Schedules of Larch Sawn Timber Drying in Intermittent Kiln

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UDС

674.047

DOI:

10.17238/issn0536-1036.2018.5.151

Abstract

The article provides development of drying schedules of larch sawn timber based on con-cepts fundamentally different from those incorporated in present-day schedules. It is assumed that wood moisture is redistributed being a part of extractives water solution during drying. The pressure difference is a factor of mass transfer. Thus, it is possible to consider drying as a type of barmembrane transfer. At the initial stage of drying only a polymer film formed on the board surface from extractives provides resistance to moisture transfer. The purpose of the research is laying out the fundamental principles of formation of drying schedules of larch sawn timber. It is assumed that thermal energy brought to the drying lumber is expended for creating conditions of excessive pressure generation. This effect is explained by the formation of a steam gas mixture as a result of the chemical and physical activity of larch wood. Therefore, the wood temperature is a peculiar parameter of physical and chemical processes group. As a result mixture chemical composition and volume are established. The temperature level also determines the permeability of the intercellular membrane system. The contents of the larch wood cells lumen are derived to the board surface as a result of the mass transfer: moisture in liquid and gaseous state, water-soluble sub-stances (arabinogalactan) and a gas mixture which consists of sulfur-containing compounds, water, alcohols, phenols, carboxylic acids. There is a significant amount of water-soluble substances, mainly consist of arabinogalactan, in the liquid component. This substance has polyelectrolyte properties. All these substances are capable to change their physical state depending on external conditions. The next stage of removing the moisture from larch wood is mass exchange. It should be considered as a process of substances separation into three main groups. The first is a steam gas mixture and a part of moisture. It evaporates. The se-cond is drained on the floor of the drying chamber. The third includes substances (arabino-galactan) accumulated on the surface. Experimental drying showed that the presence of the third group of substances in the form of polymer film on the board surface has a significant effect on the moisture removal from larch wood.

Authors

Sh.G. Zaripov, Doctor of Engineering Sciences, Professor

Affiliation

The Lesosibirsk branch of the Reshetnev Siberian State University of Science and Technology, ul. Pobedy, 29, Lesosibirsk, Krasnoyarsk region, 662543, Russian Federation; 
e-mail: zaripov_sh@mail.ru

Keywords

mass transfer, mass exchange, larch sawn timber, drying schedules, arabinogalactan

For citation

Zaripov Sh.G. Schedules of Larch Sawn Timber Drying in Intermittent Kiln. Lesnoy Zhurnal [Forestry Journal], 2018, no. 5, pp. 151–160. DOI: 10.17238/issn0536-1036.2018.5.151

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Received on April 25, 2017