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Firstly, the part that is most prone to damage during the operation of industrial ovens is the electrical control system. The second is the sheet metal structure. Anyone who has used an industrial oven knows this.   2. In an electronic control system, the most vulnerable components are generally contactors, especially those devices that directly use relay outputs. During the constant temperature process, frequent jumping of the relay often indicates that the electrical life of the contactor has not yet reached its end, but its mechanical service life has. There is a problem with the equipment. Therefore, when choosing an industrial oven, it is necessary to pay attention to what the control output is in the electrical parameters of the equipment? It's very important. (Generally, it is recommended to choose: SSR. If conditions permit, SCR can be selected.) Although the equipment was a bit more expensive when customized at that time, the service life of the contactor was prolonged and energy consumption could also be saved. Note: Frequent starting and stopping of the contactor also require current. The reason why equipment control output manufacturers have to think of things for customers before they make any requests. If the customer uses it for a long time, this cost can be directly saved over a period of time.   3. The sheet metal structure is of course also very important. The sheet metal frame structure of industrial ovens is directly related to the service life of the equipment. Because industrial ovens are constantly in a cycle of heating and cooling during operation, thermal expansion and contraction are quite common. The design requirements for the frame structure of the equipment are very high.   4. After-sales service: After-sales service for equipment is of great significance.

Vacuum drying has been widely used in food industry. In recent years, with the combination of vacuum technology, microwave heating technology and other drying technologies, some new types of vacuum drying devices have appeared.0. Introduction at present, an important development trend of food processing technology is * big limit to keep the food nutrition and tasty, and the choice of drying technology and equipment has a great influence on the food product's nutrition, color, flavor.Food drying has many characteristics related to "food". It is different from the drying of chemical products. The former needs to consider food hygiene, nutritional loss, color and flavor changes, etc.Food drying is different from the drying of medical products, because food is often a low added value product, and drugs are generally high added value products, the former must consider the economy of the drying process.Around the "quality and economy", in recent years, food drying technology and equipment has made a lot of progress, and the vacuum and other drying methods or heating technology combined, gave the vacuum drying device new connotation and vitality.1. The characteristics of vacuum drying of food: Vacuum drying is based on the fundamental principle that the saturated vapor pressure of water is closely related to temperature. Under vacuum conditions, the boiling point of water decreases. That is, operating under vacuum, that is, operating at low temperatures, can avoid the destruction of nutrients such as vitamins at high temperatures, and at the same time increase the drying speed. In addition, in a vacuum system, the content of air per unit volume is lower than that in the atmosphere. Drying food in this relatively oxygen-deficient environment can reduce or even avoid the oxidation of fat, Browning of pigments or other oxidative deterioration in food. Therefore, vacuum drying can achieve better food quality. 2 Traditional vacuum drying equipment is widely used in the food, pharmaceutical, chemical and other industries. Various vacuum drying devices have also been developed and introduced in China, and their structural forms are diverse. The commonly used forms in the food industry mainly include box-type, double-cone vacuum dryers, belt vacuum dryers, etc. These traditional vacuum drying devices mainly use hot air, steam or electricity for heating, and transfer heat from the outside to the inside of the material by the principles of heat conduction, convection or radiation. 2.1 Box-type vacuum dryer Box-type vacuum drying is the oldest and simplest type of vacuum dryer. Inside the vacuum drying chamber, there are multiple hollow heating plates. Generally, steam is passed through the heating plates for heating, but electric heating or other radiation heating can also be used. The materials are placed in a metal tray on the heating plate. Heat is conducted to the interior of the materials, causing the moisture to evaporate. Box-type vacuum dryers are still widely used in practice at present and are suitable for the drying of liquid, slurry, powder and bulk food materials. 2.2 Double-cone Vacuum Dryer: The double-cone vacuum dryer rotates a conical container with a symmetrical jacket. The material is continuously stirred by the inherent inclination of the internal cone. Steam or heating carriers are fed into one side of the rotating shaft through a rotary joint, and the material is discharged through an exhaust pipe with a filter screen at the center of the other end of the shaft. The double-cone vacuum dryer can achieve a high vacuum degree, has a simple internal structure, is easy to clean, and all materials can be discharged. 2.3 Vacuum Belt Dryer The vacuum belt dryer is composed of a continuous stainless steel belt, which is wound around the heating drum and the cooling drum. The structure is multi-layered, forming the main body of the dryer, and then it is placed in a closed vacuum chamber. The materials are spread thinly on the belt heating plate and move along with it. Due to the vacuum conditions, the materials are in a boiling state and foaming on the heating plate, so the finished product has porosity. The entire system operates in a closed manner with good hygiene conditions. The actual operating vacuum degree is between 100 and 10Kpa, and the heating temperature is around 150℃. Its operating conditions (drying temperature and time) lie between freeze-drying and spray drying. The quality of the finished product is very close to that of freeze-drying, but freeze-drying is intermittent operation while the vacuum belt dryer operates continuously. It is particularly suitable for drying heat-sensitive and highly oxidized foods. It can be used for liquid or paste materials. It is commonly used in food to dry orange juice, tomato juice, instant tea, etc. 2.4 Vacuum Drum Dryer The vacuum drum dryer seals the drum in a vacuum chamber. In the vacuum drum dryer, feeding, discharging and scraping must all be controlled from outside the drying chamber, so the drying cost is very high. Therefore, it can only be used for drying very heat-sensitive foods, such as fruit juice, yeast, baby food, etc. 3 New Progress in vacuum Drying equipment: Traditional vacuum drying equipment mostly uses heat conduction, convection or radiation for heating, which is slow and not uniform. In recent years, researchers have combined vacuum technology with microwave heating technology and other drying technologies, giving rise to some new types of vacuum drying equipment. 3.1 Vacuum freeze-dried water has three aggregated states, namely liquid, solid and vapor. As the pressure keeps decreasing, the freezing point changes little, while the boiling point side gets lower and lower, getting closer and closer to the freezing point. When the pressure drops to a certain value, the boiling point combines with the freezing point, and solid ice can directly transform into vapor without passing through the liquid state. The triple point pressure of water is 610.5Pa, and the triple point temperature is 0.0098℃. When the pressure is lower than the triple point pressure, solid ice can absorb heat and directly transform into gaseous water vapor. The principle of freeze-drying lies precisely here. During vacuum freeze-drying, the product is placed in a vacuum chamber between two heating plates. Low-temperature far-infrared heating is utilized to ensure uniform drying. The temperature of the heating plates is precisely controlled according to the heating curve of the drying process. The selection of vacuum degree should ensure that all moisture remains in the form of ice throughout the drying process and does not dissolve. For most vegetables and meats, a vacuum degree of 0.5 to 1Pa, corresponding to a sublimation temperature of around 25℃, is appropriate. Because vacuum freeze-dried food is dehydrated at a very low temperature, the loss of nutrients and flavor substances in the food is minimal, which can retain the original nutrition and flavor to the greatest extent. It has excellent rehydration properties and can be restored within seconds to minutes. Its color, taste and shape are basically the same as those of fresh products. There are many vacuum freeze-dried products: coffee, instant tea, fruit juice, herbs, etc. For vegetables, there are scallions, garlic, ginger, mushrooms, meat, scallops, etc. Vacuum freeze-drying requires a large one-time investment, which departs many food manufacturers. For instance, the RAY50 freeze-drying equipment from ATLAS in Denmark (with a freeze-drying area of 45 square meters) The quoted price is as high as 1.05 million US dollars. Domestic freeze dryers are just getting started, and there is still a considerable gap in quality compared with foreign products. In addition, the production cost of vacuum freeze-drying is also relatively high. This is because it requires maintaining a high vacuum and a low temperature of (-25℃), with a long drying time and high energy consumption. These factors bring great resistance to the application of freeze-drying in the food industry. 3.2 The jet continuous vacuum dryer is also known as (Filtermat spray dryer) The jet continuous vacuum dryer, also known as the Filtermat spray dryer, is essentially a combination of a belt vacuum dryer and a spray dryer. Niro The dryer developed by Hudson Company has successfully solved the drying problem of sticky foods ----, such as food materials with high sugar content, high fat content or high acid content. Materials with high viscosity will stick to the wall when using traditional spray dryers, making drying difficult. During the drying process, the material is sprayed vertically downward into the spray drying chamber through pressure nozzles, and hot air is also sprayed downward. The semi-dry powder material accumulates on the moving mesh belt, and the exhaust gas is discharged by the fan. The dried material further moves, cools and is collected on the mesh belt. Due to the maintenance of a moderate vacuum degree inside the spray tower, the hot air temperature only needs to be around 100℃, while the general hot air temperature for spray drying is about 150℃. Therefore, the loss of heat-sensitive materials is less, and at the same time, the height inside the spray tower is reduced. 3.4 Microwave Vacuum Drying Microwave is an electromagnetic radiation wave with a wavelength of 1.0 to 0.001 meters and a frequency of 300 to 300,000 MHZ, which is penetrating. The principle of microwave drying is: The microwave generator radiates microwaves onto the drying materials. When the microwaves enter the interior of the materials, they cause polar molecules such as water to rotate synchronously with the frequency of the microwaves. For example, when drying vegetable products with 915MHz microwaves, the polar water molecules inside the vegetables rotate 915 million times per second. The result of such high-speed rotation of polar molecules like water is that the materials generate frictional heat instantaneously. This causes the surface and interior of the material to heat up simultaneously, allowing a large number of water molecules to escape from the material, achieving the effect of material drying. Traditional heating methods such as steam, hot air and electricity transfer heat from the outside to the inside of the material by the principles of heat conduction, convection and radiation. It takes a certain amount of time for the heat to spread from the outside to the inside. The poorer the heat conduction performance of the material, the longer the time required. Therefore, the heating speed is slow, the heating is uneven and the energy consumption is high. Microwave heating makes the object to be heated itself the heat source, thus it is called an internal heating method. Microwaves pass through the food from all directions, heating both the inside and outside of the food simultaneously. It neither requires a heat transfer medium nor utilizes convection. The temperature of both the inside and outside of the food rises at the same time. The heating speed is fast and uniform, requiring only a fraction or a few tens of the temperature of traditional heating methods. It can also better preserve the vitamins in food and the original color, aroma and taste of food. Experiments have shown that the chlorophyll, vitamins and other nutrients in sun-dried fresh vegetables remain at only 3%, while those in air-drying can retain 17%, those in rapid hot air drying can retain 40%, those in microwave drying can retain 60% to 90%, and those in vacuum freeze-drying can retain 97%. Microwave vacuum drying is an organic combination of microwave technology and vacuum technology, fully leveraging the characteristics of rapid and uniform microwave heating and low water vaporization point under vacuum conditions. It is a very promising drying technology. Microwave vacuum drying technology has been advanced from laboratory to industrial production in France, Japan and the United States in recent years. This technology is very suitable for the deep processing of heat-sensitive foods. The University of California in the United States has collaborated with a certain company to use microwave vacuum drying for seedless raisins, which has maintained the original shape and color of the grapes and avoided the shortcomings of the traditional process (drying in 65℃ hot air for 24 hours), such as changes in product color, shape, flavor and nutritional components. The product quality has been greatly improved. The microwave vacuum dryer (2450MHz, 48Kw) manufactured by the French International Microwave Company has a diameter of 1.5 meters and a length of 12 meters in the microwave vacuum drying chamber. It is used to process instant orange powder. The product not only retains the original color, aroma and taste, but also has a much higher retention of vitamins than spray drying. In recent years, there has been a huge demand for high-end dehydrated vegetables both at home and abroad. The drying process is the key to determining the quality of dehydrated vegetables. Although vacuum freeze-drying is used to prepare dehydrated vegetables with good quality, the vacuum freeze-drying equipment is expensive and the production cost is high. Since the 1980s, vacuum microwave-hot air (45% to 55%) has been used abroad to produce dehydrated vegetables. In terms of quality, it is comparable to the products made by freeze-drying process, but with less one-time investment and a significant reduction in total cost. 4 Closing Remarks (1 Vacuum drying has a series of advantages such as low drying temperature, relatively anoxia in the drying room, avoiding fat oxidation and pigment Browning, which is suitable for the drying of heat-sensitive food materials. In addition, the equipment cost and drying cost are relatively low, and vacuum drying plays an important role in food drying. (2 Vacuum drying combined with microwave heating technology or other drying methods, there are many new vacuum drying devices, giving vacuum drying new connotation and vitality. (3 Vacuum microwave drying to absorb the advantages of both microwave and vacuum drying, the drying technology is a promising, suggested to speed up the development, the development of vacuum microwave drying device in our country.

There are many types of vacuum drying equipment, which have a wide range of applications and are developing rapidly. This article only elaborates on the domestic and international development trends of several types of vacuum drying equipment, with the aim of exchanging information, identifying the problems that need to be solved in the development of vacuum drying equipment, and improving the level of vacuum drying equipment in our country.   Key words: Vacuum drying Drying equipment; Freeze-drying   Vacuum drying has many advantages: when drying under low pressure, the oxygen content is low, which can prevent the oxidation and deterioration of the material being dried, and it can dry flammable and explosive dangerous goods. It can vaporize the moisture in the material at low temperatures, making it easy to dry heat-sensitive materials. It can recover the valuable and useful components in the dried materials. It can prevent the emission of toxic and harmful substances in the dried materials and can become an environmentally friendly type of "green" drying. Therefore, the application of vacuum drying equipment is becoming increasingly widespread.   The main drawback of vacuum drying is that it requires a vacuum system capable of extracting steam, which leads to high equipment investment and operating costs. The production efficiency of the equipment is low and the output is small. To overcome these shortcomings, many scientific and technological workers have made a lot of efforts. At the same time, due to the many advantages of vacuum drying, some products have to use vacuum drying equipment. Therefore, the development of vacuum drying equipment will have a very promising future.   1. The development of continuous vacuum drying equipment at home and abroad is unbalanced   To increase the output of equipment and ensure product quality, various continuous vacuum drying devices were developed abroad over a decade ago. However, in China, due to the limitations of technological levels and people's cognitive concepts, its development has been relatively slow.   1) Belt continuous vacuum drying equipment   The WL-VAQ type belt continuous vacuum drying equipment produced by Nisaka Manufacturing Co., Ltd. of Japan is suitable for drying liquid materials, slurries, pastes, high-concentration and high-viscosity materials. The BV-100.5 vacuum belt continuous drying device produced by Okawara Co., Ltd. of Japan adopts steam and conduction heating. The temperature of each section is adjustable, and the tension and speed of the conveyor belt are also adjustable. The Buch-Gade company of Switzerland has developed a series of belt continuous vacuum drying equipment with automatic cleaning devices.   Since 1995, we have been engaged in the design, manufacture, installation and service of belt continuous vacuum drying equipment, and our technology is relatively mature.   Domestic belt continuous vacuum drying equipment is not common. In 2004, the Guangdong Academy of Agricultural Sciences successfully developed a small-scale experimental device for the drying of banana powder, with very good results.   2) Continuous vacuum drying equipment for grains   The amount of grain to be dried is very large, so continuous drying equipment must be used. In the past, many countries around the world developed a large number of grain drying equipment. Vacuum drying of grains was mostly used for seed drying because the cost of vacuum drying was too high. In fact, this is a misunderstanding. According to Senior Engineer He Xiang from Zhengzhou Grain Research and Design Institute, the continuous corn vacuum drying equipment they developed has a production capacity of 60 tons per day. The fixed investment is slightly higher than that of hot air drying, and the operating cost is the same as that of hot air drying. If the quality of the dried product is taken into account, such as the breakage rate and the rate of bulging during the drying process, the total cost of vacuum drying at low temperatures is not higher than that of hot air drying.   3) Continuous vacuum freeze-drying equipment   Food raw materials are abundant, and the output of products that need to be freeze-dried is very large. Therefore, continuous food freeze-drying equipment emerged relatively early. In 1985, the Danish company ATLAS produced the CONRAD - 800 continuous freeze-drying equipment for freeze-dried coffee production, with a daily production capacity of 13 tons. Figure 2 is a schematic diagram of this equipment. Figure 3 shows a continuous freeze dryer produced in Germany.   The first domestic continuous vacuum freeze-drying equipment was successfully developed by the Shenyang Refrigeration Technology Research Institute in 2000. The vacuum chamber adopts a rectangular structure. Isolation plates are set between the feeding and discharging bins and the drying bin. Both the feeding and discharging bins are equipped with automatic weighing systems, which can determine the drying rate, water output and final drying degree of freeze-dried food. Two external water traps work alternately to achieve continuous water capture and ice melting.   There is a significant gap in the sales volume of continuous freeze-drying equipment at home and abroad. From 1985 to 1990, the Danish ATLAS Company sold 18 continuous freeze-drying machines in just five years. Among them, one was purchased from Taiwan, China. However, no such equipment has been introduced to any province or city on the Chinese mainland to date. Only one domestically produced machine has yet to be sold.   2 The varieties of vacuum drying equipment both at home and abroad are increasing   For different purposes, various new types of vacuum drying equipment have been developed.   1) Microwave vacuum drying equipment is energy-saving and increases the drying rate.   2) The combination of spray and freeze-drying in spray freeze-drying equipment is determined by the nature of the material and the output of the product. The material must be a liquid slurry. After being sprayed and frozen, it forms micro-nano scale particles, which increases the drying rate and enhances the output of the product.   3) Vacuum vapor phase drying equipment is a device specifically designed for drying large oil-immersed transformers and other similar electrical equipment. Switzerland developed this product in the 1970s. China introduced this kind of equipment in the 1980s. After the 1990s, the introduction and digestion were basically completed, and now it can be produced in complete sets.   4) Small-scale laboratory freeze-drying equipment: To meet the needs of schools and research institutions, several types of small-scale laboratory freeze-drying equipment with different functions have been developed successively at home and abroad. Figures 4 to 7 show several small-scale laboratory freeze dryers produced by the German company Martinchrist. They are small in size, light in weight and have multiple functions. It can basically meet the freeze-drying experiments of various materials. Several domestic manufacturers, such as the Fourth Factory of Haimen Light Industry Machinery, have begun to digest, absorb and introduce designs, and have developed new products, but their performance is still not stable enough.   Single-chamber system   Under aseptic conditions, both pre-freezing and drying are carried out in the condensation chamber.   Dual-chamber system   Pre-freezing is carried out in a low-temperature refrigerator or a rotary freezer, and drying is conducted in a drying chamber above the condensation chamber.   5) Freeze-drying separation type freeze dryer for pharmaceutical use   Food freeze dryers all operate the freezing and drying processes separately to achieve the goals of energy conservation, time saving and increased output. In traditional medicine, freeze dryers complete both freezing and drying in one go within the machine. Some companies in Western Europe and the United States, in order to achieve the same purpose as freeze-drying food, pre-freeze medicines and then send them into dryers for drying. Figure 8 shows a photo of the continuous drug pre-freezing equipment.   3 The functions of vacuum drying equipment are increasing   With the advancement of electronic and computer technology, the control systems and display functions of vacuum drying equipment have generally increased. The corn vacuum drying equipment developed by Zhengzhou Grain Science Research Institute has the functions of automatic control and simulation screen display. Vacuum freeze dryers produced by manufacturers such as Shanghai Dongfulong and Beijing Suyuan have multiple functions including determining the end point of freeze-drying, designing freeze-drying curves, checking the operation status, storing multiple freeze-drying curves, and printing production information.   Vacuum drying equipment from abroad has more functions. Most of them are equipped with mechanical arms and can take samples for testing during the drying process. Some rotary vacuum drying equipment has the functions of crushing and granulation. Pharmaceutical freeze-drying equipment can also be used for granulation.   4 Several views on the Development of vacuum drying equipment   Innovation is the fundamental way out for the development of vacuum drying equipment   At present, the development of vacuum drying equipment is relatively slow. One important reason for this is the mutual imitation, remaining at the same technical level and lacking innovation. The ability to imitate is strong, the speed is fast, the concept of innovation is poor, and the investment is low. They focused their competitive efforts on seizing the market, building connections and engaging in price wars. A better approach is to put in some effort in terms of quality and after-sales service. However, none of these are good ways to develop vacuum drying equipment. It is necessary to invest human, material and financial resources to innovate.   Energy conservation is the key to the development of vacuum drying equipment   Energy shortage has drawn worldwide attention. The traditional view holds that vacuum drying equipment has high energy consumption because it requires a vacuum pump. However, I have never witnessed a true comparison of energy consumption for the same material when it is dried to the same moisture content. In fact, vacuum drying is a low-temperature drying process carried out in a closed space, resulting in relatively less energy waste. Despite this, energy conservation of vacuum drying equipment remains the key to its development. Compared with other types of drying equipment, the energy-saving focus of vacuum drying equipment should be   It should be placed on the rational design, selection and use of vacuum systems.   There are not many vacuum systems capable of extracting steam. Currently, there are mainly two categories. One is pumps that can directly extract steam, including water jet pumps, steam jet pumps, water ring pumps and wet Roots pumps. Another type is to capture water by condensation. Both of these methods consume relatively high energy. The direction of energy conservation for the first type should be to enhance the pumping efficiency of the pump. The latter type of energy-saving direction is to design the structure and thermal efficiency of gas-solid phase change heat exchangers.   3) Continuous vacuum drying equipment is an important method to increase product output and save energy   Compared with periodic vacuum drying equipment, continuous vacuum drying equipment requires less auxiliary time, saves time and increases output. At the same time, it does not have to be like the periodic vacuum drying equipment, where the temperature of the equipment changes once after each production cycle, resulting in some energy being wasted on the repeated heating of the equipment components. Therefore, energy was saved.   4) The combination of vacuum drying equipment with other drying methods is a production approach that should be advocated   The combination of vacuum drying and other drying methods can enhance production efficiency and reduce product costs. For instance, for products such as vegetables, aquatic products and fruits, vacuum drying can ensure product quality. If, before vacuum drying, they are washed and blanched, then subjected to centrifugal dehydration, followed by cold air drying to remove surface water, and then sent into vacuum drying equipment, it can significantly improve production efficiency and reduce production costs at the same time. The combination of spray and freeze-drying is also one of the combination methods. This kind of similar   There are many combination methods that can be found through experiments, but of course, it also requires a certain amount of time, energy and financial resources.   5 Closing remarks   Vacuum drying equipment is constantly being innovated There are still quite a few existing problems. If industry, academia and research can cooperate closely, the results will be more remarkable.   The materials I have consulted are limited and my insights may not be accurate. Corrections are welcome.

With the development of society and the advancement of technology, the requirements for trolley ovens are getting higher and higher. From the old-fashioned electrical appliances in the past to the current intelligent control, there has been a qualitative leap in safety performance and energy conservation. The following is a brief introduction to several aspects of trolley ovens: I. Main performance of Trolley Oven 1. The temperature is controlled by an intelligent program temperature controller, with PID parameter self-tuning, solid-state relay power regulation, contactless continuous adjustment, and automatic completion The entire drying process can meet the requirements of any curing curve, is easy to operate and reliable in performance. We carefully select electrical control components both at home and abroad to ensure that the reliability of the electrical control part of the curing oven reaches the optimal level. 2. It can achieve timed intermittent automatic exhaust function within the process temperature range (optional according to user requirements). 3. Paper feed recorders, print recorders or paperless recorders can be selected to monitor the entire process and analyze the results of drying and curing. 4. According to the different placements of the products to be dried, select a reasonable hot air circulation method (top heating with vertical air supply, bottom heating with horizontal air supply, side heating with vertical air supply, etc.) to make the temperature inside the working chamber more uniform and the drying and curing effect of the coil better. 5. An independent over-temperature alarm system is also provided. When the temperature is abnormal, it can cut off the heating power supply and issue an audible and visual alarm. 6. A set of low-voltage lighting system can be optionally equipped. The door is equipped with an observation window, allowing the curing status of the workpiece to be observed at any time. 7. It adopts sealed electric heating tubes for heating, which are resistant to oxidation, have stable performance and a long service life. 8. Tracks are laid at the bottom, and different trolley drive methods such as manual drive, blunt rack drive, roller drive, and traction trolley drive can be selected according to the weight of the products to be dried. 9. According to the on-site usage conditions of the user, it can be controlled nearby. Multiple curing ovens can also be equipped with a computer distributed control system, which can centrally realize the setting of temperature control programs for multiple curing ovens, temperature curve recording and other functions. The operation is simple, convenient and the control is reliable. Ii. Uses of Trolley Oven The trolley oven is an energy-saving oven for industrial large-scale production purposes. It is mainly used for drying transformer cores and coils, painting electrical cabinets and parts, rare earth, casting sand molds, motors and many other purposes. It adopts a trolley type feeding and discharging method, which is suitable for the automatic feeding and discharging of a large number of workpieces. In the production process of dry-type transformers, the processes such as core preheating, coil pre-drying, coil impregnation and drying, and resin curing are extremely crucial, directly affecting the quality of the transformer. Therefore, the temperature uniformity of the curing furnace and the reliability of the control system are required to be very high. The transformer curing oven produced by Wujiang Junhuan Machinery Equipment Co., Ltd. features excellent temperature uniformity, various flexible air supply methods, a mature and reliable control system, and an attractive appearance. It has been widely applied in dry-type transformer manufacturing enterprises across the country. The self-driven trolley oven can be used by factories and research institutions for baking, drying, heat treatment, disinfection, heating, heat preservation and other process equipment. It is widely used in low-temperature tempering, annealing, aging treatment and hot loading process of metal workpieces. It not only ensures the processing quality of the workpieces, but also improves production efficiency. The trolley is equipped with a drive device. Once the switch is turned on, it can automatically enter and exit. The working temperature of this box can range from room temperature to the maximum operating temperature. Within this range, the desired temperature can be freely selected. After reaching a constant temperature, the temperature can be automatically controlled by the electrical control system. Heaters and air ducts are installed on the left and right sides of the working chamber. There is a blower on the top of the working chamber. The blower mechanically convinizes the air inside the box through the air ducts, making the temperature inside the working chamber uniform and consistent. The temperature control of the oven adopts electronic temperature regulation automatic control and thermocouple sensors. Iii. Precautions for the Use of Trolley Ovens The trolley oven is a device that dries objects by heating them through layers of electric heating wires. It is suitable for baking, drying, heat treatment, etc. within the range of 5 to 300℃ (some up to 200℃) higher than room temperature, and the sensitivity is usually ±1℃. There are many models of trolley ovens, but their basic structures are similar. Generally, they consist of three parts: the box body, the electric heating system and the automatic temperature control system. Its usage and precautions are summarized as follows: 1.. The oven should be placed in a dry and level indoor area to prevent vibration and corrosion. 2. Pay attention to safe electricity usage and install a power switch with sufficient capacity according to the power consumption of the oven. Select sufficient power supply wires and there should be a good grounding wire. For ovens equipped with an electrical contact mercury thermometer type temperature controller, the two wires of the electrical contact thermometer should be respectively connected to the two terminals on the top of the oven. Insert another ordinary mercury thermometer into the exhaust valve. (The thermometer in the exhaust valve is used to calibrate the electrical contact mercury thermometer and observe the actual temperature inside the box.) Open the hole of the exhaust valve. After adjusting the electrical contact mercury thermometer to the desired temperature, tighten the screws on the steel cap to achieve a constant temperature. However, it must be noted that when adjusting, the indicator iron must not be turned outside the scale. 4. Only when all the preparations are completed can the test samples be placed in the oven. Then connect and turn on the power. A red indicator light on indicates that the oven is heating up. When the temperature reaches the set temperature, the red light goes out and the green light comes on, marking the beginning of a constant temperature. To prevent the temperature control from malfunctioning, it is also necessary to keep an eye on it. 5. When placing the test samples, it should be noted that the arrangement should not be too dense. No test samples should be placed on the heat dissipation plate to avoid affecting the upward flow of hot air. It is prohibited to bake flammable, explosive, volatile and corrosive items.

Article Details When it comes to the microwave heating function, it is necessary to mention the heated materials. Generally speaking, microwaves can only act on materials that can absorb microwaves, generating heat energy through the vibration of material molecules. So let's talk about four types of materials in the industrial microwave high-temperature field.   Microwave selective heating refers to the fact that microwaves can only heat certain materials but not some others. Therefore, they are introduced in four major categories according to the properties of the materials:   The first type of material is absorbing materials, such as copper oxide. These materials have a good absorption capacity for microwaves. Due to their high dielectric loss, they can convert the electromagnetic energy in microwaves into thermal energy.   The second category is transmissive materials, such as quartz and polytetrafluoroethylene. On the surface of these materials, microwaves are partially reflected and partially penetrated, and are rarely absorbed. Therefore, they cannot or are difficult to be heated by microwaves.   The third category is reflective materials, typically conductive materials such as metal iron blocks and graphite pressed products. They have a reflective effect on microwaves and cannot be heated by microwaves. However, when iron blocks, copper blocks, and graphite blocks are processed into powder form, they have an excellent absorption capacity for microwaves and can rapidly heat up to hundreds of degrees Celsius or even 1000 degrees Celsius within a relatively short period of time. Therefore, whether the material can be heated by microwave is related to the material's own properties as well as its physical state.   The fourth type of material is heterogeneous material, which has been one of the research hotspots in recent years. In the fields of microwave metallurgy and material synthesis, the objects of microwave heating are mostly two-phase or multi-phase heterogeneous materials, and the mechanism of action is very complex. The characteristic of this type of material is that it has a local field enhancement effect under microwave irradiation, which can cause discharge and generate ultraviolet light to promote photocatalysis. This is a new mechanism of microwave-assisted catalysis.     Microwave equipment is a new type of industrial equipment. Its energy conservation and environmental protection have been recognized by many enterprises. Enterprises with relatively serious environmental pollution have begun to choose to use environmentally friendly microwave equipment to replace traditional drying, sintering and other equipment in enterprises.

Drying is a crucial step in the production of traditional Chinese medicine, widely applied in the manufacturing of pharmaceutical excipients, raw materials, intermediates and finished products, especially in the drying of traditional Chinese medicine extracts. The quality of the operation directly affects the performance, quality, appearance and cost of the product. At present, the drying of extracts mainly relies on traditional drying equipment such as hot air circulation ovens and vacuum drying ovens. However, in recent years, new drying technologies such as spray drying, vacuum freeze drying, and microwave vacuum drying have been widely applied and promoted in the drying process of Chinese herbal extracts.   Due to the high viscosity and poor air permeability of traditional Chinese medicine extracts, the general drying process of traditional Chinese medicine extracts has disadvantages such as long drying time, low output, high energy consumption, low production efficiency and poor product quality. It is far from meeting the requirements of modernization of traditional Chinese medicine for efficient, energy-saving, environmentally friendly and advanced drying processes of traditional Chinese medicine extracts. The microwave vacuum drying equipment that has emerged in recent years can effectively solve the problem of drying traditional Chinese medicine extracts. The particles obtained after drying by a microwave vacuum dryer have micro-pores inside from a microscopic structure perspective. After being directly crushed to the required particle size, the particles have excellent fluidity and can be directly pressed into tablets or filled into capsules. At the same time, due to the microscopic loose structure of the particles, they have excellent instant solubility and a good appearance. For instant (powder) products, it can greatly enhance the grade of the products. The entire drying process is completely enclosed and does not come into contact with the external environment, meeting GMP standards. Features of the microwave vacuum drying equipment for traditional Chinese medicine extracts: (1) Low drying temperature, suitable for drying heat-sensitive traditional Chinese medicine extracts; (2) Suitable for dry and easily oxidized traditional Chinese medicine extracts; (3) Suitable for drying high-concentration and high-viscosity traditional Chinese medicine extracts; (4) The product has excellent solubility. After drying, micro-pores can be seen inside the material from a microscopic structure. When directly crushed to the required particle size, the fluidity of the particles is very good. At the same time, due to the microscopic loose structure of the particles, the instant solubility is extremely good. (5) During the drying process, the product is constantly in a vacuum state, which reduces product oxidation and makes it less likely for the material to adhere. To retain its original color, aroma and taste to the greatest extent and obtain a high-quality final product. Vacuum microwave equipment is a brand-new concept of highly efficient, energy-saving and environmentally friendly drying equipment. It has been successfully applied to the drying of Salvia miltiorrhiza extract, Notoginseng extract, Angelica sinensis extract, as well as foods such as wheat extract, coffee and milk powder, achieving good results. For food, due to its short drying time, low temperature, vacuum state, no oxidation, and good retention of aroma; In the field of pharmaceuticals, it has a very good effect on preserving the activity and aroma of some active substances, apis, heat-sensitive substances, vitamins, aromatic substances, etc.

Control characteristics It features parameter memory protection against data loss due to power outages or system crashes, as well as power-on recovery functions. This function is mainly achieved by control instruments, the common ones being liquid crystal regulators or paperless recorders. Performance features It adopts the first streamlined arc design in China. The shell is made of cold-rolled steel plate and the surface is electrostatically sprayed with plastic. The temperature control system of this machine adopts microcomputer single-chip technology for temperature control, timing and over-temperature alarm. The reasonable air ducts and circulation system ensure that the temperature uniformity within the working chamber changes little. The display is a dual-screen high-brightness digital tube display, with accurate and intuitive readings, superior performance, and touch keys for setting and adjusting parameters. The temperature control sensor adopts original imported capacitive components. It has timing and timekeeping functions. The inner tanks are all made of mirror-finish stainless steel. The four corners of the semi-circular shape are easy to clean. The height and number of shelves in the studio can be adjusted freely according to the user's requirements. Adopting imported motors and fan blades, with a micro-air circulation, it can eliminate users' concerns about blowing away fine or powdered items during cultivation. The box door is equipped with large-angle insulated tempered glass, which is convenient for users to observe. The use of nano-material door sealing strips and insulation materials makes the overall performance of the machine more superior. Principle and function of electric heating blower drying oven This product is specially designed for drying heat-sensitive, easily decomposable and easily oxidized substances. It can be filled with inert gas inside, and even some complex items can be dried quickly. The box structure of the electric heating blower drying oven The design is perfect. The box body is formed by CNC machine tools, and the box door adopts an upward opening type, making operation easy. The inner tank is made of SUS304 stainless steel plate, and the outer shell is made of A3 plate with plastic spraying treatment, which is more lustrous and beautiful. The circuit system side adopts a door-type opening, which is convenient for maintenance and repair. The tightness of the box door closure can be adjusted. The integral formed silicone rubber door seal ring ensures the height inside the box. Storage, heating, testing and drying are all carried out in an oxygen-free or inert gas-filled environment, so oxidation will not occur. Electric heating blower drying oven control execution system The temperature controller adopts touch keys, digital LED display and PID intelligent control instrument. Pt100 platinum resistance temperature sensor Electric heating blower drying oven protection system The overall machine protection system is composed of over-temperature protection and alarm devices. It ensures the integrity of the execution components and test pieces. Product Description Purpose: This machine is suitable for drying, baking and preheating various materials or test pieces. The inner box structure adopts a hot air circulation method, ensuring uniform temperature distribution. Inner box dimensions A. 40×40×45cm B. 50×50×60cm C. 60×50×90cm (Other sizes can be customized according to customer requirements). Distribution accuracy: ±1%(1℃) at room100ml100℃ Temperature analysis: Displayed in 0.1℃ units Heating method: Hot air circulation Temperature range: Room temperature to 300℃ Attachment: Double over-temperature protection and 2 shed boards Timer: 0 to 999.9 hours (minutes), power-off memory type Power supply: 1φ, 200v/50Hz

Microwave is a type of electromagnetic wave with an extremely short wavelength, ranging from 1mm to 1m, and its corresponding frequency is between 300GHz and 300MHz. To prevent microwave interference with radio communication, broadcasting and radar, the international community stipulates that there are four frequency bands used for microwave heating and microwave drying, namely: Band L, with a frequency of 890 to 940MHz and a central wavelength of 0.330m; The S segment has a frequency of 2400 to 2500MHz and a central wavelength of 0.122m. Section C, with a frequency of 5725 to 5875MHz and a central wavelength of 0.052m; The K band has a frequency of 22,000 to 22,250 MHZ and a central wavelength of 0.008m. Only the L and S segments are used in household microwave ovens. Microwaves are obtained by passing direct current or 50Hz alternating current through vacuum devices or semiconductor devices and utilizing the special movement of electrons in a magnetic field. This kind of motion can be simply explained as follows: From the perspective of electrical structure, there are two types of molecules in a medium: one is called electropolar molecular dielectrics, and the other is called polar molecular dielectrics. Under normal circumstances, they are all arranged randomly. If they are placed in an alternating electric field, the orientation of the polar molecules of these media will also change along with the polarity of the electric field. This is called polarization. The stronger the applied electric field is, the stronger the polarization effect will be. The faster the polarity of the applied electric field changes, the faster the polarization will be, and the more intense the thermal motion of the molecules and the frictional action between adjacent molecules will be. During this process, the conversion of electromagnetic energy to thermal energy is completed. When the heated substance is placed in the microwave field, its polar molecules swing and rub back and forth at a high frequency of several billion times per second with the microwave frequency, generating sufficient heat to heat food thoroughly in a very short time. Magnetrons are used in household microwave ovens to convert electrical energy into microwave energy. There are two types of magnetrons: pulse magnetrons and continuous magnetrons. Continuous wave magnetrons are used in microwave ovens. The propagation speed of microwaves is close to the speed of light. During its propagation, it can undergo reflection and refraction. It has three important characteristics related to heating. When microwaves encounter metallic objects such as silver, copper and aluminum, they are reflected just like visible light in a mirror. Therefore, metals are commonly used to isolate microwaves. In microwave ovens, metal is commonly used to make the box body and waveguide, and metal mesh with tempered glass is added to make the observation window of the oven door. When microwaves encounter insulating materials such as glass, plastic, ceramics, mica, etc., they will pass through as smoothly as light does through glass. Therefore, insulating materials are often used to make plates and pans without affecting the heating effect. When microwaves encounter food containing water or fat, they can be absorbed in large quantities and converted into heat energy. The microwave oven takes advantage of this feature to heat food.   Is microwave-processed food good? Is there any scientific basis for this?   Microwaves are high-frequency waves that change at a speed of 2.4 billion times per second, causing high-speed rotational motion of water molecules. They rub against each other, generating tremendous heat, which makes it convenient to cook food.   The pathogen contains a large number of water molecules. Under the action of microwaves in a microwave oven, all the bacteria can be killed within one or two minutes. It has been determined that when red intestines containing 1.92 million Escherichia coli per gram were heated in a 500-watt microwave oven, only 260 survived per gram after half a minute, and all were killed after one minute.   When cooking food in a microwave oven, since the heat is inside the food, it heats evenly and does not require stir-frying, thus avoiding the phenomenon of being burnt on the outside but burnt on the inside.   Nitrosamines are produced during the processing of foods such as cured meat, preserved meat, salted fish and smoked duck. Nitrite, as a preservative, can also react chemically with food to form nitrosamines, which can cause cell canceration. American pharmacologists have found that when cured meat is baked in a microwave for 45 minutes and taken out, it is both fragrant and crispy, with a delicious taste. Moreover, no trace of chalcosamine can be found through chemical analysis.   In addition, cooking meat products in a microwave oven can also fully protect the nutritional components of the meat products.   Mysterious stainless steel furnace cavity   A stainless steel microwave oven refers to a microwave oven with a cavity made of stainless steel. Stainless steel is an alloy steel made by adding a certain proportion of special elements such as nickel and chromium and through a special process. It has high corrosion resistance.   There are many types of stainless steel due to their different compositions and smelting processes. Among them, austenitic stainless steel is not easily magnetized due to the special internal molecular structure. On the surface, it seems that this kind of stainless steel cannot "attract" a magnet. Therefore, it is incorrect for users to use a "magnet" to test whether it is stainless steel. The microwave oven cavity made of stainless steel has the most prominent features of high surface strength, higher temperature resistance and rust resistance, etc.   The ordinary steel plate furnace cavity that has undergone surface coating treatment may have its surface coating layer fall off or crack after accidental bumps, thus losing its anti-rust effect on the ordinary steel plate. Compared with the ordinary steel plate furnace cavity that has undergone surface coating treatment, the stainless steel furnace cavity ensures that it is not prone to rust from the perspective of steel plate material. Even if there are large dents from bumps, it will not lose its "rust-free" characteristic.   It is a consensus that stainless steel is not prone to rust. For stainless steel microwave ovens in general household environments and usage conditions, it can also be considered that the stainless steel oven cavity will never rust. However, the ordinary steel plate furnace cavity that has undergone surface coating treatment may also experience rusting after long-term use, especially in the corner areas of the furnace cavity where rusting is more likely to occur.   Of course, this does not mean that the ordinary steel plate oven cavity treated with surface coating is extremely prone to rust. Judging from the current material, technological level, manufacturing cost and market acceptance, the ordinary steel plate microwave oven is not at a disadvantage, and there is no trend of being phased out due to the introduction of stainless steel microwave ovens.   As for some media's evaluation that stainless steel microwave ovens have higher heating effects and are more energy-efficient and time-saving, it is somewhat too one-sided. Compared with ordinary steel plates that have undergone surface coating treatment, the surface resistance of stainless steel materials is smaller. Under the action of microwaves, the surface eddy currents of this material are also smaller, which is manifested as low microwave loss and high reflectivity of this material. However, under the conditions of general household use, this difference is not easily noticeable.

During the production process of microwave equipment (especially when it operates for a long time), the heating box of the equipment will heat up. In severe cases, the overheating may cause the microwave electrical components to be burned out. However, before selling the equipment, microwave equipment manufacturers usually introduce to customers: "Since metal does not absorb waves, the heating box of the microwave equipment will not heat up normally, so the production workshop can maintain a good environment."   But what are the causes of fever? The specific reasons are:   1. The microwave equipment itself has relatively poor wave absorption performance. After the microwave is fed into the box, some of it cannot be absorbed by the product in time and remains inside the box, refracting back and forth. When there is a gap at the connection part of the box, a "spark" will occur and heat up, causing the equipment box to gradually rise.   2. The ventilation system in the workshop environment and the exhaust system of the equipment are not good. After long-term operation and use of the equipment, the heat generated by the electrical components of the microwave equipment accumulates over time, causing the equipment to overheat.   3. When using microwave equipment to bake materials, high-temperature baking is required. When the materials are heated and baked inside the box, some of the heat will also be conducted to the top of the box. If it lasts for a long time, it will overheat and cause the electrical appliances to burn out.   4. The long-term use of industrial microwave equipment without a good heat dissipation and ventilation system causes the electrical components and equipment to overheat!   5. During the production process of the equipment, some materials fell to the bottom of the box and were not cleaned out for a long time, causing the materials to absorb microwaves for a long time and heat up or catch fire, resulting in local heating of the equipment!

Domestic food machinery has introduced microwave technology into the design and application of drying equipment, and has developed industrial food-grade microwave dryers. Microwave dryers generate energy conversions such as thermal effects, biological effects, and chemical effects, thereby producing a large amount of heat to achieve the purposes of heating, drying, and sterilization.     The seafood microwave dryer converts electrical energy into ultrashort waves for penetrating heating and baking. It adopts low-temperature flexible baking technology, with a low baking temperature and minimal loss of nutrients in the baked shrimp. The quality of the grilled shrimp obtained is good. It mainly replaces the traditional wood-fired baking equipment. The equipment features high energy conversion efficiency and fast heating speed.     During baking, the expansion force of the gas causes the structure of the high-molecular substances in the components to denature, thus transforming them into a multi-microporous substance with a reticular organizational structure and a fixed shape. Compared with traditional baking equipment, there is no open flame, no smoke, no dust, which is environmentally friendly and hygienic. The prawns baked in this way have a bright surface color, no impurities, and the prawn meat retains its original flavor, with a tender and delicious taste.     The good market benefits achieved in microwave baking equipment are inseparable from the economic benefits it brings. In terms of energy consumption rate, productivity, labor force, product quality, floor space, production and labor conditions, operating costs and technical level, the baking technology of Boda microwave dryer is in the leading position.