Drying chambers for lumber: design and manufacture. Drying for wood - buy ready-made or make it yourself? DIY wood dryer

15.06.2019

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

Humidity indicators

Based on the degree of humidity, the following states of wood are distinguished:

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

Why is proper drying so important?

Boards with natural moisture are larger in size than dried ones and are cheaper. This is because lumber manufacturers set tolerances based on future shrinkage and trimming.

Humidity standards:

for building and carpentry materials – 10-18%. When manufacturing building materials, the production moisture content of wood should be equal to or be 1.25-3.5% lower than the operational moisture content in order to avoid natural drying.
For furniture production – 8-10%.

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

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

Methods for professional drying of wood

1. Convective (chamber) drying

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

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

Systems are installed in the room supply and exhaust ventilation and heating (usually air heaters). Humidity parameters are measured psychrometer and are adjusted automatically. Waste is used as fuel for producing hot water or steam in small production wood production: wood chips, slabs, sawdust. It is profitable to use electricity and gas only for large production volumes, otherwise high consumption and the cost of resources will significantly reduce the cost of lumber.

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

Price – from 160,000 rub.(depending on configuration and cargo capacity).

2. Atmospheric drying

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

To avoid deformation of the boards during the drying process, the following conditions are necessary:

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

Rice. Air dryer arrangement diagram

Main disadvantages: the design takes up a lot of space, the drying process is uncontrolled, and in areas with high humidity there is a high risk of lumber being damaged by fungus. For such terrain it is recommended Preliminary processing boards with antiseptic.

3. Vacuum dryer

Used for drying large section wood, deciduous hardwoods (for example, oak), valuable wood which is susceptible to cracking. The dryer is a sealed stainless steel chamber into which boards are placed between aluminum heating plates. The top of the chamber is covered with an elastic rubber covering attached to a metal frame.

Circulates continuously across the plates hot water, which is heated by an external boiler. The vacuum inside the chamber is ensured by a pump that pumps moisture out of the room.

Rice. Vacuum chamber operation diagram

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

Flaws: small chamber capacity (up to 10 m3), high energy consumption, high internal tension due to the uneven distribution of final moisture content throughout the thickness of the material. These shortcomings are eliminated in new vacuum models, where drying is carried out using hot steam.

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

4. Microwave dryer

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

The electromagnetic field affects stacked lumber in the space of a metal chamber. Wood is heated at a level of 50-60 degrees, therefore it is considered close to natural conditions.

Main advantages:

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

Flaws:

small loading volumes (up to 4.5 m 3 for solids hardwood and up to 7 m 3 - coniferous);
the high price of magnetron generators with a fairly short service life (no more than 650 hours);
uneven drying;
the possibility of ignition of the material inside the chamber - the microwave method is quite new, and drying modes have not yet been developed.

5. Condensation drying

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

Dehydration of lumber is carried out using the method closed loop– without access of air from outside.

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

Rice. Operating principle of equipment with condensation drying technology

Main advantage: energy consumption is 3 times less compared to dryers periodic action(up to 0.5 kW/h per 1 liter of evaporated water). Such cameras are used in cases where electricity is the only available or most cheap look coolant.

For the quality of any type of structure, it is important that the materials used are also of high quality and durable. And when we're talking about about wood, it must be dry, strong and resistant to rotting.

To give the tree such properties, it needs to be dried. But purchasing equipment to implement heat treatment wood is very expensive, so many craftsmen try to assemble their own.

Drying chamber DIY lumber may be a good value for money, but it is far from perfect. Indicators such as 6% humidity in a couple of days with less than 1% defects in it are clearly unattainable, since assembly is usually carried out from improvised means without the use of sensors and various smart systems for monitoring various parameters of wood, and most importantly, with virtually no experience in creating drying chambers.

Features of self-made drying chambers

A homemade drying chamber is a room in which a heater is installed. Now it’s worth thinking about, if for drying 1 cubic meter. m will require at least 16 kW of energy, then as much as will be required within 3-4 weeks (this is usually the standard drying time in such chambers. Costs can be many times higher than the prices of the materials themselves. Plus, if the temperature conditions are not observed, poor-quality heating length and without controlling the percentage of humidity, the boards are deformed in almost 100% of cases, which makes them very difficult to work with.

The design of such cameras must be realized using detailed calculations. If technology is not followed, various accidents occur. For example, the chamber body under the influence of vacuum can shrink like an aluminum can and other moments are often life-threatening for workers.

It is also necessary to take into account the source of energy. Running on electricity is expensive. It is more efficient to operate a drying chamber using wood using a solid fuel boiler.

The indisputable advantages include the opportunity significant savings funds. Because high quality camera, acquisition is often expensive. But the expected savings may actually turn into significant losses.

pros

There are many reasons for this.

For example:

task self-made drying chamber is very complex. To solve it, you will need to purchase starting materials, necessary equipment. And, most importantly, the presence of specialists on staff who can do everything necessary calculations, and build this object;
The slightest inaccuracies in calculations and construction technology can lead to a significant increase in the volume of defects. And these are direct losses, violation of delivery deadlines, loss of business reputation and image of the enterprise. Moreover, these errors can lead to destruction of the chamber itself (for example, the vacuum chamber will “collapse” like a tin can);
significantly higher energy consumption.

Example.

Drying a cubic meter of lumber in a homemade chamber requires an average of at least 16 kW. Calculate monthly expenses (even with an 8-hour working day and a 5-day working week).

The parameters of finished lumber, which are provided by vacuum chambers manufactured by a specialized enterprise (for example, a moisture level of 6%, achieved in two days of work, or a defect rate not exceeding 1%), are practically unattainable in home-made devices.

Possible design options

If objective analysis showed that the company is capable of solving all the upcoming difficulties associated with manufacturing, commissioning and subsequent operation, it is possible to begin a detailed study of this issue.

To do this, you need to answer several questions:

what drying mode will be implemented in it (the required temperature in the chamber depends on this): low temperature or high temperature;
its future structure (prefabricated metal, or built from existing building materials (concrete, brick, blocks, etc.);
installation location (separate building, workshop area). Since such a decision depends on the calculation of subsequent work (foundation, laying engineering communications, delivery of raw materials, etc.);
loading option (forklift, rail cart);
heat supply option ( hot air, radiant energy, superheated steam, electric current, other options);
decide on the required equipment for the future furnace (main and auxiliary).

The first group necessarily includes a humidification and ventilation system (supply and exhaust), heat supply. Secondly, psychrometric and insulated door blocks, electric motors for fan drives, stacking trolleys, etc.

option for organizing process control (manual mode, semi-automatic mode, automatic mode). Ideally, remote control of processes can be provided.

All of the above issues are resolved in the context of the selected type of drying chamber. Today there are chamber and tunnel options (they implement convective heat transfer).

The first ones are shorter than the second ones and, most often, for loading raw materials and unloading finished products one door is used. As a rule, this option is chosen.

Tunnel systems provide for the movement of materials during operation along the entire length of the chamber. Loading, on the one hand. Unloading from the opposite side. These cameras are used in large enterprises.

There are condensation type drying chambers. They have significant efficiency, but the drying process is very long in time (the equipment is not able to work in conditions high temperatures). This leads to significant heat loss and increases energy consumption.

There are many more criteria that must be taken into account when making calculations:

method of circulation of the agent used for drying;
its characteristics;
type of fencing being performed;
operating principle;
circulation method.

Each of these issues directly affects the drying speed, the possible volumes of lumber loaded at a time, and the characteristics of the finished product.

In addition, it is necessary to take into account the type of wood, its initial moisture content, geometric dimensions lumber.

Careful analysis and detailed calculation, with high degree chances are that they will prove the economic feasibility of purchasing and installing a ready-made drying chamber. Although, in some cases, making it yourself can also be cost-effective.

How can we help?

The Falcon company has been producing vacuum chambers for drying wood for almost two decades. Cooperation with us is beneficial both for those who are going to make their own drying chamber, and for those who want to purchase ready product to have guaranteed quality products in commercial volumes.

We are ready to offer our partners from the first group the equipment and units that are necessary for the functioning of the cameras in our range. An example is heating panels in which the coolant is water.

They can be installed in structures of any volume, are designed for operation in a vacuum environment, and are capable of operating at high temperatures.

Panels can be selected according to a number of characteristics:

according to the volume of the chamber for which they are purchased (we offer 4 design options - for volumes up to 3 cubic meters, up to 8, up to 15, up to 21);
they can be equipped with automatic equipment in a standard, maximum or optimal version for the customer;
by size: 2000*3000 or 1500*3000.

In addition, we offer thermal units fully equipped, pyrolysis boilers, liquid NPs, vacuum units and automation completely ready for installation.

We manufacture automation for chambers of each type: Convective, aerodynamic, vacuum, etc.

Significant advantages of purchasing ready-made solution are:

significant time savings (it takes at least 14 months to independently develop a project and complete it);
savings on unplanned expenses. Practice shows that bringing the performance characteristics of a homemade camera to the required parameters requires an amount comparable to (or exceeding) the price of a finished camera;
guaranteed release of only high-quality products;
The company begins to receive net profit immediately after completion of the commissioning project. No time is required to fine-tune the equipment and characteristics of the finished product (downtime).

If you need to design a vacuum dryer, it is better to seek the help of professionals. We are engaged in production:

mobile,
stationary,
high efficiency,
low power consumption.

It is possible to design not only drying, but we can also supply new equipment at an affordable cost. Powered by both electricity and industrial waste: slabs, firewood, etc.

For those who know how to count money, save their own time and pay primary attention to quality, a wide range of vacuum chambers of our production is available, the main characteristics of which can be found on the website, in the company catalog or by personally contacting the nearest office.

We also sell more budget options from heating plates. You can find out more from the manager by phone or email on the main page.

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

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

Maintenance problem optimal humidity in lumber is relevant both among builders and among those who like to make something in their own carpentry workshop. Drying wood at home allows you to save a lot on its purchase, because dry raw materials are always more expensive than wet ones.

By the way, if you don’t have any time for construction work, then you can dry the wood at home or in the country even under atmospheric conditions.

Some owners already adapt for these purposes ready premises haylofts, barns or other suitable buildings. Here is a way out of the situation that one of our forum members found.

Timakval member FORUMHOUSE

I used the yard attic (former hayloft) size 10*5 m for drying. I laid it out, as it should, through spacers in each row. Total 3.5 cubes of boards of different categories. The advantages of this drying place are always shade, finished roof and is well ventilated. Took it last May different sizes boards, bars and beams - blanks for small construction. The boards were too heavy to lift due to moisture. During the time they were lying in the hayloft (1.5-2 months) they dried to fluff, they did not curl or bend.

Drying under atmospheric conditions is a rather lengthy process, and since we have decided to take a comprehensive approach to this issue, let’s look at the sequence of building a home dryer with our own hands, which allows us to more effectively achieve the required humidity levels. As suitable premises We invite you to choose a building required size, and after that you can start working. The room can have dimensions of 2*3 m or 4*3 m (more is possible). It all depends on your needs and the scope of your activity. But when choosing a building, you should remember that there should not be much left in the dryer. free space. After all, drafts and chaotic air movement negatively affect the quality of wood.

DIY wood dryer

The room chosen for arranging a homemade dryer must be heated by a stove or a specially installed fireplace. It is good if a heater is pre-installed in the room. If you don't have one, be sure to leave room for it.

This is the project for making a home dryer suggested by a member of our forum.

Nikolay Valen member of FORUMHOUSE

Available capital garage with water heating, a potbelly stove using wood and exhaust is installed as a boiler. There is a pipe with a diameter of 800 mm and a length of 2.2 meters (a former ventilation duct from an industrial plant). The idea is as follows: install sealed covers on both ends of the pipe, leave fittings with a diameter of 150-200 mm for the supply and removal of hot air. The air is heated by a radiator (this can be a car heater). Air supply - table fan. 0.3-0.5 cubic meters of lumber are loaded into the pipe, the stove is heated (the coolant temperature reaches 90 degrees, I think that the supplied air can actually be heated to 50-60 degrees).

If you have chosen a room that is too large, then the space you plan to use for a homemade dryer should be made insulated and sealed. For these purposes they are made wooden partitions, you can use insulation, brick and other materials that allow you to create your own microclimate in the dryer. Do not forget that it is necessary to leave a window in the chamber for ventilation and front door. After all, we shouldn’t end up with a hut without windows and doors.

Fans installed in the drying chamber will help create forced air flow and make the drying process more efficient.

mfcn FORUMHOUSE member,
Moscow.

It is advisable to place fans on the floor to the side of the stack so that the blowing is parallel to the spacers. Remember that when drying wood, you need to evaporate about several hundred liters of water from each cubic meter of wood.

To place lumber in the dryer, special shelves or flooring should be installed. These products can be made of metal so that the structure can withstand relatively large loads. Wood should be dried to levels corresponding to 8–12% humidity. Its measurements are carried out using a special moisture meter.

Drying wood is necessary following certain rules. Otherwise, the material will be hopelessly damaged and cannot be used in construction. To do this, the wood must be stacked. And between each new layer, spacers made of boards of the same thickness should be placed. Wood of any species, stacked in neat stacks, will never suffer from fungal infections and will retain its integrity and excellent consumer qualities.

Lao Czy member FORUMHOUSE

The spacers need to be made higher for better air ventilation between the boards. They will dry out better. You can place your cut 25*30 or 25*40 cubes on edge. The reason for limiting the height of the stack is to prevent the boards from being driven by a “helicopter blade”, secure the topmost layers of boards in the stack with self-tapping screws. I have been storing my boards using this method for the 3rd year at my dacha in the Moscow region. They are in excellent condition!

Gaps should also be left between boards located in the same row. This will ensure unhindered air movement inside the stack and improve drying quality.

Wood drying chamber project

Wood can be dried quickly and efficiently in well-equipped and free-standing drying chambers. Construction of such a chamber on the scale of a dacha or suburban area is not always advisable. After all, this type of construction will be very expensive, and its construction will take a lot of time.

The construction of such a premises can well be called the implementation of a full-scale construction project. You cannot avoid labor-intensive operations associated with pouring the foundation, erecting walls and installing complex equipment.

How to make drying for wood can be understood from the diagram.

DIY chamber drying

Such a mini-wood dryer requires the placement of not only basic equipment (heating and ventilation), but also additional systems automatic control.

Operating modes of the drying chamber

The chamber dryer does not involve strong heating when normal mode work. And the full cycle of work associated with drying one batch of wood can be divided into several stages.

The first stage lasts from 15 to 20 hours. During this period, the air in the chamber warms up to 45С. The ventilation does not turn on, and condensation forms on the walls of the room.

The second stage lasts about 48 hours. It involves connecting ventilation and heating the air in the chamber dryer to 50°C.

The third stage lasts until the required final moisture level is reached in the internal structure of the wood (8...12%). At this time, the air temperature rises to 55 C, the exhaust dampers open completely, and the fans operate at full power.

Once the humidity reaches the required levels, the heat supply should be stopped. The fans should remain on for another 24 hours. As a result of this heat treatment, you will receive dry wood, completely ready for use during carpentry or construction work.

You can get acquainted with the practical developments of our forum members regarding the correct construction of a stack in the “” section. Those who want to learn more about the technology of drying lumber can visit the “” section. For those who want to see a master class on wood aging technology, we recommend watching the corresponding video.

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

The need to dry wood

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

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

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

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

Wood moisture concept

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

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

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

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

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

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

Wood drying modes

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

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

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

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

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

Drying chamber concept

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

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

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

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

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

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

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

Types of drying chambers

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

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

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

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

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

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

Wood drying procedure

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

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

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

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

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

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

Making a drying chamber

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

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

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

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

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

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

High-quality dried lumber has always been the key to quality, durability and reliability of any structure in which wood occupies a significant share. But it is difficult to obtain it under natural conditions without it spoiling. Drying time under normal atmospheric conditions can range from 6 to 12 months, depending on the temperature and humidity of the environment. During natural heat treatment, the material is subject to unwanted deformation, warping and cracking.

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

What is vacuum drying of wood with your own hands?

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

Main design elements:

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

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

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

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

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

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

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

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

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

full color change
fire resistance
increased resistance to rotting

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

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

Our company produces high-quality and highly efficient drying chambers vacuum type not the first year, so I’m ready to offer a truly reliable and practical option.

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

If you are still going to purchase ready-made equipment, then the most effective option is chambers with contact technology for heating lumber along the entire length, the percentage of defects is less than 1, and the drying time is up to 6-8% humidity pine boards 30mm thick will only take about 60 hours.