Types of drying chambers for wood. Methods and equipment for professional drying of wood Drying chambers for wood types

As you know, freshly cut wood is not used in production and construction, due to the presence of a large amount of moisture in it. Such lumber is called wet. To improve its mechanical and physical performance, a drying chamber for lumber is used. As a result, biological stability increases, the level of strength and other qualities of wood rise.

The need for drying lumber

Previously, in the manufacture of various fakes using wood, timber that was chopped years earlier was used so that they could dry out evenly.

It is very important to get rid of wood moisture. For example, when making wooden furniture from lumber, which is too wet will cause it to dry out over time. After all, a tree can dry out, its size decreases and leads to damage.

Making a door with a very dry material can cause it to swell, causing it to not close. If the door panel is selected from blanks that are dried intermittently in volume, then a rupture may occur or it will warp. Its deformation is noticeable in different planes and at different speeds. As a result, tension lines appear inside the material, which cause cracks.

In addition to the fact that the board is cracking, transverse deformation is also possible, it can arch and raise the edges unevenly.

Basically, cracks in the board are observed along the fibers, initially from the end.

Therefore, all logging is advised to dry. Moreover, drying the wood protects the material from damage by a fungus that destroys the tree, prevents the change in the shape and size of the tree, and improves the physical and mechanical qualities of the wood.

Drying takes a long time, this procedure is complicated and expensive. According to established technologies, the material is heated with superheated steam or hot air flow.

Dried, it lasts longer. And also during use lumber does not give in to deformation. Drying takes place in steam chambers, where damage to the material inside is excluded.

The concept of lumber moisture

Absolute humidity is the percentage of the weight of the liquid present to the weight of the dried material of a specific volume. The presence of relative humidity is characterized by the percentage of the weight of the eliminated liquid (by 2 weighings) to the initial mass of the material.

The usability level is calculated taking into account the relative humidity. The value indicates the readiness of lumber for gluing, drying out. With a moisture value of more than 30%, the tree is considered damp, there is a threat of the formation of a fungal infection.

Moisture in wood is divided into two groups.

Free moisture- present in cell cavities and intercellular spaces. The presence of such moisture is calculated by the conditions in which the tree grew and how the sawn blanks were stored. When drying, free moisture leaves the board very quickly.

Related (structural)- a liquid that is part of the walls, cells. Each type of wood has its own norm for the presence of structural moisture. Liquid elimination is slow, so drying can take months or years in a typical environment.

Wood is divided into three categories:

• Wet - the relative moisture content is more than 23%.
• Semi-dry - moisture content 18–23%.
• Dry - moisture content value 6–18%.

Moisture indicators of lumber for different types of work

Depending on the purpose of the wooden blank, the material is dried in different ways. Wood is dried to 6–8% moisture if it requires mechanical processing and collection of products for combination with high precision that affect the level of use (skiing, parquet, musical instruments).

The transport presence of moisture contains 18–22%. This presence of water in lumber corresponds to long transits during the warm season. Wood that is dried to this moisture content is most often used in building a house, making containers, or if there is no need for interchangeability during installation.

Carpentry moisture has subspecies. The molded material includes a board for terraces, sheathing, floorboard, in which the humidity should be 15%. Lumber products, such as doors, windows, stairs, made of solid or glued material, endure 8-15% humidity.

Furniture humidity, depending on the degree of the product and the use of solid or glued material, is 8%. It is at this humidity that the wood exhibits optimal qualities for finishing, gluing, and subsequent use. Basically, the moisture content is reduced to 7–10% with the completion of partial disinfection of wood and taking into account the regularity of moisture throughout the material, maintaining the mechanical qualities of the board, and the absence of cracks that form outside and inside the lumber.

Features of drying chambers

The industries that process wood process up to 1 thousand cubic meters every year. lumber. The main role in this process is played by the drying chamber, which provides the material with the required quality.

Drying equipment is used to quickly dry wood, which makes it possible to harvest high-quality products and immediately send them for further processing. Boards that dry out on their own can delay production by weeks or sometimes months. In addition, such material may have defects and shortcomings that are unacceptable in mass production.

Industries that produce wood drying chambers provide a full service to their customers. They design modern chamber dryers and professionally install equipment, run it, set it up and provide service.

When manufacturing a drying chamber, specialists calculate the acceptable volume and number of chambers, providing customers with big choice equipment for different needs. Chambers for drying wood produce a volume of 30-300 cubic meters. m and more. In addition, the equipment may differ in the type of chamber loading and warming method. The most popular are cameras that are heated by water, steam, electricity.

Structural Benefits

The advantages of drying chambers that are made to order include:

• design and creation of drying plants for the required volume and needs of the buyer;
• production of drying equipment made of aluminum and stainless steel;
• remote control of material drying via the Internet.

The lumber dryer has modern ventilation equipment, which is equipped with fans from German and Italian manufacturers. Installation, start-up and configuration of the device is carried out at a professional level.

Which drying kilns for lumber are better

In the industry for wood processing, various methods of drying timber are used. These are atmospheric, chamber drying, contact, drying in liquids, as well as induction, rotational, radiation and PAP drying.

The required energy in convective drying equipment for wood is transported by air circulation, and the necessary heat transfer to the material comes from convention.

Camera types

There are 2 types of convection chambers - tunnel dryers and chamber dryers.

tunnel dryer is a deep chamber where bales of stacks are pushed from the wet end to the dry end.

Such chambers must necessarily be filled at one end and empty at the other. The process of pushing the stacks is carried out by 1 piece, the interval between each is 4-12 hours. They are used by large sawmills, they only do transport drying of lumber.

Chamber installation most commonly used in industry. The process takes place in a gaseous environment. This is heated air or superheated steam at atmospheric pressure. Drying in such equipment is carried out regardless of climatic and atmospheric conditions. The whole process is adjustable, which allows to obtain material with different final moisture content.

Atmospheric drying of hardwood takes place in an open warehouse or under a canopy. At low temperatures, the air has a low ability to absorb moisture vapor, so it passes slowly, and in winter it may stop. This method is used for drying exported lumber at factories with shipment of material during the season.

According to the circulation method, there are chambers that have incentive and natural circulation. The chamber for drying wood with natural circulation is outdated, inefficient.

The drying mode in them is practically not regulated, and the rate of uniformity of lumber drying is unsatisfactory. Such drying is not recommended for modern construction.

Making a drying chamber for lumber with your own hands

To make a drying chamber yourself, you first need to choose a material for the frame. Most often, metal racks from a corner or are used, and wooden bars treated with an antiseptic are also needed. The walls are covered with metal sheets, moisture-resistant plywood panels, profiled rolled products. Thermal insulation is carried out with the help of polystyrene foam, mineral moisture-resistant wool.

Before construction, they determine the location of the dryer to make a concrete foundation. The foundation is necessary so that the structure is stable and the load on the ground is evenly distributed.

The frame is assembled by welding or bolted connections. Then you should sheathe the walls from the inside, insert doors and windows. The layer of the heat-insulating floor should be at least 12–15 cm. Then you need to check the chamber for leaks by placing a powerful fan heater with hot air directed parallel to the boards.

Drying boards is necessary to obtain high-quality raw materials. After all, building a house using wet lumber will lead to distortions and a violation of its integrity. Therefore, it is important to take seriously the elimination of excess moisture from wood.

Video: Do-it-yourself drying

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 the 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 a certain time so that the material was steamed.

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.

My recently published A new book 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.

Committed to top speed assembly 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 space 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 cameras without floor insulation is lower, we need more work to install.

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 transitional version allows the customer to organize the most efficient continuous technological process and increase the productivity of 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 more efficient and stable operation of the 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 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 capabilities for the manufacture of monolithic polyurethane foam insulation from closed enclosures 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 of rigid polyurethane foam and mineral wool, see here.) Interior 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 the wood 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 case of occurrence emergency in the event of a fire in a disaster, this same humidity must be used by a conventional 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 service.

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 at high frequency currents; 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.

Unloaded lumber from drying (dried at a temperature of 60-70 ° C to a moisture content of 10-12%) before putting it into production is kept in the conditions of the production workshop for 2-3 days to release wood from internal and surface stresses (normalization) obtained in drying result.

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 are used, operating on natural gas, with the presence of a furnace in which the gas temperature reaches 1000-1300 ° C, but after circulation in the chamber, the mixture is supplied 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 cameras 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 would be to use a boiler that runs on wood waste.

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 costs.

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.

Any woodworking enterprise cannot do without such a procedure as wood drying. And so that no defects appear in the process, a special drying chamber for lumber should be used. Such a dryer will also be useful for those who are engaged in the production of wood products at home, in such cases it can be done by yourself.

Importance of drying for wood

Wood for the manufacture of various products must first be dried so that it is suitable for subsequent use. So, if your furniture is made on the basis of too wet wood, then it will quickly dry out and become unusable. And if the tree is too dry, then, for example, the door will quickly swell and will not close.

Also, drying a tree is useful for the following reasons:

• the material is protected from fungal attack;
• change in size and shape is prevented;
• improved mechanical and physical properties material.

Drying is a lengthy process, the wood is heated with hot air or superheated steam. After drying, the tree can be stored and transported longer, it will not be deformed.

Drying chamber for lumber

Kiln drying is a key way to dry wood. With the help of dryers, deciduous and coniferous species are dried to different types quality. The most common and economical drying technique is as follows. Free and bound moisture is removed from the wood by supplying heat to the damp wood using hot air. Further, the removal of excess evaporated moisture occurs with the help of humidified and partially cooled air.

The drying chamber is a completely finished installation, equipped with all the necessary equipment for work. By their design, such chambers are prefabricated metal or assembled from building materials. The latter are made directly in the workshops or as free-standing buildings based on industrial materials.

The chamber can be entirely made on the basis of monolithic reinforced concrete, the walls can be made of solid red bricks, and the ceiling can be made of reinforced concrete.

If several chambers are used in production, they can be combined into one block, which has a corridor with heat supply wiring and a system automatic control. Depending on the volume of loaded wood, the air circulation can be horizontal-transverse or vertical-transverse.

Lumber can be loaded into the chamber on trolleys along the rail track or as packages using a forklift. Heat is transferred to wood in the following ways:

• through the air;
• through the products of combustion;
• using superheated steam;
• radiant warmth;
• solid body;
• through current;
• through an electromagnetic field.

The equipment for this device is basic and additional. The main includes the following:

• fan system;
• heating system;
• humidification and supply and exhaust ventilation.

Additional equipment includes:

• blocks (door, psychrometric and insulated);
• fan drive electric motor;
• stacked carts.

The drying control process can be automated, which helps to maintain the temperature and humidity inside the chamber at a certain level. The temperature is regulated by supplying the coolant to the heaters or by turning the electric heater on or off.

Humidity can be adjusted using a remote moisture meter, which allows you to check the condition of the material remotely at several points at once. If there are no external sources of heat supply, then autonomous heating means powered by electricity, coal, gas, lumber or diesel fuel can be used.

Structure classification

In convection-type chambers, energy enters the wood through the air cycle, and heat transfer occurs through convection. Such structures are tunnel or chamber.

Tunnel dryers have a greater depth, they push stacks of stacks from one end (wetter) to dry. They are obligatory filled from one end, and emptied from the other. Stacks are pushed one at a time every 4-12 hours. These dryers are used for large sawmills and help carry out transport drying.

Chamber dryers are shorter; during the drying process, the same parameters are maintained throughout the chamber. If the blowing depth is from 2 meters, then in order to equalize the drying conditions, the method of reversing the ventilation direction is used. The chamber is filled and emptied from one side if there is only one door. Lumber can be dried any to different indicators of humidity. It is these designs that are most often used in our country.

The condensation type of dryer is different in that the moisture that has arisen in the air begins to condense on special coolers, and then the liquid is removed. The efficiency here is high, but the cycle is long, since devices with a high temperature do not work and large heat losses are observed. These types of equipment are more suitable for processing small volumes of materials or drying wood of dense species - ash, beech or oak. But condensation chambers also have a number of advantages:

• no need for a boiler room;
• the cost of the camera and the cost of operation are low.

Drying chambers also differ in the way of circulation and the nature of the drying agent, the principle of operation and the type of fence.

For example, circulation can be natural or forced. The designs of the first type are outdated and inefficient, it is almost impossible to control the modes, and the uniformity of the drying of the material leaves much to be desired. With modern requirements, it is better not to use such dryers.

By the nature of the drying agent, the chambers are:

• air;
• gas;
• high temperature.

Drying modes

Depending on the quality requirements, lumber drying in a special apparatus is carried out in different modes, which differ from each other in temperature. If it is a mini chamber, then in the process the temperature slowly rises and the relative humidity of the agent decreases.

One or another mode is selected taking into account the following factors:

There are modes of high-temperature and low-temperature process. In low-temperature applications, moist air is used as an agent, the initial temperature is less than 100 degrees. There are three categories of these types of modes:

• soft - drying is carried out without defects, the mechanical and physical properties of the wood are preserved, including its color and strength;
• normal - drying is also carried out without defects, strength is retained almost completely, color may vary slightly;
• forced - the strength for static bending, tension and compression is maintained, but the strength for chipping and splitting with darkening may decrease.

In high temperature conditions there is a two-stage change in the agent's indicators, it is possible to switch to the second stage from the first only when the wood reaches a transitional moisture content of 20 percent.

Such modes are assigned depending on the species and thickness of the wood, and are assigned for drying materials used in the production of load-bearing structures of buildings and those products where dark wood with reduced strength can be used.

Before starting work on a particular mode, the lumber must be heated with steam supplied through humidifying pipes with fans running, closed exhaust ducts and heating devices.

Be sure to calculate the chamber for lumber. The temperature of the drying agent at the beginning of heating should be 5 degrees higher than the first stage of the mode, but not higher than 100 degrees. The saturation level of the environment for a material with an initial moisture content of 25% is 0.98−1, and if the humidity is below this indicator, then 0.9−0.92, respectively.

The duration of the initial period depends on the type of tree. For conifers, it is up to 1.5 hours per centimeter of thickness. For soft hardwoods it will be 25 percent more, and for hard hardwoods it will be half as much compared to softwoods.

After preheating, it is necessary to bring the indicators of the drying agent to the first stage of the operating mode. Then drying is switched on directly in compliance with the selected mode. Humidity and temperature can be controlled using valves on the steam lines or dampers on the supply and exhaust ducts.

During the operation of an infrared dryer, residual stresses appear in the materials, which can be removed by intermediate and final moisture and heat treatment in an environment of high humidity and temperature. It is necessary to process those lumber that are dried to operational performance and then need to be machined.

Intermediate moisture heat treatment must be carried out during the transition from the second stage to the third, or from 1 to 2 when using a high temperature. Coniferous species 60 mm in thickness or hardwood with a thickness of 30 mm or more are subjected to such processing. The temperature of the medium should be 8 degrees higher compared to the second stage, but not more than 100 degrees, provided the saturation is 0.95-0.97.

When the final average moisture content of the material is reached, the final moisture heat treatment can be performed. It is carried out at a temperature of 8 degrees above the previous stage, but not higher than 100 degrees. Further, the tree must be kept in the chamber for another 2-3 hours at the parameters of the last stage of the mode and only then stop the operation.

Drying chamber manufacturing

If you are engaged in the manufacture of wood products at home, then you will need to dry the material yourself. You can also make your own dryer., but you must follow all the rules of work. For manufacturing you will need:

• camera;
• heating device;
• fan;
• insulation.

One wall and ceiling of the chamber should be made of concrete, and the remaining walls will be made of wood, they will need to be insulated. There will be several layers:

• Styrofoam;
• boards wrapped in foil.

Now you need to install a heating element, it can be in the form of batteries. Water can be supplied to them from the stove in a heated form at a temperature of 60 to 95 degrees. It is best to ensure a continuous process circulation of water by means of water pumps in the heating element. You will also need to install a fan in the chamber, with the help of which warm air will be distributed throughout the room.

It is imperative to provide a method for loading wood into the chamber. For example, it can be a rail cart. To control the temperature and humidity in the work area, you need to install wet and dry thermometers. And also inside the dryer You need to put shelves to expand the workspace.

During processing, a sharp change in temperature should not be allowed, otherwise the wood may crack or warp.

Work on the construction of the chamber must be carried out in compliance with fire regulations, so be sure to install fire extinguishers.

And instead of a heating element you can use an electric stove with two burners. The walls of the chamber can be insulated with wood shavings, and instead of foil, you can take penofol, which can reflect heat well from the surface of the walls. Drying in such a chamber is carried out within 1-2 weeks.

Thus, there are a large number of different modifications of wood drying chambers. One or another option should be chosen depending on the material itself and the expected results. And if we are talking about the manufacture of various wooden products at home, then the camera is easy to do with your own hands.

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 yourself want to engage in the production of wood products, you will also need a drying chamber for drying wood. Today we will talk about how to do it right.

The need to dry wood

How to dry a board efficiently and quickly? This question has been of interest to every carpenter since ancient times. Since ancient times, people have been storing forests for many years in order to have time to evenly dry it. The grandfather prepared a tree for his grandson, using the very material that his grandfather had left him.

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

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

Drying wood is a long, complicated and expensive procedure. According to traditional technologies, wood is heated with superheated steam or hot air. Dried wood can be transported and stored longer. In addition, during operation, it is not deformed. Drying of boards is carried out in steam chambers, where the possibility of internal damage is excluded.

The concept of wood moisture

For a complete perception of the essence of the drying process, it is worth plunging into theory a little. 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 in the walls of cells and in their cavities, filling the microcapillary system. Moisture that is present in the spaces between cells and in their cavities is called free intercellular, and moisture in the cell walls is called bound intracellular.

The content of bound moisture in wood is limited. The state when the cell walls are characterized by maximum moisture 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 averages 30%. If the moisture content of a tree is above 30%, then it contains free intercellular moisture. The wood of a freshly cut or growing tree has a moisture content greater than the saturation limit, that is, it is raw.

Depending on the purpose of the wood blanks, it is customary to dry the wood 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 joints that affect performance (ski, 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 weather. Wood dried to such a moisture content is mainly used in standard housing construction, in the production of ordinary containers and when there is no need for interchangeability during assembly.

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

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

Wood drying modes

Depending on the requirements that apply to the quality of wood, lumber can be dried in different modes, which differ in temperature level. In the mini wood drying chamber, 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 dried wood and the design of the chamber.

There are modes of low- and high-temperature process. The first modes involve the use of moist 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 able to provide defect-free drying of the material while maintaining the natural physical and mechanical properties of wood, including color and strength, which is important for drying wood to the transport moisture content of export sawn timber.
• Normal mode guarantees a defect-free drying of wood with almost complete preservation of the strength of the material with slight color changes, which is suitable for drying sawn timber to the final moisture content.
• Forced mode retains strength for static bending, compression and tension, but some reduction in splitting or chipping strength with wood darkening is possible, which is intended for drying wood to operational moisture.

According to low-temperature regimes, a three-stage change in the parameters of the drying agent is assumed, and from each stage to the next transition can be carried out only after the material reaches certain level humidity, which is provided for by the regime.

High-temperature regimes provide for a two-stage change in the indicators of the drying agent, and it is possible to switch 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 regimes can be used for drying wood, which is used for the manufacture of non-load-bearing elements of buildings and structures in which darkening of wood and a decrease in strength are allowed.

The concept of a drying chamber

Chamber drying is the main method of wood drying. Drying chambers are required for drying 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 damp tree with hot air and carrying away the evaporated excess moisture by humidified and partially cooled air.

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

If several dryers are used, they are often combined into a single unit, constructing a common control corridor, where the heat supply wiring and the automatic control system for all chambers are located. Depending on the volume of wood loaded into the chamber, there can be horizontal or vertical transverse air circulation.

Loading 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; a solid body, if contact is made with a heated surface; current that passes through wet wood; high-frequency electromagnetic field that penetrates wet wood.

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

The process of controlling the drying of wood in the chamber can be automated. Automation is able to maintain the humidity and temperature of the environment in the dryer at a given level. The temperature is regulated by supplying the coolant to the heaters or by turning the electric heater on and off, and the humidity is controlled by using the supply and exhaust ventilation and humidification system.

The wood drying control system may provide for remote control of 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. With absence external sources Heat supply for the dryer can use independent heating modules and use gas, coal, wood waste, electricity and diesel fuel.

Types of drying chambers

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

Tunnel convection kilns are deep kilns where stack stacks are pushed from the wet end to the dry end. These chambers must be filled from one end and emptied from the other. The pushing of the stacks (the process of filling the chambers and emptying) is done one by one with an interval of 4 - 12 hours. These chambers are designed for large sawmills and allow only transport drying of wood.

Chamber convection kilns are shorter than tunnel kilns and vacuum kilns for wood, the same parameters are maintained throughout the kiln during operation. With a blowing depth of more than 2 meters, the method of reversing the direction of ventilation is used to equalize the conditions for drying wood. Emptying and filling the chamber occurs on the one hand, if it has one door. Other loading systems are known, which are similar to the procedure for loading tunnel chambers. Any lumber can be dried to any final moisture content, so 90% of wood in Europe and Russia is dried in chamber dryers.

The condensation drying chamber differs from the previous ones in that the moisture that occurs in the air condenses on special coolers and water comes out of the drying process. The efficiency of such a process is large, but the cycle is long, because the devices do not operate at high temperatures, and the total heat loss is also significant. The condensation chamber is mainly suitable for drying small volumes of wood, or for drying dense woods such as oak, beech or ash. The big advantage of such chambers is that there is no need for a boiler room, the price of a drying chamber for wood and the cost of drying is less.

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. Drying chambers of periodic action are characterized by the fact that they can be loaded completely for simultaneous drying of all material, and the drying mode of wood changes in time, in this moment remaining the same for the entire chamber.

According to the circulation method, there are chambers with incentive and natural circulation. Dryers with natural circulation are outdated, inefficient, the drying mode in them is almost uncontrollable, the uniformity of wood drying is unsatisfactory. For modern construction, such devices are not recommended, and the existing ones must be upgraded. According to the nature of the drying agent, gas, air and high-temperature chambers are distinguished, which operate in an environment of superheated steam.

wood drying process

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

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

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

During the operation of the 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 process sawn timber, which is dried to operational humidity and subject to mechanical processing in the future.

Intermediate moisture heat treatment takes place during the transition from the second stage to the third or from the first to the second in high-temperature conditions. Coniferous species with a thickness of 60 millimeters or more and hardwoods with a thickness of 30 millimeters or more are subjected to moisture heat treatment. The temperature of the medium in the process of heat and moisture treatment should be 8 degrees higher than the temperature of the second stage, but not higher than 100 degrees, at a saturation level of 0.95 - 0.97.

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

Drying chamber manufacturing

If you decide to make wood products with your own hands, then you simply need a drying chamber for wood. However, during the construction of the dryer, comply with all required standards. You will need a camera, a fan, a heater and a heater.

Build a dryer or allocate a 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 a foam plastic, the second is wooden boards, which are usually wrapped in foil in advance.

After that, you should install a heating element, which can be made in the form of batteries. Water must be supplied to the batteries from the stove, in which it will heat up to 60-95 degrees Celsius. It is desirable to continuously circulate water by means of water pumps in the heating element. Also, a fan should be placed in a home-made drying chamber for wood, which contributes to the distribution of warm air throughout the room.

Think about how the wood will be loaded into the drying chamber. One of the loading options can be a rail trolley. To regulate the humidity and temperature in the room of the drying chamber, it is necessary to use the appropriate thermometers in the working area - wet and dry. Provide shelves inside the dryer to increase the working space.

In the process of drying lumber, a sharp change in temperature in the working room is not allowed, otherwise this will cause the wood to warp or cracks appear in it. When building a drying chamber, it is extremely important to comply with fire safety requirements. Therefore, in the immediate vicinity of the dryer in without fail install fire extinguishers.

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 with your own hands using wood shavings. It can be used instead of foil in the chamber with penofol, which is able to provide good reflection from the heat surface. In such a dryer, the wood is dried in advance for 1-2 weeks.

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. Sun rays the outer and inner layers of the tree are heated unevenly, 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 geographical location terrain. 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 controlled.

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 machines and mechanical devices for storing blanks in a stack or package, 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 designed for organized movement air masses in the drying room. 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. By using 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 great results at a low cost.

Construction stages

You will need material for the frame, usually these are metal racks from a corner or channel, used wooden beam 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 roll material. After that, the camera is checked for tightness. For laying the first layer, stationary supports made of metal or wood are placed. 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.