The structure, function and working principle of wood drying kiln

When trees are felled and brought to the lumber mill, the first step is usually to debark and sort the logs by species, size or end use. For example, logs for making wood flooring are then sawn into logs of the required size. These are often trimmed or pruned to length before drying.

Drying can be done by air or kilns, which use circulating heated air to remove excess moisture from the wood more quickly. Each charge (or kiln load) is sorted by species and size to optimize the process and ensure that the final moisture content level is uniform throughout the charge. After the wood has reached the correct moisture content for that species, it is fed into a planer and planed to the final size, sorted, graded and shipped out. For wood flooring or other specific end products, the wood is often shipped to a manufacturer for further planing, processing and finishing. Mills and manufacturers alike invest time, money and training into their drying processes in order to provide their customers with the best grade product with the correct moisture content.

What is wood drying kiln?

Wood drying kiln is a large drying equipment used in wood industry production, and is widely used in wood drying and other production. The kiln reaction temperature is high during the production process of wood drying kiln, so the collection and monitoring and control of process parameters such as kiln temperature is an important link to ensure roasting quality.

Features of wood drying kiln

1. Low energy consumption, high thermal efficiency, and low power consumption.

2. Low investment, using wood processing residues as fuel, low drying cost, only 1/3 of the cost of steam drying.

3. Convenient humidity adjustment, good heat and humidity treatment effect, uniform air circulation, and good wood drying quality.

4. Simple operation and easy maintenance.

5. Compact structure, light weight, movable, independent and modular, easy to install and debug.

Structure of wood drying kiln

The wood drying kiln is mainly composed of the drying furnace body, drying room, hot air steam delivery pipeline, recovery pipeline, gate valve and temperature and humidity instrument, etc. The RHM drying furnace body is mainly composed of furnace door and furnace, heat energy exchange system, steam generation device, combustion support device, ash cleaning port, fan, chimney and other parts.

The function of wood drying kiln

1.Improve wood quality

Reduce cracking and deformation: If the moisture content of wood is uneven during the drying process, defects such as cracking and deformation are prone to occur. The wood drying kiln can accurately control the drying process of wood, so that the moisture content of each part of the wood decreases evenly, thereby reducing the occurrence of cracking and deformation.
Enhance wood strength: Properly dried wood has a tighter bond between its fibers and a correspondingly higher strength. This makes the wood stronger and more durable during use.
Improve the appearance of wood: The surface of the dried wood is smoother and the color is more uniform, which improves the beauty of the wood and increases its market value.

2.Increase the stability of wood

The moisture content of wood will change with changes in ambient humidity. If the moisture content of wood is too high, it is easy to absorb moisture during use, resulting in dimensional changes and deformation. Drying the wood to a suitable moisture content through a wood drying kiln can keep the wood in a relatively stable size and shape under different environmental conditions and improve its performance.

3.Extend the service life of wood

Undried wood is susceptible to decay fungi and insects, which reduces the service life of wood. Wood drying kilns can reduce the moisture in wood to a certain extent, inhibit the growth and reproduction of decay fungi and insects, and extend the storage time and service life of wood.

4.Improve wood processing efficiency

The dried wood has moderate hardness and is easy to process and cut, which can reduce energy consumption and tool wear during processing. At the same time, the dried wood has stable dimensions, which can better ensure accuracy and quality in subsequent processing and assembly processes, and improve production efficiency.

5.Save energy and resources

The rational use of wood drying kilns can improve energy utilization efficiency and reduce energy waste. By precisely controlling the drying process, overdrying can be avoided, thereby saving wood resources. In addition, some advanced wood drying kilns also use technologies such as waste heat recovery to further reduce energy consumption.

In short, as an indispensable equipment in the wood processing industry, the wood drying kiln is based on the principle of heat transfer and water evaporation. By precisely controlling the drying process, it can effectively improve wood quality, increase wood stability, extend wood service life, improve wood processing efficiency, and save energy and resources. With the continuous advancement of science and technology, the technology of wood drying kilns is also constantly developing and improving. In the future, it will be more intelligent, efficient and environmentally friendly, providing strong support for the sustainable development of the wood processing industry.

Working principle of wood drying kiln

The wood drying kiln plays a vital role in the wood processing industry. It effectively removes moisture from the wood to the right moisture content, thereby improving the quality and stability of the wood.

Principle of wood drying kiln

The principle of wood drying kiln is mainly based on heat transfer and water evaporation. By heating the air, making it circulate in the kiln, heat exchange with the wood, so that the water in the wood evaporates and is discharged out of the kiln.

1.Heat transfer method

Convection heat transfer: The hot air circulates in the kiln, directly contacts the surface of the wood, and transfers heat to the wood. This method is more efficient and can quickly increase the surface temperature of the wood.
Conduction heat transfer: After the water inside the wood is heated, the heat is transferred from the surface of the wood to the inside through the conduction effect between molecules. Conduction heat transfer is relatively slow, but it plays an important role in uniformly drying wood.
Radiation heat transfer: In some drying kilns, radiation heating methods such as infrared radiation are also used. Radiation energy directly penetrates the surface of the wood and penetrates deep into the wood, causing the internal water to evaporate by heat.

2.Water evaporation and discharge

When the wood is heated to a certain temperature, the water in it begins to evaporate. The water diffuses from the inside of the wood to the surface of the wood in the form of water vapor, and then is carried away by the hot air. In order to ensure that moisture can be discharged smoothly out of the kiln, the drying kiln is usually equipped with a ventilation system, which exhausts the humid air through the fan and introduces fresh dry air at the same time.