Optimal design of sintering furnace for the hottes

2022-09-19
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Abstract: This paper introduces the optimization design process of ceramic capacitor kiln. The application results show that this high-temperature sintering equipment has the characteristics of good consistency of product size and performance after sintering, high yield, low operation cost and so on

key words: pusher kiln; Ceramic capacitor; Energy saving

1. Preface:

with the rapid and vigorous development of the electronic industry, high-voltage ceramic capacitors with high breakdown voltage, small size and high reliability are urgently required. At present, the ceramic materials of medium and high voltage ceramic capacitors are mainly barium titanate based and strontium titanate based ceramics. For these two kinds of ceramic materials, high temperature and good uniformity of furnace temperature are required in the sintering process of medium and high voltage capacitor products. To meet this requirement, we designed clqj series energy-saving pusher type capacitor sintering electric kiln

2. Introduction to electric kiln:

the electric kiln is an energy-saving fully automatic 1300 C single hole pusher kiln, and the equipment is composed of furnace body and intelligent temperature control system. The furnace body adopts the split structure of taking away wheel, which is convenient for transportation, installation and maintenance. After the connection of the furnace body, it is directly laid horizontally on the steel rail. The furnace adopts computer positioning software to optimize the design structure, and the overall equipment is compact and reasonable. The temperature control system adopts the original imported Japanese conductive intelligent temperature instrument, thyristor module voltage regulation, high temperature control accuracy, long-term stable and reliable operation. The kiln shell and the control system shell adopt the double-layer structure of electrostatic spraying hanging plate, which is beautiful and elegant

3. Structural form of the kiln:

in the design process of the kiln, we fully according to the process and energy-saving requirements of electronic ceramic products, reasonably select the furnace structure, thermal insulation materials, heating elements, temperature control methods, etc., to ensure the firing quality of capacitor products

l design for process requirements:

ceramic capacitor tiles contain substances such as binders and solvents that volatilize during heating. In the process of heating, the direction of heat transfer is opposite to that of moisture transfer. In the heating stage of the furnace body, if the temperature difference between the furnace temperature and the product is too large, the product surface dries rapidly. Due to the large temperature gradient of the product section, the lower pressure plate is placed on the internal temperature workbench of the product, and the internal volatiles have not been discharged. When the internal temperature of the product rises, the formation of volatile matter is not easy to be discharged. The surface of the product is also easy to form cracks, which will affect the product quality. In view of this situation, in the heating stage of the furnace body, we reasonably arrange the glue discharge chimney so that the generated colloid can be discharged quickly. At the same time, this method can be adopted to reasonably select the surface power of heating elements: reduce the surface temperature of heating elements and the temperature difference between the furnace, so as to achieve the purpose of low internal and external temperature difference of products. So as to ensure the quality of products in the pre burning stage

in the firing stage, because the product requires high uniformity of furnace temperature, we have adopted the method of refining the heating zone and controlling the temperature up and down. At the same time, because the heat transfer in the furnace is dominated by radiation and convection, according to the structural type of the furnace, the radiation shielding in the upper heating area is small, and the lower heating area is shielded by the bottom plate, so the radiation shielding to the lower heating element is large; On the other hand, because the heated air floats due to the temperature head, the upper temperature is also higher. In order to improve this situation, we reasonably arrange the distance between the upper and lower heating elements and the product, and the upper and lower heating elements adopt different power configurations. The uniformity of furnace temperature is guaranteed. In the cooling area of the furnace body, according to the characteristics of electronic ceramics, an emergency cooling air curtain is arranged, so that the products can be cooled quickly, the kiln time is shortened, and the production efficiency is improved

l design of furnace structure:

on the premise of energy saving requirements, according to the characteristics of continuous tunnel furnace, try to reduce the surface temperature of furnace wall, so as to achieve the purpose of reducing heat loss. At the same time, the weight of furnace lining should be reduced as much as possible to achieve the purpose of reducing heat storage loss. According to the above requirements, in the selection of furnace body, furnace and insulation materials, in order to ensure that the furnace has sufficient high-temperature strength, the inner furnace adopts heavy refractory materials. In the high-temperature area, we use corundum mullite shaped bricks with excellent temperature resistance, and in the low-temperature section, the furnace uses first-class high aluminum shaped bricks. The outer insulation material adopts the composite structure of light insulation brick and fiber material. Because the bottom insulation material must bear the pressure of the side wall, top wall, inner furnace and products of the furnace body. This is a recent big move, so the bottom insulation material is light insulation brick. In order to ensure the stability of the furnace, light insulating bricks are used to support the furnace side every certain distance, and high-grade fiber cotton is filled between them. Fiber cotton is also used on the furnace top. In this way, the pressure of the furnace top on the inner furnace is reduced. At the same time, fiber cotton has low thermal conductivity, good heat preservation performance and low density, which greatly reduces the furnace wall surface temperature and reduces the heat storage loss

4. Design results

according to the above design characteristics and the sintering process for ceramic capacitors, we designed and manufactured a 12.7-meter-long pusher electric kiln. The main technical parameters are as follows: (for reference only)

L rated temperature: 1380 C

L rated power: 93 kW because of its large specific surface area: many characteristics of nanoparticles are related to its large specific surface area

L furnace size (L × W × H): 9260 × three hundred and twenty × 190 mm

l furnace body size (L × W × H): 9260 × one thousand three hundred and sixty × 1510 mm

L number of temperature zone groups: 11 groups

L number of temperature control points: 15 points

L push plate size: 250 × two hundred and fifty × 30 mm

L temperature control accuracy: ≤± 1 C

L propulsion speed: 200~1000 mm/h

5. Conclusion

to sum up, the rationality of the structure of the pusher electric kiln can meet the production needs of mass production of electronic ceramics to the greatest extent. The overall equipment integrates modern automatic control technology and high-temperature heating technology, and is another new generation of high-tech ideal firing equipment to replace the traditional kiln. (end)

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