layer, the panels may all oxidize when the kiln leaks fire, causing the ceiling bricks to fall into the kiln, causing a kiln shutdown accident. Ceramic parts are used as hanging parts, and the top insulation can also be poured with insulation materials, making the use of insulation materials more flexible. This will greatly improve the thermal insulation performance and air tightness of the kiln roof, and greatly reduce the heat dissipation at the top.
2. Choose materials with higher quality and better thermal insulation properties
Materials with better quality and better thermal insulation performance are constantly emerging, which also brings convenience to kiln engineering designers. Better insulation materials can be used to make the insulation layer thinner than before, and the insulation effect can be improved. better than before to minimize energy waste. Use lightweight refractory insulation bricks and insulation cotton blankets with better thermal insulation performance for insulationThe plate has been optimized and adopted a more reasonable structural improvement design in order to reduce the heat dissipation of the kiln. Some companies use lightweight bricks with a bulk density of 0.6, and some companies use special-shaped lightweight bricks. Grooves of a certain size are provided on the contact surfaces between lightweight bricks for air insulation. In fact, the thermal conductivity of air is around 0.03, which is much lower than almost all insulation materials. This will definitely effectively reduce the heat loss on the surface of the kiln. At the same time, the kiln body should be sealed tightly, and the accident treatment opening, expansion joint, fire baffle opening, around the burner brick, inside the roller rod and the roller hole brick should be fully filled with ceramic fiber cotton that is more resistant to high temperatures, less prone to powdering and has better elasticity. , to reduce the heat loss of the kiln body, ensure the stability of the temperature and atmosphere in the kiln, improve thermal efficiency, and reduce energy consumption. Domestic kiln companies have done a good job in kiln insulation.
3. Benefits of waste heat ducts
Some domestic companies bury the waste heat air ducts in the insulation bricks of the bottom and top insulation layers of the kiln. This will maximize the insulation of the waste heat air ducts and greatly reduce the heat dissipation of the kiln. It will also increase the thickness of the insulation layer. Data shows that compared with other similar kilns under the same operating conditions, the comprehensive energy saving rate is more than 33%. It can be said that it has brought about an energy-saving revolution.
4. Utilization of waste heat from kilns
This waste heat mainly refers to the heat taken away by the kiln when cooling the product. The lower the temperature of the bricks coming out of the kiln, the more heat is taken away by the waste heat system. Drying Kiln Most of the heat required to dry the bricks comes from the waste heat of the kiln. The greater the amount of waste heat, the easier it is to utilize it. The utilization of waste heat can be subdivided. The high-temperature part can be driven into the spray drying tower for utilization; the medium-temperature part can be used as combustion-supporting air; and the remaining part can be driven into the drying kiln to dry the bricks. The pipes that deliver hot air must be adequately insulated to minimize heat loss to improve utilization efficiency. Be very careful when the waste heat exceeding 280 ℃ is injected into the dryer. Excessive temperature will directly cause cracking of the bricks. In addition, many factories have hot water tanks installed in the cooling section. The waste heat from the kiln cooling section is used to heat offices and dormitories, and to provide hot water for employees to bathe. Waste heat can also be used to generate electricity.
5. High-temperature zones adopt vault structures
The use of a dome structure in the high-temperature zone is beneficial to reducing cross-sectional temperature differences and conducive to energy saving. Since high-temperature heat conduction is mainly based on radiation, the middle space of a vault kiln is large and can accommodate a lot of high-temperature flue gas. In addition, due to the normal radiation heat reflection of the vault arc, the temperature in the middle is often closer to the kiln wall than at the sides. The temperature should be slightly higher, and some companies report that it will increase by about 2℃. In this case, the pressure of the combustion air must be reduced accordingly to ensure the consistency of the cross-section temperature. In the high-temperature zone of many wide-bodied flat-top kilns, the temperature is high on both sides of the kiln wall and low in the middle.Furnace operators increase the combustion air pressure and increase the combustion air supply volume to solve the cross-section temperature difference.
This will bring several consequences. First, the positive pressure of the kiln is too large, which increases the heat dissipation of the kiln body; second, it is not conducive to atmosphere control; third, the load of the combustion air and exhaust fans is increased, and the power consumption is increased. ; Fourth, too much air entering the kiln requires additional heat consumption, which will inevitably lead to a direct increase in gas consumption or gas consumption and an increase in costs. The correct methods are: first, switch to a burner with high combustion speed and high injection rate; second, change the burner brick to a longer length; third, change the outlet size of the burner brick to reduce it and increase the injection speed, which should be adapted to the gas flow of the burner. Mixing speed with air and combustion speed. It is possible to use high-speed burners, but the effect of low-speed burners is not very good. Fourth, a recrystallized silicon carbide roller rod is inserted into the mouth of the burner brick to enhance the heating of the middle part of the kiln by gas. Such burner bricks can be arranged at intervals. ; The fifth is to use a combination of long and short recrystallized silicon carbide spray gun holsters. The best solution is one that does not increase energy consumption, or even reduces it.
6. Use high-efficiency and energy-saving burners
Some companies have improved the burner and optimized the air-fuel ratio. By adjusting the reasonable air-fuel ratio, the burner does not input too much combustion air during use, thereby improving the combustion efficiency and saving energy. Some companies develop high-speed isothermal burners to enhance the heat supply in the middle of the kiln, improve the cross-section temperature difference, and achieve energy saving. Some companies have developed multiple mixing methods of combustion air and fuel to increase the combustion speed and efficiency, making the gas combustion cleaner and more complete, and the energy saving is also obvious. Some companies promote proportional control of the combustion air in each group of branches in the high-temperature section, so that the combustion air and gas supplied are adjusted in proportion simultaneously. At any time period when the PID regulator adjusts the temperature, a reasonable air-fuel ratio is maintained, so that the input Neither the gas nor the combustion air will be excessive, thus saving the consumption of fuel and combustion air and maximizing fuel utilization. There are also companies in the industry that have developed energy-saving burners such as premixed secondary combustion burners and premixed tertiary combustion burners. According to some data, the use of premixed secondary burning burners can achieve an energy saving effect of 10%. Continuously improving and innovating more advanced combustion technology, using better quality burners, and controlling a reasonable air-fuel ratio are always the best ways to save energy.
7. Combustion air heating
Combustion air heating is used in the Hansoff and Sacmi kilns introduced in the early 1990s. The combustion air is heated when it passes through the heat-resistant stainless steel heat exchanger above the quench zone kiln. The maximum temperature can reach about 250~350℃. At present, there are two ways to use domestic kiln waste heat to heat combustion-supporting air. One is to use the Hansoff method to absorb heat from the heat-resistant steel heat exchanger above the quench zone kiln to heat the combustion-supporting air. There is another way: Heated by slow cooling with cold air ductThe air is delivered to the combustion fan as combustion air.
The former method uses waste heat and the air temperature can reach 250~330 ℃. The latter method uses waste heat and the air temperature is lower and can reach 100~250 ℃. The effect will be worse than the first method. In fact, in order to protect the combustion fan from overheating, many companies use part of the cold air, which results in a reduction in the waste heat utilization effect. At present, there are still very few domestic manufacturers that use waste heat to heat combustion-supporting air. However, if this technology is fully utilized, it is possible to achieve an energy-saving effect of reducing fuel consumption by 5% to 10%, which is also very impressive. There is a problem in use. According to the ideal gas equation "PV/T≈constant, T is the absolute temperature, T=Celsius + 273 (K)", assuming that the pressure remains unchanged, the combustion air temperature rises from 27℃ At 300°C, the volume expands 1.91 times of the original volume, which will lead to a reduction in the oxygen content of the same volume of air. Therefore, the fan selection must consider the pressurization and hot air characteristics of hot air combustion.
If this factor is not considered, problems will arise during use. The latest report shows that foreign manufacturers have begun to try to use 500~600 ℃ combustion air, which will be more energy-saving. Gas can also be heated using waste heat, and some manufacturers have begun to try this. The more heat brought into the gas and combustion air means more fuel is saved.
8. Reasonable combustion air preparation
The combustion-supporting air before the calcination temperature is 1080°C requires complete oxygen combustion. The oxidation section of the kiln needs to introduce more oxygen into the kiln to accelerate the chemical reaction speed of the green body to achieve fast burning. If this section is replaced with a reducing atmosphere, the temperature of some chemical reactions will have to be increased by 70°C before the reaction can begin. If there is too much air in the highest temperature section, the green body will undergo excessive oxidation reaction, causing FeO to be oxidized into Fe2O3 and Fe3O4, which will make the green body appear red or black instead of white. If the highest temperature section is a weak oxidizing atmosphere or just a neutral atmosphere, the iron in the green body will appear completely in the form of FeO, making the green body appear more bluish white and the green body will also be whiter. The high-temperature zone does not require excess oxygen, which requires that excess air must be controlled in the high-temperature zone.
Air at room temperature does not participate in combustion chemical reactions and is driven into the kiln as excessive combustion-supporting air to reach 1100~1240°C. This undoubtedly consumes huge energy and will also bring greater positive pressure to the kiln in the high-temperature area, resulting in Too much heat is lost. Therefore, reducing excess air into the high temperature zone will not only save a lot of fuel, but also make the bricks whiter. Therefore, it is best to supply the combustion-supporting air in the oxidation section and the high-temperature zone independently in sections, and ensure different operating pressures in the two sections through regulating valves. Foshan Ceramics has Mr. Xie BinghaoA special article by a student confirmed that the careful and reasonable allocation and supply of each section of the combustion air distribution can lead to a reduction of up to 15% in fuel energy consumption, not counting the current of the combustion fan and exhaust fan caused by the reduction of combustion pressure and air volume. The savings on electricity bills achieved through the reduction appear to be very substantial. This shows how necessary refined management and control under the guidance of expert theory is.
9. Energy-saving infrared radiation coating
The energy-saving infrared radiation coating is applied to the surface of the refractory insulation bricks in the high-temperature zone kiln, effectively closing the opening pores of the lightweight refractory insulation bricks, which can significantly increase the infrared heat radiation intensity in the high-temperature zone, strengthen the heating efficiency, and can The maximum firing temperature can be reduced by 20~40℃, effectively reducing energy consumption by 5%~12.5%. Suzhou Rishang Company's use of two roller kilns in Foshan Sanshui Shanmo Company has proven that the company's HBC coating can effectively save energy by 10.55%. The use of coatings in different kilns will significantly reduce the maximum firing temperature by 20~50℃. Roller kilns can achieve a temperature drop of 20~30℃, tunnel kilns can achieve a temperature drop of 30~50℃, and the exhaust gas temperature will decrease by 20~30℃. Therefore, it is necessary to partially adjust the firing curve, appropriately reduce the maximum firing temperature, and appropriately increase the length of the high-fire heat preservation zone.
High-temperature blackbody high-efficiency infrared radiation coating is a very popular technology promoted in countries that have done well in global energy conservation. When selecting coatings, firstly, whether the radiation coefficient of the coating at high temperature reaches above 0.90 or above 0.95; secondly, attention should be paid to the matching of expansion coefficient and refractory materials; thirdly, it is necessary to adapt to the atmosphere of ceramic firing for a long time without weakening the radiation performance; fourthly, It is well bonded with refractory insulation materials, without cracks or peeling off. Fifth, the thermal shock resistance must meet the standards of mullite. It can be heated and insulated at 1100°C and placed directly in cold water for many times without cracking. High-temperature blackbody high-efficiency infrared radiation coating has been recognized by everyone in the global industrial field. It is a mature, effective, and immediate energy-saving technology. It is an energy-saving technology worthy of everyone's attention, use, and promotion.
10. Oxygen-rich combustion
Separate part or all of the nitrogen in the air through a molecular membrane to obtain oxygen-rich air or pure oxygen with a higher oxygen concentration than the air, which is used as combustion-supporting air to supply the burner. As the oxygen concentration increases, the burner reacts faster and the temperature is higher, which can save more than 20% to 30% of fuel. Since the nitrogen in the combustion air is absent or reduced, the amount of flue gas is also reduced, and the current of the exhaust fan is also reduced. , there are less or no nitrogen oxides that need to be removed for environmental protection. Dongguan Hengxin Energy Saving Technology Co., Ltd. provides energy contract management services for pure oxygen supply burners. The company provides investment in modified equipment, and the savings are shared according to the contract between the two parties. This is also the result of nitrogen oxide emissionsMaximize effective control, thereby reducing the expensive cost of nitrogen oxide removal in environmental protection facilities. This technology can also be used in spray drying towers. an>℃, the exhaust smoke temperature will be reduced by more than 20~30℃, so it is necessary to partially adjust the firing curve, appropriately reduce the maximum firing temperature, and appropriately increase the length of the high fire insulation zone.
11. Kiln and pressure atmosphere control
If the kiln generates too much positive pressure in the high-temperature zone, it will cause the product to have a reducing atmosphere, which will affect the mirror effect of the surface glaze layer, make it easier to appear orange peel, and also rapidly increase the heat loss of the kiln. As a result, more fuel is consumed, the gas supply requires higher pressure, and both the pressurizing fan and the exhaust fan consume more electricity. The appropriate approach is to maintain a maximum positive pressure of 0~15Pa in the high temperature zone. The vast majority of building ceramic products are fired in an oxidizing atmosphere or a slightly oxidizing atmosphere. Some ceramics require a reducing atmosphere, such as talc porcelain, which requires a strong reducing atmosphere. Reducing the atmosphere means consuming more fuel, and the flue gas will contain CO components. Properly adjusting the reduction atmosphere with the mission of energy saving will undoubtedly save energy than random adjustments. It is necessary to explore how to ensure the most basic reduction atmosphere while also reasonably saving energy. Careful and meticulous operation and continuous summary are necessary.
