How vacuum drying of lumber works. Press-vacuum drying chambers - principle and technology of operation

High-quality dried lumber has always been the key to quality, durability and reliability of any structure in which wood occupies a significant share. But get it in natural conditions difficult and at the same time so that it does not deteriorate. Drying time under normal atmospheric conditions can range from 6 to 12 months, depending on temperature and humidity environment. During natural heat treatment, the material is subject to unwanted deformation, warping and cracking.

To improve the quality of drying lumber, many equipment options have been invented; people often try to make a vacuum drying chamber for wood with their own hands - because this technology is considered one of the most effective. But the problem is that it is quite difficult to make such a unit yourself. Still, there are craftsmen who make them from old tank bodies or thickened sheet steel. These are mainly mini cameras with a loading volume of 5-10 cubic meters.

What is vacuum drying of wood with your own hands?

Vacuum drying of wood with your own hands is quite possible if you have a shell from a rocket, tank, or any other similar type of product from which you can make a shell for the equipment.

Main design elements:

• frame
• Vacuum pump
• heating elements (heaters, plates, steam generator, microwave emitters, etc.)
• trolley for loading lumber
• automation

You will need a pump to pump out air and create a vacuum. You can warm up lumber using any in a known way, which can be the contact method, air-gas and water vapor.

A do-it-yourself vacuum chamber is quite technically complicated, because it will be quite difficult to find many parts for its manufacture. And ordering them specifically is tantamount to ordering the camera itself. Therefore, before you start constructing vacuum drying chambers for wood with your own hands, you should consider whether it is advisable or whether it would be better to order it from a specialized company.

Do-it-yourself thermal chamber for wood - production of thermal wood

Thermal vacuum chamber technology has been around since the last century. The thermal dryer has much in common with a vacuum chamber for drying lumber.

To make a vacuum chamber for thermowood, you need to take into account the technical features:

• Wood processing occurs at high temperatures
• The chamber body must withstand high pressure

These 2 points are important to consider for the safety of personnel.

An important task is the choice of agent: oil or steam. Also technical modes. If the conditions are incorrect, thermal drying takes place only on the surface of the wood, and the lumber may not acquire the desired properties:

• full color change
• fire resistance
• increased resistance to rotting

Make a homemade chamber for thermowood, just like thermowood itself, at home difficult task. It is unlikely that you will be able to find competent specialists ready to share their experience on forums, videos, or somewhere on the Internet. If you have any questions, you can contact the manufacturers.

Vacuum dryers for wood: do it yourself or from professionals?

Our company has been producing high-quality and highly efficient vacuum-type drying chambers for several years, so we are ready to offer a truly reliable and practical option.

But if you need a vacuum wood dryer small sizes for heat treatment of small parts and you want to make it yourself, then you need a drawing. Drawings on this topic are quite a rare occurrence; of those that occur, it is unlikely that a camera capable of working in production conditions will be produced.

If you are still planning to purchase finished equipment, then effective option are chambers with contact technology for heating lumber along the entire length, the percentage of defects is less than 1, and the drying time to 6-8% moisture content of a 30 mm thick pine board will be only about 60 hours.

See also:

Contents Features of do-it-yourself infrared drying There are many ways to dry wood to obtain the necessary qualities. One of the popularly known is the infrared method. It consists of the action of infrared radiation on organic matter, heating it, thereby evaporating moisture from the structure of the tree. At its core, it is a simple IR heater made from thermoplates or thermal film. Infrared drying […]

Contents Vacuum drying as an alternative to a DIY microwave chamber Today there are many known methods for drying lumber, each with advantages and disadvantages. As an example, do-it-yourself microwave drying of wood. The technology is no longer new and quite productive. Microwave chambers are used for drying hardwood, large-section lumber, veneer, timber, and logs. Basically, after drying the material […]

There is not a single woodworking enterprise that can do without the wood drying procedure. To prevent the occurrence of various defects, it is customary to use a special technology for drying wood in a drying chamber. If you want to produce wood products yourself, you will also need a drying chamber for drying wood. Today we will talk about how to do it correctly.

The need to dry wood

How to dry a board efficiently and quickly? This question has interested every carpenter since ancient times. People have long been engaged in storing wood for many years in order to have time to dry it evenly. The grandfather prepared wood for his grandson, using the very material that his grandfather left him.

The importance of properly dried wood is colossal! For example, if wooden furniture, which is in the room, is made of too wet wood that has just been cut down, then it will dry out over time, because wood can dry out and decrease in size, which means it will deteriorate!

If the door to the house is made of excessively dry wood, it will swell over time and will not be able to close! If the door panel is assembled from blanks that are unevenly dried in volume, then it may burst or warp! Therefore, it is recommended to dry all wood blanks. In addition, drying protects the material from damage by wood-destroying fungi, prevents the size and shape of wood, and improves the physical and mechanical properties of wood.

Drying wood is a lengthy, complex and expensive procedure. Tree by traditional technologies heated with superheated steam or hot air. Dried wood can be transported and stored longer. In addition, during operation it does not deform. The boards are dried in steam chambers, where the possibility of internal damage is excluded.

Wood moisture concept

To fully understand the essence of the drying process, it’s worth diving a little into the theory. The procedure for removing moisture from wood is not entirely simple, because there are two types of moisture in the material itself. Wood consists of elongated plant cells. Moisture can be found in the cell walls and in their cavities, filling the microcapillary system. The moisture that is present in the spaces between cells and in their cavities is called free intercellular, and moisture in cell walls- bound intracellular.

Content in wood bound moisture limited. The state when the cell walls are characterized by maximum humidity when in contact with liquid moisture is called their saturation limit. It is generally accepted that the moisture content of the saturation limit does not depend on the rock and is on average 30%. If the wood's humidity is above 30%, then it contains free intercellular moisture. The wood of a freshly cut or growing tree has a moisture content above the saturation limit, that is, it is raw.

Depending on the purpose of wood blanks, wood is usually dried in different ways. The wood is dried to a moisture content of 6 - 8%, when the material is needed for mechanical processing and assembly of products for high-precision critical connections that affect performance (the production of skis, parquet or musical instruments).

Transport humidity is 18 - 22%. It is with this water content that lumber is suitable for transportation over long distances in warm seasons. Wood dried to such a moisture content is used mainly in standard house construction, in the production of ordinary containers and when there is no need for interchangeability during assembly.

Carpentry dampness is divided into several subspecies. Molded products ( terrace board, sheathing, floor boards, casing) must have a humidity of 15 ± 2%. Wood products (windows, doors, stairs and interior elements) made from solid or laminated wood can withstand humidity fluctuations from 8 to 15%.

Furniture humidity, depending on the level of the product and the use of solid or laminated wood, is 8 ± 2%, because it is at this humidity that the wood exhibits the most optimal characteristics for processing, gluing and subsequent use. But it is usually customary to reduce the humidity to 7-10%, performing partial sterilization of the wood and taking into account the uniformity of humidity throughout the tree, preserving mechanical properties material, absence of surface and internal cracks.

Wood drying modes

Depending on the requirements for the quality of wood, lumber can be dried in different modes, which differ in temperature level. In a mini drying chamber for wood, during the drying process, the air temperature gradually increases in stages and the relative humidity of the agent decreases. Drying modes are selected taking into account the thickness of the lumber, the type of wood, the final moisture content, the quality category of the wood being dried and the design of the chamber.

There are low- and high-temperature process modes. The first modes involve the use humid air as a drying agent, the temperature of which in the initial stage is less than 100 degrees. There are three categories of these modes:

• The soft mode is capable of ensuring defect-free drying of the material while maintaining the natural physical and mechanical properties of the wood, including color and strength, which is important for drying wood to the transport moisture content of export lumber.
• The normal mode guarantees defect-free drying of wood with almost complete preservation of the strength of the material with minor color changes, which is suitable for drying lumber to its final moisture content.
• The forced mode maintains strength for static bending, compression and tension, but there may be a slight decrease in splitting or spalling strength with darkening of the wood, which is intended for drying wood to operational humidity.

For low-temperature modes, a three-stage change in the parameters of the drying agent is assumed, and from each stage to the next one the transition can be made only after the material reaches a certain level of humidity, which is provided for by the mode.

High-temperature modes provide for a two-stage change in the parameters of the drying agent, and you can move from the first stage to the second after the wood reaches a transitional moisture content of 20%. The high temperature regime is determined depending on the thickness and type of lumber. High temperature conditions can be used to dry wood, which is not used for manufacturing. load-bearing elements buildings and structures in which wood darkening and strength reduction are allowed.

Drying chamber concept

Chamber drying is the main method of drying wood. Drying chambers are required to dry softwood and hardwood to different quality categories. One of the most popular and economical methods of artificial dehydration of lumber is drying, when bound and free moisture is removed from the tree by supplying heat to the wet wood with hot air and carrying away the evaporated excess moisture with humidified and partially cooled air.

The drying chamber is completely ready installation, which is equipped with all the equipment necessary for drying wood. According to their design, wood drying chambers are divided into prefabricated metal and made of building materials. The latter are constructed directly in workshops or as separate buildings from materials that are widely used in industry. The camera can be made entirely from monolithic reinforced concrete. Its walls can be made of solid red brick, and the ceiling can be made of monolithic reinforced concrete.

If several dryers are used, they are often combined into a single block, constructing common corridor control, where the heating distribution and system are located automatic control all cameras. Depending on the volume of wood loaded into the chamber, there may be horizontal or vertical transverse air circulation.

Loading of lumber into the chamber can be carried out in the following ways: on trolleys in the form of stacks along a rail track, like packages with a forklift. Heat transfer to wood can be carried out: by air, combustion products or superheated steam; radiant heat that comes from special emitters; solid body, if you organize contact with a heated surface; current that passes through wet wood; high frequency electromagnetic field, which penetrates wet wood.

Equipment for a wood drying chamber is divided into basic and additional. The main ones include the fan system, heating system, supply and exhaust ventilation and humidification, additional components include an insulated door and psychrometric unit, stacking trolleys, and a fan drive electric motor.

The process of controlling wood drying in a chamber can be automated. Automation is capable of maintaining the humidity and temperature of the environment in the dryer at a given level. The temperature is regulated by supplying coolant to the heaters or by switching on and off electric heater, and humidity - through the use of supply and exhaust ventilation and a humidification system.

The wood drying control system may have the ability to remote control humidity and temperature in the chamber. When drying lumber in a drying chamber, it becomes necessary to control the moisture content of the wood, for which a remote moisture meter is used, which allows you to check the moisture content of the wood at several points without entering the chamber. In the absence of external sources of heat supply, autonomous heating modules can be used for the dryer and gas, coal, wood waste, electricity and diesel fuel.

Types of drying chambers

In real life, it is common to use the following types of drying chambers. The necessary energy in convective drying chambers is transported into the material using the air cycle, and heat transfer to the wood occurs through convection. There are two types of convection chambers - tunnel and chamber.

Tunnel convection dryers are deep chambers where stacks of stacks are pushed from the wet end to the drier end. These chambers must be filled at one end and emptied at the other. Pushing the stacks (the process of filling the chambers and emptying them) is done one stack at a time with an interval of 4 - 12 hours. These chambers are designed for large sawmills and allow exclusively transport drying of wood.

Chamber convection drying chambers are shorter than tunnel and vacuum drying chambers for wood; during operation, the same parameters are maintained throughout the chamber. When the blowing depth is more than 2 meters, the technique of reversing the direction of ventilation is used to equalize the drying conditions for the wood. The emptying and filling of the chamber occurs on one side if it has one door. Other loading systems are also known that are similar to the procedure for loading tunnel chambers. Any lumber can be dried to any final moisture content, which is why 90% of wood in Europe and Russia is dried in chamber dryers.

The condensation drying chamber differs from the previous ones in that the humidity that arises in the air condenses on special coolers and water comes out of the drying process. Coefficient useful action This process is large, but the cycle is long, because the devices do not work with high temperature, and the total heat losses are also significant. The condensation chamber is primarily suitable for drying small volumes of wood, or for drying dense wood species - oak, beech or ash. The big advantage of such chambers is that a boiler room is not needed, the price of a wood drying chamber and the cost of drying are lower.

Drying chambers are also classified according to the method of circulation and the nature of the drying agent used, the type of enclosure and the principle of operation. Batch drying chambers are characterized by the fact that they can be fully loaded to simultaneously dry all the material, and the wood drying mode changes over time, depending this moment remaining the same for the entire camera.

According to the method of circulation, there are chambers with incentive and natural circulation. Dryers with natural circulation are outdated, low-performance, the drying mode in them is almost uncontrollable, and the uniformity of wood drying is unsatisfactory. For modern construction such devices are not recommended, and existing ones must be modernized. Depending on the nature of the drying agent, the chambers are divided into gas, air and high-temperature chambers that operate in a superheated steam environment.

Wood drying procedure

Before drying according to the selected mode, the wood is heated with steam, which is supplied through humidifying pipes, with fans running, heating devices turned on and closed. exhaust ducts. First you need to calculate the drying chamber for wood. The temperature of the agent at the beginning of heating the wood should be 5 degrees higher than the first stage of the regime, but not more than 100 degrees Celsius. The level of saturation of the environment should be 0.98 - 1 for material with an initial humidity of more than 25%, and 0.9 - 0.92 for wood with a humidity of less than 25%.

The duration of the initial heating depends on the type of wood and for coniferous species (pine, spruce, fir and cedar) is 1 - 1.5 hours for each centimeter of thickness. The duration of heating of soft deciduous trees (aspen, birch, linden, poplar and alder) increases by 25%, and for hard deciduous species (maple, oak, ash, hornbeam, beech) - by 50% compared to the duration of heating of coniferous species.

After preheating, it is customary to bring the parameters of the drying agent to the first stage of the mode. Then you can begin drying the lumber, subject to the established regime. Humidity and temperature are regulated by valves on the steam lines and gates of the sugar-exhaust channels.

During the operation of an infrared drying chamber for wood, residual stresses arise in the wood, which can be eliminated by intermediate and final moisture-heat treatment in an environment of increased temperature and humidity. It is customary to subject lumber to processing, which is dried to operational humidity and is subject to further mechanical processing.

Intermediate moisture-heat treatment is carried out during the transition from the second stage to the third or from the first to the second at high temperature conditions. Subjected to moisture and heat treatment conifers from 60 millimeters thick and deciduous from 30 millimeters thick. The temperature of the environment during the heat and moisture treatment process should be 8 degrees higher than the temperature of the second stage, but not higher than 100 degrees, with a saturation level of 0.95 - 0.97.

When the wood reaches its final average moisture content, final moisture-heat treatment can be carried out. IN this process maintain the temperature of the environment 8 degrees above the last stage, but not higher than 100 degrees. At the end of the final moisture-heat treatment, the wood that has undergone drying must be kept in the chambers for 2 - 3 hours at the parameters provided for by the last stage of the regime. Then the drying chamber is stopped.

Making a drying chamber

If you decide to make wood products yourself, then you simply need a wood drying chamber. However, when constructing a dryer, comply with all required standards. You will need a chamber, a fan, insulation and a heating device.

Line up the dryer or highlight separate room, one wall and ceiling of which will be made of concrete, and the other walls will be made of wood that need to be insulated. To do this, it is customary to create several layers: the first of them is polystyrene foam, the second is wooden boards, which are usually wrapped in foil in advance.

After this you should install a heating element, which can be manufactured in the form of batteries. Water must be supplied to the batteries from the stove, in which it will be heated to 60-95 degrees Celsius. It is advisable to continuously circulate water using water pumps in the heating element. Also, a fan should be placed in a homemade wood drying chamber, which helps distribute warm air throughout the room.

Consider how the wood will be loaded into the drying chamber. One loading option could be a rail cart. To regulate the humidity and temperature in the drying chamber, you need to use the appropriate thermometers in the work area - wet and dry. Provide shelves inside the dryer to increase work space.

During the drying process of lumber, sudden changes in temperature in the working room are not allowed, otherwise this will cause the wood to warp or cracks to appear in it. When constructing a drying chamber, it is extremely important to observe fire safety requirements. Therefore, be sure to install fire extinguishers in the immediate vicinity of the dryer.

And finally, remember that instead of a heating element at home, you can use a two-burner electric stove. You can insulate the walls of the drying chamber yourself using wood shavings. Instead of foil in the chamber, you can use penofol, which can provide good reflection of heat from the surface. In such a dryer, the wood is pre-dried 1-2 weeks in advance.

The wood harvesting process includes a drying operation. It prevents future defects and damage to the material. The procedure takes place in a special chamber. Any logging enterprise cannot do without it. Vacuum drying of wood is most often used. It has a number of advantages over other methods. For example, short process times, uniform processing of all material and ease of installation and dismantling of the plant.

• Wood drying technology
• Vacuum drying
• We build a dryer with our own hands

A tree is a living organism. Like others organic compounds, it contains water. Freshly cut wood has a moisture content of more than 30%. To use it in the future for construction needs or making crafts, excess moisture must be removed. The excess water in the material may vary. Its standards depend on where the wood is planned to be used. For the manufacture of musical instruments, sports equipment and parquet, humidity is set at 6-8%. If the raw material will be subjected to further processing, then it is enough to leave 20% moisture in it. For the manufacture of building structures and finishing materials, the parameter is controlled at the level of 8-15%.

Wood drying technology

Vacuum drying

The wood drying process consists of several stages. First, it is evaporated from the surface of the material, and then from its interior. Thin places dry out first, then moisture moves to them from thicker layers. If the process is disrupted, the thin layers begin to shift and the material is destroyed. To prevent this from happening, the workpieces are treated with a special mixture. It is made from drying oil and chalk. The end parts of the workpieces are treated with the resulting composition. They usually always have the shape of an equilateral geometric figure.

Accelerated drying mode is distinguishing feature vacuum drying chamber. It is known that water begins to evaporate when it boils. A very low pressure is created in the chamber. Due to this, water boils at more low temperatures, than usual. This way the process time is significantly reduced.

Another significant advantage is that vacuum drying significantly saves energy. Heating occurs by contact method. Temperature inside chambers and pressure are adjusted automatically. A vacuum is maintained in the chamber at 0.95 MPa. It ensures the heat and mass transfer process. Moisture is released from wood in the form of steam. After drying, raw materials are obtained with a given level of humidity. During the process, it completely retains its structure - it does not collapse.

This drying eliminates the use of fans. Humidification systems are also not needed. Neither dry nor wet bulb thermometers are used in the chambers. Humidity sensors are installed inside. They are controlled from outside. The entire control system is usually located in a separate vestibule.

Vacuum installations are often used for processing expensive types of raw materials: wenge, oak, rosewood, teak, angera. They use a convector type heating element. The maximum temperature in the chamber is +65 degrees. However, the process of moisture evaporation begins already at 45.5 degrees. The process completely eliminates the impact high temperatures. Wood is practically not destroyed.

All the structural changes that accompany drying occur inside the tree. First, the moisture evaporates from the surface, then from the inside it approaches the surface again, and so on, up to 250 times over the entire time. Over the entire surface of the raw material, a humidity difference of 0.5-1.5% is allowed. Here are some indicators at which vacuum drying works:

We build a dryer with our own hands

It is not always possible for an entrepreneur to buy expensive equipment and use vacuum technology. For starters there are more simple methods.Do-it-yourself wood drying also occurs in drying chambers. To arrange it you will need the room itself, good insulation and a fan.

The design of the drying chamber with your own hands assumes that one wall and ceiling will be made of reinforced concrete. The remaining elements can be made of wood. The walls are insulated with polystyrene foam, lined with clapboard and covered with foil. Penofol can be used as a reflective material. It also reflects heat well and helps keep it inside the camera.

Mobile drying chamber.

Next, the heating device is installed. The most commonly used heating radiator. Its power should allow you to heat water to 65-90 degrees. The entire system is mounted separately from others heating circuits. It must work constantly, regardless of the time of year. Electrical and gas appliances. A fan is necessary to distribute air evenly in the chamber. Without this, it is impossible to dry the material evenly with your own hands.

It will also be necessary to build a system for loading lumber into the chamber. Usually they have big sizes and considerable weight. It is convenient to load boards on trolleys moving on rails or with a forklift. Inside the chamber, the material is placed on shelves or simply on the floor. It is also necessary to install control devices over the process, which will be carried out with your own hands. Without this, it is impossible to properly dry the wood so that it later has a marketable appearance and its inherent properties.

When building a drying chamber with your own hands, you need to adhere to the following rules:

When building a dryer with your own hands, the main thing is to ensure that the parameters required by the technology are maintained within it. The materials and equipment that will be used do not matter. Drying the wood in such a chamber, built with your own hands, will take from one to two weeks.

This technological process allows you to remove residual moisture and solvents from the structure of materials and various products. Vacuum drying – drying under reduced pressure (vacuum). The process is carried out at low temperatures. As a result, there are no structural defects in the processed raw materials. This indicator is important when working with explosive substances. The risk of oxidation on the surface of the material is minimized.

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Vacuum drying of vegetables, fruits and other food and non-food products has a number of advantages:

• processed products retain their original technical characteristics: size, taste, color, smell;
• vacuum drying of fruits allows you to preserve all the components in them: vitamins, amino acids and other enzymes;
• low percentage of moisture in the structure of processed raw materials;
• the possibility of creating new consumer characteristics of dried products;
• reduction in product weight, which significantly reduces transportation costs;
• increasing the shelf life of materials.

The technology has found wide application in Food Industry. Vacuum drying of products is carried out: meat and bread products, vegetables, juice concentrates, drinks and other products. Drying of wood raw materials is also carried out.

Vacuum drying technology

There are two ways to remove moisture from products: with positive or negative temperatures dried product. The first method is called cold vacuum drying. In it, the process of removing moisture and unnecessary components from products is carried out at temperatures from +4 to +6 degrees. The boiling point of the liquid drops to +25 degrees. This technology allows us to obtain high quality products.

Note. The final drying of the starting material is carried out using vacuum-sublimation drying.

Freeze drying in a vacuum is one of the ways to preserve food. Frozen dried products. During the process, a pressure of at least 1 mmHg is created in the installation. The temperature of the dried products must be at least -20 or -25 degrees. This approach to processing products allows you to preserve protein and other useful enzymes in them.

Vacuum drying chambers

The equipment is used in various industries industry. Vacuum drying chambers allow you to process food and non-food products. There are several types of such units, which differ in their operating principle.

Vacuum drying units come in the following types:

• conductive;
• condensation;
• convective;
• dielectric;
• aerodynamic.

The first type of installation is used for drying wood materials. In it, the working electrodes are made in the form of plates. In order to process the material efficiently, it is first placed in a steaming chamber. After this, it is transferred to vacuum drying equipment.

The condensation chamber operates in a closed cycle. The moisture released from the material is not removed from the installation, but washes the inner walls of the working chamber. It is worth considering that the efficiency of the unit decreases with increasing processing temperature.

Convection chambers are installations that are equipped with centrifugal or axial fans. Heating of air masses occurs through hot water circulating in radiators. The equipment is considered the most promising in the field of wood processing.

Dielectric installations are autoclaves with vacuum drying, the diameter of which reaches 2.5 m. Electrodes are placed inside the housing. The material to be processed is placed between them. The process of drying material in such equipment is quite lengthy.

The aerodynamic vacuum drying unit has become popular due to its low cost. It is characterized by reliability, practicality, wear resistance and durability. The only drawback of the equipment similar type is a high rate of electricity consumption at the maximum permissible operating mode.

Based on the type of design, vacuum chambers are divided into rack and rotating units. The first type of equipment is used for processing products that are sensitive to high temperatures. The units are designed with a sealed chamber with an O-ring and heated shelves. Products are laid out on them.

Rotating drying chambers are made in the shape of a cylinder. With their help, they provide high-quality and uniform drying of materials. Most often, such installations are used for drying crystalline and powdery substances.

Vacuum freeze drying

With the help of this technology it became possible to dry various materials and products. To fulfill this, several conditions must be met. First, at least 70% of the moisture contained in the product must be in the form of ice. In other words, the products are pre-frozen at a certain low temperature. Secondly, during processing it is necessary to maintain an optimal partial pressure difference.

Vacuum freeze drying can be carried out in two ways: by heating from plates or by sublimation of ice. The first method is the most popular. The drying chamber contains plates. They are heated by supplying hot liquid. Frozen foods are placed next to these plates. Under this influence, the ice evaporates. The duration of the process depends on the structure of the material being processed. After the moisture evaporates, the mass of the product decreases. To remove remaining moisture, special plates are used, which are also located in the working chamber. They act as capacitors. Their temperature reaches -55 degrees and below. If the temperature of these elements is different, the correct execution of the technical process is impossible.

Note. The range of maintenance measures for such installations includes regular cleaning of condensing plates from icing.

Ice sublimation is a long and complex technological process. The initial temperature of the material being processed should be from -40 to -50 degrees. The product in the chamber passes through several zones with different temperature conditions. As the surface dries, it moves deeper into the installation. The entire process may take 24 hours. It all depends on the type of product being dried. This method is used to vacuum dry vegetables and fruits.

Vacuum drying of wood

To perform this process, the material must be dried. As a result of this effect, the final product is characterized by a reduction in its dimensions. Vacuum drying of wood is a process that consists of three stages: circulation of liquid through the material, exposure to moisture from the core to the surface, evaporation - removal of water. The process takes a little time. This vacuum drying technology is called “artificial drying”. This can only be done with special equipment.

Note. The vacuum chamber for drying wood can be different sizes. Large structures They are used in enterprises, while less massive ones are used in everyday life.

Vacuum drying of wood begins with circulation. It takes much longer than the evaporation process. If the material has been pre-treated qualitatively (surface moisture has been removed), it will dry quickly and evenly. If this treatment is not performed before drying, the wood structure begins to deform.

The device for circulating moisture from the core to the surface is a complex installation. It is equipped with special liquid inlets and channels for its removal.

Evaporation is carried out by heating the working space to the boiling point of the liquid (+100 degrees). The temperature can be reduced using created pressure, that is, vacuum.

Vacuum chambers for drying wood, the price of which is set by the manufacturer, come in various configurations. Some units contain several installations for material processing (preliminary and final). The chambers of most drying installations combine several functions simultaneously. They are more effective and practical, but also expensive.

All wood processing enterprises make a profit from the sale of manufactured products. And the deeper the wood processing, the more profitable the production. Before purchasing equipment, every entrepreneur asks the following questions: What types of wood drying chambers are there, what devices are they equipped with, and which one to choose for your production?

If you choose the wrong equipment, then profitability will drop. And the larger range of drying chambers for wood on the market makes the task of choosing even more difficult.

The main types of drying chambers include:

1. Dielectric.
2. Convector
3. Vacuum
4. Aerodynamic

Wood drying method different ways was invented back in the 60s, but due to the high costs of electricity and the complexity of the design, the technology began to be used only in Lately. Most often, convector type dryers are used all over the world. Why is this happening? Other designs can be used with a number of restrictions and subtleties of use. The main disadvantages of using induction, condensation and vacuum dryers for wood:

1. Aerodynamic chambers require more power consumption;
2. Condensation structures are expensive, and drying in them lasts 2 times longer than in convector ones.
3. Vacuum dryers are expensive and are also expensive to maintain.
4. Dielectric ones require high energy costs, although they are considered one of the best.

Convector dryers

Convectors of different designs are used for drying wood of various species and sizes. Due to the simplicity of their design, convection chambers are inexpensive to maintain, which indicates reliability. Therefore, to increase profitability, in 90 cases out of a hundred they purchase them.

Operating principle of a convection dryer

Heating occurs from a gaseous carrier (drying agent). When heated, the raw material is tapped. The drying agent can be steam, flue gas, or air. The moisture released from the wood serves as an additional humidification of the agent; the excess is drawn into the atmosphere through ventilation.

Air exchange in a convection dryer is not higher than 2% of total number, so the energy efficiency is noticeable.

Convection dryer components and equipment

There are many configurations from different manufacturers, but there are basic options:

1. Equipment for a drying hangar that has already been built or is just under construction.
2. Full construction with hardware.

Equipment housing

The body is made entirely of metal and is assembled on a monolithic columnar foundation. The metal used for manufacturing is carbon steel or aluminum with a corrosion-resistant coating. The outside and inside of the hangar is covered with aluminum sheets. Individual elements inside the structure (deflectors, false flows, amplifiers, etc.) are also made of aluminum. The chamber is insulated with mineral wool in the form of slabs.

The structure is assembled in compliance with GOSTs and SNiPs. Options requiring additions and extensions are carried out according to an additionally developed scheme. The basic assembly is designed for an average snow load.

Models of convection chambers

Convection drying chambers are produced by domestic and foreign companies. The most common are Helios: ASKM-7, ASKM-10, ASKM-15, ASKM-25. They are used for drying any type of wood of drying categories I, II, III and 0. According to reviews, these models work quickly, since German fans are used in the mechanism. And installation and maintenance of ASKM models is simple. Price from 700,000 rubles, depending on size and power.

Vacuum drying chambers

The designs are designed specifically for expensive types of raw materials (teak, wenge, rosewood, oak, angera, etc.). Vacuum dryers can also be used for any coniferous or deciduous wood.

Working principle of a vacuum dryer

The vacuum dryer operates by convection heating of wood and vacuum removal of excess moisture. Temperature maximum +65 0С. But due to the vacuum, 0.09 MPa boils at 45.5 0C. This allows the drying process to be carried out without the aggressive effects of high temperatures, which does not create high internal tension, and the wood does not crack.

During operation, the temperature rises to 65 0C, the automation is activated and the electric boiler is turned off. The top part of the wood begins to cool and moisture from within begins to flow to the drier parts. During the entire drying process, such processes can occur up to 250 times. This way the moisture is evenly drawn out along the entire length and depth of the raw material. The maximum moisture difference in different parts of the tree can be 0.5-1.5%, and completely dried wood has a moisture content of 4-6%.

Models of popular vacuum designs

The most common model of vacuum chambers is Helios. Helios wood drying chambers differ in power, loading volume and other technical characteristics. More details about TX Helios in the table:

Aerodynamic wood drying chambers

These drying chambers resemble metal box, finished with aluminum professional flooring. An aerodynamic chamber of various modifications is used to dry all types of wood, with a load of 3-25 m3. To order, you can purchase individually designed chambers with a loading capacity of up to 43 m3.

The good thing about the aerodynamic chamber is that the operation is fully automated and requires a minimum number of workers.

The frame of the aerodynamic chamber consists of solid metal sewn onto load-bearing frame. The chamber is made in the form of a quadrangular box, into which it is convenient to load wood by machine or by train. ways. All internal structure equipped with automatic condensate collectors.

Principle of operation

Drying is carried out under the influence of aerodynamic energy. Heated air circulates in the chamber under the influence of a specifically designed aerodynamic fan. Due to compression, the air in the chamber increases the temperature by centrifugal fan, specifically on his shoulder blades. This is how aerodynamic losses are converted into thermal energy.

Heat is pumped into the chamber, depending on the design, reversely or dead-end. The aerodynamic chamber is started with one “start” button and opens only after the cycle is completely completed.

Models of air dryers

The most common aerodynamic dryers are Gelos SKV-25F, SKV-50F, SKV-12TA, SKV-25TA, SKV-50TA, as well as Italian EPL 65.57.41, EPL 65.72.41, EPL 65.87.41, EPL 125.72.41, EPL 125.87.41. Helios was developed specifically for drying coniferous material. They cost from 1,500,000 rubles.

Dryers with microwave chamber

Microwave chambers were invented quite recently. This dryer resembles a closed metal container. It works under the influence of the reflective surface of microwave waves. Reminds the operating principle microwave oven. Using a microwave chamber you can dry material of any cross-section and size. Microwave chambers have simple design and you can adjust the wavelength to any length. This made it possible to dry any raw material using a microwave chamber. The microwave wave attenuation mode allows you to regulate the temperature inside the chamber. And reversible fans remove excess moisture from the system. Microwave drying is compared with dielectric drying, which is considered the most effective, but is not used in Russia due to high energy costs.

The main disadvantages of microwave chambers include control of wood moisture and the high price of microwave dryers and electricity costs.

Models of microwave dryers

In Russia, this drying technology is offered by the engineering company in Moscow “Investstroy” - “SHF-Les”. A similar installation costs from 1,300,000 rubles. Microwave-Les needs to be serviced once every six months, at a price of 100,000 rubles.

Only half of the future profit depends on which camera the buyer chooses. Building and insulating a box is only part of all the work. It is important that the component equipment is of high quality.

Equipment for drying chambers

Equipment for dryers can be divided into types:

1. Thermal system.
2. Exhaust and humidification system.
3. Rail structure for loading and unloading

Ventilation equipment plays the role of uniform distribution of heated air. Installing a low-quality fan results in uneven drying of raw materials. According to GOST, the air movement inside the chamber should be optimally about 3 m/sec. This can be achieved using high-quality and powerful fans. All fans have a rotary or axial connection system.

This equipment depends on the power and model of the drying chamber. The heat generator can be an electric heater or a heat exchanger. They are installed only by specialists, and are used to pump and transfer thermal energy to the wood. A system such as a mini-boiler house running on liquid, gaseous or hard fuel can also act as a heat generator. It is convenient when work is carried out on wood production waste.

The Electra heater has a design consisting of a pipe and a chrome spiral wound around it. This generator has a small advantage: a simplified process for controlling the temperature inside the chamber.

Humidification system

To ensure constant uniform air humidity in dryers, humidification and exhaust equipment are used. Humidification is carried out through a complex system of nozzles, pipeline, and solenoid valve.

Extraction is carried out using a fan (usually a rotary one). The equipment operates using the following technology: when the humidity drops, the fan automatically turns off and the hood does not function. In this case, air humidification occurs through the evaporation of liquid, which enters the nozzle automatically when the valve opens.

When humidity rises, the valve closes and the fan turns on.

Rail loading and loading system

This equipment is installed at the camera assembly stage. The system consists of rails that are permanently mounted. On top of them are mounted stacking trolleys, which are needed for storing wood. Raw materials are placed on them and placed in a chamber; after drying, the carts are rolled out onto the street and packaged.

When choosing a chamber for drying wood, it is better to use the services of professionals, but do not neglect the information of specialists on the Internet.