Industrial microwave ovens of continuous action. Infrared or microwave dryer for drying wood: choosing equipment for work

Description
Industrial microwave WSZ is a tunnel type of sterilizers. Typically, heat transfer occurs as follows: the surface of the equipment transfers heat to the surface of the material, which further transfers heat to inner part material. Heat conduction occurred with the help of convection or a radiated wave. This method always had a negative factor, slow to achieve desired temperature for sterilization. Microwave units radiate in such a way as to respond directly and quickly to existing bacteria in the material. The thermal and non-thermal effects are both effective in this case, thus reducing the processing time. The sterilization process, depending on the properties of the material, usually lasts 3-5 minutes. The sterilization temperature in the chamber varies from 70℃ to 90℃.

Application
This equipment is used to sterilize and dry the following types of materials: spices, food additives, protein powder, meat products, seafood, fruits, legumes, vegetables, mushrooms, wheat, starch, compound feed and so on, spreading to a wide variety of industries, including food, pharmaceutical, agricultural.

Peculiarities
1. It has automatic temperature control system, microwave density control system, heating time control system, alarm system, and video surveillance system.
2. Small space occupancy, instantaneous heating rate, even heat transfer, good maneuverability and controllability, easy operation, energy saving and low cost.
3.Transformer can be with various types cooling, including water, air and self-cooled. Able to work 24 hours in a row, continuously.
4. Leak rate complies with national and American UL quality standards.

Specifications industrial microwave installation

Model	WSZ-1	WSZ-2	WSZ-3	WSZ-4
Frequency (MHz)	2450+150MHz
Power, kWt)	9 kW, customizable	12 kW, customizable	24 kW, customizable	48 kW, customizable
Drying process (kg/kW.h)	1 kg/kW.h
Conveyor width (mm)	450	450	450	450
Conveyor speed (rpm)	0.4-6	0.4-7	0.4-10	0.4-15
Power (kW)	< 15	< 20	< 40	< 80
Dimensions (mm)	6000×800×1500	8000×800×1500	10000×800×1500	16000×800×1500

Yangzhou Yutong Drying Equipment Co., Ltd is a manufacturer and supplier of industrial microwave equipment in China. In addition, we also supply mixing, granulating equipment, extractors and concentrators. The enterprises received a credit rating of “AAA” from Jiangsu International Credit Assessment Company. Our industrial microwave units have long been trusted by manufacturing companies.

microwave The setup consists of a microwave chamber, a magnetron, a waveguide, a power supply unit, a cooling system, and various devices security.

From the magnetron, through a rectangular waveguide, electromagnetic radiation enters the microwave chamber. The heat removal from the magnetron is an air cooling system made with a fan and air ducts passing through the microwave chamber. Thus, the body in the chamber is heated not only with the help of microwaves, but also with the warm air removed from the magnetron. Further, the air in the chamber is saturated with water, that is, it turns into steam and exits through non-radiated holes (transcendental waveguides) to the outside. The power supply of the magnetron is high-voltage and consists of a diode, a capacitor and a transformer. To achieve normal operation without excessive radiation to the outside, interlock microswitches (from 2 to 5 pieces) are used to confirm that the door of the microwave chamber is closed tightly. If there is lighting in the chamber, then an incandescent lamp is usually used inside the duct. Using the control unit, made in the form of an electromechanical timer or an electronic unit, the operating mode is set in the microwave chamber. Many furnaces have thermal relays located on the magnetron and on the chamber on the outside to prevent overheating and failure.

Figure 1.7.1. The design of the microwave installation

1.7. 2 The principle of microwave heating

In a furnace, the body can be heated by the principle of "dipole shift", which occurs in materials that contain a polar nye molecules. The energy of electromagnetic waves sets in motion molecules that have a dipole moment. Thus, the temperature of the material increases.

Most household and industrial microwave ovens operate at 2450 MHz and at 915 MHz.

Based on practical and design considerations, the indicated frequency was chosen:

The magnetron must have a power of over 500 W, the required efficiency, cost and certain dimensions;

The frequency must meet the international and national standards for allowed frequencies.

The depth of penetration of microwaves into the working fluid should be about a few centimeters. (The higher the frequency, the lower the penetration depth).

Conveyor-type microwave devices

Microwave devices of the pass-through type are used in the production of heat-insulating materials using dry and liquid silicates, for example, from a mixture of hydroaluminosilicates bound by liquid glass. There are devices designed for fast temperature treatment (blowing) and for slow one. Such an abundance of heat treatment rates gives a similar set of bubble heat-insulating substances, with different properties. Microwave heat treatment devices are made in such a way that inside them, if the radiation has not been absorbed by the material, it is repeatedly reflected from the walls and still reaches its goal. The basic rule for uniform microwave heating is multiple low-power microwave generators (from 0.6 kW to 0.85 kW) with air cooling, which are located inside in a strict order. At an operating frequency of 2450 MHz, microwave radiation generators have a waveguide output with a cross section of (72 34) mm. Figure 3 shows the design of a device for microwave heat treatment for the manufacture of heat-insulating plates with a size of 60060050 mm from expanded vermicuite bonded with liquid glass.

The raw material is installed on the lower collapsible tray made of fluoroplastic, which transmits microwave radiation, and enters the installation, where it is emitted. When passing through the chamber, the processed substance becomes lighter by 30-40%, while increasing its volume from two to six times due to the fact that liquid glass swells.

At the same time, for these microwave installations, the efficiency of the radiated energy reaches 90%, taking into account the heating losses environment and internal walls of the device. At this stage, such a device can pass through itself 117 plates in an eight-hour working day, while the microwave power is 27 kW. To achieve this power, it is necessary to install 45 low power generators (0.6 kW).

The layout of sources on the chamber is shown in fig. 1.7.3. .

Rice. 1.7.3.

1 - body; 2 - source of microwave energy; 3 - fan;

4 - ventilation window; 5 - conveyor belt; 6 - flange.

Microwave devices of periodic type

A microwave installation of a periodic type, for example, is a device for drying wood. On the walls of the chamber are installed generators of microwave radiation, each of which is 0.6 kW.

Waveguide energy outputs are installed in microwave generators, each of which has a cross section of 72mm (2450 MHz) and mm (915 MHz). Since the generators are placed along the walls in this way, the wood heats up evenly.

Technological modes of wood drying were made for all generators, taking into account multiple reflections from the side surfaces inside the microwave unit. The calculation of temperatures at each point of the chamber was made both for the start of the process, when the moisture content of the raw material is maximum, and for the end, when the moisture content of the material is much less. The condition under which the temperatures of all points of the chamber were calculated was that the uneven distribution of the temperature of the raw material in any section of the stack of wood should not exceed 20°C.

Also, for example, an installation for soil disinfection in greenhouses is a small microwave device that travels from one greenhouse to another and is structurally similar to the installation described above, only instead of wooden planks a stack of boxes with soil is placed in it.

So, for all types of installations, it is important that the generators of microwave radiation inside the chambers are distributed inside them, this allows you to heat the materials evenly. This is essential for positions such as:

Obtaining new heat-insulating building materials by the swelling method (based on liquid glass with fillers, cement-bonded expanded polystyrene granules, etc.);

Heating and drying of raw materials (bales of tobacco before fermentation and cutting, food products and others).

Structurally, these devices must be designed so that the heating of the raw material inside the chambers occurs evenly. In addition, it is desirable to make the internal cavities of these units spacious enough so that large production volumes of raw materials can be processed per unit of time.

Industrial microwave ovens used in public catering establishments for rapid heating, as well as cooking and defrosting various products and ready meals using high-frequency current electromagnetic field. Industrial microwave ovens operate in the following modes:

• microwave,
• convection,
• grill.

In addition, they can be combined for a more varied preparation of common dishes. Today, mechanical, electronic, as well as electromechanical control of microwave ovens is used.

As for the differences between professional and household equipment, in general, professional ovens are similar to household ones, but they cook, reheat and defrost food much faster and in large quantities. That is why most entrepreneurs try to buy branded food equipment, and not be content with much less productive household counterparts.

In addition, industrial microwave ovens are more reliable and durable than domestic ones. They are able to withstand intensive use, that is, they can work continuously for a long time. Often they are equipped additional programs, and almost always have a larger volume of the inner chamber.

One more distinguishing feature professional microwave ovens from household - ultra-reliable shielding. It is for this reason that such furnaces practically do not emit harmful electromagnetic waves. The door mechanism has a reinforced structure, and the professional microwave ovens themselves are built very rationally, which makes it possible to use the working volume of the chamber most efficiently.

Microwave ovens are not included necessary equipment for professional kitchens, since they are not so actively involved in the cooking process. But recently, professional microwave ovens are increasingly being used in bars, restaurants and fast food establishments, which are characterized by high traffic.

Such equipment is already absolutely indispensable for restaurants and cafes, which offer full meals. Industrial microwave ovens work successfully in large kitchen shops of hotels and airports.

Professional furnaces, like any other similar equipment, are characterized by increased wear resistance and high performance. They are designed for really tough operation, and in almost round the clock. The quality of such equipment is ensured by an extremely careful selection of structural materials with excellent properties. operational characteristics. Also, a great advantage of professional ovens is the greater mobility of heating and defrosting dishes, which becomes an indispensable quality when you need to increase the throughput of a certain catering establishment.

Compared to other professional equipment, the advantage of microwave ovens is the economy in power consumption, since most models operate on a single-phase current network and bring products to readiness in very a short time. Most microwave ovens are made of stainless steel, lined with plastic or the same stainless steel on the outside. The inner chamber is made without seams, which greatly facilitates its care.

No matter how fans of a healthy lifestyle stand up for valuable properties and a storehouse of vitamins in salads from fresh vegetables, most people still prefer to combine them with hot meals. Compact, powerful, professional microwave ovens for restaurants and cafes from the WhiteGoods online store will heat up meat, side dishes, soups, pies, hot dogs, pizza, hot sandwiches and any cooked dishes in seconds. This is a reliable, convenient and affordable solution for catering enterprises of any level.

Microwave oven - a wise compromise in a limited space

Microwave ovens have become a reasonable compromise for cafes and catering outlets, where the shortage of production space barely allows you to place a refrigerator, coffee maker, etc., and not just an oven and, even more so, a hot shop. This compact appliance is able to meet the needs of customers in hot food and provide you with the right level of sales. Modern microwave ovens for restaurants from the line of advanced models combine innovative technologies, as a convection function, multi-level power adjustment, several defrost modes, preset programs for up to 360 recipes, an exhaust air purification system (catalytic converter), etc. Extensive functionality turns these small appliances into versatile equipment that will become a lifesaver in your restaurant, diner or cafe.

Thermal equipment of express class for a successful business!

Professional microwave ovens are absolutely indispensable equipment for grocery stores with hot snack stands, cafes without their own kitchen, bistros, food courts based on convenience foods and other ready-to-eat outlets. Due to the ergonomic shape of the case, the devices are easy to maintain and maintain hygiene standards. The main differences between a professional microwave oven and household models:

• increased power, thanks to which you will reduce the heating time by 42% -60% (hot sandwich / pizza in 4-9 seconds, cheeseburger - 20 seconds);
• uniform heating of dishes without drying out the edges or undercooking of the middle, inherent household microwaves, exclude marriage or dissatisfied reviews of restaurant visitors;
• increased useful volume of the working chamber;
• extended timer up to 60 min;
• many combined modes: microwave technology, grill, defrost, cooking, convection, etc.;
• The vitreous enameled durable restaurant microwave housing is impact-resistant and designed for heavy use in commercial kitchens. Plus durable reliable parts of the mechanism.

Thanks to stylish design and a rich color range, a microwave oven for a cafe will be an interesting addition to the interior and will take its rightful place on the bar counter. good model professional microwave will help you pamper your visitors with both juicy meat or fish with delicate taste, and fragrant pastries with a delicious golden crust that will look fresh, like fresh from the oven.

Where to buy good microwave ovens for restaurants and cafes?

Flexibility of use and versatility, with the greatest preservation of usable space, explain the high demand for equipment this class. A high-speed, easy-to-operate restaurant microwave will save cooks time and add convenience to the professional kitchen. Prompt customer service will have a beneficial effect on the profitability of the institution.
In the WhiteGoods online store you can buy the most popular, universal, professional microwave ovens for cafes, restaurants and other catering establishments. Outstanding reliability and high efficiency distinctive features professional equipment from the WhiteGoods catalog. Our microwave ovens will perfectly fit into the concept of any kitchen, save time and money!

It is possible to single out the main areas of application of microwave heating - food, rubber and textile industries. Here, characteristics such as process efficiency, the possibility of automation and high product quality play an important role. There are prospects for the introduction of microwave heating and drying in the pharmaceutical industry, wood processing and Agriculture. The use of fast heating technology in canteens, hospitals, schools, etc. is expanding, the massive use of microwave ovens in everyday life is already well known to our readers.
The effect of microwave heating is based on the absorption of electromagnetic energy in dielectrics. Microwave fields penetrate to a considerable depth, which depends on the properties of the materials. Interacting with matter at the atomic and molecular level, these fields affect the movement of electrons, which leads to the conversion of microwave energy into heat.
Microwave energy is a very convenient source of heat, which has undoubted advantages over other sources in a number of applications. It does not introduce pollution when heated, when using it, there are no combustion products. In addition, the ease with which microwave energy is converted into heat allows very high heating rates to be obtained without damaging thermomechanical stresses in the material. The generator equipment is fully electronic and operates almost without inertia, due to which the microwave power level and the moment of its supply can be changed instantly. The combination of microwave heating with other heating methods (steam, hot air, infrared radiation, etc.) makes it possible to design equipment to perform various functions, i.e. Microwave heating allows you to create new technological processes, increase their productivity and improve product quality. A proper assessment of the applicability of microwave energy in special processes requires a detailed knowledge of the properties of the material at various frequencies and at all stages of the process. The absorbed power and the depth to which this power penetrates are determined by three factors: permittivity, frequency, and geometry of the microwave system.
The permittivity of lossy materials is a complex value:
,
where ε is the relative permittivity, tgδ = ε1 / ε is the dielectric loss factor of the material, or the loss tangent.
The penetration depth in microwave energy is understood as the distance d at which the power density decreases to 37% of the value on the surface, i.e. in other words, 63% of the initial energy of an electromagnetic wave is absorbed in the material and converted into heat. For a small value of tgδ, the penetration depth is determined by a simple expression:

where d is the penetration depth, cm; f is the frequency, GHz.
The power absorbed per unit volume will be, W/cm3:
Р = 2.87  10-4 Е2f  tgδ,
where E is tension electric field, V/cm; f is the frequency, GHz.
The calculated values ​​of the depth of penetration of microwave energy into food products at a widely used frequency of 2.45 GHz are given in Table 1. If tgδ decreases with temperature, then the heating process is stable (microwave energy absorption decreases with temperature). This automatic temperature limitation occurs when dielectrics are heated, in which the losses are due to the water content with its special dependence of dielectric properties on temperature.
Heating by infrared or light sources operates, in comparison with microwaves, at higher (by about 2–3 orders of magnitude) frequencies. Accordingly, the penetration depth decreases and only the surface of the processed object is heated. The rest of the volume receives heat only due to the slower heat conduction process. This can lead to thermomechanical overstresses and loss of material quality. Where time is of the essence (cooking, drying or reheating), microwaves have a decisive advantage over heat radiation. For example, when cooking vegetables or fruits, microwave heating helps to maintain a fresh look and taste, and the vitamin content is slightly reduced.
Microwave heating is economically efficient when drying hard wood species, since the temperature rise at a rate of up to 1000°C/s can be realized at a field strength of 5 kV/cm.
Compared to infrared heating, the use of microwaves has the great advantage of almost instantaneous switching on and off, as well as precise temperature control. High power density and better focusing result in great energy savings. Useless radiation and the need for concomitant cooling of surrounding parts are eliminated.
The integration of an electronic microwave generator into an automatic production line is quite simple due to its reasonable cost, economy and compactness. A combination with other types of processing is also possible. For example, when processing poultry carcasses, microwaves and steaming are used simultaneously.
Of course, factors such as product quality, processing speed, space requirements, energy cost, and investment need to be accurately assessed for a particular application to determine if microwave heating is superior to conventional methods.

Industrial magnetrons
Magnetrons and klystrons are used as high power generators. Due to the higher efficiency below 50 kW, magnetrons dominate. The two most commonly used frequencies are 915 and 2450 MHz. Since the frequency of 915 MHz may not be used in all cases, the optimal international practice usually considered a frequency of 2450 MHz. Table 2 gives an idea of ​​modern Russian magnetrons produced by CJSC NPP Magratep in comparison with foreign devices.
The M-116-100 magnetron (Fig. 1) is used in fish defrosting, rock softening and in other cases where an increased penetration depth into the material is required.

The world's only M-137 magnetron with a power of 50 kW at a frequency of 433 MHz (Fig. 2) was successfully used in experimental facilities for soil softening in Yakutia. Such a low operating frequency provides the required depth of penetration of microwaves into frozen rocks.
The M-168 magnetron with a power of 5 kW (Fig. 3) is widely used in installations for rubberizing cables, vulcanizing rubber parts, and polymerizing plastic.
Microwave Processing Plants
Microwave heating processes are divided into two groups: continuous processes and batch processing. In continuous processes, for example, on a conveyor, the "raw" material continuously passes through the processing zone, while the load at the output of the microwave generator remains practically unchanged. When processing in batches, the heated material is in the processing zone until the required temperature is reached, therefore, with a change in temperature, the permittivity and loss factor change significantly. This leads to a change in the load (and within a wide range) for which the microwave generator must operate. Even in well-used economical installations, VSWR loads can exceed 4. In this case, magnetrons are preferred because of their ability to operate on a load with a high VSWR.

Fig.4. Scheme of an installation for heating oil products in railway tanks (Elvis enterprise, Nizhny Novgorod). Microwave generator descends from above

The new technology of high-intensity heat treatment is to heat the grain in a combined way: first convective - up to a temperature of 95 ° C and then - in an electromagnetic microwave field up to a temperature of 120–150 ° C (Fig. 6). With the rapid heating of the grain "from the inside", capillary moisture boils, the partial pressure of water vapor increases, and the starch shells break. At the same time, indigestible starch is broken down into dextrins - easily digestible forms. With this processing of grain, containing about 40% starch, its nutritional value increases by 20-30% and taste improves.
Other promising microwave technologies are drying, disinsection and disinfection of grain, thermal stimulation of grain during pre-sowing treatment, improvement of baking qualities, and a number of others. Pasteurization and sterilization of liquid food products using microwave energy. These methods are distinguished by high process productivity and compact installations. Among other things, microwave processing plants have the ability to accurately maintain technological regimes, which makes it possible to obtain high-quality products, for example, during drying medicinal herbs(Fig. 7).
In some cases, one has to deal with such large-sized objects that it is impossible to use resonators or pipeline processing. Then, for example, the package wooden beam for drying, it is loaded into a box, inside which it is processed by microwave energy using a system of special waveguide-slot emitters (Fig. 8).
Radiant systems are particularly suitable for heating thin films or microwave hyperthermia of malignant neoplasms.
The essence of the method lies in heating the tumor with the help of electromagnetic radiation to a temperature level of 42–44°C. The advantages of microwave hyperthermia are that the affected area is heated from the inside, while heating the tissues evenly, without damaging the skin. The modern installation for local microwave hyperthermia "Yakhta-3" (FSUE "NPP "Istok", Fryazino) allows you to create and maintain a hyperthermia zone in a tumor of almost any configuration for a long time with minimal impact on surrounding organs and tissues. Microwave hyperthermia is used as in an independent form, and as a means of enhancing the effect of chemotherapy and radiation therapy.

Literature
1. Microwave energy / Trans. from English. Ed. Shlifera E.D., vol. 2. - M .: Mir, 1971.
2. IR, 2008, No. 12;