STUDY OF THE POSSIBILITY OF USING LOGGING RESIDUE FOR THE PRODUCTION OF WOOD PROCESSING ENTERPRISES

As analysis of the results of numerous studies has shown, the raw material for the production of wood fi ber material can be chips from wood residue. In the process of producing high-quality wood fi ber semi-fi nished product, high-quality wood chips are subjected to hydrothermal processing and further grinding in disk blade grinding machines in two stages. Signifi cant energy intensity of the process of wood fi ber production is caused not only by the grinding of chips in two steps, but also by overcoming the hydrodynamic resistance of the aquatic environment in which grinding is carried out. In order to solve the problem of expanding the raw material base for the production of wood fi ber semi-fi nished product and reduce the energy intensity of the grinding process, research has been carried out on the process of grinding chips from logging residues in an aerodynamic environment in a modernized plank-cross grinder. An analysis of the features of the process of grinding chips in an aerodynamic environment has been performed and an estimate of its effectiveness has been formed. The infl uence of the main structural and technological parameters of the process of production a wood fi ber semi-fi nished product in an aerodynamic environment on its quality indicators is shown. Statistical-mathematical equations and graphical dependences are obtained that allow predicting the quality indicators of a wood fi ber semi-fi nished product for given structural and technological parameters of the grinding equipment.


INTRODUCTION
Due to the fact that the need for wood raw materials is constantly increasing, the question of its complex use becomes relevant. Meeting the needs of wood processing industries for raw materials should be carried out both at the expense of economical and the most complete use of wood resources [1]. As a result, one of the main directions of development of the forest complex is to increase the use of all wood material. For that purpose, it is necessary to improve the structure of the production of the timber and woodworking industry further, the improvement of technological processes for the production of technological chips, fi ber board, plywood, cardboard and other sawn timber substitutes [2]. One of the priorities of the use of logging residues such as knots, branches and toppings is the production of semi-fi nished wood fi ber [3]. However, it should be noted that traditional grinding technologies and grinding equipment do not allow producing semi-fi nished wood fi ber with the required quality characteristics from the chips left from the processing of logging residues.

EXPERIMENTAL PART
In order to expand the raw material base for the production of wood fi ber semi-fi nished product and increase the effi ciency of the grinding process of phytogenic residue, the plank-cross grinder design was developed at the laboratory of "Forestry and chemical technology" of the Lesosibirsk Branch of Reshetnev Siberian State University [4]. It allows the process of knife-grinding in the aerodynamic environment.
The grinding chamber of the grinding machine is presented in Figure 1  Due to the design features of this grinding machine, the raw materials go through four grinding zones during the grinding process. In zone I, grinding is carried out in the working gap between the rotor knives and knives of the *ale-mokhirev@yandex.ru corrugated stator strap. An intense effect on the fi brous semi-fi nished product proceeds, which is accompanied by crushing, cutting, crumpling and friction. In the sector between the rotor knives (zone II), the wood fi ber mass is mixed due to friction forces and centrifugal force according to aerodynamic laws, which promotes fi brillation of wood fi ber [5]. In zone III, located in the area of the base of the rotor knife with knife openings, fi brillation of wood fi ber occurs due to sharp teeth in the knife openings. In the inter-knives cells of the corrugated straps (zone IV), fi brillation takes place, the alignment of geometric dimension of the fi ber happens, and the fi ber is divided into fractions due to the knife openings [6]. Zone IV is the fi nal, wood fi ber semi-fi nished product having the required geometrical dimensions passes through the knife openings and leaves the grinding chamber. The studies of this work were put into practice using pine (Pinus sylvestris) chips in the form of knots, branches and toppings left from logging residues. In order to weaken the inter-fi ber bindings, chip was conditioned with acetic acid aqueous solution before loading in the grinding chamber [7,8]. An active multifactorial experiment was taken as the main method of obtaining a statistical-mathematical description of the process using a second-order B-plan [9,10]. The following technological and design parameters of the process were selected as input factors for the experiment: γ-angle of inclination of the front edge of the knife, degrees; z -the size of the gap, mm;τ -the exposure time of the chips in acetic acid aqueous solution, min. The levels and intervals of variation of these factors are presented in the table 1.

RESULTS AND DISCUSSION OF EXPERIMENT
As a result of processing experimental data using modern experimental and laboratory-measuring base at the appropriate level of metrological support of research, equations describing the change in the increase in the grinding size and the fractional quality indicator of grinding from the technological and design parameters of the grinding machine have been obtained.Calculations confi rmed that all coeffi cients of the regression equation are signifi cant. (1) For clarity and a more complete assessment of the infl uence of the factors under study on the quality indicators of the wood fi ber semi-fi nished product, response surfaces are constructed using equations 1 and 2. The response surfaces give a more complete demonstration of the dependence of the quality indicators of the semi-fi nished wood fi ber from the design and technological parameters of the plank-cross mill.
As it can be seen from the presented in fi g. 2a, graphical dependencies and equation 1, with an increase in the exposure time of the chips in an aqueous solution of acetic acid, the degree of mass grinding increases. It happens due to the fact that with longer time of exposure of chips in an acetic acid aqueous solution increases the plasticity of the wood. In the future, with the mechanical impact on the wood a large amount of fi nes is formed. So, when the chips are conditioned in an acetic acid aqueous solution from 18 to 20 minutes, the grinding size of the mass reaches 20-22 DS and tends to increase with longer conditioning.
As it can be seen in the graphical dependence presented in Figure 2b With a further increase in the angle of inclination of the front edge of the rotor knife, the value of the fractional indicator of the grinding quality decreases.

CONCLUSION
Thus, statistical and mathematical equations obtained in during the research and graphical dependencies describing the process of grinding chips from logging residues in a plank-cross grinder make it possible to predict the production of high-quality semi-fi nished wood fi ber, depending on the established modes of the grinding process. The presented research results show that wood chips semi-fi nished product suitable for further use in the production of structural, fi nishing and insulating materials can be made from the chips left as a result of processing forest residues. Using the technology of grinding chips in the aerodynamic environment will signifi cantly reduce the energy intensity of the process of producing wood fi ber semi-fi nished product.