Novosibirsk State Technical University (NSTU) has proposed a method that reduces energy consumption for the process of removing moisture from wood and provides uniform heating to prevent cracking and warping of the material.
When the pores of wood are filled with water and air, it is a wet dispersed material that can be dehydrated in several ways: drying in special chambers, vacuum, infrared and microwave drying. Moisture is removed by evaporation from the surface of the "water–air" interface. In this case, the main energy is spent on heating the material and on evaporation of moisture inside the wood. There is also convection drying, when moisture evaporates under the influence of circulating air, but this is a rather lengthy process, says Evgeny Porsev, Professor of the Department of Electrical Engineering at NSTU-NETI, Doctor of Technical Sciences.
NSTU-NETI scientists proposed dewatering wood using electroosmosis, that is, by forcing moisture inside the wood under the influence of an external electric field.
"Needle electrodes are installed in the stack of wood, which are energized. Under the influence of an electric field, moisture inside the capillaries of the tree begins to move from the anode to the cathode. The electric field, in fact, pushes moisture to the surface, where it is removed by convection — natural or artificial. The process is controllable due to the fact that the potential difference can be changed. The higher the voltage, the more intense the dewatering process is," said Evgeny Porsev.
Since moisture is removed using an electric field, it is not necessary to spend a large amount of energy on heating the entire volume of wood to high temperatures, explains the scientist. Electroosmotic dewatering ensures uniform heating of the wood due to internal heat generation that occurs when an electric current passes through the wet material. Eliminating the temperature gradient allows you to preserve the natural elasticity of wood fibers, prevent the formation of cracks and warping, which is especially important for valuable wood species.
NSTU-NETI scientists conducted experiments to determine the energy characteristics of the electroosmotic dewatering of wood. The experimental setup consists of a power source and electrodes that were connected to a stack of wood products stacked on dielectric gaskets. The installation also provided devices for measuring electricity consumption and fixing wood moisture.
Based on the results of the experiments, it was concluded that the resulting drying rate during electroosmotic dewatering of wood exceeds the drying rate in traditional technologies by 60-100%. This allows you to significantly save energy on removing moisture.