Drying chamber is the most important equipment in woodworking enterprises, as it allows you to remove moisture from lumber, thermally treat the wood to prevent biological destruction, impart resistance to decay, maintain mechanical strength at the lowest density, and create minimal thermal and electrical conductivity in wood.
What are drying chambers and complexes?
Drying chambers are industrial equipment used for drying various types lumber and wood species, deciduous or coniferous, for fumigation of pallets. To process large volumes of wood, modular chambers are combined to create large-sized drying complexes.
Types of drying chambers and drying modes
MAKIL PLUS LLC offers drying chambers for lumber, with boilers (heating units) that burn (recycle) wood waste, which are divided into two types, depending on the coolant used:
- Coolant - water. These installations consist of a boiler and water heaters, circulation pumps, automation adapted for use in cold weather (anti-freezing system), and a water treatment system. The system copes well with water softening, and the boiler power is selected based on the volume of drying chambers and additional consumers. Based on the above, a drying complex for drying water-type lumber has a high initial cost of the project, since it includes many expensive elements and requires specialized installation.
- Coolant - air. The system includes an air heating unit with a capacity of 100 - 500 kW, a centrifugal fan and an air duct system. The initial costs for this equipment are included in the price of the camera, the customer receives ready-made solution without additional capital investments. The universal air heating unit has a higher efficiency compared to a water boiler and is capable of producing both minimum and higher temperatures than a water-type wood drying chamber.
To process wood in drying complexes, three main modes can be used: soft, medium and forced. When maintaining a soft mode with a temperature of up to 55°C, during the drying process the wood retains all its properties without changing in strength or color. When using the average (normal) mode with temperatures up to 67-70°C, the shade of the wood changes slightly. For high temperatures up to 85-90°C with forced mode, rapid drying is characteristic, but with darkening of the wood.
Technologies used by the company in the manufacture of cameras
The main advantage of drying kilns for wood is:
- Autonomous operation of the system in the absence of heating networks
- Minimum costs for fuel with simultaneous waste disposal
- Compact placement of main and auxiliary equipment
- Possibility of dismantling equipment and moving it to a prepared foundation
- High degree of thermal insulation of the chamber as a whole, tightness and insulation of sliding gates
- Fast warm up to required temperature
- Minimum heat loss through structures
- The drying agent and coolant are both air and water.
- Possibility of quick conversion to coolant.
- Easy to maintain, easy to control.
- Possibility of drying in any mode.
- Drying complexes are made of 80% Russian materials not requiring a long wait when replacing.
- The modular design allows you to add new drying chambers without stopping existing chambers.
- Thermally protected reversible axial fans with Siemens/ electric motors
- Litouch drying process control system from the world leader Logika concern
- The ability to program the controller up to 16 phases of lumber drying, which allows you to create special climatic conditions inside the chamber for the drying process.
- High maintainability during operation
These technologies not only make it possible to dry lumber without changing color or cracking, but also ensure trouble-free operation of the equipment.
Economic payback of wood waste chambers
Economic payback is one of the benefits of equipment from the MAKIL PLUS company. A wood drying complex, on average, pays for itself within a year, since the cost of drying 1 cubic meter, including the cost of servicing the device, is about 450 rubles. In addition, purchasing a completely ready-to-use installation solves the problem of wood waste disposal. At the same time, mixed waste even with a high percentage of moisture is suitable for work.
The MAKIL PLUS company produces drying equipment with chambers with a volume of 10 to 140 m 3, which are manufactured according to ready-made projects, and according to individual customer requirements. Drying complexes for wood “MAKIL PLUS” are already operating in every region of Russia and are becoming more in demand every day.
More detailed information By this equipment and its purchase can be obtained by contacting the managers of our company.
Drying is a mandatory stage in preparing wood before processing. To prevent logs from becoming deformed, they are dried under certain conditions, which are created in drying chambers. For your home workshop, you can make a wood dryer with your own hands.
The importance of drying
Since ancient times, wood that was cut down several years ago was used to make wood products. Furniture made from damp or improperly dried boards will warp or dry out and crack. When drying, the material shrinks, raw wooden beams will begin to move over time, and cracks the width of a palm will appear in the walls of the log house. Mold grows in damp wood. But overdried boards are also bad - the material begins to absorb moisture and swells.
Drying is carried out with hot air or steam, the process is long and expensive, but it gives the wood additional strength, prevents changes in shape and size, and the lumber is stored longer.
Drying modes
There are several modes of drying lumber. In self-made chambers, the temperature increases in stages, removing moisture from the raw materials. Drying technology is selected taking into account:
- wood species;
- dimensions of lumber;
- final and starting humidity;
- dryer features;
- raw material quality categories.
The drying process can be high temperature or low temperature. In the second case, primary processing is carried out at a temperature not reaching 100 degrees.
Low temperature regimes are divided into categories:
- soft - during the drying process, lumber retains all its properties, strength and color do not change;
- normal - color changes slightly, strength decreases slightly;
- forced - when chipped and split, brittleness is possible, the color darkens.
The change in ambient temperature in low-temperature conditions occurs in three stages. The transition to the next stage is possible when the wood reaches the specified moisture content.
High-temperature treatment is carried out in two stages. The second stage occurs when the moisture content of the raw material decreases to 20%. This technology is used when preparing wood for the construction of secondary structures, allowing for color changes and a decrease in strength.
Types of drying chambers
Drying wood in industrial scale produced in special chambers. Moisture is removed from the lumber by heated air and carried outside. The device carries out a full wood drying cycle. The room can be:
- prefabricated metal;
- constructed from building materials.
The latter are installed directly in carpentry shops or as free-standing buildings. The walls are made of reinforced concrete or brick. On large enterprises set up several chambers combined into a module with common system control and communication lines. Air circulates in the dryer horizontally or vertically-transversely. Wood can be transported to industrial dryers on rails on carts or laid out using forklifts.
Heat sources in the dryer:
- hot steam;
- radiant heat from special devices;
- heated shelves;
- electric current that passes well through wet logs;
- high frequency electromagnetic field.
The camera is equipped with basic and additional equipment. The main consists of systems:
- supply and exhaust ventilation;
- heat supply;
- hydration.
Additional equipment includes insulation of walls and doors, trolleys for laying material, psychometric equipment, and electric drive.
Industrial dryers are controlled automatically, small homemade dryers are controlled manually. Humidity is regulated by supply and exhaust ventilation and humidifiers. To measure the humidity in a room, a moisture meter is installed that collects data simultaneously in several places.
The following energy sources can be used to heat air: electricity, wood processing waste, liquid and solid fuel.
Types of dryers
According to the method of air movement, chambers are divided into:
- with natural;
- with forced air exchange.
Chambers with natural air exchange are low-performing and the process in them cannot be controlled. Therefore, they are used less and less.
Based on the principle of action, the following are distinguished:
- convective;
- condensation dryers.
In convection chambers, the wood is blown with streams of hot air, and heat is transferred by convection. They can be deep tunnel or chamber. Logs are loaded into tunnel chambers from one end and unloaded from the other, moving through the chamber, the material is gradually dried. The cycle duration ranges from 4 to 12 hours. Such cameras are installed in large sawmills. Chamber dryers are more compact; a single microclimate is maintained throughout the entire volume. Allows you to prepare any type of wood to the required condition. Therefore, most industrial dryers are chamber type.
Using condensation drying technology, moisture released from the material is deposited on coolers, accumulates in containers and is drained outside. The efficiency of such a device is very high, but the process is long and accompanied by high heat losses. The technology is good for preparing hard lumber in small batches. The price of equipment and the cost of condensation drying are lower than convective drying.
Setting up a homemade dryer
In order to make a dryer with your own hands, you can do without drawings. It is necessary to provide:
- camera room;
- insulation;
- heat source;
- fan.
The area of a dryer built by yourself usually does not exceed 9 square meters. meters. In a square-shaped room it is easier to ensure optimal movement of warm air. It is desirable that one wall of the chamber be made of concrete slabs, the others made of wood. All walls are insulated from the inside in two layers: polystyrene foam and foil board. An excellent and free insulation material is wood shavings. And the foil can be replaced with penofol, which perfectly reflects heat.
You can build a separate drying room with your own hands from aluminum; such a structure will last a long time. The frame is made of profile, it is sheathed with sheet metal, which is insulated from the outside. The thickness of the insulation is at least 15 cm. The floor is covered with roofing felt, and a thick layer of shavings is poured on top as thermal insulation.
Care must be taken to thoroughly seal the front door!
The heat emitter can be made in the form of pipes or heating radiators. The water temperature should be 65-95 degrees. It is heated by an electric boiler, wood stove, or gas boiler. For a small chamber, even a two-burner electric stove is sufficient. If the stove is located directly in the room, you need to line it with bricks. The brick will accumulate heat and gradually radiate it into the dryer. It’s easy to equip a convection chamber with your own hands by installing a fan heater as a heat source.
When setting up a dryer for your home woodworking workshop with your own hands, it is important to observe preventive measures. fire safety. There should always be a fire extinguisher near the building.
Constant circulation of warm water, which is provided by the pump, is important. To ensure that heat is evenly distributed throughout the room, a fan is installed. Workroom Equipped with a wet and dry thermometer.
To make it easier to load the board into the chamber, you can use a trolley on rails. And to increase the usable area, shelving is built on the walls.
The step-by-step instructions are as follows:
- We are building the foundation.
- We are building the frame.
- We cover the frame with sheets of metal.
- Installation of thermal insulation.
- Cover the floor with film and sawdust.
- Installation of supports from bars.
- Installation of heaters and fans.
The design of a homemade chamber for drying lumber in the video:
Since ancient times, dry wood has been used to make wood products. Products made from a damp wood base quickly became unusable, so specifically to obtain high-quality material, the wood was kept for several years, trying to dry it.
When wood dries, it shrinks, compacts and curls, so before making log houses or lumber, it is necessary to dry the wood thoroughly. The wood also needs to be dried correctly; it is necessary to achieve a certain percentage of humidity; the materials should not be overdried, since the dried wood will strongly absorb moisture, swell and crack.
Cut trees are dried, as a rule, in special drying chambers that resemble an oven. Next, we will discuss what drying devices exist, how to use them, and whether it is possible to make a dryer with my own hands.
Types of devices for drying wood
In large quantities industrial production The cut trees are dried in specialized drying buildings that look like huge ovens. The moisture content in wood is reduced by treating the source material with heated air. This design provides process drying the wood for further processing. Such devices are made in several versions; it is possible to manufacture the dryer body from:
- Metal, in one-piece version;
- A variety of building materials as a prefabricated structure.
Prefabricated structures are installed directly on site, in the form of structures and free-standing buildings. The walls are welded from a frame and sheathed with metal sheets; you can fill the walls with concrete mortar or use brick. Large timber processing plants create a whole system of drying rooms, combining several modules with a single central control and control over the technological process. Prefabricated structures in the form of free-standing buildings are welded from a frame and covered with a metal sheet; they can be filled with concrete mortar or bricks can be used.
The basic principle is heating the wood with warm air. Due to its circulation inside the drying chamber, the lumber is actively heated and dried. There can be several heat sources:
- hot steam;
- smoke from burning wood;
- just heated air;
- electric heating elements;
- infrared energy;
- electromagnetic fields in the high frequency range.
In addition, drying devices are equipped with additional systems that help carry out the wood drying process more efficiently. This:
- supply and exhaust air injection and removal systems;
- additional heat sources;
- moisturizing systems.
Drying rooms differ in their operating principle; they can function:
- on convection equipment;
- on condensing boilers;
- on wood;
- as aerodynamic dryers;
- on solar infrared batteries;
- like vacuum ones.
Operating principle of convection dryers
Convection drying devices built on the principle of circulating warm air between the original lumber. In one cycle, which lasts from 5 to 14 hours, the wood is dried to the desired percentage of humidity. In addition, the fundamental difference between convection dryers is that the wood is heated by a gaseous coolant. It could be:
- heated air-gas mixture;
- gases products of combustion.
When wood material is heated, moisture is released, which is thrown out with the coolant.
Closed-type drying chambers in the form of a separate box are more compact and are distinguished by the fact that a constant set temperature and humidity are maintained throughout the entire volume of the chamber. This design of ovens allows you to dry the original wood material of any type to the required humidity.
Building a drying chamber, step-by-step instructions
To make a drying chamber with your own hands, there is no need to prepare complex technical drawings. You just need to provide the following:
- Place for installing a drying chamber.
- Insulation (thermal insulation) of the entire structure.
- Heating sources.
- Ventilation or air circulation system.
The area of drying chambers built by yourself is usually small, usually up to 10 square meters. meters. These are square rooms suitable for the circulation of warm air flows. It is recommended to build at least one wall of concrete, the rest can be made of wood. The inside of the chamber must be lined with a heat insulator; a good material should be selected to retain heat inside.
For example, an excellent and at the same time inexpensive insulation material is wood shavings. It is also necessary to lay a layer of foil, which will retain heat.
You can make a dryer for lumber from an aluminum sheet by constructing a frame from wood or a profile, and covering it with metal sheet aluminum, you can get a structure that will last a long time. It is important to take care of a good thick layer thermal insulation material, thickness not less than 150 mm. Otherwise, you may encounter large heat losses, i.e. the street will be heated. The floor must be covered with roofing felt or similar rolled material; a layer of wood shavings is poured over the top, which will serve as an additional heat insulator.
Theoretically, after harvesting and sawing wood raw materials, you don’t have to dry the wood. There is also a demand for raw goods, but dried material is almost twice as expensive. And the deeper the processing of lumber, the higher the selling price and, accordingly, economic efficiency companies.
Their main disadvantages of convection drying systems include:
- Increased electricity consumption in air dryers;
- The high price of condensation drying devices, and the duration of the drying cycle is increased by 1.5-2 times;
- increased price of vacuum devices, as well as problems in their maintenance and operation.
The convective drying method is the most advantageous for industrial volumes of wood of various species. Such devices are much cheaper, easier to operate and maintain, and therefore more reliable. To increase efficiency, convection dryers will remain the best option.
Complete set of drying chambers
Let's say a few words about the configuration of dryers for lumber in various designs. Is there a minimum required set of equipment that makes up the “basic” package?
Experts say that standard solutions, as a rule, does not exist. Most manufacturers of drying devices for lumber have an individual approach to the requirements and conditions of each specific technology. The complete set of drying structures can be almost anything - from the minimum required to fully equipped complexes of drying ovens with boilers operating on forest waste. Experience shows that the most common configuration options are the following:
- supply of devices and instruments to complete an existing or newly constructed drying building;
- complete delivery together with the design of the prefabricated structure with equipment and controls.
Another characteristic feature of the operation of convection drying devices for lumber is humidity control systems. The moisture content of the air inside the chamber is an important parameter that affects the technology of drying sawlogs. The higher the temperature of the coolant in the chamber, the faster the lumber dries, but at high temperatures the humidity is several times higher than the moisture content environment. And in convection dryers, air exchange volumes exceed 2% of the total circulating air per hour.
Dryer body
The body of the kiln for drying lumber is a metal structure built on a foundation. The frame and walls are usually made of aluminum or sheet metal carbon steel with anti-corrosion coating. Internal structural elements: deflectors, suspended ceilings and control system units, as well as auxiliary structures are made of aluminum, and mineral wool is used as insulation.
Special attention should be given mineral wool, since the use of low-quality products can give a negative result. Therefore, you should use only well-known mineral wool from trusted companies, which will prevent the heat insulator from settling, and the gaps will allow the insulation to dry even if moisture gets in.
Conclusion
The main thing to remember is that it is impossible to allow sudden changes in temperature limits indoors while drying lumber, otherwise this will lead to damage to the material, warping of the wood and the occurrence of cracks. When constructing a drying structure, it is necessary to comply with fire safety standards. Fire extinguishers must be installed near the stove.
You can insulate the walls of a drying oven yourself using wood shavings. As an option, use penofol instead of foil in the chamber, which can create a good reflection of heat from the surface. In this design, the wood dries for 1-2 weeks.
The drying process is the initial point in the entire preparation of the semi-finished product (wood) before processing.
A drying chamber for lumber and wood is an excellent solution to the problem; you can make it yourself. In order to avoid deformation of the logs, drying is carried out in specialized conditions, which are carried out exclusively in a drying apparatus.
Why is drying needed?
For a long time, when making any wood crafts, they used timber that had been cut down several years earlier. Products made from damp or under-dried boards will warp or develop numerous cracks.
When the tree dries out, it shrinks, the raw wood material will “deform” over time, and huge wide cracks will form in the log house. Under-dried semi-finished products are likely to develop fungus. But it is not advisable to overdry the tree, because it will begin to absorb water, which will lead to swelling.
What are the modes of drying chambers?
There is a whole list of drying modes for wood materials. In machines built with one’s own hands, the mode changes gradually from lowest to highest, extracting all excess water from the semi-finished product. The drying process is carried out based on the following characteristics material:
- wood species;
- overall dimensions of the semi-finished product;
- final and initial humidity levels;
- specifics of the unit;
- quality indicators of lumber.
The drying process can be characterized by high temperature or low temperature. The second case is notable in that primary drying is performed at a mode that does not reach 100ºC.
Low temperature conditions may be as follows:
- soft - after drying is completed, semi-finished products have their original properties without changing strength or color;
- moderate - the color changes slightly, the strength characteristics are slightly reduced;
- accelerated - during subsequent processing (breaking, sawing, cutting), increased fragility is possible, the color fades.
Changing the temperature regime during low-temperature processing is carried out in three stages.
High temperature processing is carried out in two stages. The second stage begins when the moisture level of the semi-finished product decreases to 15%. This technological process is used when it is necessary to further construct secondary structures.
Main types of drying chambers
Drying of semi-finished wood products in industrial volumes is carried out in specialized drying apparatuses. Moisture is removed from the wood by heated air, which subsequently escapes into the atmosphere. The device ensures a full drying cycle for lumber. The machine body can be:
- solid/prefabricated metal;
- made using building materials.
The latter are mounted directly in carpentry workshops in the form of a structure, or as free-standing ones. The walls are made using reinforcement and concrete mortar. As an alternative, you can use brick. Large factories They make a system of cameras, combining them into entire modules with centralized control and communications. Air moves inside the dryer in a horizontal plane or vertically transversely.
Heat sources in the dryer:
- radiant source from specialized units;
- hot shelves;
- electric current, which passes through raw semi-finished products;
- high frequency electromagnetic field.
The cameras are equipped with basic and auxiliary equipment. Basic systems:
- supply and exhaust equipment;
- heat sources;
- humidifiers.
Based on the principle of operation, drying machines are divided into:
- convective equipment;
- condensation equipment.
In convection machines, semi-finished products are “battered” with hot air waves, the heat is directed by the convection method. Travel time full cycle varies from 5 to 13 hours. Similar units are installed in large-scale sawmills.
Chamber-type dryers are more compact; a constant temperature and environment as a whole are maintained throughout the entire volume. This type of dryer will allow you to dry any type of wood material to the required condition, which is why many entrepreneurs who need to dry lumber choose chamber dryers.
Based on the technology of the drying process, the moisture that is released from the wood settles on the cooling elements, is directed into containers and then drained. The efficiency of such a unit is quite impressive, but it is time-consuming and leads to large heat losses. Pricing policy machines and the profitability of condensation drying is lower than convective drying.
Drawing
Drying chamber for lumber: step-by-step instructions
To build a drying apparatus with your own hands, you do not need to use technical documentation. You just need to provide:
- the area where the camera will be installed;
- insulation materials;
- source and communications for creating high temperature;
- blowing
The area of a personally built car is usually no more than 10 square meters. A square-section room is more suitable for ensuring the movement of warm air flows. It is preferable that at least one of the walls of the equipment be concrete, the others can be made of wood. The inside of the chamber must be insulated. An excellent insulation material is wood shavings. If you don’t have foil on hand, you can replace it with penofol.
A separate extension for the dryer can be constructed from aluminum sheets; this design will serve for a very long time. The base is made on the basis of profiles, it is covered with sheets of metal, which is then insulated. The thickness of the insulation must be at least 150 mm. The floor is covered with roofing felt material, a thick layer of shavings is poured on top, which will be excellent for heat conservation.
The heat source can be supplied as a heating pipe system. The liquid temperature in the pipes should be 60...90ºС. For an oversized chamber, having a two-burner stove would be quite acceptable. If the source is located directly in the room, it must be lined with bricks. Brick is able to perfectly collect heat and direct it to a machine for drying lumber.
Continuous circulation of liquid is important, which is ensured by a compressor or an entire station. The room must be equipped with wet and dry thermometers.
For more convenient loading of semi-finished products into the chamber cavity, you can use a rail cart.
Video: DIY lumber drying chamber.
Wood products that meet modern requirements can only be obtained from specially selected and prepared raw materials. The humidity indicator becomes decisive in this situation. It takes a long time to bring natural material to the desired condition using the natural method. Depending on the breed, this can take up to several to several decades. If you use a wood drying chamber, the time is significantly reduced. Large production associations Such equipment has been used for lumber for a long time.
For small companies, individual entrepreneurs and for home craftsmen, this issue becomes relevant, since boards and timber with natural moisture are significantly cheaper, but they are not suitable for the production of high-quality products. Waiting for the wood to dry naturally is too long. When choosing a method of forced high-quality drying, the question arises whether to purchase ready-made chambers or make them yourself. But first of all, it is necessary to understand the theory, principles and features of this operation.
Experience has shown that the process of removing moisture from lumber will be effective if general rules. They are determined by the following criteria:
- Drying chambers must meet performance and safety standards;
- Strict adherence to drying regimes;
- Correct placement and fixation of workpieces, eliminating warping and cracking;
- Control at all stages of the operation, from preparing raw materials to unloading wood from the chamber.
If the wood dryer is made by yourself, then test drying should be carried out to ensure compliance with industry standards. This will make it possible to adjust the operation mode for a specific device. The basic parameters are the initial moisture content of the wood, the thickness of the timber, boards, and species. According to the rules of the procedure, the drying speed is determined. Deviations are not desirable. Forcing the operation by increasing the temperature will lead to changes in the color of the array and deterioration in performance.
A typical mistake is the incorrect laying of lumber. While in the wood drying chamber, the workpieces undergo structural changes and strong internal stresses arise. When laying, it is necessary to forcefully fasten the material. The boards are laid out tightly to the base and spacers between them for free air movement. Distortions and deviations from the flat plane of each workpiece are eliminated. Otherwise, drying wood can hopelessly damage the lumber. High-quality products will no longer be possible.
Forced air supply significantly speeds up the process. Drying technology has been developed by several generations of craftsmen, and the accumulated experience shows that neglect of the rules causes unnecessary costs, increased cost of the final product and a decrease in its quality.
Wood moisture content
To determine the processing mode, it is necessary to check the lumber according to basic indicators. These include species, board thickness and humidity. Drying fresh wood is more difficult. In addition to high humidity, conifers produce resin and a significant shrinkage rate. In such cases, the operation is carried out in two stages with different modes. Pre-drying to 20%, then subsequent drying to the desired value, usually 8-12%. This amount of moisture during the manufacturing process of a product is considered acceptable.
It is impossible to bring the workpiece to lower humidity values, with the exception of special cases of preparing wood with special qualities. An overdried tree begins to absorb moisture from the air, the product swells, changes its geometry until the finished structure is partially or completely destroyed. It is recommended to stop the process when the recommended values are reached. A wood dryer must be equipped with humidity control devices.
Why is drying needed?
When executing construction work and on furniture production V design and estimate documentation The permissible moisture content of wood is indicated. Raw materials are brought to the required condition in drying chambers of various designs. For certain operations in construction, a humidity of 20% is allowed. Furniture is made from 8-10% solid wood. The values are determined taking into account possible changes in structure and geometry during further operation. Workpieces that have not been brought to the required characteristics by drying cannot be used in production.
Wood products are mostly used indoors, where humidity is lower than natural outdoors. Inevitable significant changes sizes and the occurrence of stress in the product due to drying. Cracks that appear and warping worsen appearance and performance characteristics finished product. It is not cost-effective to remove moisture in a natural way on an industrial scale, since the raw materials will have to be procured several years before their use. Only a dryer for boards and other lumber can quickly and efficiently remove excess moisture and make the material suitable for producing high-quality products.
Drying modes
The effectiveness of drying directly depends on the composition of the air, its humidity and temperature. It’s not worth experimenting with time and temperature without experience, as you can ruin the workpiece. The following values of the normal drying mode for a 40-50 mm board in a convective type chamber can serve as a guide:
- Beech, maple, larch. Temperature 60°C. Drying time at humidity > 35% is at least 130 hours, at 20-25% - about 40 hours;
- Oak, ash, walnut. Temperature 50°C. Drying time at humidity > 35% is at least 255 hours, at 20-25% - 95-100 hours;
- Alder, birch. Temperature 60-65°C. Drying time at humidity > 35% is at least 90 hours, at 20-25% - 30-40 hours;
- Pine, cedar, spruce, fir. Temperature 70°C. Drying time at humidity > 35% is about 70 hours, at 20-25% - at least 30 hours.
Pre-drying of wood with excess moisture content of more than 60% is carried out in a forced mode, increasing the temperature by 10-20%. Deciduous ones can be dried at higher temperatures than coniferous ones.
DIY drying chamber
If you decide that you are making the dryer yourself, then you should know the main structural elements, their purpose and installation or construction methods. In this case, only those materials are used that can withstand the upcoming loads. Conventional building materials cannot be used. Drying chambers for lumber consist of the following elements:
- A room equipped with a thermal insulation system;
- Heat sources;
- System of forced air supply to the processed material;
- Equipment for laying workpieces;
- Shipping and loading system;
- Devices and tools for controlling humidity and temperature.
Various devices are used as heat sources. Electric heating elements that consume significant amounts of energy. Gas burners are considered more efficient. Sometimes boiler equipment is installed that has high efficiency indicators. The easiest way to make drying chambers for lumber is the convective type. It is difficult to independently assemble an aerodynamic or microwave structure without certain knowledge and skills.
Selection of premises
Choosing the right place for drying will guarantee the effectiveness of the design. You can use either an existing premises or a building erected specifically for this purpose. It must meet the following conditions:
- Thermal insulation. The temperature difference inside and outside the dryer is significant, and in order to maintain it at the required level, heating devices are turned on. Ideally, walls and insulation should have energy efficiency ratings similar to those of a residential building. Thermal insulation layer is made on the walls, floor, ceiling. In this case, the heating devices are turned on short term during critical temperature drops, and the rest of the time they are switched off, which significantly saves energy consumption;
- Ventilation or dehumidification of air by convection along the internal circuit. Timely removal of moisture will be the key to reducing drying time, so effective ventilation or condensate collection on a cold heat exchanger is necessary in the room. When designing a dryer, this aspect should be emphasized;
- Safety. The electrical circuit, devices and mechanisms are taken from samples intended for operation at high humidity and temperature, for example, from equipment for the construction of saunas and baths. Fire safety requirements, protection of human health and life must become a priority.
The operating principle of the wood camera is not complicated. But it can only be implemented in a suitable room. The costs of erecting and re-equipping the chamber are one-time. If all requirements are met, then in further operation the dryer, with minimal energy and maintenance costs, is able to produce the required volume of dried wood within the stated period with the desired percentage of humidity.
Construction and installation of drying chamber equipment
There are ready-made cameras on sale with excellent performance characteristics, however, their cost may not pay off even over many years with small production volumes. Choice small companies, individual entrepreneurs often have to independently build the required structure. The design of a convective type drying chamber is simple. You can use an existing room or building, which is equipped with the devices, instruments and mechanisms necessary to solve the problem.
Please remember that the connection gas equipment must be carried out by authorized organizations. Electrical diagram designed by a qualified electrician taking into account the use of equipment at elevated temperatures inside the chamber. Devices, cables, fans, lighting sources are marked with markings indicating the appropriate temperature and humidity conditions of operation. The premises belong to the category with increased fire danger. Fire extinguishing systems are provided at the design stage to avoid problems with regulatory authorities. The design capacity is consistent with the resource supply capabilities. In some areas there are restrictions on the supply of gas and electricity.
Equipment
The set of equipment is small, but requires careful selection when purchasing. The design of the drying chamber, in addition to the standard set of heating element, forced air supply systems can be additionally equipped with devices that increase productivity and automation systems. Temperature sensors included in the circuit can turn on or off the heat source in a timely manner, without human intervention. The equipment for drying chambers includes a device for collecting and removing condensate. High temperature is not enough to quickly remove moisture if there is excess moisture in the air. The cold circuit effectively traps water particles on the surface and is recommended to be installed to increase productivity. Improves performance and preheating of incoming air, which does not cool the processed lumber, thereby reducing drying time.
Drying chamber operation
Maintenance of the structure, when it is assembled correctly, does not seem to be a difficult process. Drying chambers are not recommended for storing, even temporarily, any foreign objects or goods. Cleanliness is maintained inside the premises. Regular cleaning is required. Removal of dust, dirt, and sawdust is necessary, since sufficiently powerful air convection inside the chamber will inevitably lead to the ingress of foreign substances onto heat sources, which will reduce their performance, and in the case of using electric or gas heating elements, to the risk of fire. Regular inspection of all structural elements is carried out: thermal insulation, ventilation, heat sources.
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