DIY wood drying chamber. Do-it-yourself drying chambers for lumber

A lumber dryer is an industrial piece of equipment that 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 type of timber. Using the latest drying chambers, we provide high-quality drying of wood of even the most exotic and expensive varieties, for example, rosewood, beech, wenge or teak. There is no cracking or other defects.

Types of drying chambers

A large number of wood processing industries process almost 10,000 m³ of lumber every year. The wood drying chamber is a decisive link in the process chain for quality assurance. The volume of one-time loading of timber into the drying chamber varies greatly. Sometimes you need to dry 6 m³, and sometimes you need to dry up to 100 m³. The main factor when choosing the size of the drying chamber can be called production capacity.

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

• dielectric - require high energy costs
• convector
• vacuum Such devices are characterized by high prices and expensive maintenance.
• aerodynamic. Such devices require a lot of energy.

Chamber drying of wood different methods was invented in the 60s of the last century, but due to high energy costs and design complexity, drying became popular only in the last decade. Convection type cameras are the most popular all over the world.

Convector dryers

A convector-type wood drying chamber is used for various types of timber. Such devices have a simple design, they are inexpensive to maintain and reliable. That is why they are most popular in production.

The work is carried out due to heating from a gaseous carrier (drying agent). When heated, the raw material dries out. The drying agent can be steam, flue gas or air. The moisture 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 a convection dryer does not exceed 2% of the total amount, therefore, energy savings are felt.

The camera body is made of metal and is placed on a monolithic columnar foundation. The metal used for the body is carbon steel or aluminum with anti-corrosion coating. The body is sheathed on both sides with aluminum sheets. The chamber is insulated using mineral wool in the form of slabs. You can purchase a convection chamber of both domestic and foreign production.

Vacuum drying

The vacuum drying chamber for wood is designed for valuable types of timber, such as teak, wenge, rosewood and others. This unit operates from convection heating of wood and vacuum removal of excess moisture. The process takes place at a maximum temperature of +65. However, due to a 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 temperature. Thus, high internal stress does not arise 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 upper layers of timber slowly cool, and moisture from within flows to drier areas. During one drying period, 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 within 4-6%.

Aerodynamic drying

Chamber drying of lumber under aerodynamic conditions has become widespread due to its fairly low price and simple design. In addition, no specific knowledge is required to operate such a device. service personnel. Profitability is achieved by drying up to 2000 m³ per year of coniferous timber.

The disadvantages include:

• high level of energy intensity of the drying process. In order to dry freshly sawn wood, 1.15-1.3 kWh is required to evaporate 1 liter of moisture. Electricity is approximately 240-290 kWh/m³
• There is no way to regulate the temperature. There is only the opportunity to slow down the rate of its increase by changing the flow area of ​​the centrifugal fan
• It is not possible to organize technological drying according to the schedule of the “Guiding technical materials on the technology of chamber drying of wood” regimes.

This chamber is a rectangular box. It is convenient to load wood into it by machine or along railway tracks. Drying occurs under the influence of aerodynamic energy. Warm air moves in the chamber under the influence of a special aerodynamic fan. Due to the compression of air in the chamber, the temperature on the centrifugal fan increases, namely on its blades. Consequently, aerodynamic losses become thermal energy. Heat can be driven into the chamber in reverse or deadlock, it all depends on design features. The chamber opens only upon completion of the drying cycle.

Microwave drying

Such devices were invented quite recently. They look like a closed metal container. The work is carried out under the influence of the reflective surface of microwave waves. The operating principle is similar to that of a conventional microwave. Using a microwave chamber, raw materials of any cross-section and dimensions are dried. Microwave cameras have a simple design; settings allow you to select any wavelength.
Therefore, a wide variety of timber products can be dried. The microwave wave attenuation mode guarantees temperature control inside the chamber. Using reversible fans, excess moisture is removed from the system. Microwave drying is compared with dielectric drying, which is considered the most effective, but is not used in Russia due to high energy costs.

Any woodworking enterprise cannot do without such a procedure as wood drying. And to prevent defects from appearing in the process, a special drying chamber for lumber should be used. Such a dryer will also be useful for those who produce wood products at home; in such cases, you can make it yourself.

Drying value for wood

Wood for making various products must be dried beforehand to make it suitable for subsequent use. So, if your furniture is made from wood that is too wet, it will quickly dry out and become unusable. And if the wood is too dry, then, for example, the door will quickly swell and will not close.

Drying wood is also useful for the following reasons:

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

Drying is a long process, the wood is heated by hot air or superheated steam. After drying, the wood can be stored and transported longer, it will not be subject to deformation.

Drying chamber for lumber

Kiln drying is a key way to dry wood. Dryers are used to dry deciduous and coniferous wood until different types quality. The most common and economical drying method is as follows. Free and bound moisture is removed from the wood by supplying heat to the wet wood using hot air. Next, excess evaporated moisture is removed using humidified and partially cooled air.

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

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

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

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

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

The equipment for this device can be basic or additional. The main ones include the following:

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

TO additional equipment relate:

• blocks (door, psychrometric and insulated);
• fan drive electric motor;
• stacking trolleys.

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

Humidity can be adjusted using a remote moisture meter, with which you can 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 running on electricity, coal, gas, lumber or diesel fuel can be used.

Classification of structures

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

Tunnel dryers are deep and push stacks of stacks from one end (wet) to the dry end. They are filled at one end and emptied at the other. The stacks are pushed one at a time every 4-12 hours. These dryers are used for large sawmills and help with transport drying.

Chamber dryers are shorter; during the drying process, the same parameters are maintained throughout the chamber. If the blowing depth is more than 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 on one side if there is only one door. Lumber can be dried in them any up to different humidity levels. These are the designs that are most often used in our country.

The condensation type of dryer is different in that the moisture that appears 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 high temperatures do not work and large heat losses are observed. These types of equipment are more suitable for processing small volumes of materials or drying dense wood - 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 method of circulation and the nature of the drying agent, operating principle and type of enclosure.

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

Depending on the nature of the drying agent, the chambers are:

• air;
• gas;
• high temperature.

Drying modes

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

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

There are high-temperature and low-temperature process modes. In low-temperature ones, 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 preserved almost completely, color may vary slightly;
• forced - static bending, tensile and compressive strength is maintained, but the chipping and splitting strength may decrease with darkening.

In high temperature conditions There is a two-stage change in the agent's performance; it is possible to move 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 type and thickness of the tree, and are intended for drying materials used in the production of load-bearing structures of buildings and those products where it is possible to use dark wood with reduced strength.

Before starting work in one mode or another, the lumber must be heated with steam supplied through humidifying pipes with the fans running and closed. exhaust ducts and heating devices.

Be sure to calculate the lumber chamber. 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 level of environmental saturation for a material with an initial humidity of 25% is 0.98−1, and if the humidity is below this indicator, then 0.9−0.92, respectively.

Duration initial period depends on the type of wood. For conifers it is up to 1.5 hours for each centimeter of thickness. For soft hardwoods it will be 25 percent more, and for hardwoods it will be half more compared to softwoods.

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

When an infrared dryer operates, residual stresses appear in materials, which can be removed through intermediate and final moisture and heat treatment in an environment high humidity and temperature. It is necessary to process those lumber that is dried to operational specifications and then requires mechanical processing.

Intermediate moisture-heat treatment must be performed during the transition from the second stage to the third, or from 1 to 2 when using high temperature. Coniferous species with a thickness of 60 mm or deciduous species with a thickness of 30 mm or more are subjected to this treatment. The ambient temperature should be 8 degrees higher than 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 8 degrees higher than the previous stage, but not higher than 100 degrees. Further, the tree needs to 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 work.

Making a drying chamber

If you are making wood products at home, then you will need to dry the material yourself. You can also make a dryer yourself, but you must comply with all work standards. To make it you will need:

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

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

• Styrofoam;
• boards wrapped in foil.

Now you need to install the heating element, it can be in the form of batteries. Water can be supplied to them from the stove in heated form at a temperature of 60 to 95 degrees. It is best to ensure a continuous process circulation of water through 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 could be a rail cart. To regulate temperature and humidity in work area You need to install wet and dry thermometers. And also inside the dryer you need to install shelves to expand the work space.

During processing, sudden changes in temperature should not be allowed, otherwise the wood may crack or warp.

The construction of the chamber must be carried out in compliance with fire safety requirements, so be sure to install fire extinguishers.

And instead of 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 use penofol, which can well reflect heat from the surface of the walls. Drying in such a chamber is carried out for 1-2 weeks.

Thus there is a large number of various modifications of drying chambers for wood. One or another option should be chosen depending on the material itself and the expected results. And if we're talking about about making various wooden products at home, then it’s easy to make a camera with your own hands.

Friends!
Those who deal with wood, process it and use it in any way are forced to deal with the problem of drying it. Drying wood is always relevant and pays off, because “wet” wood is much cheaper, and dry, ready-made wood is very expensive. It is necessary to remove excess moisture from the wood so that the process of uneven evaporation of water and juices does not occur, which is associated with the heterogeneity of the wood structure along the longitudinal and transverse fibers. But damp wood is unsuitable for serious processing, much less for construction, otherwise it will deform, crack, warp, and “lead.” How can you make a wood dryer with your own hands?

How to make a wood dryer with your own hands at home or in the country

If space permits, then it roughly looks like this:

1. First, we free up space in the kitchen near the stove or electric stove, fireplace, etc. You need to carefully calculate and measure how everything will function and look.
2. Partitions are installed from old doors and window frames, and other available materials; for tightness, everything needs to be adjusted and sealed. The size can be, for example, 2x2 or 3x3, depending on capabilities and needs.
3. Of course you have to leave it entrance doors and vents, and during drying keep them tightly closed so that there are no unnecessary drafts or simply excessive air movement. Otherwise, this may lead to a less predictable drying process, loss of control over the process and loss of quality of the resulting wood.
4. The fenced-off area must be covered with insulation, all cracks must be sealed, plugged, caulked, etc. That is, to seal the space of the future dryer as much as possible to enclose the space and improve the quality of drying.
5. Since there is a high temperature near the stove or heating electrical appliance, then, if necessary, it is better to cover it with bricks that will accumulate heat and release it into a closed room. If the air does not circulate actively enough, a fan should be installed.
6. If you plan to dry a lot of wood or finished products made from it, then you need to build strong metal shelves. It is better to secure it with anchors so that it can be loaded with serious weight.
7. To prevent the workpieces from bending, you need to fasten the edges of the material with pins. If the length of the wood is large, then several pairs of pins (3-4) are used. Of course, it is better to use wood of the same species, thickness, size and weight, otherwise drying will be very uneven. It is imperative that the material for drying should be laid out with thin strips, bars, spacers for better ventilation. You need to carefully monitor the uniformity of temperature and air flow, then drying will proceed more smoothly and the quality of the output material will be higher. Moreover, building several dryers is not very good big size more profitable than one larger one.

Do-it-yourself wood dryer, as a separate structure

1. First, a frame is constructed from an aluminum profile; it will not rust, is lightweight and durable.
2. Then it also needs to be sheathed with aluminum sheets, and thermal insulation 10-15 cm thick must be fixed on top. This insulation must be fire-resistant, strong and flexible. Roofing felt should be laid on the floor and sawdust should be poured on top.
3. Next, you need to ensure the tightness of the building and seal all possible exit routes for heated air. The tightness of the structure is great value for high-quality drying.
4. The boards intended for drying should be laid out in narrow (1-1.5 m) stacks and spacers made of bars should be placed between the rows and boards. And the height of the stack can correspond to the height of the room.
5. Drying can be done using, for example, fan heaters, which should be installed across the air flow. Or choose another drying tool that suits your individual needs and capabilities.

A simple effective way of tubeless infrared drying of wood from 1 board

If you don’t want to build a dryer yourself or you don’t have the opportunity to do this, then you can use a ready-made solution.

There is a relatively recently used method of drying wood using infrared radiation. The process itself looks like in the following way: the wood is heated with infrared rays using a tubeless cassette dryer. What is the design of such a dryer? It consists of several thermoactive cassettes 1.5 mm thick. The cassettes are stacked in a stack of wood prepared for drying, alternating with spacer bars. That is, the coolant is already among the lumber intended for drying. Therefore, there is no need for a separate heat source, ventilation, maintaining precise parameters, or complex electronics and automation. The drying is controlled by a thermostat, which sets the required temperature for individual layers of the stack. For more optimal performance drying design, the stack is covered with a material with a reflective layer so that the condensate drains outside the stack. It is important that the process can take place both outdoors (preferably under a canopy to avoid possible precipitation) and indoors.

The advantages of this type of drying are

• ease of maintenance,
• equipment mobility,
• high rates (8% humidity can be achieved).
• high quality of the final material (no warping or internal stress),
• speed (from 3 to 7 days),
• variability, i.e. You can dry individual boards, or even just one, or entire large stacks.

You can watch a video about this technology here:

Drying wood from scrap materials. FlexiHIT.

Drying lumber in a tubeless cassette dryer

So, if you have a constant need for dry wood, then you can build a dryer, it’s not that difficult. Or buy a ready-made one and enjoy the finished dry lumber, which can be used to make various useful and interesting products.

For various wood products (furniture, musical instruments, parquet, etc.), their own drying temperature is used and a certain humidity is maintained.

Wood, despite the development of modern technologies, still remains an indispensable material in many sectors of the economy. It surrounds us everywhere, it is used in the production of furniture, in the construction industry, even in aviation it still finds its application. Of course, various polymers, synthetic resins, steels and alloys various metals actively replace wood even in its traditional niches. But complete refusal is impossible. Therefore, there will always be a need to prepare wood for use in various branches of human activity, and to dry it. We will try to give answers to questions related to such necessary equipment as a lumber dryer, made and debugged with our own hands.

Why do you need to dry wood?

Drying lumber is an extremely necessary process, without which the wood simply cannot be used.

The quality of wood depends on proper drying.

If you have your own business related to the production of wood products, then you cannot do without your own drying chamber. But first, let’s try to understand why this dryer is needed, why we need to dry lumber. It's all about natural humidity any tree. If you make a product from undried wood, it will dry out over time, crack, and all you have to do is throw it away. In addition, properly dried wood improves its performance, becomes more durable, resistant to environmental influences and is less susceptible to destructive mold. In the old days, to prepare the forest for use, it was dried not even for years, but for decades. Often, logs prepared for grandchildren were laid under a special canopy. Imagine, not even for children, but for grandchildren.

Luckily for us modern technologies allow us to significantly speed up this process. And although this process is still quite long and complicated, it still cannot be compared with traditional technologies, and the result is even better.

Return to contents

Moisture content of lumber

It is important to understand that a tree is a living organism and its cells contain moisture while it is alive. In general, the moisture content of a freshly cut tree is 30 percent or higher. If we want to use wood, then we need to get rid of excess moisture. What kind of moisture is excess? It depends on what we are going to use the board or log prepared for production for. If the tree is used to make products where it is required highest precision assembly (for example, for production musical instruments, sports equipment, parquet and some types of furniture), then its humidity should be reduced to 6-8 percent. If you are simply preparing lumber for long-distance transportation, for example, for export, then it is enough to reduce the humidity to 20 percent.

The same wood is also suitable for some types of buildings, for the production of containers and other goods. Other products require wood moisture content between these two extremes. Floor boards, casing, and cladding boards can have a moisture content within 15 percent. A window frames, doors, staircase elements or decorative items will require wood from 8 to 15 percent moisture content.

Return to contents

Making a dryer with your own hands

Let us finally consider the construction of the drying chamber itself. To begin with, you need, in addition to the basic building materials for making the chamber room, to purchase a heating device, a fan and good insulation.

Drying chamber diagram.

You can use a ready-made room for drying construction, or you can build it specially. It is advisable that the ceiling and one wall be constructed of reinforced concrete, while the remaining walls are made of wood, which must later be covered thermal insulation materials: first we cover them with foam plastic slabs, cover them with clapboard and then cover everything with sheets of foil. The next step is to install some kind of heating device, for example, a heating radiator, in which the water should be heated to 65-90 degrees. Since continuity of heating is necessary, it is better to immediately make the heating system autonomous, with its own stove and pump for constant circulation of the coolant. A fan is also absolutely necessary in the drying chamber, which, by dispersing the air throughout the room, should ensure uniform heating of the entire drying space and the stacked wood.

You need to think in advance about the placement of wood material for drying, how the wood will be brought into it, whether it will lie in the middle of the chamber or on special shelves, etc. Good options for loading wood are a rail cart or a forklift. Make sure you have instruments for recording humidity and temperature in the drying chamber; without them, effective control over its operation is impossible.

Diagram of air temperature and wood humidity in the drying chamber.

During construction, consider some more nuances. The temperature in the drying chamber should not fluctuate sharply; make sure that it changes smoothly. Otherwise, you risk destroying all the wood reserves stored for drying. It may crack and warp. It is also worth remembering fire safety, because you are dealing with heating devices and large supplies of dry wood. To do this, keep a fire extinguisher nearby. Of course, some of the above can be replaced with analogues available in the house, in particular, a water heating radiator can be replaced with electric heating devices, even an electric stove with a pair of burners turned on. Just remind you again about fire safety, be careful. The walls of the dryer can be insulated not only with polystyrene foam, but also with other suitable materials, up to the same wood shavings, and foil can be replaced by penofol, which is quite capable of reflecting thermal radiation back into the camera.

The main thing during construction is to achieve the creation suitable conditions inside the camera, and what material or technology you used is not critical. In such home drying, lumber will dry for about 1-2 weeks.

How to make a cheap one vacuum dryer for wood with your own hands

Hello dear readers and subscribers of Andrey Noak's Blog! Do you know what is most important about wood materials? This is high quality drying.

Each enterprise uses a special drying technology. But if you want to dry the material yourself, then I will tell you how to make a vacuum dryer with your own hands. But first, a little theory.

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

Each wood material has varying degrees of moisture content, depending on storage conditions and the environment.

Why dry wood?

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

When a tree grows, its metabolism is carried out by the circulation of moisture through the trunk. When cutting, the circulation stops and the moisture begins to evaporate.

To build a house or do any wooden product, you need to properly dry the logs.

Purchased vacuum dryer

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

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 considered to be 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 exactly 0.

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

Properties of dry wood

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

Ancient drying methods

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

In houses you can find wooden utensils. Therefore, it was necessary to come up with ways to properly dry logs as the main building material.

At that time, people used several drying methods.

For this method, they took the necessary piece of wood, water and sawdust. The water was heated to 70 degrees, the workpiece was placed in it, then it was 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 denser and more flexible.

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

Here wooden blanks dipped in 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 must 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.

Craftsmen used this drying method to make wooden utensils, then ready product skillfully painted.

Wood moisture content, measurement methods

There are many ways to determine humidity.

To accurately determine wood moisture content, special devices. Electric moisture meters are capable of determining humidity with an accuracy of 2-3%. The basic principle of such devices is based on the fact that wood of different humidity levels has different electrical resistance.

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

• By weight, weighing identical pieces of wood of the same species in hand or on scales one by one.
• Experienced specialists determine humidity “by eye”, by the presence of cracks and breaks.
• According to the shavings.

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

• By cutting. If, when processing wood with a chisel, a wet mark is noted, and the material is easily and 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.

Assembling a vacuum dryer at home

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

But buying vacuum drying from factories is quite 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 set it up you will need large room, a heat source, as well as a fan to distribute heat within the structure.

The floor, walls and ceiling of such drying must be very strong; reinforced concrete or an iron conveyor is best.

If you take a cheap used iron conveyor for example with railway, then it will be even 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 reinforce the walls with foam plastic and line them with clapboard.

Instead of polystyrene 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 will also work, especially since its heat-reflecting and preserving qualities are much better.

We proceed to installing the heating device.

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

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

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

When building your own drying facility, 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. Carts running on rails or a forklift work well for this. The material inside is placed on shelves or simply on the floor. To control the drying process you must install special sensors, and these are thermocouples and vacuum (pressure) sensors.

If you do everything right you can get very quality wood with good presentation.

The main point in the construction of a dryer 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 to 2 weeks.

How does vacuum drying work?

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

Thanks to this technology, bound and free moisture will move evenly 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 dry ones, thereby moisturizing them. If this process is interrupted, the material may collapse as thinner layers begin to shift.

Coating 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 made from chalk and drying oil.

Often the end parts of workpieces need to be processed.

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

Often vacuum installations used for drying expensive species such as oak, merbau, padauk, wenge, zebrawood.

It is very convenient, since the wood is practically not destroyed when dried.

My help

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

You can contact me through SUPPORT.

Recently my A new book which provides recommendations for the operation of drying complexes in production. The information given in the book is simply unique, you definitely won’t find it anywhere else.

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

Good luck and see you again!

vacuum dryer

This blog is read by 3875 professionals in their field.
Read it too!

your comment

Purpose of modular wooden drying chambers.

Drying chambers SCM series, students in the "100" category best products in Russia.", They are designed for drying hardwood and coniferous species 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 monitoring and control systems environment drying chambers" and "Requirements for quality drying" in accordance with the guidelines of the Russian technical material(RTM) for drying the chamber in wood.

Installation, design features of SCM wooden dryers.

Striving for maximum build speed and speed wooden drying chamber partially included in 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 produces wooden drying chambers and complexes with pneumatic load from 6 to 180 m³ , operating on thermal energy generated during combustion wood waste or stationary boiler houses.

Drying chambers with a load capacity of up to 20 cubic meters. 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 underfloor 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 clamp the cement cement independently along the height of the already welded track at our company's location, on the transverse stiffener. mollusk Drying chambers volume 20 cubic meters up to 180 m3. They are made in the form of modular blocks, are easily transported, and are easily connected with screw connections. The time required to assemble a modular drying chamber ranges from 4 to 8 hours, proportional to the number of modules.

Seams are sealed when installing drying modules using 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 loading volume, is made one-sided or two-sided. All SCM drying chambers are equipped with a condensate collection and removal system, which increases the service life of the fence. For better sealing Wooden loading doors of the drying chamber are made with a floating hinge, closing the door door at four points using screws.

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

proposed wooden drying chambers manufactured both in a state of 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 of 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, transportation of strings can be longitudinal or transverse. When drying wide untreated wood, excluding the transverse tip of the tree, the pedestal is equipped clamping mechanism block type.

In this case, the force on the upper types of beams is equal to the force on the lower types of lumber. In numerical terms, this force is equal to the force of the fund's weight.

Heating system.

Modular drying chambers and wooden complexes produced 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 a supply pipe 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 bimetallic tube heaters (steel bolts with aluminum plates). It refers to the drying chamber of a specific boiler acting on the loaf (chips, leftovers, stove - 70 ... 100 vol.%) in a mixture of wood waste (30%).

When a large number of chips (100%) solid equipped with a boiler funnel - relying on sawdust, feeding a screw mixer or carburetor with mechanical load, which allows heating wood products of each fraction (slabs, shavings, shavings, bark). In case of insufficient wood waste we can fill the supplied heat source directly to the burners, gas ovens or liquid fuel 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 flues.

Air exchange system, fans, brackets.

For heat exchange between water registers and internal air wooden drying chamber Installed centrifugal fan, Electrical engine which is installed outside Drying chamber for drying wood.

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

In addition, blood 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 vented.

The loss of fan motor power is directly proportional to the cubic speed 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 adjusted by CNIIMOD for drying wood under mild and normal conditions.

Because the domestic industry does not produce specialized fans for Drying chambers(high performance, low pressure) - all fan wheels are of their own shape.

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

Fan for wooden drying chambers with a wood volume of more than 12 m ³, carried out through bearings and pulleys. The fan bearing bearing is the most heavily loaded device in the dryer 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 can 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 allows easy access to inspection and maintenance of the rotating fan and registers. To exchange air with the atmosphere in Ljubljana wooden drying chamber Aluminum inserts and exhaust valves are installed.

Fences, wall insulation.

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

All steel elements that prevent corrosion in the drying chamber are protected by a corrosion-resistant coating and a waterproof coating. When shipping In regions with other 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 production of monolithic polyurethane foam insulation from closed enclosures wood dryingFists, 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 / M º K), low weight (40-60 kg / m³), ​​high adhesive strength and corrosion protection.

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

Outer envelope drying chamber walls made of galvanized, corrugated film 0.8 mm thick. Places where dew is likely to occur (the inner surface of the door, inlet and outlet valves) are made of aluminum.

Thermal treatment 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 done universal humidification, conditioning and steam system - development and production by TERMOTEH.

The diversity of the system is achieved by generating dry entropic 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 conifers.

The processing device must remove the internal tension in the wood when the wood is already dry to ensure the stability of the workpiece geometry after processing in woodworking machines. This is a concept, a textbook. Very often, storage conditions for joinery products are violated after sawing wood, for example: lack of sunscreen for protection from the sun, uneven air flow of the chimney with natural air circulation, loading one drying chamber into several packages with different periods sawmilling (sometimes for important months).

Therefore, there is an uneven distribution of moisture throughout the volume of one plate and the volume of the foundation. This leads to stress and inappropriate 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 necessary to create a uniform color palette for wood of different ages. The color intensity is proportional to the duration of the steam.

In any case, when heat treating wood, temperature acts as a catalyst (fast) in the process of uniform redistribution of moisture through 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 moistening depends on the thickness and type of wood. Woodworking recommendations for woodworking is “wood drying technology”, which is equipped with drying chambers for our products. 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 emergency in the event of a fire disaster, the same humidity should 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 available premises that are outdated Drying chambers for drying wood we are ready to provide technical solutions and equip them with the necessary equipment for their conversion or modernization of drying chambers.

Convective drying chambers for wood

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

Board dryer: creating and using a drying chamber

Convection-type drying chambers have found wide application both in Russia and abroad. Convective wood drying technology makes it possible to obtain high-quality lumber with the required moisture content. Modern drying chambers are equipped with automation that allows you to control and monitor the drying process remotely.

Negotsiant-engineering company supplies drying chambers for wood Russian production.

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

Features and advantages of drying chambers

Automatic control and monitoring of the wood drying process

Minimum delivery, installation and commissioning times for drying chambers

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

The ventilation and heating system is equipped with reversible fans made in Germany

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

Inspection door as standard

Sales and service of drying chambers

We supply, install and commission drying chambers.

We provide warranty and service.

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

Loading volume from 45 m

We offer comprehensive solutions for organizing a wood drying area using boiler equipment and wood waste recycling equipment.

The cost of drying chambers is lower than competitive ones.

Technical characteristics of drying chambers

Optional

Supervision of installation and commissioning works

A specialist arrives to carry out installation supervision work, takes measurements of the foundations in accordance with the documentation provided in advance, and then begins assembling the drying chamber with the customer’s team.

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

Catalog drying chambers for wood

A detailed description of the design of a convective wood drying chamber 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 or 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.

DIY lumber drying chamber

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

Rice.

6. Scheme of drying methods:

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

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

The drying temperature of lumber should not exceed 80° C, since with more high temperature the structure changes surface layers wood, 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 relatively high humidity and low temperature.

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

To dry coniferous and hardwood lumber of various sizes, most factories in model shops use periodic steam-air chambers with stimulating reverse circulation.

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

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

In a batch drying gas chamber, smokeless gas is used to evaporate moisture, obtained in the furnace by burning raw wood waste, which is pumped through flues onto stacks of lumber using an axial high-pressure fan. The chamber design includes a steam humidifying device.

In the woodworking industry, batch gas dryers are used, operating at 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 operating gas chambers does not darken. Each of the drying chambers can accommodate 4 stacks of boards, each with a volume of 1.8X2.6X6.5 mm. Gas chambers are used for routine drying of softwood lumber.

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

Wood waste during such drying is significantly less than in steam and gas dryers, and amounts to no more than 5%.

Features of heating semiconductors and dielectrics, which include wood, in high-frequency electric field consist in the fact that heat is released directly in the heated material and the temperature of the material can increase over a short period of time.

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

The following should not be considered a DIY tutorial. Homemade chambers for drying wood exist and there are quite a lot of them. But at the same time, the vast majority of them are far from perfect.

Drying chambers are calculated and designed, which means this must be done by specialists.

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

Woodworking, its cost, and the quality of products depend on the quality of drying of lumber. In turn, high-quality chamber drying of wood depends not only on adherence to technology (correct laying of lumber, adherence to regimes), but also on the design of the drying chamber.

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

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

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.

Convective drying chamber for 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 Fig.

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

Diagram of a convective drying chamber (sectional view)

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.

Wood drying kilns must be designed to allow air to flow only through the stack of lumber.

Loose passages reduce the air flow through the stack (therefore drying the wood more slowly) and make it uneven, which increases the unevenness of the moisture content of the dried lumber.

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

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

Air circulation during chamber drying of wood

Circulation is carried out using fans, the air passes across the stack. The fan compartment is separated from the stacks of lumber by a false ceiling and has a baffle designed to prevent “short circuits” in the air flow. It is very important!

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

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

Requirements for fans for drying chambers

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

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

If the fan performance is insufficient, chamber drying of wood proceeds more slowly, and the unevenness of humidity across the width of the stack increases.

Heating of convective drying chambers.

The heat required to evaporate moisture from the wood is supplied by heaters, their power is determined at the rate of 3 - 4 kW per cubic meter of lumber.

To ensure this, the heat removal surface of the heaters should be about 3.5 square meters per cube of lumber. It is not recommended to use electric heaters: drying wood will have a higher 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 convective drying chambers during ventilation should pass through heaters before entering the stack.

Therefore, if there is a reverse fan, 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 should be located between the ventilation ducts of the pressure side and the vacuum side.

This drying chamber design is characterized by slightly higher heat losses, but lower manufacturing costs.

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

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

Thermal insulation of drying chambers for wood.

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

In addition, if the thermal insulation is poor, moisture will condense on the walls, floor and ceiling of the drying chamber, which will not allow maintaining the air humidity set according to the mode. initial stages drying wood.

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

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 if and only when it is required by the regime.

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

Therefore: wood drying chambers must be sealed, have no cracks, and sealing gaskets must be installed on the gates. Homemade drying chambers especially often have poor sealing.

In industrial chambers, 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 design of drying chambers provides supply and exhaust ventilation due to overpressure on the pressure side and reduced pressure on the vacuum side, additional fans are not used.

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

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

Humidification system for chamber drying of wood

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

Indeed, when drying freshly sawn wood, the air humidity required by the regime is gained in 6 - 12 hours. However, if chamber drying is carried out on wood that has lain for 2-3 days after sawing, then this time can extend for a day or more, which is no longer desirable.

Drying chambers for lumber - choosing equipment for drying wood

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

It is unacceptable.

About the requirements for gaskets.

Gaskets are not an element of the design of the drying chamber and, of course, are not supplied with it, but without complying with the requirements for them, high-quality drying of wood is impossible, so let’s talk briefly about gaskets.

The gaskets must be made of dry lumber and have strictly the same thickness. The thickness of the gaskets with a total stack width of 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.

If the thickness of the gaskets is insufficient, chamber drying of wood proceeds more slowly, and the unevenness of humidity 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 correct installation lumber, so be sure to study this issue.