Vacuum dryer is another modern invention that allows you to quickly and efficiently dry wood. But the scope of its application is not as wide as that of an infrared dryer. Let us consider in more detail the properties of both devices.
One of the properties of wood is hygroscopicity, the ability to absorb moisture. A freshly felled tree is saturated with moisture, and raw wood is unsuitable for making furniture and creating building structures. It is highly susceptible to biological damage, warping and cracking.
For further use, freshly harvested lumber must be dried. Natural drying is a long process, so equipment was invented to speed up the drying of wood.
Different dryers differ from each other in the principle of operation and performance. You can choose the optimal equipment for specific operating conditions by comparing them. In this article, we will focus on infrared and vacuum dryers, figure out how they work, how much lumber and how long they can dry, how much energy is consumed, and what is their market price.
Principle of operation
IR dryers produce infrared rays, which, by heating the wood, dry it to the required moisture level. These rays are of the same nature as visible light. They pass freely through the air. Nitrogen and oxygen molecules do not absorb infrared radiation, so all the energy is directed to warming the wood, not the air.
This method of drying does not involve the use of a coolant, which eliminates the need to monitor its performance and equip equipment with complex automation.
Infra-red heat acts gently on the wood, without causing strong internal stresses and warping.
Vacuum dryers The market offers two main types: with cyclic and contact heating of the material. The principle of operation of the former is based on convective heating of wood and vacuum removal of excess moisture. The operating temperature usually does not exceed 65°C, but a pressure of 0.09 MPa causes moisture to boil already at 45.5°C. Vacuum allows lumber to dry without exposure to high temperatures, so that the tree does not crack. During drying, when the temperature reaches 65°C, the boiler switches off automatically. The surface of the wood begins to cool, and moisture from the inside flows to drier areas. Over the entire drying period, shutdown and restart occurs many times, while moisture is drawn out evenly.
In contact heated dryers, heat is transferred to the material by means of thermoset plates which are stacked. The plates are heated either by water or electricity.
Appearance
infrared dryer- this is a set of thin thermoactive cassettes that are stacked in a pile of lumber in a certain sequence and connected to a power source. The stack prepared for drying is covered with a material with a reflective layer so that the condensate drains outside the stack. The drying process is controlled by a temperature controller responsible for maintaining the set temperature. The equipment is compact and easy to use, if necessary, can be easily transported from place to place in the trunk of a car 
vacuum dryer is a sealed chamber made of stainless steel, made in the form of a cylinder or parallelepiped. The chamber of the first type is tightly closed with a door, the second one is covered with a rubber membrane in a metal frame.
In dryers with contact heating, the boards are laid inside the chamber in layers, alternating with heating plates. When hot water is used as a heating agent, its circulation in the plates is provided by a water pump. The water is heated by a boiler, and the vacuum is created by a liquid vacuum pump.
In cylindrical chambers of large volume, material is loaded along a rail track, which is mounted inside and outside.
Size and weight
Convenience infrared dryers are their small size and weight. One thermoactive cassette has a size of 1230x650x1.5 mm, that is, it is a thin plate of a small area. The weight of the cassette is 5.7 kg. A standard set for drying 1 m³ of lumber includes 12 cassettes with a total weight of 69 kg. With the crate, control panel and cabling, the weight of the equipment does not exceed 130 kg. Its transportation does not require the use of special equipment. 
vacuum the press dryer, even with a small load volume, has a significantly larger size and weight. Thus, a parallelepiped-shaped unit with a loading volume of 4 m³ has dimensions of 4800x1700x2005 mm and weighs 2300 kg without aluminum plates. The size of the heating plate is 4000×1400 mm. To transport such equipment, a rail or road container is required.
Autonomy of work
IR dryer works completely offline. By installing and connecting the equipment correctly, you will not have to perform additional control of operating parameters. You only need to set the drying mode, based on the quality of the source material, and in the future, the thermostat will monitor the maintenance of the set temperature.
The drying process in vacuum chamber is also automated, but in this case more complex automation is used, since it is necessary to monitor the parameters of the coolant (if any) and pressure. In some types of dryers, the process can be carried out manually. In most models, an alarm condition indication is provided, which is activated when the temperature is exceeded, the degree of vacuum decreases, the coolant parameters change, etc.
Drying time
The drying time depends on the wood used and its initial moisture level. The process of drying a pine board to a moisture content of 8% using infrared equipment can last from 3 to 7 days. The thinner the boards, the faster they dry.
In different types vacuum dryers the time indicators are slightly different, but on average, the drying time of a pine board with an initial moisture content of 50% to a final moisture content of 8% lasts 16-18 hours.
Loading volume
IR cassettes can be used to dry any amount of lumber.
Vacuum chambers are offered with different loading volumes: from 4 to 20 m³.
Source of power
infrared cassettes are connected through the control panel to the 220 V network, the voltage of 380 V is also suitable.
Vacuum chambers Requires a 380V power supply.
Power and electricity consumption
Max Power infrared dryer- 3.3 kW/m³. During the drying time of 1 m³ of lumber, from 200 to 400 kWh of electricity is consumed.
Average power consumption vacuum chambers is 15-37 kW. Unfortunately, cameras with truly fantastic energy costs are often found on the market - from 50 kW / m³.
Price
Price is a weighty argument when buying equipment.
Prices on IR dryers FlexiHIT is very affordable:
- a set for drying 1 m³ of a three-meter board - 59,288 rubles;
- a set for drying 1 m³ of a four-meter board - 69,329 rubles;
- set for drying 1 m³ of a six-meter board - 70,007 rubles.
Prices on vacuum chambers domestic production fluctuate between 500 thousand-1.5 million rubles, imported equipment costs 3-4 times more expensive.
conclusions
IR dryers easy to use, can be used in production and at home, suitable for drying any amount of lumber and have a reasonable price.
in vacuum chambers wood dries quickly and evenly, does not deform and even levels out, its color remains unchanged. But due to the high cost and high energy consumption, it is advisable to use them mainly for drying expensive wood species.
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