The invention relates to the woodworking industry, namely to the technology of drying bog oak wood, and can be used, for example, in the manufacture of furniture. To implement the method, at the first stage, billets from bog oak wood are placed in an autoclave and carried out hydrothermal treatment dry saturated steam when heated to a temperature of 120-122 ° C and under a pressure of 1.4-1.5 atm with holding, respectively, for 1-2 hours. At the second stage, the heated workpieces are placed in a sodium chloride solution at a temperature of 20-22 ° C and kept at atmospheric pressure for 1.5-2.5 hours. The blanks extracted from the solution are placed in a convective forest drying chamber and convective drying is carried out to the final moisture content of wood blanks of 7.9-8%. Drying modes are selected depending on the thickness of the workpieces. The invention should shorten the drying time and improve the quality.
The invention relates to the woodworking industry, namely to the technology of drying stained oak wood, and can be used, for example, in the manufacture of furniture.
Technological processes for obtaining high quality dried lumber and bog oak blanks are characterized by complexity, long duration.
There are several approaches to solving this problem. One of them is convective drying of sawn timber by low-temperature modes in batch chambers and includes technological operations of heating, drying, moisture-heat treatment and wood conditioning. The known technology provides for a stepwise change in the parameters of the drying agent depending on the moisture content of the wood ("Guiding technical materials (RTM) on the technology of chamber drying of wood". - Arkhangelsk, 2000).
The known method of drying difficult to dry tree species, including oak, improving the known technology (description for patent RU 2263257, IPC 7 F26B 1/00, F26B 3/04, 19.04.2004, prototype). To accelerate the drying process and eliminate cracking, the known method additionally provides for the formation of a layer of hygroscopic substance on the outer surface of the workpieces, which provides an optimal moisture difference between the outer and inner surfaces of the workpieces in the process of stepwise convective drying. To do this, before convective drying with a four-stage temperature increase, lumber is boiled at atmospheric pressure in a 15-17% sodium chloride solution for 2.5-3.0 hours.
The known method is characterized by a long duration and does not provide high Quality dried blanks. This is due to the fact that the specificity of stained oak wood is not fully taken into account, associated with the presence of teal in vessels that prevent the removal of moisture from the wood, and the achievement of maximum moisture due to a long stay in fresh running water.
In addition, the welding operation in the known method requires additional costs to improve production conditions, in particular, to ventilate production areas.
The task of the invention is to develop an effective technological process drying oak wood.
The technical result from the use of the invention is a reduction in the duration of drying, an increase in the quality of dried workpieces and an improvement in production conditions.
The technical result is achieved by the fact that in the method of drying bog oak wood, which provides for hydrothermal treatment in a sodium chloride solution and convective drying, hydrothermal treatment is carried out in two stages, while at the first stage, heating in an autoclave with dry saturated steam is carried out with exposure for 1-2 h at a temperature of 120-122 ° C and a pressure of 1.4-1.5 atm, and on the second, the heated wood is immersed in a sodium chloride solution at a temperature of 20-22 ° C and kept at atmospheric pressure for 1.5-2.5 hours.
The essence of the technical solution lies in the fact that at the stage of heating wood in an autoclave with dry saturated steam with exposure at a temperature of 120-122 ° C and a pressure of 1.4-1.5 atm, conditions are created for the destruction of teal in the wood of stained oak and during subsequent stages drying conditions are created for the smooth removal of moisture from wood. The exposure time is selected empirically, depending on the size of the blanks and the initial moisture content of the wood within the interval of 1-2 hours, which is optimal for the destruction of teal in the selected mode of autoclaving.
At the second stage, when the heated wood is immersed in a sodium chloride solution at a temperature of 20-22 ° C and atmospheric pressure, due to the temperature difference and external pressure, during the aging process, favorable conditions not only for the formation of a hygroscopic layer on the outer surface of the workpieces, but also for the removal of moisture from the wood. A two-stage hydrothermal treatment of stained oak wood in the selected modes allows to reduce the initial moisture content of blanks before convection drying in comparison with the prototype by 2-3% and significantly reduce the duration of the drying process. Thus, in a stepwise convective drying process, the number of temperature rise steps is reduced by at least one.
Examples of implementation of the method.
Three batches of billets made of stained oak wood in the form of bars measuring 19 × 100 × 500 mm, 32 × 100 × 500 mm and 50 × 100 × 500 mm with an initial moisture content W n \u003d 90% at the first stage of hydrothermal treatment were placed in an autoclave and hydrothermal processing with dry saturated steam, heating them to a temperature of 120-122 ° C and further holding under a pressure of 1.4-1.5 atm, respectively, for 1 hour for the first batch, 1.5 hours for the second and 2 hours for the third ...
From the autoclave, the heated workpieces were placed into a sodium chloride solution with a concentration of 15-17% at a temperature of 20-22 ° C and kept at atmospheric pressure for the first batch for 1.5 hours, the second for 2 hours and the third for 2.5 hours.
The blanks extracted from the solution were placed in a convective timber drying chamber.
Drying of the first batch was carried out at a temperature of 64 ° C. When the billets reached 8% moisture, drying was stopped. Drying time was 18 hours.
Drying of the second and third batches of blanks was carried out with a three-stage increase in the temperature of the drying agent. Drying modes were selected according to the "Guidelines technical materials (RTM) by the technology of chamber drying of wood ", - Arkhangelsk, 2001, carrying out the transition to the next stage of increasing the temperature of the drying agent as the current moisture content of the wood decreases to the value of the transitional relative humidity. The final moisture content of wood blanks in batches was 7.9%. The drying time for the second batch of blanks was 2.5 days, for the third - 4 days.
Dried billets in all batches corresponded to the second quality category.
CLAIM
A method of drying bog oak wood, providing for hydrothermal treatment and convective drying, characterized in that the hydrothermal treatment is carried out in two stages - at the first stage, heating in an autoclave with dry saturated steam with exposure for 1-2 hours at a temperature of 120-122 ° C and pressure 1.4-1.5 atm, on the second - heated wood is immersed in a sodium chloride solution at a temperature of 20-22 ° C and kept at atmospheric pressure for 1.5-2.5 hours.
Oak - very popular materialwhich is widely used:
- Construction.
- Finishing work.
- Furniture creation.
- Making art objects and souvenirs.
Naturally, not just cut and sawn wood is used, but processed and high-quality dried material. This is a prerequisite in order to avoid cracking, changes in the shape and dimensions of the product in the future. An oak used in construction or furniture must have certain physical and mechanical properties.
Therefore, when the sawing is completed, the question arises: “ How to dry oak properly". We will give the answer to it in this article.
Features of oak wood: what should be the result of drying
Oak lumber is quite capricious, it is difficult to dry naturally. It is not enough just to leave the stack under a canopy or in the open sun in order to get the desired result after a certain time.
Before how to dry oak planks
, you need to understand the features of the material:
- Oak wood is subject to dryness. This means that when the moisture level falls below the critical mark, internal and external cracks can form.
- The most difficult thing to dry is freshly sawn oak, the moisture content of which exceeds 25%.
- Temperatures above 55 degrees are unacceptable initial stages drying. This leads to the collapse of the wood capillaries, that is, to the appearance of multiple internal cracks.
- It is not recommended to send freshly sawn material with a moisture content above 40% for drying.
- Proper drying of oak requires maintaining a certain level of temperature and humidity.
Features of drying oak wood are such that to obtain quality material without defects with a certain percentage of moisture, it is necessary to draw up a preliminary plan for this procedure, use special means.
There are several tasks for drying oak:
- Shrinkage with prevention of changes in linear dimensions. Here the humidity is reduced by up to 30%.
- Drying to transport moisture content of 20-22%.
- Full volume dryer for direct use. The humidity level should be 6-12%.
Oak drying methods: chamber and tubeless methods
From the foregoing, it is obvious that obtaining wood from a freshly cut oak that meets all the necessary parameters is a laborious and time-consuming process.
There are many ways to reduce the moisture content of planks, logs and beams, but they can all be divided into two broad categories:
- Tubeless (atmospheric) drying.
- Chamber drying.
Atmospheric drying is ideally the most affordable and in a natural way lowering the humidity level. The technique has been used in sawmills and woodworking industries for centuries. It is believed that naturally dried wood is of the highest quality, it can be used for decades without changing its original qualities. But the method has one significant drawback - the length of time.
Since modern life is very dynamic, buyers are interested in the fastest possible acquisition of material. Logging enterprises, in turn, prefer to sell wood in the shortest possible time. Therefore in XIX-XX centuries many techniques have been invented using electrical energy. Chamber drying is carried out in convection chambers, the condensation method and vacuum drying are also used. 
All work is carried out in an industrial environment, as a rule, are divided into the following stages:
- Warming up.
- Drying directly.
- Cooling, obtaining a given humidity threshold.
Chamber drying is similar to multiply accelerated atmospheric drying, the required result is achieved many times faster. But the disadvantage is the high cost of the procedure. It is necessary to use expensive equipment, most often this is possible only in an industrial environment.
Fortunately, infrared dryers have appeared not so long ago, which make it possible to shorten the time of atmospheric drying, to obtain the required result in terms comparable to chamber processing. At the same time, all features of drying oak wood, the material does not undergo aggressive effects that destroy the structure. At the end of the process, the humidity reaches the required level.
Infrared drying of oak: the advantages of a modern way
Competent drying of oak now it has become possible even at home. Infrared dryers, manufactured under the FlexiHIT brand, have a cassette form factor, are easily positioned inside stacks, and can also be used for drying a small piece of material. In this case, the volume of wood does not matter, it is enough to use required amount dryers and position them correctly. The result is achieved in 3-7 days.
The properties of infrared-dried oak are similar to those of atmospheric-dried wood:
- The material has a given moisture content.
- Fibers do not warp, cracks and stressed areas do not form.
- Appearance matches appearance naturally dried oak.
It is noteworthy that everyone can use IR dryers; you do not need to have special skills to get the result. The equipment operates from conventional electrical network, while consuming very little. To dry one cubic meter of wood, no more than 200-400 kW is required.
To check the humidity, it is enough to use a moisture meter, when the required indicator is reached, the infrared dryers are turned off. The oak can be used immediately for its intended purpose.
Oak wood is quite capricious when drying, in order to obtain an optimal result in the shortest possible time, it is better to prefer tubeless drying in combination with IR dryers.
Dear Sirs,We ask you, if possible, to send us recommendations on drying oak (what features should you pay attention to when drying this type of wood).
Thanks in advance,
Respectfully,
Natalia Titova
The technology of drying oak wood does not fundamentally differ from the technology of drying coniferous and soft-leaved species. Distinctive feature is that when moving from one stage of drying to another, it is necessary to equalize the moisture content of individual boards in the stack, taking into account that drying is carried out on the wettest material. The process of drying wood in a drying chamber is divided into several stages: I. Initial heating of wood. II. Drying the wood itself. III. Moisture heat treatment. IV. Conditioning. Drying always begins with heating the wood, regardless of the initial moisture content of the sawn timber. During warming up, water (steam) is fed into the chamber through the humidifying pipes with the heat exchangers turned on, the fans running and the supply and exhaust ducts closed. The moisture content of the drying agent is kept close to saturation. After warming up, the moisture content of the lumber is additionally measured, by which it is judged from which stage to start the actual drying. It should be borne in mind that drying is carried out on the wettest material. It is forbidden to switch to another drying stage until the moisture content of all boards has reached the transition moisture content. Wood drying itself is divided into steps. IN initial stage process, it is necessary to maintain a small value of the moisture difference in thickness, which is achieved by using a drying agent with a high degree of saturation. As the wood dries, it is advisable to lower the degree of saturation in order to bring the material to the specified final moisture content. The transition from stage to stage in the presence of a moisture meter is judged by its readings. The temperature of the medium should be increased by the end of drying. With a decrease in humidity, an increase in temperature will not cause a decrease in strength, but at the same time will significantly speed up the process. The actual drying ends when the final humidity is reached according to the data of all sensors. Then they move on to the stages of moisture-heat treatment and conditioning treatment. Moisture-heat treatment is necessary to remove or reduce the "residual" internal stresses that arise in the wood during drying. To create an environment high humidity The following is supplied to the drying space of the chamber: steam or sprayed water when the heaters are on, the fans are running and the supply and exhaust ducts are closed. The moisture content of the drying agent is kept close to saturation. When drying hardwoods, conditioning is required. Conditioning is carried out to equalize the moisture content of the wood by the volume of the stack and the thickness of the lumber. In the drying chamber, with the help of heaters and humidifying devices, the environment is maintained in such a state that under-dried assortments dry up and overdried ones are moistened. After equalizing the final moisture content of the sawn timber, the stacks must be cooled at closed door and open supply and exhaust ducts. In summer it is allowed to turn on the fans.
Bog oak is one of the most valuable types of wood. It is used for the manufacture of art and decorative items... But the extraction and processing of bog oak is a long and costly process. Therefore, the price of the material is high. Dry stained wood traditional ways problematic due to the peculiarities of its structure. We will tell you in more detail how to dry bog oak in compliance with all technologies.
Bog oak is obtained from river banks. Wood can lie in water for over a hundred years, and then it is taken out and processed. Products made of stained material have a pleasant dark color and are durable. In terms of density, the moraine material is compared to iron, so it is difficult even to saw it. The moisture content of the freshly mined product can reach 117%. Compared with natural humidity in 50–65% the figure is impressive.
The material is obtained in three ways:
- At bottom - deep work - the most costly and laborious.
- When developing peat bogs, it is less labor intensive.
- Manufacturing in specialized workshops is the simplest, but multi-stage method.
Wet weight oak wood - 1500 kg / 1 cubic meter Therefore, immediately after extraction from water, the material is cleaned of silt and sand and cut into small pieces. Otherwise, transportation becomes more difficult.
The tree is afraid of sharp contact with hot air and direct sunlight, so drying is performed in a gentle mode. Verified grandfather's way how to dry bog oak - place small blocks in the grain in the fall and leave until spring. Natural drying is also allowed, but it should be carried out in a room with good ventilation and constant humidity and temperature. Dry the material in short time became possible only in the last 10 years, with the advent of new technical means.
The following methods are used to dry bog oak in a short time:
- Vacuum chamber.
- Pulse.
- Adsorption.
- Infrared.
But when dried in chambers, the moraine material becomes discolored and becomes not so dark. Therefore, many people criticize unnatural drying methods. But with natural drying, the areas where the sun came in also brighten. Chamber drying of bog oak saves time, and if it is carried out in compliance with the technology, then cracks will not appear and the product will not be subject to internal stress.
When drying in a chamber to a different moisture content, slight changes in geometric shapes are allowed. But if you pre-process the product chemical compositionthen changes decrease. More details are shown in the table below:
| Moisture indicator | Changes in geometric shapes,% | |
|---|---|---|
| Chemically treated wood | Untreated | |
| 50% | 3,5 | 7,2 |
| 25% | 4,8 | 10,7 |
| 15% | 6,3 | 12,6 |
A penetrating antiseptic solution is used as a chemical treatment. The product is soaked in it for 2-3 hours. And also the temperature regime in the chamber and air humidity affect the shrinkage. Maximum allowable temperature 50 degrees - shrinkage is maximum. Smaller changes are acceptable when temperature conditions 25 degrees.
The main stages of processing
How oak is dried different ways we'll tell you more. The technology is followed step by step and it is unacceptable to skip one of the stages. Otherwise, the wood will crack and become brittle.
Vacuum impact
Vacuum drying oak is carried out in special chambers, where, under the influence of low atmospheric pressure, the excess moisture... It takes place in several stages:
- Bog oak is soaked in an antiseptic solution for 2-3 hours. Sanezh will do.
- The product is placed in a drying chamber, where it is kept at a temperature of 25 degrees and a humidity of 50% for 5 to 10 days. Temperature and humidity must be constant.
- The oak is placed in a sealed chamber, where it is treated with an antiseptic solution under the influence of vacuum.
- Dries at a temperature of 35 degrees and a humidity of no more than 25% for 10 days.
The method has advantages:
- Oak wood dries to a predetermined temperature.
- The color change is only 2-7%.
- Full readiness within 4-5 weeks.
Of the minuses stand out high costs on electricity and the complexity of the process. If you do not keep track of humidity or temperature, the wood will crack and become unusable.
Impulse method
The impulse method of drying bog oak in Russia is rarely used due to high costs... But it is considered effective and the material dries evenly.
It is carried out in the following stages:
- TO wooden blank conductors are connected on both sides.
- The second ends of the conductors are connected to a special electrical appliance that will supply current.
- Under the influence of electrical impulses, the workpiece gradually dries out to the required moisture content.
If you have the skills and knowledge, then such a device can be assembled with your own hands and used for work.
Adsorption method
The adsorption method resembles the old grandfather's and is available to everyone at home. For drying, a small piece of oak is placed in a material that absorbs moisture as much as possible. Craftsmen use special mineral granules. But newsprint will do.
Drying is carried out in the following stages:
- Small workpieces are soaked for 3-4 hours in a container with an antiseptic solution. But do not use solutions with whitening effects, otherwise the black color of the valuable breed will disappear.
- The workpiece is wrapped in several layers of paper and placed in a well-ventilated and dry place.
- Every day the product is unfolded and folded into new newspaper sheets.
Drying is carried out for 1–2 months. The wood will not crack and will retain its noble color.
Infrared plates
The infrared light heats the wood evenly and dries gently. The workpiece is not heated and there is no internal deformation. The method is available at enterprises and at home. It is enough to purchase several infrared heating elements and place them on a frame made of timber or metal.
Drying is carried out in the following stages:
- The workpiece is soaked in an antiseptic solution for 3-4 hours.
- Put on flat surface under infrared heaters.
- The workpieces should be turned over once an hour so that the heat is evenly distributed.
Humidity is checked using a hand-held moisture meter. When the product dries up, it is allowed to rest for 3-4 days in a dark and cool place with a humidity of 15-25%. Then they are used for their intended purpose.
Among the advantages of drying under infrared plates stand out:
- The wood does not deform or crack.
- Does not lose its black color.
- Drying occurs evenly over the entire depth and length.
- Electricity costs are minimal.
The method has no disadvantages, but due to its novelty it is little trusted. The video below details one of the available ways drying hard wood:
How to dry bog oak properly is the secret of wood carvers. It was passed from father to son and was carefully preserved. But with the advent of new technologies, it is not difficult to dry stained wood at home. The main thing is to follow the technology and adhere to our instructions.
The invention relates to the woodworking industry, namely to the technology of drying bog oak wood, and can be used, for example, in the manufacture of furniture. To implement the method, at the first stage, billets of bog oak wood are placed in an autoclave and hydrothermal treatment is carried out with dry saturated steam when heated to a temperature of 120-122 ° C and under a pressure of 1.4-1.5 atm with exposure, respectively, for 1- 2 hours. At the second stage, the heated workpieces are placed in a sodium chloride solution at a temperature of 20-22 ° C and kept at atmospheric pressure for 1.5-2.5 hours. The workpieces extracted from the solution are placed in a convective timber drying chamber and convective drying is carried out to the final moisture content of the timber of the workpieces of 7.9-8%. Drying modes are selected depending on the thickness of the workpieces. The invention should shorten the drying time and improve the quality.
The invention relates to the woodworking industry, namely to the technology of drying stained oak wood, and can be used, for example, in the manufacture of furniture.
Technological processes for obtaining high-quality dried lumber and billets from bog oak are characterized by complexity and long duration.
There are several approaches to solving this problem. One of them is convective drying of sawn timber by low-temperature modes in batch chambers and includes technological operations of heating, drying, moisture-heat treatment and wood conditioning. The known technology provides for a stepwise change in the parameters of the drying agent depending on the moisture content of the wood ("Guiding technical materials (RTM) on the technology of chamber drying of wood". - Arkhangelsk, 2000).
There is a known method of drying hard-to-dry wood species, including oak, which improves the known technology (description for patent RU 2263257, IPC 7 F26B 1/00, F26B 3/04, 19.04.2004, prototype). To accelerate the drying process and eliminate cracking, the known method additionally provides for the formation of a layer of hygroscopic substance on the outer surface of the workpieces, which provides an optimal moisture difference between the outer and inner surfaces of the workpieces in the process of stepwise convective drying. To do this, before convective drying with a four-stage temperature increase, lumber is boiled at atmospheric pressure in a 15-17% sodium chloride solution for 2.5-3.0 hours.
The known method is characterized by a long duration and does not provide high quality dried blanks. This is due to the fact that the specificity of stained oak wood is not fully taken into account, associated with the presence of teal in the vessels that prevent the removal of moisture from the wood, and the achievement of maximum humidity due to a long stay in fresh running water.
In addition, the welding operation in the known method requires additional costs to improve production conditions, in particular, to ventilate production areas.
The objective of the invention is to develop an effective technological process for drying bog oak wood.
The technical result from the use of the invention is a reduction in the duration of drying, an increase in the quality of dried workpieces and an improvement in production conditions.
The technical result is achieved by the fact that in the method of drying bog oak wood, which provides for hydrothermal treatment in a sodium chloride solution and convective drying, hydrothermal treatment is carried out in two stages, while at the first stage, heating in an autoclave with dry saturated steam is carried out with exposure for 1-2 h at a temperature of 120-122 ° C and a pressure of 1.4-1.5 atm, and on the second, the heated wood is immersed in a sodium chloride solution at a temperature of 20-22 ° C and kept at atmospheric pressure for 1.5-2.5 hours.
The essence of the technical solution lies in the fact that at the stage of heating wood in an autoclave with dry saturated steam with exposure at a temperature of 120-122 ° C and a pressure of 1.4-1.5 atm, conditions are created for the destruction of teal in the wood of stained oak and during subsequent stages drying conditions are created for the smooth removal of moisture from wood. The exposure time is selected empirically, depending on the size of the blanks and the initial moisture content of the wood within the interval of 1-2 hours, which is optimal for the destruction of teal in the selected mode of autoclaving.
At the second stage, when the heated wood is immersed in a sodium chloride solution at a temperature of 20-22 ° C and atmospheric pressure due to the difference in temperatures and external pressure during the holding process, favorable conditions are created not only for the formation of a hygroscopic layer on the outer surface of the workpieces, but also for removing moisture from wood. A two-stage hydrothermal treatment of stained oak wood in the selected modes allows to reduce the initial moisture content of blanks before convection drying in comparison with the prototype by 2-3% and significantly reduce the duration of the drying process. Thus, in a stepwise convective drying process, the number of temperature rise steps is reduced by at least one.
Examples of implementation of the method.
Three batches of billets made of stained oak wood in the form of bars measuring 19 × 100 × 500 mm, 32 × 100 × 500 mm and 50 × 100 × 500 mm with an initial moisture content W n \u003d 90% at the first stage of hydrothermal treatment were placed in an autoclave and hydrothermal processing with dry saturated steam, heating them to a temperature of 120-122 ° C and further holding under a pressure of 1.4-1.5 atm, respectively, for 1 hour for the first batch, 1.5 hours for the second and 2 hours for the third ...
From the autoclave, the heated workpieces were placed into a sodium chloride solution with a concentration of 15-17% at a temperature of 20-22 ° C and kept at atmospheric pressure for the first batch for 1.5 hours, the second for 2 hours and the third for 2.5 hours.
The blanks extracted from the solution were placed in a convective timber drying chamber.
Drying of the first batch was carried out at a temperature of 64 ° C. When the billets reached 8% moisture, drying was stopped. Drying time was 18 hours.
Drying of the second and third batches of blanks was carried out with a three-stage increase in the temperature of the drying agent. Drying modes were selected according to the "Guiding technical materials (RTM) on the technology of chamber drying of wood", - Arkhangelsk, 2001, carrying out the transition to the next stage of increasing the temperature of the drying agent as the current moisture content of the wood decreases to the value of transitional relative humidity. The final moisture content of wood blanks in batches was 7.9%. The drying time for the second batch of blanks was 2.5 days, for the third - 4 days.
Dried billets in all batches corresponded to the second quality category.
A method of drying bog oak wood, providing for hydrothermal treatment and convective drying, characterized in that the hydrothermal treatment is carried out in two stages - at the first stage, heating in an autoclave with dry saturated steam with exposure for 1-2 hours at a temperature of 120-122 ° C and pressure 1.4-1.5 atm, on the second - heated wood is immersed in a sodium chloride solution at a temperature of 20-22 ° C and kept at atmospheric pressure for 1.5-2.5 hours.
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