Due to the characteristics of simple structure, low construction cost, small temperature difference in the kiln and high energy-saving efficiency, batch shuttle kiln is becoming the preferred furnace type for small and medium-sized ceramic enterprises at home and abroad, and has been popularized on a large scale. At present, many building and sanitary ceramics enterprises use advanced shuttle kilns for product firing. Now on the structure of the shuttle kiln, as well as the operation method of loading and firing, etc., some energy-saving measures and schemes.
Choose a good kiln structureThe new energy-saving shuttle kiln, depending on the size of the kiln volume, staggered four or six jet high-speed fire channels in the same horizontal plane in the kiln, the shuttle kiln with liquefied petroleum gas as fuel, breaks the working state of the traditional ceramic kiln based on natural flow, and uses the pressure to cause the induction of high-speed airflow, so that the air flow is recirculated, the rate flow is formed, and the flue gas convection heat transfer process is strengthened, so that the temperature in the kiln rises uniformly, so that the products appear to be heated quickly and evenly, which greatly saves the consumption of fuel and achieves obvious energy-saving effects.
Secondly, when choosing a kiln, the structure of the kiln should have a reasonable size. Because of the large size of the kiln, the heat dissipation area occupied by the unit product is small and the heat consumption is small. If the size of the kiln is too large, the temperature in the kiln is not easy to be uniform, the firing time is long, and the heat consumption increases. In addition, if the product structure and firing method are unchanged, the firing time and fuel consumption of kilns with different ratios of length, width and height of the same volume kiln will be very different. On the other hand, if the length and width of the kiln increase and the height decreases for the same volume, the firing effect will not be the above. Therefore, in the design of the kiln, the length and width of the kiln can be increased appropriately without affecting the variety of fired products and production specifications, and its height should be low. In this way, it can not only reduce the temperature difference between the upper and lower parts of the kiln, but also shorten the firing time and achieve the purpose of saving fuel.
Improvement of thermal insulation refractories used in shuttle kilnsThe integral module of ceramic fiber is a kind of large-scale fiber blanket block assembly developed for the thermal equipment or local part of the equipment with complex structure and fast flue gas velocity, which is an integral large-scale fiber blanket block that is cut into neat small pieces and interspersed with anchors in the middle. The overall module has low thermal conductivity, smooth surface, flexible size, thickness between 150mm-300mm, and a bulk density of 160 240kg m3, which can meet the thermal insulation requirements of thermal equipment from 600 to 1350 different temperature grades. During installation, the module can be compressed in multiple directions to eliminate the thermal expansion stress in high temperature environments. The integral ceramic fiber module does not need to be bundled with straps, and the anchor is composed of a cowyoke-shaped metal skeleton and a round tube support, which makes the production process of the whole module simple and fast compared with the traditional ceramic fiber module, which greatly shortens the production time.
Improve the tightness of the kilnThe sealing performance of the sanitary ceramic kiln directly affects the consumption of fuel. The heat storage of lightweight foam insulating bricks and aluminum silicate fiber blankets used in kiln masonry is only about 10% of that of refractory bricks. Adopt the above-mentioned thermal insulation material masonry kiln wall, kiln roof, the thermal insulation performance of kiln is good, the surface iron plate combustion chamber at the high temperature stage, measured by the surface thermometer, the temperature is only 50 80, can reduce fuel consumption by 10 15%. The shuttle kiln, which is made of lightweight foam insulation bricks and aluminum silicate fiber blanket masonry, although it is said that the one-time engineering cost is more, due to the significant energy-saving effect, the construction cost can be recovered within a few months after it is put into operation.
The joints of the kiln car, the periphery, the periphery of the kiln and the contact between the kiln body and the kiln body are pasted with a 30mm thick aluminum silicate refractory fiber blanket, which effectively prevents the flue gas heating and cold air infiltration in the kiln, increases the sealing performance of the kiln, narrows the temperature difference between the upper and lower furnaces, reduces heat loss, shortens the heat preservation time of high fire, and promotes the reduction of fuel consumption.
Develop a reasonable operating planThe firing of building sanitary ceramic products should be based on the characteristics of billet and glaze, kiln structure, fuel type, etc. During firing, attention should be paid to mastering the three stages of firing: oxidation flame, reducing flame and neutral flame. Due to various flame requirements, the temperature and atmosphere are different, and the amount of fuel is different. Therefore, in the implementation of the operation of product firing, the amount of fuel used in each stage should be determined according to the kiln structure, the temperature difference in the kiln, the size, thickness, dry and wet, the requirements of the sintering temperature range, the high fire holding time and other factors, and the specific operation should pay attention to the following points.
1) In the ignition stage of 1050, it should be the oxidation stage, and the heating rate should be 210 hours. At this stage, the amount of fuel is from small to large, the total oxidation firing is controlled, there should be no carbon monoxide from the observation hole, the flame in the kiln should be completely clear, and the heating time is 45-5 hours.
2) In the 1050 and 1360 phases, it should be the reducing flame stage. At this time, the amount of fuel is controlled in the current fire hole, and the flame of 250 300mm (the flame of the LPG kiln is slightly shorter) is observed, indicating that the reducing atmosphere in the kiln is sufficient. When the temperature of the kiln top reaches more than 1250, it can be converted to high fire insulation. When holding at a high temperature, it is fired for a short time at a higher temperature (i.e., the upper limit of the sintering range), which can save fuel. General restore time 2 25 hours, half an hour of high fire holding time, can meet the requirements of fired products.
Oxy-fuel combustion technology is adopted1.The oxygen-rich air combustion technology can reduce the scouring of the kiln wall by the flue gas jet and prolong the service life of the kiln wall material. When oxygen-rich air with an oxygen concentration of more than 24% is used for combustion, the temperature of the kiln roof can be reduced, thereby prolonging the service life of the kiln roof material.
2.The use of oxygen-rich air combustion technology can increase the temperature at the bottom of the flame, enhance the heat exchange in the kiln, and the long-term use of oxygen-rich combustion mode will make the kiln car table (kiln bottom) be burned out, resulting in unstable material stacking, billet collapse phenomenon, and the kiln car needs to be checked regularly.
3.The use of oxygen-rich air combustion technology will make the temperature difference in the kiln larger, and the temperature difference in the kiln can be reduced by adjusting the position of the smoke exhaust port and changing the stacking and stacking method.
Promote boxless firingIn the past, firing building sanitary enamel products, many enterprises adopted the method of sagger firing products, because the weight of the sagger itself is several times larger than the product, and its thermal conductivity is poor, the heat transfer speed is slow, and the heat absorption and heat dissipation are large. The existence of the box not only occupies the space of the kiln, but also makes the flame unable to directly radiate the heat to the product, which increases the fuel consumption and prolongs the firing time. At present, the firing of building sanitary ceramic products has generally canceled the box, and the method of non-box firing and open flame bare firing has been adopted. According to the relevant tests, the firing time can be shortened by one hour by extending the firing time of non-box burning compared with box-based burning, and the fuel consumption of each kiln can be reduced by about 15%.
In addition, it is necessary to study the density of the kiln when the product is fired. When the product is too dense, it can reduce the unit heat consumption, but when the kiln is too dense, it will directly lead to large air flow resistance in the kiln, which is not conducive to ventilation and uneven temperature in the kiln. The minimum distance between the green body and the green body gap should be controlled at about 5mm. When the blank is loaded, it is burned with an open flame in the structure of shed slabs, and each slab is supported by three pillars. The upper and lower shed boards are kept flat, straight and stable, evenly arranged, and the products on each layer are basically the same in height as much as possible, and the shape and size are different. The whole car should be loaded with the shortest body in the middle position; The body is high, and the column length is placed in the lowest or uppermost part, so that it is conducive to maintaining the heat balance of the body under the high-temperature air flow, thereby shortening the firing time and reducing fuel consumption;
Strengthen the thermal insulation performance of the kiln roof of the gateThe kiln body of the shuttle kiln is rectangular, the masonry of the kiln wall is divided into three layers along the thickness direction, the working lining is made of refractory insulation bricks, the interlayer is a heat-insulating refractory material, and the outer layer is made of aluminum silicate fiber board pasted on the kiln wall. The kiln roof adopts a flat ceiling structure, and the masonry is also divided into three layers, the inner layer is a degree of thermal insulation brick, which is hung below the ceiling brick, the interlayer is a thermal insulation brick, and the top layer is made of aluminum silicate fiber blanket for both the thermal insulation layer and the sealing layer.
Because the kiln door is often moved, the masonry of the kiln door is two layers, the inner layer is high-strength high-grade thermal insulation bricks, and the outer layer is the thermal insulation layer, and the aluminum silicate fiber blanket is attached to the metal shell of the kiln door. The burners are installed on the kiln wall, and there are one or two rows depending on the height of the kiln. The kiln car table is the bottom of the kiln, and the kiln roof and kiln wall constitute the firing space of the kiln, and the main flue is left in the center of the kiln car lining brick, which is connected with the underground flue. One end (or both ends) of the kiln is provided with a kiln door, and the kiln door can be set separately or masonry at the end of the kiln car. The skirts on both sides of the kiln car are inserted into the sand sealing groove of the kiln wall, and between the kiln car and the kiln car, between the kiln car and the end wall and the kiln door, there is a curved sealing groove, and the refractory fiber is squeezed to play a sealing role. There are many ventilation holes left in the lower part of the sand sealing groove of the kiln wall, which is conducive to the heat dissipation at the bottom of the kiln car and prolongs the service life of the kiln car.
Interstitial production kiln, suitable for small batch and multi-variety production, due to the flexibility of production, many small and medium-sized ceramic porcelain factories now still use this kiln. However, due to the interstitial type, the kiln wall and trolley need to absorb heat and consume energy, and the overall energy consumption is relatively high, but through the efforts of the kiln design and manufacturer, such as the use of high-speed burner for rapid firing, the use of lightweight refractory insulation materials to reduce the heat storage of the kiln, and some rapid firing shuttle kilns have achieved energy-saving effects comparable to those of the old tunnel kilns.