Development and application of the hottest fully a

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With the rapid development of high-tech ceramics and high-quality refractories, domestic high-temperature firing technology has also been developed accordingly. The advent of some new high-temperature kilns not only meets the production requirements of small batch and multiple varieties, but also improves the quality of fired products to a new level. The XZH series full automatic control high-temperature shuttle kiln developed and designed by our company has been optimized in the kiln structure, working system and control system. Some unique new technologies have been adopted, and the performance is advanced and reliable. After being put into operation, all technical and economic indicators have met the design requirements, and the operation effect is ideal. It is worth using for reference when relevant manufacturers build or transform high-temperature shuttle kilns. Here is a detailed introduction to the 6m3 gas fully automatic control high temperature shuttle kiln designed and built by our company for Jiangsu Ruifeng new materials Co., Ltd

1 main technical parameters and economic indicators

fired products: high temperature sintered materials; Geometric volume: 6.0 m3; Inner cavity size: 2.9m × 1.6m × 1.3m; Kiln car table size: 2.8m × 1.5m; Number of kiln cars: 4, including 2 inside the kiln and 2 outside the kiln; Number of material stacks in the kiln: 2; Stack size: 1.0m × 1.4m × 1.2m; Service temperature: 1700 ℃; Fuel: liquefied petroleum gas; Number of Burners: 6, high-speed temperature regulating burners; Firing method: side firing, open flame firing; Smoke exhaust method: the smoke enters the underground flue through the smoke exhaust outlet under the vehicle and is discharged by the smoke exhaust fan; Kiln door structure: hanging translational pneumatic pressing kiln door; Control mode: temperature, pressure and the food safety law have clearly stipulated that the production enterprise has fully automatic control of the qualified incoming and outgoing products; Temperature control accuracy ≤± 2 ℃; Number of thermocouples: 6 B-type, 1 S-type, 1 K-type; Kiln system settings: kiln body, kiln door, kiln car and ferry, combustion system, smoke exhaust and heat exchange system, measurement and automatic control system, etc

2 kiln body structure

the kiln body is a section steel frame structure, covered with steel plates, with stable structure, good sealing and beautiful appearance

alumina hollow ball brick is selected as the lining of the kiln, which requires that the material has sufficiently high load softening temperature and good thermal stability to meet the requirements of the maximum firing temperature of the kiln. The middle layer of the kiln is light mullite brick, and the outer layer is aluminum silicate refractory fiber felt and asbestos free calcium silicate board for insulation. The use of light materials in the kiln body can reduce the thickness of the kiln body and the heat storage and dissipation of the kiln wall, which is conducive to automatic control and energy conservation

the kiln top structure is α= For the 75 ° arch roof structure, in order to avoid longitudinal cracks after the arch roof is cooled due to high-temperature expansion, in addition to alumina hollow ball bricks, the arch roof lining is also built with high-temperature refractory bricks of different materials in a certain part. The application results show that the high-temperature structure of the arch roof of the kiln is stable, and there are basically no obvious longitudinal cracks. Due to the large transverse thrust of the arch crown, the outside of the arch foot brick of the traditional tunnel kiln is built with heavy bricks, which has poor heat insulation. In this design, heavy flat bricks are placed laterally at a certain distance from the outside of the arch foot bricks, and light heat insulation bricks and loose heat insulation materials are filled between the flat bricks, which can effectively improve the thermal performance of this part when the oil delivery handwheel is closed. High temperature kilns have strict requirements for burner bricks

after a period of production and operation, the internal walls on both sides of the traditional high-temperature shuttle kiln will protrude into the kiln to varying degrees due to high-temperature expansion. In order to overcome this problem, in addition to designing the fire-resistant brick lining of the kiln wall as a meshing structure, we also adopt a special movable anchor connection between the kiln wall masonry and the kiln steel frame, which allows the free expansion of the kiln masonry at high temperature and avoids the convex deformation of the kiln wall due to high temperature

due to the large temperature difference between the cold end and the hot end of the burner brick, it is easy to crack during use, with short service life and troublesome replacement. The burner bricks of the kiln are divided into four pieces during production, and then built and pieced together into a whole, which greatly prolongs the service life of the burner bricks

3 kiln door

the kiln door adopts the hanging translational kiln door, and the masonry structure is the same as the kiln wall. The whole kiln door is hung on the I-steel beam track at the kiln head according to the fixed height, and is equipped with vertical and horizontal movement trolley. The opening and closing of the kiln door is realized through their respective independent speed change devices, that is, the kiln door can be opened or closed when translating along the longitudinal direction of the kiln body, and the kiln door can be removed or reset when translating along the transverse direction of the kiln body. The advantage of the hanging translational kiln door is that it can move up, down, left and right, which is convenient for closing the kiln door

the kiln door and kiln body adopt zigzag sealing structure and pneumatic pressing mode

4 kiln car and ferry car

kiln car is made of section steel. High temperature bearing is used as the bearing, and the maximum temperature resistance is 300 ℃. The refractory material of the car body is: the electric melting and sintering mullite brick with good thermal shock resistance is selected for the car platform face brick, and it is dry built; The surrounding area is built with meshing bricks; Insulating bricks are used in the middle. The advantage of dry brick laying on the platform is that it can greatly reduce the maintenance times of the kiln car and prolong the service life of the kiln car

due to the high pressure in the high-temperature shuttle kiln, the sealing measures between the kiln car and the kiln body are particularly important. In addition to the curved seam structure, the manual lifting frame sealing structure is also designed to replace the traditional shuttle kiln sand sealing structure. The lifting frame is set along the length of the kiln and driven by a lever. Zirconium containing refractory fiber is pasted in the lifting frame. When burning, the lifting frame can be raised to the level between the kiln wall and the lower surface of the kiln car chassis

the number of kiln cars is 4, including 2 cars when burning in the kiln and 2 cars outside the kiln for standby during enhanced production

the ferry is an electric ferry with a positioning device

5 combustion system

six gas air premixed high-speed temperature regulating burners are selected for the kiln, which are arranged staggered up and down on both sides of the wall, forming three fire passages with the two kiln cars parked in the kiln. At low temperature, the high-speed temperature regulating burner has a high ejection speed of air flow, sweeping the gas circulation in the kiln, strengthening the convection heat transfer of the kiln and homogenizing the temperature in the kiln. The use of temperature regulating burners is conducive to the low temperature control of the kiln, ensuring that the products entering the kiln can rise slowly in the low temperature stage of firing, which is very beneficial to improving the firing qualification rate. Liquefied gas is supplied by the gas tank after pressure reduction through the pressure reducing valve, and the combustion air and temperature regulating air are supplied by a high-pressure fan respectively. The combustion supporting air is preheated to about 300 ℃ by the flue heat exchanger and supplied to the burner. The use of hot air combustion supporting can effectively ensure that the maximum firing temperature and the heating rate in the high temperature stage meet the process requirements. The temperature regulating air is cold air supplied to the burner. Generally speaking, the temperature regulating air volume is large in the low-temperature stage, and the temperature regulating air volume is generally reduced or closed in the high-temperature stage to ensure the requirements of high-temperature combustion. The gas and air pipelines in front of the kiln are designed as annular pipelines to balance the medium resistance in front of the burner

the high-speed temperature regulating burner provides a means to make the temperature and atmosphere in the kiln uniform in the low-temperature stage of firing, strengthen convective heat transfer, easily realize the fine adjustment of the temperature in the kiln, meet the rigorous process requirements, help to improve the firing quality of products, and is especially suitable for the low-temperature control in the initial stage of kiln ignition. However, it should be pointed out that the energy-saving effect is not ideal because the high-speed temperature regulating burner mainly depends on blowing in excess cold air to regulate the temperature at the low temperature stage

6 smoke exhaust and heat exchange system

the smoke enters the underground branch flue at the bottom of the car through the smoke exhaust hole on the table of the kiln car, and is led into the smoke exhaust fan by the main flue after being summarized. In the underground main flue, a stainless steel heat exchanger is installed, and the temperature of combustion air through heat exchange can reach more than 300 ℃. A cold air distribution outlet is set on the main flue, and the air distribution volume is adjusted according to the flue gas temperature, so that the smoke extractor and heat exchanger can operate at a safe working temperature

7 measurement and automatic control system

measurement system includes temperature measurement and pressure measurement. Six thermocouples are installed in the kiln for temperature measurement; A thermocouple is installed in front of the inlet of the smoke exhaust fan and the inlet of the heat exchanger to detect the flue temperature. A pressure measuring point is set on one side of the inner wall of the kiln to detect the pressure in the kiln through a pressure transmitter. A pressure transmitter is also installed on the main pipeline of the temperature regulating fan and the combustion supporting fan to detect the air pressure. A high and low pressure switch is set on the gas main pipeline to detect the pressure change of liquefied gas

the kiln adopts computer automatic control, including computer, AI Artificial Intelligence regulator, solenoid valve, electric actuator, air-fuel proportional control valve, etc., and is equipped with data acquisition card and isolation devices inside and outside the machine, which are programmed and developed by using the special industrial control software package of the computer. The automatic control system is composed of temperature control, automatic ignition and flameout protection device of burner, pressure control, automatic vehicle entry and exit system, safety interlock control alarm system, etc

temperature control is divided into 6 zones, and each burner is 1 zone. Control principle: the AI Artificial Intelligence Instrument in each zone receives the measured temperature signal value of the thermocouple and compares it with the set value of the temperature curve. If the measured value is less than the set value, the ai artificial intelligence instrument outputs Ma signal, increases the opening of the combustion air duct butterfly valve through the electric actuator, and synchronously increases the gas flow through the proportional valve of the gas pipeline to raise the temperature in the kiln. If the measured value is greater than the set value, Ai Ai artificial intelligence instrument will conduct reverse adjustment on the experimental machine produced by Jinan new period assay instrument Co., Ltd. for several 10 years, so as to ensure that the kiln temperature curve is carried out according to the set firing curve

pressure control includes kiln pressure, combustion air pressure and temperature regulating air pressure control. The pressure control in the kiln is realized by frequency conversion control of the smoke exhaust fan, that is, take out the kiln pressure signal from the pressure measuring point in the kiln, send the signal to the ai artificial intelligence instrument through the pressure sensor, compare it with the set value of the kiln pressure, and the output signal controls the speed of the smoke exhaust fan through the frequency converter to make the pressure in the kiln follow the set kiln pressure curve. The pressure in the kiln can be controlled by constant pressure in the whole process to reduce the interference to the temperature. The control of combustion supporting air pressure and temperature regulating air pressure is realized by taking out the pressure signal from their respective main pipes and controlling the fan speed through frequency conversion

the automatic entry and exit system is equipped with an electric ferry, which can automatically run on the return line and realize its own positioning; The electric ferry car is equipped with a small tractor, which can automatically reverse, advance and retreat, so as to realize the automatic entry and exit of the kiln car. The control cabinet is located near the kiln body and connected with the central control room, which can realize remote full-automatic and on-site step-by-step manual operation. The on-site travel position switches are all double measuring points. When a travel switch fails, the system will operate as usual, and an alarm will be sent to remind the user of maintenance

safety interlock control alarm system: since the fuel of the kiln is LPG, in order to ensure the safety of gas supply, a main solenoid valve is set on the main gas supply pipeline. When the system is powered off or the liquefied gas pressure exceeds the range of use, the solenoid valve automatically cuts off the gas circuit; When the fan system fails and the wind pressure changes too much, the alarm system sends an alarm signal, and the solenoid valve automatically cuts off the air circuit to ensure safety

ionization flame detection/automatic ignition device is set in front of each burner. If the burner stalls, the system will send an alarm signal and turn to the automatic ignition operation program at the same time. If the ignition fails within the specified time, the gas solenoid valve in front of the burner will automatically close, cut off the gas supply, and prompt manual treatment

the smoke exhaust fan, temperature regulating fan and combustion supporting fan are interlocked and controlled according to the set starting and stopping sequence to ensure the safe operation of the kiln

the opening and closing of the kiln door is interlocked with the vehicle entry and exit system and the automatic ignition system of the burner. When the kiln door is not fully opened

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