(Source: China ceramic net)

Ceramic factory is an enterprise with high energy consumption, such as high power consumption and high fuel consumption. These two costs together account for almost half or more of the ceramic production costs. Facing the increasingly fierce market competition, how to stand out in the competition and how to effectively save energy consumption and reduce costs are the topics they have been concerned about. Now we will introduce several energy-saving measures of ceramic kiln. 

11 energy saving measures for Ceramic Kilns: 

1.Increase the temperature of refractory insulation brick and insulation layer in high temperature zone

Data show that the heat storage loss of kiln masonry and the heat dissipation loss of furnace surface account for more than 20% of fuel consumption. It is meaningful to increase the thickness of refractory insulation brick and insulation layer in high temperature zone. Now the thickness of kiln top brick and kiln wall insulation layer in the designed kiln high-temperature zone has increased differently. The thickness of kiln top brick in the high-temperature zone of many companies has increased from 230 mm to 260 mm, and the thickness of kiln wall insulation layer has increased from 140 mm to 200 mm. At present, the thermal insulation at the bottom of the kiln has not been improved accordingly. Generally, a layer of 20 mm cotton blanket is paved at the bottom of the high-temperature zone, plus 5 layers of thermal insulation standard bricks. This 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, and use the insulation brick 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 the vault is used for the top part of the high-temperature zone kiln, it is very convenient to increase the thickness and tightness of the insulation layer to reduce heat dissipation. If the ceiling is used, it is better to use ceramic parts instead of heat-resistant steel plates for the ceiling, supplemented by heat-resistant steel hooks. In this way, all the hanging parts can also be embedded to increase the thickness and tightness of the insulation layer. If the heat-resistant steel is used as the hanging board of ceiling brick and all the hanging boards are embedded in the insulation layer, the hanging board may be oxidized completely in case of fire leakage of the kiln, causing the ceiling brick to fall into the kiln, resulting in kiln shutdown accident. Ceramic parts are used as hanging parts, and thermal insulation materials can also be used for pouring at the top. The use of thermal insulation materials becomes flexible. This will greatly improve the thermal insulation performance and air tightness of the kiln top and greatly reduce the heat dissipation at the top.

2.Select materials with higher quality and better thermal insulation performance

The continuous emergence of materials with better quality and thermal insulation performance also brings convenience to kiln engineering designers. Better thermal insulation materials can be used to make the thermal insulation layer thinner than before, and the thermal insulation effect can be better than before, so as to minimize energy waste. The light fire-resistant insulation brick and insulation cotton blanket insulation board with better insulation performance are adopted. After optimization, the more reasonable structure improvement design is adopted in order to reduce the heat dissipation of the kiln. Some companies use light bricks with a unit weight of 0.6, while others use special-shaped light bricks. Grooves of a certain size are set on the contact surface between light bricks and light bricks for heat insulation with air.  In fact, the thermal conductivity of air is about 0.03, which is much lower than that of almost all thermal insulation materials, which will certainly effectively reduce the heat dissipation loss on the kiln surface. At the same time, strengthen the tight sealing of the kiln body, and fully fill the accident treatment gap, expansion joint, fire baffle opening, around the burner brick, in the roller rod and at the roller hole brick with ceramic fiber cotton with higher temperature resistance, less pulverization and better elasticity, so as to reduce the outward heat loss of the kiln body, ensure the stability of 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. Advantages of residual hot air pipe 

Some domestic companies embed the residual hot air pipe in the insulation brick of the insulation layer at the bottom and top of the kiln, which will maximally improve the insulation of the residual hot air pipe and greatly reduce the heat dissipation of the kiln. It will also increase the thickness of the insulation layer. The data show that compared with other similar kilns under the same working conditions, the comprehensive energy-saving rate is more than 33%. It can be said that it has brought an energy-saving revolution. 

4. Waste heat utilization of kiln

 This waste heat mainly refers to the heat taken away by the kiln when cooling products. The lower the brick outlet temperature of the kiln, the more heat taken away by the waste heat system. Most of the heat required for drying bricks in drying kiln comes from the waste heat of kiln. If the heat of waste heat is greater, it will be more conducive to use. Waste heat utilization can be subdivided, the high-temperature part can be pumped into the spray drying tower for utilization; The medium temperature part can be used as combustion air; The rest can be driven into the drying kiln to dry the bricks. The pipes for hot air supply must be kept warm enough to minimize heat loss and improve utilization efficiency. Be very careful when the waste heat exceeding 280 ℃ is pumped into the dryer as excessive temperature will directly lead to brick cracking. In addition, many factories have hot water tanks in the cooling section to heat offices and dormitories with the waste heat from the kiln cooling section, and to supply hot water for employees' baths. Waste heat can also be used to generate electricity.

5. The high temperature zone adopts vault structure 

The adoption of vault structure in the high temperature zone is conducive to reducing the section temperature difference and saving energy. Because the high-temperature heat conduction is mainly radiation, the central space of the vault kiln is large and contains more high-temperature flue gas, coupled with the effect of arc normal radiant heat reflection of the vault, the temperature in the middle is often a little higher than that close to the kiln wall on the side. Some companies report that it will increase by about 2 ℃, so it is necessary to reduce the pressure of combustion supporting air to ensure the consistency of section temperature. The high temperature zone of many wide body flat roof kilns has the phenomenon of high temperature near both sides of the kiln wall and low temperature in the middle. Some kiln operators solve the section temperature difference by increasing the pressure of combustion supporting air and increasing the air supply volume of combustion supporting air.

This will bring several consequences. First, the positive pressure of the kiln is too large, and the heat dissipation of the kiln body increases; Second, it is not conducive to atmosphere control; Third, the load of combustion air and smoke exhaust fan has increased, and the power consumption has increased; Fourth, excessive air entering the kiln needs to consume additional heat, which will inevitably lead to a direct increase in coal consumption or gas consumption and a rise in cost. The correct method is: first, change to high combustion speed and high injection speed burner;Second, change to the long burner brick; Third, change the outlet size of burner brick to reduce it and increase the injection speed, which should be adapted to the mixing speed and combustion speed of gas and air in the burner. It is possible for high-speed burners, but the effect of low-speed burners is not good; Fourth, insert a section of recrystallized silicon carbide roller into the burner brick mouth to make the gas strengthen the heating in the middle of the kiln. In this way, the burner bricks can be arranged at intervals; Fifth, use the combination of long and short recrystallized silicon carbide spray gun sleeve. The best solution is not to increase energy consumption, or even reduce energy consumption. 

6. High efficiency and energy-saving burner

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 in the process of use, so as to improve the combustion efficiency and save energy. Some companies develop high firing rate isothermal burners to strengthen the heat supply in the middle of the kiln, improve the section temperature difference and save energy. Some companies have developed multiple mixing of combustion air and fuel, so as to improve the combustion speed and efficiency, make the gas combustion cleaner and more complete, and save energy obviously. Some companies promote the proportional control of the combustion air of each branch in the high-temperature section, so that the combustion air and gas supplied can be adjusted synchronously in proportion. At any time when the PID regulator regulates the temperature, a reasonable air-fuel ratio is maintained and the injected gas and combustion air will not be excessive, so as to save the consumption of fuel and combustion air and optimize the utilization rate of fuel. Other companies in the industry have developed energy-saving burners such as premixed secondary combustion burners and premixed tertiary combustion burners. According to the data, the use of premixed secondary burner can achieve 10% energy-saving effect. Continuous improvement and innovation of more advanced combustion technology, adoption of higher quality burners and control of reasonable air-fuel ratio are always the best way to save energy.

7. Combustion air heating 

Combustion air heating is used in hansov and sakmi kilns introduced in the early 1990s. It is heated when the combustion air passes through the heat-resistant stainless steel heat exchanger above the quench zone kiln, and the maximum temperature can reach about 250 ~ 350 ℃. At present, there are two ways to use the waste heat of kiln in China to heat the combustion supporting air. One is to use hansov method to absorb heat from the heat-resistant steel heat exchanger above the quench belt kiln to heat the combustion supporting air, and the other is to use the air heated by the slow cooling belt cooling air pipe to deliver it to the combustion supporting fan as the combustion supporting air.

The wind temperature of the first method using waste heat can reach 250 ~ 330 ℃, and the wind temperature of the second method using waste heat is lower, which can reach 100 ~ 250 ℃, and the effect will be worse than that of the first method.  In fact, in order to protect the combustion supporting fan from overheating, many companies use a part of cold air, which leads to the reduction of waste heat utilization effect. At present, there are still few manufacturers using waste heat to heat combustion supporting air in China, but if this technology is fully utilized, the energy-saving effect of reducing fuel consumption by 5% ~ 10% can be achieved, which is also very considerable.There is a problem in use, that is, according to the ideal gaseous equation "PV / T ≈ constant, T is the absolute temperature, T= Celsius temperature + 273 (K)", assuming that the pressure remains unchanged, when the combustion supporting air temperature rises from 27 ℃ to 300 ℃, the volume expansion will be 1.91 times of the original, which will lead to the reduction of oxygen content in the air of the same volume. Therefore, the pressurization and hot air characteristics of hot air combustion supporting must be considered in the selection of fan. 

If this factor is not considered, there will be problems in 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 by waste heat, and some manufacturers have begun to try this . The more heat brought in by gas and combustion supporting wind means that more fuel is saved. 

8. Reasonable combustion air preparation

The combustion supporting air before the calcination temperature is 1080 ℃ requires complete peroxide combustion, and more oxygen needs to be injected into the kiln in the oxidation section of the kiln to accelerate the chemical reaction speed of the green body and realize fast combustion. If this section is changed to reducing atmosphere, the temperature of some chemical reactions must be increased by 70 ℃ to start the reaction. If there is too much air in the highest temperature section, the green body will undergo excessive oxidation reaction and oxidize FeO into Fe2O3 and Fe3O4, which will make the green body red or black rather than white. If the highest temperature section is a weak oxidizing atmosphere or just neutral atmosphere, the iron in the green body will completely appear in the form of FeO, making the green body more cyan and white, and the green body will also be whiter. The high temperature zone does not need excess oxygen, which requires that the high temperature zone must control the excess air. 

The air at room temperature does not participate in the combustion chemical reaction and enters the kiln as excess combustion supporting air to reach 1100 ~ 1240 ℃, which undoubtedly consumes huge energy, and will also bring greater kiln positive pressure in the high-temperature area, resulting in excessive heat loss. So reducing the excessive air entering the high temperature zone will not only save a lot of fuel, but also make the bricks whiter. Therefore, the combustion air in the oxidation section and the high-temperature zone should be supplied independently by sections, and the different service pressure of the two sections should be guaranteed through the regulating valve. Foshan ceramics has a feature article by Mr. Xie Binghao confirmed that the careful and reasonable fine allocation and supply of each section of combustion air distribution leads to a reduction of fuel energy consumption of up to 15%. It does not count the electricity saving benefits obtained from the reduction of current of combustion supporting fan and smoke exhaust fan due to the reduction of combustion supporting pressure and air volume. It seems that the benefits are very considerable. This shows how necessary the fine management and control under the guidance of expert theory.  

9. Energy saving infrared radiation coating

The energy-saving infrared radiation coating is applied on the surface of the fire-resistant insulating brick in the high-temperature zone kiln to effectively close the open air hole of the light fire-resistant insulating brick, which can significantly improve the infrared heat radiation intensity of the high-temperature zone and strengthen the heating efficiency. After use, it can reduce the maximum firing temperature by 20 ~ 40 ℃ and effectively reduce the energy consumption by 5% ~ 12.5%. The application of Suzhou RISHANG company in two roller kilns of Sanshui Shanmo company in Foshan proves that the HBC coating of the company can effectively save energy by 10.55%. When the coating is used in different kilns, the maximum firing temperature will be significantly reduced by 20 ~ 50 ℃, the roller kiln can reach a temperature drop of 20 ~ 30 ℃, the tunnel kiln can reach a temperature drop of 30 ~ 50 ℃, and the exhaust gas temperature will be reduced by more than 20 ~ 30 ℃. Therefore, it is necessary to partially adjust the firing curve, appropriately reduce the maximum firing temperature and appropriately increase the length of high fire insulation zone.  

High temperature blackbody high efficiency infrared radiation coating is a popular technology in countries with good energy conservation all over the world. When selecting the coating, first, whether the radiation coefficient of the coating at high temperature reaches more than 0.90 or more than 0.95; second, pay attention to the matching of the expansion coefficient and refractory materials; third, adapt to the atmosphere of ceramic firing for a long time without weakening the radiation performance; fourth, bond well with the refractory insulation materials without cracks and peeling off; fifth, the thermal shock resistance should meet the standard of Mullite and heat preservation at 1100 ℃, put it directly into 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 attention, use and promotion. 

10. Oxygen enriched combustion 

Part or all of the nitrogen in the air is separated through the molecular membrane to obtain oxygen enriched air or pure oxygen with higher oxygen concentration than the air, which can be used as combustion supporting air to supply the burner.As the oxygen concentration is increased, the burner reaction is faster and the temperature is higher, which can save more than 20% ~ 30% of the fuel. As there have no any or less nitrogen in the combustion supporting air, the amount of flue gas is also reduced, the current of the exhaust fan is also reduced, so there is less or no nitrogen oxide to be removed for environmental protection. Dongguan Hengxin Energy Saving Technology Co., Ltd. provides services on the energy contract management mode of providing pure oxygen supply burner. The company provides equipment investment for transformation and shares the savings in accordance with the contract between both parties. This is also the most effective control of nitrogen oxide emission, thus reducing the expensive cost of nitrogen oxide removal by environmental protection facilities. This technology can also be used in spray drying tower. When an > ℃, the exhaust gas 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 high fire insulation area. 

11. Kiln and pressure atmosphere control

If the kiln produces too much positive pressure in the high temperature zone, it will make the product have a reducing atmosphere, which will affect the mirror effect of the surface glaze layer, make it easier to show orange peel, and quickly increase the loss of heat in the kiln, resulting in more fuel consumption,the gas supply needs to give higher pressure, and the pressurizing fan and smoke exhaust fan need to consume more power. It is appropriate to maintain a positive pressure of 0 ~ 15pa at most in the high temperature zone. The vast majority of building ceramics are fired in oxidizing atmosphere or micro oxidizing atmosphere, some ceramics need reducing atmosphere. For example, talc ceramics need strong reducing atmosphere. Reducing atmosphere means consuming more fuel and the flue gas should contain CO. With the mission of energy saving, reasonably adjusting the reduction atmosphere will undoubtedly save energy consumption than random adjustment. The explore not only to ensure the most basic reduction atmosphere, but also to reasonably save energy. Careful operation and continuous summary are necessary.