Vacuum Pump in Wood Drying

The amount of moisture in wood varies with tree species, tree age, and cutting season. In order to ensure the quality of wood and wood products and extend the service life, appropriate measures must be taken to reduce the moisture (moisture content) in the wood to a certain level. To reduce the moisture content of the wood, the temperature of the wood must be increased, so that the moisture in the wood evaporates and moves outwards. In the air with a certain flow rate, the moisture leaves the wood quickly to achieve the purpose of drying.

Application of Vacuum Pump in Wood Drying

In order to ensure the quality of the wood to be dried, the humidity of the drying medium (such as the currently commonly used humid air) must also be controlled to obtain the effect of drying the wood quickly and with high quality. This process is called wood drying. Wood drying is an important link to ensure and improve wood quality, reduce wood loss and other losses, and increase wood utilization. At the same time, wood drying is also the most energy-consuming process in the production of wood products, accounting for about 60% to 70% of the total energy consumption of enterprises in my country. Therefore, the overall goal of wood drying is to explore ways to increase the drying speed under the premise of ensuring the drying quality, so as to reduce energy consumption and drying costs.

The common artificial wood drying methods that have been industrialized so far include conventional drying, high-temperature drying, dehumidification drying, solar drying, vacuum drying, high-frequency drying, microwave drying, and flue gas drying.

In a sealed drying room (mostly metal cylinders), the wood is heated and the pressure of the indoor medium is reduced, so that the wood is dehydrated and dried under the condition of below atmospheric pressure (absolute pressure of 13 to 4 kPa). Also known as vacuum drying.

The wood vacuum drying method is characterized by a fast drying speed, which can greatly shorten the drying time and save energy for hardwood, especially thick boards, but for coniferous wood, the above effect is not obvious. Furniture and handicraft materials use this method to dry more.

Vacuum Pump in Wood Drying

The principle of wood vacuum drying:

When the pressure of the medium in the drying chamber decreases, the boiling point of the water decreases, and a large vapor pressure difference is formed inside and outside the wood, which makes the moisture inside the wood move to the surface quickly and quickly vaporize under the low boiling point. Under vacuum conditions, a lower drying temperature can be used to obtain a rapid drying effect. The better the air permeability of wood, the higher the degree of vacuum, the more obvious the effect.


According to the operation process, it is divided into continuous vacuum method and intermittent vacuum method.

①Continuous vacuum method: The drying operation is continuously heated under vacuum conditions. Generally, a heating plate is used to heat the wood in a conductive manner. Part of the water evaporated from the wood is condensed by the indoor cooler and discharged, and part is pumped out by the vacuum pump. The wood is always in the process Dry gradually at the required pressure and temperature.

②Intermittent vacuum method: The drying operation is divided into two alternate stages: normal pressure heating and vacuum dehydration. Generally, hot air (or steam) is used as the medium to heat the wood to a certain temperature by convection heating. After the heating is stopped, vacuum is drawn to dehydrate the wood. This is repeated until the moisture content of the wood reaches the requirement. Compared with the continuous vacuum method, the batch vacuum method has a slower drying speed and higher energy consumption. But its equipment is relatively simple. This method can dry wood of various specifications and shapes, and the drying quality is better.

wood vacuum drying

The vacuum required for wood vacuum drying is about 100mbar. The 2BV series single-stage water ring vacuum pump has become the first choice in this field due to its small size, good performance, and low energy consumption. The 2BV series vacuum pump produced by Kanter Vacuum covers 27 ~ 500 m3/h, with energy consumption between 0.81 ~ 15 kw. It is widely used in the wood vacuum drying industry. Below is a photo of the 2BV just shipped this month and shipped to Europe. , Photos for reference.

2BV series vacuum pump

Edited by: Emily Fu; Copyright: EVP Vacuum Solutions

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