Kinetic Parameters of Wood Drying Process

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UDС

674.047

DOI:

10.17238/issn0536-1036.2017.6.114

Abstract

Heat treatment is widely used to modify the mechanical, physical and chemical, thermophysical, biological and other properties of wood. Drying is one of the types of thermal impact. We should develop mathematical models of the processes occurring in wood under thermal action to determine the optimal modes of drying and minimize energy costs. The author faces a task of describing internal heat and mass sources to make the mathematical descriptions of heat and mass transfer during drying. The moisture removal is regarded as a complex multi-stage physicochemical process. The stage of the drying process is due to the moisture in wood, connected with wood substance. The destruction of bonds occurs in their (different) temperature ranges. Individual stages are considered as parallel, independent chemical reactions and are described by kinetic equations. We develop and produce an experimental plant to study the kinetics of bound moisture removal in wood. This unit allows conducting thermogravimetric experiments in a controlled humidity environment. Samples for the study have different initial humidity at different environmental relative humidity. The results of thermogravimetric experiments are processed using a method separating the process into the stages. The bound moisture removal from wood proceeds in seven stages. For each stage, we determine the activation energy, the pre-exponential factor, and the initial mass fraction values. The dependence of kinetic parameters on the environmental relative humidity is studied. The author assumes that only the activation energy depends on the humidity of the drying agent. Empirical dependences of the activation energy on the environmental relative humidity for the first, second and third stages are obtained; thermogravimetric studies of the drying kinetics of wood with an initial moisture exceeding the fibre saturation point, i.e. in the presence of free moisture are undertaken; stepwise kinetic parameters are established.

Authors

M.G. Ermochenkov, Candidate of Engineering Sciences, Associate Professor

Affiliation

Mytishchi Branch of Bauman Moscow Stade Technical University, ul. Pervaya Institutska-ya, 1, Mytishchi, Moscow oblast, 141005, Russian Federation;
е-mail: ermochenkov@mgul.ac.ru

Keywords

wood drying, drying kinetics, thermogravimetric study, kinetic parameter, environmental relative humidity

For citation

Ermochenkov M.G. Kinetic Parameters of Wood Drying Process. Lesnoy zhurnal [Forestry journal], 2017, no. 6, pp. 114–125. DOI: 10.17238/issn0536-1036.2017.6.114

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Received on February 13, 2016