Wood drying equipment. Types of drying chambers for wood: vacuum, convector, aerodynamic and additional equipment for them

The drying process is the initial moment in the entire preparation of the semi-finished product (wood) before processing.

A drying chamber for lumber and wood is an excellent solution to the task, you can do it yourself. In order to avoid deformation of logs, drying is carried out in specialized conditions, which are carried out exclusively in a dryer.

What is drying for?

From time immemorial, when performing any wood crafts, timber cut down a few years earlier was used. Products from wet or under-dried boards will warp or become covered with numerous cracks.

When the tree dries, it shrinks, the raw wood material will “behave” over time, huge wide gaps will form in the log house. In under-dried semi-finished products, a fungus is likely to start. But it is also not advisable to overdry the tree, because it will begin to absorb water, which will lead to swelling.

What are the modes of drying chambers?

There is a whole list of drying modes for wood materials. In self-built machines, the mode from the lowest to the highest changes gradually, removing all excess water from the semi-finished product. The drying process is carried out based on the following characteristics of the material:

• tree species;
• overall dimensions semi-finished product;
• final and initial level of humidity;
• unit specifics;
• lumber quality indicators.

The drying operation can be characterized by high temperature or low temperature. The second case is notable for the fact that the primary drying is carried out at a regime that does not reach 100ºС.

Low temperature conditions can be as follows:

• soft - after drying, semi-finished products have their original properties, without changing strength and color;
• moderate - the color changes slightly, strength characteristics decrease slightly;
• accelerated - in the process of subsequent processing (fracture, sawing, cutting), increased fragility is possible, the color fades.

Changing the temperature regime during low-temperature processing is carried out in three stages.

Processing in high temperature mode is carried out in two stages. The second stage begins when the moisture level of the semi-finished product drops to 15%. Such a technological process is used if it is necessary to further design secondary structures.

The main types of drying chambers

Drying of wood semi-finished products in industrial volumes is carried out in specialized dryers. Moisture is removed from the wood due to heated air, which subsequently goes into the atmosphere. The device provides the passage of a full cycle of lumber drying. The machine body can be:

• solid / prefabricated metal;
• performed using building materials.

The latter are mounted directly in carpentry workshops in the form of a structure, or as freestanding. The walls are made using reinforcement and concrete mortar. Alternatively, bricks can be used. large factories make a system of cameras, combining them into whole modules with centralized control and communications. Air moves inside the dryer in a horizontal plane or vertically transverse.

Heat sources in the dryer:

• radiant source from specialized units;
• hot shelves;
• electric current that passes through raw semi-finished products;
• high frequency electromagnetic field.

The cameras are equipped with the main and auxiliary equipment. Main systems:

• supply and exhaust equipment;
• heat sources;
• humidifiers.

According to the principle of operation, dryers are divided into:

• convection equipment;
• condensing equipment.

In convective machines, semi-finished products are "washed" with hot air waves, heat is directed by the convection method. The time for completing a full cycle varies from 5 to 13 hours. Similar units are mounted on large-scale sawmills.

Chamber-type dryers are more compact; a constant temperature and the environment as a whole are maintained throughout the volume. This type of dryer will allow you to dry any type of wood material to the required condition, which is why many entrepreneurs who are associated with the need to dry lumber choose chamber dryers.

Based on the technology of the drying process, the moisture that is released from the wood settles on the cooling elements, is sent to containers and then drained. The efficiency of such a unit is quite impressive, but time-consuming, leads to large heat losses. Price policy machines and the profitability of condensation drying is lower than that of convective drying.

Drawing

Drying chamber for lumber: step by step instructions

To build a dryer with your own hands, you can not use technical documentation. It is only necessary to provide:

• the area where the camera will be installed;
• insulating materials;
• source and communications to create high temperature;
• blowing.

The area of ​​a machine built personally, as a rule, is not more than 10 square meters. A square-section room is more suitable for moving warm air currents. It is preferable that at least one of the walls of the equipment be concrete, the others can be made of wood. Inside the chamber without fail gives in to warming. An excellent insulating material is wood shavings. If there is no foil at hand, then it can be replaced with penofol.

A separate extension for the dryer can be constructed from aluminum sheets, such a design will last a very long time. The base is made on the basis of profiles, it is covered with sheets of metal, which is further insulated. The thickness of the insulation must be at least 150 mm. The floor is covered with roofing material, a thick layer of shavings is poured on top, which will be excellent as heat saving.

The heat source can be supplied as a heating pipe system. The temperature of the liquid in the pipes should be at the level of 60 ... 90ºС. For an oversized chamber, a two-burner stove will be quite acceptable. If the source is right in the room, it must be overlaid with a brick. The brick is able to perfectly collect heat in itself and send it to the lumber drying machine.

The continuous circulation of the liquid is important, which is provided by the compressor or the whole station. The room must be equipped with wet and dry thermometers.

For more convenient loading of semi-finished products into the chamber cavity, you can use a rail trolley.

Video: do-it-yourself drying chamber for lumber.

How to make a cheap vacuum wood dryer

Hello dear readers and subscribers of Andrey Noak's Blog! Do you know what is the most important thing in wood materials? This is a quality dryer.

Each enterprise uses a special drying technology. But if you want to dry the material yourself, then I will tell you how a do-it-yourself vacuum dryer is made. But first, some theory.

Wood is a hygroscopic material, this is due to the fact that wood absorbs water vapor from the air.

Each wood material has a different degree of humidity, depending on storage conditions and environment.

Why dry wood?

Drying is the process of removing moisture from a material by evaporation.

When a tree grows, the metabolism in it is carried out with the help of moisture circulation through the trunk. When cutting, circulation stops and moisture begins to evaporate.

In order to build a house or make any wooden product, you need to dry the logs with high quality.

Purchased vacuum dryer

Well-dried material is protected from fungi, damage and cracks, and the service life will increase markedly.

If the drying was of high quality, then the product will serve you for many years.

Wood is divided into categories depending on the degree of moisture:

1. wet is the one that was in the water and its humidity is one hundred percent;
2. freshly cut, with humidity ranging from 50 to 100%;
3. air-dry, in cases where the material has been exposed to air for a long time.

   The moisture content of such wood is approximately 15-20%;

4. room-dry, with humidity 8-12%
5. absolutely dry, the humidity of which is equal to 0.

Wet material will be difficult to process, but is flexible and elastic.

Dry wood properties

Dry material has greater biological stability. After drying, the strength increases, it withstands the load better. It is easy to process, and the products do not crack after processing, unlike gray wood, in which the rotting process can even begin under suitable conditions.

Old ways of drying

A long time ago, people used only wood to build houses.

In the houses you can find wooden utensils. Therefore, it was necessary to come up with methods for high-quality drying of a log, as the main building material.

At that time, people used several methods of drying.

For this method, the necessary piece of wood, water and sawdust were taken. The water was heated to 70 degrees, the workpiece was placed in it, then covered with sawdust and left for certain time to steam the material.

After drying, the workpiece did not crack, and the structure became more dense and flexible.

Waxing is another method that has been widely used for a very long time.

Here, wooden blanks were lowered into paraffin heated to 40 degrees and left for several hours. It was important to maintain the same temperature of the substance.

After the procedure, the wood should dry for several days. The properties of the material change after drying. The workpiece does not crack, does not rot and acquires an original tinted shade.

Masters used this method of drying to make wooden utensils, then the finished product was skillfully painted.

Wood moisture, measurement methods

There are many ways to determine humidity.

Special devices are used to accurately determine the moisture content of wood. Electric moisture meters are able to determine humidity with an accuracy of 2-3%. The basic principle of such devices is based on the fact that wood of different moisture content has different electrical resistance.

There are many more "folk" ways to determine humidity, but only professionals use them:

• By weight, weighing the same pieces of wood of the same species in the hand or on the scales alternately.
• Experienced experts determine the moisture "by eye", by the presence of cracks and faults.
• By strand.

  When processing lumber, small chips are compressed in a fist. If it wrinkles easily, then the material is wet. Dry wood is indicated by the fragility of the chips, but if the chips crumble, then most likely the tree has dried out.

• By cutting. If during the processing of wood with a chisel a wet trace is noted, and the material is easily, smoothly cut, then it is not dried. It is better not to carve on such a surface, as cracks and flaws will appear when it dries.

We assemble a vacuum dryer at home

It is very profitable to dry the wood yourself, and if you do it with a vacuum dryer, the drying time will be reduced significantly.

But buying vacuum drying at factories is expensive, and I will tell you how you can make it yourself, and also save on it.

Drying at home takes place in special chambers.

To equip it, you will need a large room, a heat source, as well as a fan to distribute heat inside the structure.

Be sure the floor, walls and ceiling of such drying must be very strong, reinforced concrete or an iron conveyor is best suited.

If you take a cheaply used iron conveyor, for example, with railway, then it will be even a very cheap option. Or, for example, to reduce the cost, you can weld the conveyor yourself from old iron.

To preserve heat inside the chamber, we strengthen the walls with foam plastic and trim with clapboard.

Instead of foam, you can use mineral wool or other insulation.

To reflect heat, you need to lay a special material. You can use foil, but penofol is also suitable, especially since its heat-reflecting and retaining qualities are much better.

We proceed to the installation of the heating device.

The entire heating system must be installed separately from other heating circuits and must constantly work. You can use a heating radiator, with which water is heated to 65-90 degrees.

In order for the heat to be equally distributed in the chamber, a fan is required, otherwise there will be uneven drying of the raw materials and, accordingly, poor quality.

Another point, the temperature in the chamber should change smoothly and gradually.

When building your own dryer, you must comply with all fire safety rules.

An important point is the construction of a system for loading lumber into the chamber. You will be loading large and fairly heavy boards. For this, carts moving on rails or a forklift are well suited. The material inside is stacked on shelves or just on the floor. To control the drying process, you must install special sensors, and these are thermocouples and vacuum (pressure) sensors.

Having done everything right, you can get very high-quality wood with a good presentation.

The main point in the construction of drying is to achieve the necessary parameters inside the chamber, and the materials and equipment that were used do not matter.

In your chamber you can reduce the drying process of raw materials up to 2 weeks.

How Vacuum Drying Works

After you have put the material in the drying chamber, tightly closed the door, you can start drying. Air is extracted from the chamber to create a vacuum of about 9 - 10 bar. It is known that when the pressure is reduced, the water boils faster.

Thanks to this technology, bound and free moisture will move uniformly from the center to the periphery, thereby ensuring high-quality and uniform drying of the material, regardless of location.

Dry top wood cells will absorb moisture from those located in the core.

First, thin places dry out, then moisture from thicker layers moves to the dried ones, thereby moisturizing them. If this process is interrupted, then the material may be destroyed, since the displacement of thinner layers begins.

Covering the ends of thick lumber to prevent rapid release of moisture and the formation of cracks during drying.

To prevent displacement, lumber is treated with a special mixture, which is made from chalk, as well as drying oil.

Often it is necessary to process the end parts of the blanks.

Drying excludes the use of humidification systems, and thermometers should not be installed in the chambers. You can control the process using special sensors, which are controlled from the outside, often in a separate vestibule.

Very often, vacuum plants are used for drying expensive species such as oak, merbau, padauk, wenge, zebrano.

It is very convenient, since the wood practically does not collapse during drying.

My help

I have the opportunity to provide advice on drying technology, the selection of new and used equipment.

You can contact me through SUPPORT.

Recently, my new book has been published, which gives recommendations on the operation of drying complexes in production. The information that is given in the book is simply unique, you will definitely not find it anywhere else.

More information about the book can be found in the "MY BOOKS" section.

Good luck and see you soon!

vacuum dryer

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Appointment of modular wooden drying chambers.

Drying chambers Series SCM, students in the nomination "100 best products in Russia.", They are designed for drying hardwood and softwood in accordance with quality categories 0, 1, 2, 3, depending on the purpose of the wood. Drying chambers Our production certified and answer " General requirements to environmental monitoring and management systems drying chambers" and "Quality Drying Requirements" according to Russian Technical Material (RTM) guidelines for kiln drying in wood.

Installation, design features of SCM wooden dryers.

Striving for maximum build speed and speed wooden drying chamber partly included in the SCM models. Modular design wooden drying chamber simplifies delivery and installation.

To meet the wishes of the company's customers, many standard sizes Drying chambers. Now "TERMOTECH" develops and manufactures wooden drying chambers and complexes with pneumatic load from 6 to 180 m³ operating on thermal energy generated by the combustion of wood waste or stationary boilers.

Drying chambers with a load capacity up to 20 cu. they have a body in the form of a complete container with a supporting frame, the dimensions of which can be shipped by road or rail.

High mobility and low cost installation work allow you to build a heated drying cabinet with a heated floor. When renting production areas wooden drying chambers with floor heating is more practical. With a low probability of frequent disassembly, for example. if we have our own space, we can offer a version of the drying chamber body without floor insulation. The cost of chambers without floor insulation is lower, we need more work for installation.

It is necessary to carry out clamping of cement cement regardless of the height of the already welded track in the place of our company, on the transverse stiffener. clam Drying chambers volume 20 cu. up to 180 m3. They are made in the form of modular blocks, easy to transport, easy to connect with screw connections. The time required to assemble a modular drying chamber is 4 to 8 hours in proportion to the number of modules.

The sealing of the joints when installing the modules of the drying modules is carried out with a special rubber profile and silicone sealant, which is delivered to the customer along with the drying chamber.

The roof of modular wooden drying chambers, depending on the volume of loading, is made one-sided or two-sided. All SCM drying chambers are equipped with a condensate collection and removal system, which increases the life of the fence. For a better seal Wooden loading doors of the drying chamber are made with a floating hinge by closing the four-point door lock with the screws.

The door seal is a heat-resistant 3-strip profile. supplied drying chambers Control system, equipped with drying procedure, semi-automatic fully automatic (computer), S control of fuel supply, boiler operation, blinds, ventilation curtains, etc.

proposed wooden drying chambers manufactured both at rest and in a transitional version. The transition version allows the customer to organize the most efficient continuous process and increase the productivity of the drying chambers due to more rational use loading and unloading time compared to blindness.

Loading wood into wooden drying chamber produced by standard wheels. Depending on the load capacity of the chamber, the strings can be transported longitudinally or transversely. When drying wide raw wood, excluding the transverse tip of the tree, the pedestal is equipped with a block-type clamping mechanism.

In this case, the force pressing down on the upper types of beams is equal to the force on the lower types of lumber. When expressed numerically, this force is equal to the force of the weight of the fund.

Heating system.

Modular drying chambers and wooden complexes manufactured by "Termotech" operate on thermal energy obtained from the combustion of wood waste in the heat generators of our industrial or stationary gas boilers. Water heated to 95°C by a pump is provided through the supply pipeline to the side walls wooden drying chamber radiators, after passing through which it enters the boiler at a temperature of 75 ° C.

Useful water registers are single-sided double-sided bimetal tube heaters (steel bolts with aluminum plates). It refers to the drying chamber of a specific boiler acting on a loaf (chips, leftovers, stove - 70 ... 100 vol.%) In a mixture of wood waste (30%).

When a large number of chips (100%) of solids are provided with a boiler funnel, - relying on sawdust feeding a screw mixer or a mechanical load carburetor, which allows each fraction (boards, chips, chips, bark) to be heated wood products. In case of insufficient amount of wood waste, we can fill the supplied heat source directly on burners, gas stoves or oil stoves.

For a more efficient and stable operation boiler, a fan is installed in the turbine, and an ejector is installed in the chimney chimneys.

Air exchange system, fans, brackets.

For heat exchange between water registers and indoor air wooden drying chamber A centrifugal fan is installed, the electric motor of which is installed outside Drying chamber for wood drying.

The use of rotary fans made it possible to reduce the consumption of electricity for ventilation in wooden drying chambers manufactured by TERMOTECH by 1.7 times compared to similar manufacturers. Drying chambers. Such effective results were achieved thanks to the rational redistribution of power when installing the fan. Incorrect high pressure has been reduced resulting in improved fan efficiency.

In addition, pressure was reduced in cubic dependence, and increase power - squared. With aerodynamic calculation wooden drying chamber The greatest losses occur when the ventilation system is ventilated.

The fan motor power loss is directly proportional to the cubic velocity of the drying agent. Therefore, further optimization was carried out from the condition: The speed of the drying agent next to the sawdust storage should be between 1 and 1.5 m/s. Based on quality conditions, the same speed is regulated by CNIIMOD for drying wood in mild and normal conditions.

Because the domestic industry does not produce specialized fans for Drying chambers(high capacity, low pressure) - all fan wheels are self-shaped.

The fan wheels are static and dynamically balanced. In wooden kilns with a load of wood up to 12 m ³ Fan wheels are mounted directly on the motor shaft.

Fan for wooden kilns with wood volume over 12 m3 ³, is carried out through bearings and pulleys. The fan bearing bearing is the busiest device in the drying chamber.

For greater reliability, we use FAG, the company is the world's leading carrier (Germany) of the BND series with FAG spherical bearings. These bearings have a labyrinth seal, grease nipple during Maintenance and are centers that withstand heavy loads, as originally developed for crushing and grinding machines, roller drives for presses and wind turbines.

The most optimal cross extrusion of the chimney and the temperature regime inside drying dry baked lumber It comes with screens and external blinds. This design provides easy access to the inspection and maintenance of the rotating fan and registers. To exchange air with the atmosphere in Ljubljana wooden drying chamber installed aluminum inserts and exhaust valves.

Fences, wall insulation.

Corps of all Drying chambers they have optimal thermal insulation calculated for the middle strip, a layer of solid mineral wool board, which does not absorb moisture and has a high degree of fire resistance.

All steel members preventing corrosion in the drying chamber are protected by corrosion coating and waterproof coating. When shipping In regions with different climatic conditions, it is possible to build a thickness that provides the necessary thermal insulation.

How to make a wooden drying chamber

In accordance with the technical task of the customer, there are technological possibilities for the manufacture of monolithic insulation from polyurethane foam from closed cases wood dryingcams, or a combination of thermal insulation consisting of rigid hydrophobic, mineral wool (water absorption coefficient by volume - 1.5%), TIS mats - TIB TU 2123-299-89 and polyurethane.

Polyurethane foam has the best insulating properties, the lowest thermal conductivity coefficient (W 0.019-0.28 / Mº K), light weight (40-60 kg / m³), ​​high adhesive strength and corrosion protection.

The warranty period for insulation of aluminum sandwich panels made of polyurethane foam is 30 years. (Detailed description and comparative characteristics rigid polyurethane foam and mineral wool, see here.) Internal walls wooden drying chamber from aluminum sheet or steel with a heat-resistant coating.

outer envelope drying chamber walls made of galvanized, corrugated film 0.8 mm thick. Places of probable occurrence of "dew" (the inner surface of the door, inlet and outlet valves) are made of aluminum.

Thermal processing of wood.

At the request of the client for the production of dry wood from 0, 1, 2, 3 quality categories, wooden drying chambers they are made universal humidification, air conditioning and steam system - development and production of "TERMOTEH".

The diversity of the system is achieved by generating dry entropy steam and increasing the moisture content, i.e., creating the necessary and sufficient conditions for high-quality hardness and drying of wood, as well as thick softwoods.

The processing device of the technological operation must remove the internal tension in the wood when the wood is already dry in order to ensure the stability of the geometry of the workpiece after processing in woodworking machines. It's a concept, a tutorial. Very often, the conditions for storing joinery products after sawing wood are violated, for example: lack of sunscreen to protect against the sun, uneven air flow of a chimney with natural air circulation, loading one drying chamber into several packages with different sawing periods (sometimes important - months).

Therefore, there is an uneven distribution of moisture over the volume of one plate and the volume of the foundation. This leads to stress and improperly selected drying conditions. Avoid rejection with moisture compensation, which is achieved by conditioning the wood treatment at the beginning of drying. For the solid beech process, a steam process is needed to create a uniform color palette for wood of different ages. The intensity of the color is proportional to the duration of the steam.

In any case, during the heat treatment of wood, the temperature acts as a catalyst (fast) in the process of uniform redistribution of moisture with the help of the material (moisture transfer), and the high humidity of the desiccant slows down the drying process (stops the removal of moisture), moisturizes overdried wooden parts.

The duration of dampening depends on the thickness and type of wood. Woodworking recommendation for woodworking is "wood drying technology" which is equipped with our product drying kilns. CAM "Module C1", "C2-Module" includes the entire thermocouple drying program. In the absence of a water supply network, the humidification system, air conditioning system and water vapor can work in an unnecessary mode, an unnecessary tank with a consumer inside wooden drying chamber, whose volume is sufficient to complete the entire drying cycle.

In the event of an emergency in the event of a fire in a disaster, the same humidity should be used by the normal fire extinguishing system wooden drying chamber in accordance with PPB-01-93 "Fire Safety Rules in the Russian Federation".

If the client has vacant premises that are outdated Drying kilns for wood drying we are ready to provide technical solutions and equip necessary equipment for their transformation or modernization of drying chambers.

Drying kilns for wood convective type

The presence of drying equipment for drying wood and lumber, as a rule, is one of the main attributes of modern woodworking production.

Dryer for boards: creating and using a drying chamber

Drying chambers of convective type have found great application both in Russia and abroad. The convective wood drying technology makes it possible to obtain high-quality lumber with the required moisture coefficient. Modern drying chambers are equipped with automation that allows you to control and monitor the drying process remotely.

Company Negociant-engineering supplies kilns for wood Russian production.

The proximity of production, the introduction of the latest technologies and well-established service make it possible to provide our customers with inexpensive and high-quality drying equipment. We implement both small (with a small load volume) drying chambers, and large projects for various industries.

Features and benefits of drying chambers

Automatic control and monitoring of the wood drying process

Minimum terms of delivery, installation and launch of drying chambers

The design of the drying chambers is made of aluminum and stainless steel elements.

The ventilation and heating system is equipped with German-made reversible fans

The walls of the drying chamber building are insulated with Finnish mineral wool with basalt fiber

Inspection door as standard

Sale and service of drying chambers

We carry out delivery, installation and launch of drying chambers.

We provide warranty service and maintenance.

Drying chambers are made to order at the request of the Customer

Loading volume from 45m

We offer comprehensive solutions for organizing a wood drying site using boiler equipment and wood waste disposal equipment.

The cost of drying chambers is lower than competitive ones.

Technical characteristics of drying chambers

Optional

Installation supervision and commissioning

A specialist arrives to carry out the installation supervision work, who measures the foundations in accordance with the documentation provided in advance, then proceeds to assemble the drying chamber with the customer's team.

Upon completion of the assembly, the specialist launches the drying chamber into operation and trains the customer's personnel.

Catalog kilns for wood

A detailed description of the design of the drying chamber for convective type wood can be downloaded here

Photos of completed projects for the installation of drying complexes

The drying mode depends on the type of wood and the thickness of the lumber. To prevent the boards from cracking and warping during drying, they are pre-steamed, for which wet steam is supplied to the chamber.

First, they are heated for 1-2 hours at a temperature of 50 ° C.

Do-it-yourself drying chamber for lumber

After steaming, increase the temperature to 60°C, then repeat steaming and, if necessary, steam up to three times. With the right drying regime, the wood does not undergo much deformation.

Rice.

6. Scheme of drying methods:

a - air-steam intermittent action, b - electric dryer operating on currents high frequency; 1 - heaters, 2 - supply channels, 3 - pipes for starting steam, 4 - exhaust pipes, 5 - special trolley (track), 6 - damper, 7 - movable electrode, 8 - fixed electrode

Soft wood species are dried at a temperature of 40-75 ° C, hard - at 35-55 ° C.

The drying temperature of lumber should not exceed 80 ° C, since at a higher temperature the structure of the surface layers of the wood changes, i.e., the material is, as it were, hardened. Such material is difficult to process with cutting tools.

At the beginning of drying, the air should have a relatively high humidity and a low temperature.

The higher the moisture content of the wood, the more moisture the air introduced into the chamber must contain in order to avoid cracking the wood. Then, as the material dries, the air temperature is increased, and the humidity is reduced to a minimum.

For drying lumber of softwood and hardwood of various sizes, most factories in model shops use intermittent steam-air chambers with stimulating reverse circulation.

The unloaded lumber from the dryer (dried at a temperature of 60-70 ° C to a moisture content of 10-12%) is kept under conditions before being put into production. production shop within 2-3 days to release wood from internal and surface stresses (normalization) obtained as a result of drying.

In addition to steam-air drying chambers, there are gas chambers.

In the drying gas chamber of intermittent action, smokeless gas is used to evaporate moisture, obtained in the furnace during the combustion of raw wood waste, which is forced through the axial high-pressure fan through the gas ducts onto the stacks of sawn timber. The design of the chamber provides for a steam humidifier.

In the woodworking industry, intermittent gas dryers operating on natural gas are used, with a furnace in which the gas temperature reaches 1000-1300 ° C, but after circulation in the chamber, the mixture is fed at a temperature of about 100 ° C.

The working gas mixture is smokeless. Lumber dried in properly working gas chambers does not darken. Each of the drying chambers holds 4 stacks of boards with a volume of 1.8X2.6X6.5 mm each. Gas chambers are used for row drying of sawn softwood.

Lumber can be dried by the high-speed method in electric dryers with high-frequency currents. Drying with the use of high-frequency currents lasts only a few hours, while the material dries evenly, without cracking or warping.

The waste of wood during such drying is much less than in steam and gas dryers, and is no more than 5%.

The peculiarities of heating semiconductors and dielectrics, which include wood, in a high-frequency electric field are that heat is released directly in the heated material and the temperature of the material can rise for a short time.

For example, a wet board can be heated to 100°C in 3 minutes. The wood is simultaneously heated throughout its thickness. The current power absorbed by the material can be controlled by selecting and changing the parameters of the electric field.

The following is not to be taken as a DIY guide. Homemade chambers for drying wood exist and there are quite a few of them. But at the same time, the vast majority of them are far from perfect.

Drying chambers are calculated and designed, which means that specialists should deal with this.

Even if you decide to make a drying chamber "with your own hands", then at least, before building it, order a project from specialists or find and study literature on the construction of drying chambers.

Woodworking, its cost, product quality, depend on the quality of lumber drying. In turn, high-quality chamber drying of wood depends not only on compliance with the technology (correct lumber stacking, compliance with the regimes), but also on the design of the drying chamber.

I hope that the information given here will allow you to avoid mistakes when purchasing or help you improve the convective wood drying kilns available in your production.

Next, we consider the device of a drying chamber for wood with an upper arrangement of fans (vertical-transverse circulation of the drying agent), since this is the most common aerodynamic scheme in modern convective chambers for drying wood.

All calculations are given for easy-drying wood species: pine, spruce, cedar, and so on.

Lumber with a thickness of 50 millimeters is taken as conditional.

Drying chamber device for convective type wood

For uniform drying of wood along the height of the stack, the distance from the wall of the drying chamber to the stack of lumber must be at least a quarter of the height of the stack (see.

figure), otherwise it is necessary to ensure the narrowing of the air channel from top to bottom.

Scheme of a convective drying chamber (in section)

With two or more stacks, the distance between them (in Figure A) should be at least 15 - 20 centimeters.

For uniform drying of lumber along the length of the stack (with a board length of 6 meters), drying chambers, as a rule, must have at least three fans.

Drying kilns for timber should be designed to allow air to pass only through the stack of lumber.

Free passages reduce the airflow through the stack (hence the drying of the wood is slower) and make it uneven, which increases the moisture unevenness of the dried lumber.

The free passage of air on the sides, top, bottom of the stack must be blocked by curtains, thresholds and other things.

Side curtains are recommended to be installed in such a way that they overlap the stack by 10 - 15 centimeters from the ends, this will reduce the cracking of the ends. It is desirable to make the top curtains movable, since the drying of the wood leads to a decrease in the height of the lumber stack.

Air circulation during chamber drying of wood

Circulation is carried out with the help of fans, the air passes across the stack. The fan compartment is fenced off from the stacks of lumber with a false ceiling and has a baffle designed to prevent "short circuits" of the air flow. It is very important!

In some home-made drying chambers, this partition is absent, as a result, a significant part of the air is chasing uselessly over the false ceiling without getting into the stack.

Single-stack kilns for lumber allow the use of non-reversible fans, with two or more stacks, the fans must be reversible.

Requirements for fans for drying chambers

If the fan motor is located inside the drying chamber, it must be made in a moisture-proof design and have a heat resistance class "H" (up to 100 degrees), an electric motor that does not meet these requirements must be moved outside the chamber.

In self-made drying chambers, class F electric motors are often used. As a result, they fail at intervals of 3 to 6 months.

With insufficient fan performance, the chamber drying of wood is slower, and the unevenness of humidity across the width of the stack increases.

Heating of convective drying chambers.

The supply of heat necessary for the evaporation of moisture from wood is carried out by heaters, their power is determined at the rate of 3-4 kW per cubic meter of conventional lumber.

To ensure this, the heat removal surface of the heaters should be about 3.5 square meters per cubic meter of lumber. It is not recommended to use electric heaters: the drying of wood in this case will have a high cost. Probably for many the best option there will be the use of a woodworking waste boiler.

It is desirable that the air entering the convective drying chambers during ventilation, before entering the stack, passes through the heaters.

Therefore, if the fans are reversed, the heaters are usually arranged in two rows, as shown in the figure. If the heaters are located in one row, and the fans are reversible, then the heaters must be located between the ventilation ducts of the pressure side and the vacuum side.

Such a scheme of the drying chamber is characterized by slightly higher heat losses, but lower manufacturing cost.

Chamber drying of wood requires less heat energy if convective drying chambers are equipped with recuperators (heat exchangers). In the heat exchanger, heat exchange occurs between the incoming and outgoing air during ventilation. The use of a heat exchanger, in addition to saving thermal energy, reduces temperature fluctuations during ventilation, therefore, drying lumber will be of better quality.

Unfortunately, in Russia, convective drying chambers for wood with recuperators are practically not produced.

Thermal insulation of drying chambers for wood.

Total temperature difference is 115 degrees. Consequently, with poor thermal insulation, part of the money that you pay for heat energy will go to heat the street.

In addition, with poor thermal insulation, moisture will condense on the walls, floor and ceiling of the drying chamber, which will not allow it to withstand the air humidity set according to the regime at the initial stages of wood drying.

If possible, drying chambers should be installed indoors, this will reduce the possibility of cracking of lumber during unloading due to a sharp temperature drop. But even when installing indoors, good thermal insulation is needed.

Tightness of drying chambers for wood.

At the initial stages, chamber drying of wood is carried out at high humidity, so moist air should be removed when and only when it is required by the regime.

With poor tightness, it is impossible to withstand the specified air humidity. Using a humidification system does not help: even if steam is supplied, a significant part of it falls out as condensate due to contact with cold air.

Therefore: wood drying chambers must be airtight, not have gaps, sealing gaskets must be installed on the gates. Especially often home-made drying chambers have poor tightness.

In industrial chambers, the deterioration of tightness usually occurs due to loose closing of the gate due to careless adjustment during installation.

Supply and exhaust ventilation during chamber drying

Typically, the device of drying chambers provides supply and exhaust ventilation due to excess pressure on the pressure side and reduced pressure on the discharge side, additional fans are not used.

The required total cross-sectional area of ​​​​air ducts for such ventilation is approximately determined at the rate of 40 square meters. centimeters per cube of conditional lumber from the pressure side and the same amount from the vacuum side. Air ducts are equipped with curtains that open and close as needed.

To reduce the formation of condensate in the air ducts, their thermal insulation is desirable.

Humidification system for chamber drying of wood

There is an opinion that drying of easy-drying wood species can be carried out without moisture treatment.

Indeed, when drying freshly sawn wood, the required air humidity according to the regime is gained in 6-12 hours. However, if chamber drying of wood is carried out, which has lain for 2-3 days after sawing, then this time can stretch for a day or more, which is already undesirable.

Drying kilns for lumber - a choice of equipment for drying wood

Thus, a humidification system for chamber drying of lumber is still needed. For humidification use steam or finely atomized (drops hang in the air) with the help of nozzles water. A very common mistake in homemade drying chambers is that when spraying, water hits the thermometer and air humidity sensor. As a result, automation receives false information about climate parameters.

It is unacceptable.

About the requirements for gaskets.

Gaskets are not a design element of the drying chamber and, of course, they are not supplied with it, but without meeting the requirements for them, high-quality drying of wood is impossible, therefore, briefly about gaskets.

Gaskets must be made of dry lumber and have exactly the same thickness. The thickness of the spacers with a total width of stacks up to 4.5 meters should be at least 25 millimeters; with a larger number of stacks, it is recommended to increase the thickness to 30-35 millimeters.

With insufficient thickness of the spacers, the chamber drying of wood is slower, and the unevenness of moisture across the width of the stack increases.

The width of the gaskets is 40 - 50 millimeters.

The surfaces of the gaskets in contact with the lumber must be planed.

High-quality drying of wood largely depends on the correct laying of lumber, so be sure to study this issue.

Drying chamber for lumber is industrial equipment, which is used to dry raw timber for further processing. Today, wood drying in drying chambers is carried out by several types of such devices, each of which has its own specific functional features. However, in fact, they are all universal. With their help, you can dry any kind of timber. With the help of the latest drying chambers, even the most exotic and expensive varieties of wood, such as rosewood, beech, wenge or teak, are dried with high quality. There is no cracking or other flaws.

Types of drying chambers

A large number of woodworking industries process almost 10,000 m³ of lumber every year. The wood drying kiln is a decisive link in the process chain for quality assurance. The volume of a single load of timber in the drying chamber is very different. Sometimes you need to dry 6 m³, and there are needs up to 100 m³. The main factor during the selection of the size of the drying chamber can be called the production capacity.

Drying methods are classified according to the features of heat transfer to the dried raw material, therefore, the following types of chambers are distinguished:

• dielectric - need high energy costs
• convector
• vacuum. These devices are expensive and expensive to maintain.
• aerodynamic. Such devices need a lot of energy.

Chamber drying of wood by various methods was invented in the 60s of the last century, however, due to high energy costs and the complexity of the design, drying has become popular only in the last decade. Convector-type chambers are the most popular all over the world.

Convector dryers

The convector type wood drying chamber is used for various types of timber. Such devices have simple design, they are low maintenance and reliable. That is why they are the most popular in production.

The work is carried out by heating from a gaseous carrier (drying agent). When heated, the material dries out. The drying agent can be steam, flue gas or air. The moisture that is released from the timber serves to additionally moisten the agent, and the excess is sucked out with the help of ventilation.

The air exchange rate in the convector dryer does not exceed 2% of the total amount, therefore, energy savings are felt.

The body of the chamber is metal, placed on a monolithic-columnar foundation. The metal that is used for the body is carbon steel or aluminum with an anti-corrosion coating. On both sides, the body is sheathed with sheets of aluminum. The chamber is insulated with mineral wool in the form of plates. You can buy a convector chamber of both domestic and foreign production.

vacuum drying

Vacuum drying chamber for wood is designed for high-value timber such as teak, wenge, rosewood and others. Such a unit functions from convector heating of wood and vacuum removal of excess moisture. The process takes place at a maximum temperature of +65. However, due to the vacuum pressure of 0.09 MPa, boiling occurs at 45.5. Such conditions make it possible to dry the wood without the aggressive effects of high temperatures. Thus, there is no high internal stress, and the wood is not subject to cracking.

During drying, when the temperature rises to 65 degrees, the automation turns on and the electric boiler turns off. The top layers of timber slowly cool down, and moisture from the inside goes to drier areas. During the period of one drying, about 250 such cycles occur. Under such conditions, moisture is evenly drawn out along the length and depth of the material. After drying, the material is characterized by a moisture level in the range of 4-6%.

Aerodynamic drying

Chamber drying of sawn timber under aerodynamic conditions has become widespread due to the rather low price, uncomplicated design. In addition, to work on such a device, specific knowledge of the service personnel is not required. Profitability is achieved when drying up to 2000 m³ per year of coniferous timber.

Among the shortcomings can be identified:

• high level of energy intensity of the drying process. In order to dry freshly sawn wood, 1.15-1.3 kWh is needed to evaporate 1 liter of moisture. Electricity, approx. 240-290kWh/m³
• there is no way to regulate the temperature. There is only the possibility to slow down the rate of its increase by changing the cross section of the centrifugal fan
• there is no possibility to organize technological drying according to the schedule of the "Guiding technical materials according to the technology of chamber drying of wood.

Such a chamber is a quadrangular box. It is convenient to load wood into it by machine or by railway tracks. Drying occurs under the action of aerodynamic energy. Warm air moves in the chamber under the action of a special aerodynamic fan. Due to the compression of air in the chamber, the temperature on the centrifugal fan, namely on its blades, increases. Consequently, aerodynamic losses become thermal energy. Heat can be driven into the chamber in reverse or dead-end, it all depends on the design features. The opening of the chamber occurs only at the end of the drying cycle.

Drying in a microwave chamber

Such devices have been invented recently. They look like a closed metal container. The work is carried out under the action of the reflective surface of microwave waves. The principle of operation is similar to the operation of a conventional microwave. With the help of a microwave chamber, raw materials of any section and dimensions are dried. Microwave chambers are distinguished by a simple design, the settings allow you to select any wavelength.
Therefore, you can dry a wide variety of timber. The attenuation mode of microwave waves guarantees the regulation of the temperature inside the chamber. With the help of reversible fans, excess moisture is removed from the system. Microwave drying is compared with dielectric drying, which is considered the most efficient, but is not used in Russia due to high electricity costs.

Freshly cut wood is not used in production and construction, as it contains a large amount of moisture. Such a tree is called wet. To improve its mechanical and physical performance, a lumber drying chamber is used. In the process, biological stability increases, the strength index increases, and other qualities of wood improve.

The concept of wood moisture

The percentage ratio of the weight of the contained liquid to the mass of completely dry wood of a certain volume is called absolute humidity. The percentage of the mass of water removed (determined by two weighings) to the original weight of the wood is called relative humidity.

The degree of suitability for use is determined taking into account the relative humidity index. The value indicates the readiness of the material for gluing, shrinkage, with a value of more than 30%, there is a danger of developing a fungal infection.

Depending on the indicator, wood is divided into categories:

• wet - at a relative humidity of more than 23%;
• semi-dry - within the range from 18 to 23%;
• dry - with a humidity value of 6 to 18%.

Drying wood in natural conditions

With this method of removing moisture, a drying chamber for lumber is not used, the liquid evaporates under the influence of atmospheric air. Dry the material under a canopy located in a draft. The sun's rays unevenly heat the outer and inner layer of the tree, which leads to the appearance of deformations and cracks.

If a drying chamber for lumber is not equipped on the site, an attic room, a ventilated shed, and an equipped shed are well suited for drying. The material is stored in a pile, the first layer must be placed on stands with a height of at least 50 cm from any durable material. Rows of lumber are shifted with dried slats, all subsequent boards and logs are placed above the previous blanks so that vertical air wells appear.

Sawn logs and finished boards are placed with the inside up to reduce the size of the deformation. For the same purpose, a stack of wood is pressed from above with a heavy load. Due to the formation of cracking at the ends of the workpiece during drying of the material, the length of the workpiece is selected 20-25 cm longer than the intended part.

The ends of the lumber are carefully treated with oil-based paint, drying oil or hot bitumen to prevent cracks. Before stacking, the trunks of logs are cleaned of bark to reduce the likelihood of reproduction of wood bugs. Removing moisture from wood in a natural way is considered an economical method.

Solar Wood Dryer

The second way, the costs of which quickly pay off, are drying kilns for lumber. The drawings for manufacturing are quite simple, you just need to understand the principle of operation of such a device. The chamber is an assembled plywood or metal container, the roof of which is made of transparent materials.

The calculation of the size of the glazed surface of the roof is done depending on the total horizontal area of ​​\u200b\u200ball the lumber laid for drying. The area of ​​the transparent coating should be one tenth of the total surface of the boards. The roof of the building is made pitched, the amount of slope depends on the geographical location of the area. In the northern cold regions, where the sun does not rise high above the horizon, the slope of the roof is made steep. The southern sun heats gently sloping surfaces well.

How to make a drying chamber for lumber?

The frame of the building is made of metal or timber treated with an antiseptic under pressure. The lining of the walls and floor of the chamber is made of moisture-resistant materials, the fences are insulated with mineral wool or hard foam slabs. The inner surfaces of the walls are treated with water-repellent compounds, aluminum powder is applied to them, then painted black.

Fresh air blowers should not contain blades made of ductile fusible materials. If the lumber drying chamber is not constantly used, then the room is used for drying herbs, vegetables, berries or a seasonal greenhouse. After laying all the wooden blanks for drying, a distance of about 30-40 cm should remain between the stack and the wall on all sides.

Drying wood in artificially created conditions

When moisture is removed naturally, relative humidity values ​​of about 18% are obtained. To improve the value, drying of lumber in drying chambers is used, where the temperature, the speed of forced air supply and its humidity are regulated.

Basic equipment for dryers

Whatever type of wood forced drying chamber is used, standard equipment groups are allocated for all.

The transport equipment is designed for loading and unloading logs or boards into the drying room. Includes cars and mechanical devices for storing blanks in a stack or package, carries out raising and lowering lumber.

The thermal equipment of the chamber serves to raise the temperature of the internal air in the chamber and consists of many systems that determine the interconnected work on the production and transfer of heat. These include heat exchange tanks, heaters, pipes for the passage of steam or hot water, devices for removing condensate, shut-off valves and control devices.

The fuel is gas, liquid fuel. For small volumes of work, a drying chamber for wood-fired lumber is equipped. The heat carrier is saturated steam, water, gas obtained from the combustion of the furnace, organic fillers of the system with a high boiling point. Electric heaters are widely used, where the current energy is converted into a thermal component.

Circulation equipment is designed for the organized movement of air masses in the drying chamber. The elements of the system are fans, injectors and joint installations of these elements. To increase the efficiency of wood drying, automation of drying chambers for lumber is used.

Drying chamber guard

To isolate wood from the environment, a chamber enclosure is installed, which consists of a floor, ceiling, walls and intermediate partitions. Partition requirements:

• should not skip steam;
• fences should have low thermal conductivity;
• must have a long service life.

Fences are made separately from various building materials or are prefabricated with a set of standard metal elements.

The first type of chambers has a longer service life, but has a longer commissioning time, which is not always justified. Prefabricated metal frames are mounted quickly, they are equipped with control and thermal devices, but the steel is subjected to the destructive action of wet and thermal conditions.

Working principle of vacuum drying

After stacking the wood in a stack, the door of the chamber is hermetically closed and the drying process begins. With the help of automatic devices, part of the air is removed from the chamber until a pressure of 8-10 bar is created inside. Thanks to this scientific approach, the moisture released from the wood moves faster from the center to the outer enclosures of the chamber, thereby ensuring uniform and high-quality drying. This is how vacuum kilns for lumber work.

Making a drying chamber yourself

Private developers dry the wood in the courtyard; for this, a do-it-yourself drying chamber for lumber is equipped. Its device will require a large room, a heat source and a device for distributing air between drying packages of wooden blanks.

You can, of course, purchase used drying chambers for lumber, but the degree of wear is not always possible to determine correctly, it is much more profitable to arrange the room for drying wood yourself. This is an opportunity to get excellent results with low cost Money.

Construction stages

You will need material for the frame, usually these are metal racks from a corner or channel, a wooden bar is used after careful treatment with an antiseptic. As a wall covering, metal sheets, moisture-resistant plywood panels, and profiled steel are used. Thermal insulation is carried out using mineral moisture-resistant wool, polystyrene foam.

Before construction begins, the location of one or more dryers is determined, which serves as a plan for the concrete foundation. The base is made for the stability of the structure and uniform distribution of the load on the ground. If a ready-made railway container is taken for the chamber, then four columnar foundations are made under the corners of the car.

The metal frame is assembled by welding or bolting. During the device, they check the verticality and horizontality with a building level, trying to strictly observe the geometric dimensions. After fixing the frame in the installation position, they begin to sheath the outer walls, simultaneously inserting doors and ventilation windows.

The heat-insulating layer of the floor, walls and ceiling must be at least 12-15 cm, the base is insulated from moisture with rolled material. After that, the camera is checked for tightness. For laying the first layer, stationary supports made of metal or wood are installed. A heat source is installed, usually a powerful fan heater, positioned so that the direction of hot air is parallel to the lying boards.

Drying wood is necessary condition to obtain quality raw materials. Building a house or making fillings for openings from wet lumber is fraught with distortions and a violation of integrity. To work with wood without problems, you need to take seriously the removal of excess moisture from the material.

In this article:

Wood is a hygroscopic material that contains moisture naturally and has the ability to absorb it from the atmosphere. Sawn timber goes on sale in two forms: natural moisture and dried. Of course, the latter are more expensive, so many entrepreneurs, when equipping a sawmill, think about ways to dehydrate wood.

Humidity indicators

According to the degree of moisture, the following states of the tree are distinguished:

• wet(100% humidity) - logs that have been in water for a long time (for example, they were transported by alloy);
• freshly cut- humidity depends on the natural conditions of plant growth, and ranges from 50-100%;
• air dry- the material that is stored in the air (under a canopy) reaches the parameters of 12-20%;
• room dry(8-12%) - drying in a closed, heated and well-ventilated area;
• dry(humidity less than 8%) - prepared by the method of forced release of moisture.

Why is proper drying so important?

Boards of natural moisture are larger than dried boards in size, but are cheaper. This is because lumber manufacturers set a tolerance for future shrinkage and trimming.

Humidity standards:

• for building and carpentry materials - 10-18%. In the manufacture of building materials, the production moisture content of wood should be equal to or be 1.25-3.5% lower than the operational one in order to avoid natural shrinkage.
• for furniture production - 8-10%.

The use of lumber of natural moisture is a gross violation technological process . When the wood dries naturally, it will change the width, thickness and, accordingly, the geometry of the entire product.

For example, a 50*150mm edged pine board with a natural moisture content of more than 50% after a couple of months will have parameters of 48 * 138 mm (with tangential sawing) and 46 * 144 (with radial sawing). Even if we take into account that the length of the product will remain the same (on average, the deviation does not exceed 0.1%), the final difference is catastrophic!

Methods for professional wood drying

1. Convective (chamber) drying

The most popular type of drying equipment - convection chambers. About 80% of manufacturers use just such dryers.

Advantages: ease of use, high speed moisture evaporation, low voltage in the final product, high loading volume (up to 1000 m3).

Supply and exhaust ventilation and heating systems are installed in the room (usually heaters). Humidity parameters are measured psychrometer and adjusted automatically. As a fuel for obtaining hot water or steam in small-scale production, waste wood production is used: wood chips, slabs, sawdust. It is profitable to use electricity and gas only with large volumes of production, otherwise high consumption and cost of resources will significantly reduce the cost of lumber.

Centrifugal or axial (depending on configuration) fans provide uniform distribution of warm air and timely removal of excess moisture to avoid warping, cracking and wood production highest quality in the shortest possible time.

Price - from 160,000 rubles(depending on configuration and cargo capacity).

2. Atmospheric drying

The natural process of evaporation of moisture from wood, which requires a minimum investment, but a maximum of time. However, wood dehydrated by atmospheric drying is considered the most resistant to deformation. Most often, this happens like this: a tree cut down at the beginning of winter is disbanded into boards and aged under a canopy until the start of the construction season. For 4-6 months, the lumber has time to dry up to 15-20% moisture.

In order to avoid deformation of the boards during the drying process, the following conditions are necessary:

• stacking on a horizontal flat surface;
• to protect against excess moisture between the rows of stacks and in the area where drying is expected, waterproofing is laid;
• so that the boards are well blown, the stack is installed on concrete blocks and laid with timber or unedged boards of the same thickness (see the figure below);
• stacks are stacked at equal intervals and parallelism;
• a prerequisite for preventing deformation is a uniform load, which is carried out using wedges or clamping cords (see figure below);
• the finished stack is protected from atmospheric action, covered with a profile or slate. With this arrangement of the dryer, the edged board will reach 12-18% of the moisture content in 4-5 months. The speed and quality of dehydration depends on the climate, the amount of moisture in the atmosphere and the thickness of the board. The rules for atmospheric drying are regulated by GOST 2808.1-80 for sawn softwood and GOST 7319-80 for hardwood.

Rice. Scheme of arrangement of the dryer in the air

Main disadvantages: the design takes up a lot of space, the drying process is uncontrollable, and in areas with high humidity, the risk of fungal infection of the lumber is high. For such an area, pre-treatment of the boards with an antiseptic is recommended.

3. Vacuum dryer

Used for drying large wood, hardwoods (e.g. oak), valuable wood that is prone to cracking. The dryer is a sealed chamber made of stainless steel, in which boards are placed between aluminum heating plates. The top of the chamber is closed with an elastic rubber cover attached to a metal frame.

Hot water continuously circulates over the plates, which is heated by an external boiler. The vacuum inside the chamber is provided by a pump that pumps moisture out of the room.

Rice. Scheme of operation of the vacuum chamber

A microprocessor is used to control the processes inside the chamber. For each type of wood, the operator sets its own vacuum level and plate heating temperature. For example, a beech board with a thickness of 32 mm reaches 8% moisture in 29 hours. And a pine board with a thickness of 25 mm in 17 hours. Therefore, the main advantage of vacuum drying is the speed of processing materials..

Flaws: small capacity of the chambers (up to 10 m 3), high energy consumption, high internal stress due to uneven distribution of the final moisture content over the thickness of the material. These shortcomings are eliminated in new vacuum models, where drying is carried out using hot steam.

But the price of such cameras is high: 250,000 rubles with a load volume of 1 m 3.

4. Microwave dryer

The essence of the "microwave" method: wood is saturated with moisture, which then evaporates at the level of cellular structures. Wood dehydration is carried out by high frequency currents - 915-2500 MHz.

The electromagnetic field acts on the stacked lumber in the space of the metal chamber. Heating of wood occurs at the level of 50-60 degrees, therefore it is considered close to natural conditions.

Main pluses:

• mobility;
• compact dimensions;
• the drying speed is 30% higher than that of convective chambers, with relatively low energy costs (for drying 1 m 3 of pine - 550 kW / h, oak - 2000 kW / h).

Flaws:

• small volumes of loading (up to 4.5 m 3 for hard hardwoods and up to 7 m 3 for conifers);
• high price of magnetron generators with a rather small resource of their work (no more than 650 hours);
• uneven drying;
• the possibility of ignition of the material inside the chamber - the microwave method is quite new, and the drying modes have not yet been worked out.

5. Condensation drying

Innovative equipment that has no analogues in domestic production drying chambers (from imported manufacturers, the brands Nardi, Vanicek, Hildebrand-Brunner are represented on the market).

Dehydration of lumber is carried out by a closed cycle method - without air access from the outside.

The air inside the chamber is saturated with moisture evaporated from the wood, washes the surface of the freon cooler, and its temperature drops below the dew point. Moisture condenses, and the released heat is spent on heating the drying agent.

Rice. The principle of operation of equipment with condensing drying technology

Main advantage: energy consumption is 3 times less compared to intermittent dryers (up to 0.5 kWh per 1 liter of evaporated water). Such chambers are used in cases where electricity is the only available or the cheapest type of coolant.

Flaws: low productivity, the duration of the drying process is 2-3 times longer than in chamber equipment.

The choice of a suitable method and equipment for drying wood is considered individually for each business, as it depends on a number of factors:

• climatic conditions of the area;
• the size of the production area;
• range of raw materials and manufactured lumber;
• energy costs, investment opportunities potential consumer etc.