This work presents a study on the preparation of recycled wood fibre using different types of grinding equipment. It is also concerned with fibre preparation in an aerodynamic environment and describes the possibilities of using the material in various finished products. The authors used bio-rejects from the production of composite board materials, e.g. fibreboard and medium density fibreboard (MDF), in the form of lump scraps, as research material. In order to evaluate the efficiency of woodfibre waste recycling using various grinding equipment, the authors analysed the qualitative characteristics of the resulting semi-finished woodfibre materials and mathematically calculated the primary technological and design parameters of the grinders. The results of the study provide a scientific basis for the efficiency of a fundamentally new recycled wood fibre dry preparation method and system.

A rationale is presented for the wood fibre process modeling of internally recycled content in fibreboard production. Experimental studies were employed to obtain mathematical dependences in order to confirm the possibility of reusing wood fibre at various stages of the technological process. A wood fibre process model of internally recycled content was accrued out in which each processing stage was presented separately. Two methods for the preparation of wood fibre for reuse in fibreboard production were considered. To assess the effectiveness of the technologies proposed, the process modeling of internally recycled content was assessed from an economic and environmental point of view.

Refining of fibrous semi-finished products is an important stage in fibreboard production because the efficiency of this stage affects the resulting fibres’ dimensional and qualitative characteristics. These, in turn, determine the physical and mechanical properties of the finished products, as well as the energy intensity of the process. The efficiency of this process depends on the raw materials used and the geometry of the refiner disc working surface and its operational modes. This article presents the results of the optimisation of wood fibre refining at a low concentration (2 to 4%), using fundamentally new refiner discs in high-density fibreboard production. Based on numerous theoretical and experimental studies, and on the results of processing, the problem of optimising the refining process was solved, taking into account the use of new refiner disc geometry. As a result, the optimal values of refiner process parameters and operation modes making it possible to prepare wood-fibre semi-finished products efficiently while reducing power consumption in refining were established. After optimising the refining process, the new geometry of refiner disc working surfaces provides optimal dimensional and qualitative characteristics of wood fibres, which results in finished products with high physical and mechanical properties in accordance with GOST 4598 (2018) without using bonding resins.

A physical coagulator of fines was employed to separate suspensions comprising refined sulphate cellulose and waste paper, where no reagents were required. The physical coagulator was a porous cylinder with a rotating disk placed in its cavity. Using the MorFi Neo fibre analyser and the Hitachi SU 3500 digital microscope, a dispersed size distribution of well-developed fines in a suspension derived from softwood and hardwood pulp was obtained. The kinetics of fine sedimentation in the suspension was studied. The sedimentation rate of both individual agglomerates and a mass of them, as well as the magnitude of mass concentration in a cleared liquid, was determined. A relationship between the concentration of fines in the suspension and the structure of the pulp during their sedimentation was established. To intensify the fines sedimentation process, it was proposed to return a part of the sediment to the suspension passing into the physical coagulator. Process parameters for the sedimentation process and the construction of the sedimentation tank were obtained. The unit designed for collecting fines from the suspension is shown schematically. Use of this unit reduced the fibre sedimentation time, decreased the loads in wastewaters, and retained the consumer value of the pulp fibres.

The method for calculating the main technological parameters of a set with a curved shape of knives is presented. The aim of the work is to design a disk set with circumferential knives and to determine dependencies that allow predicting the technical and technological parameters of this set, the quality of the resulting semi-finished product during grinding, increasing the productivity of the grinding plant and reducing energy consumption during grinding. For the first time, a numerical method has been developed for calculating the second cutting length (Ls) of a knife set with a curved shape of knives, taking into account the main geometric parameters of the set. The geometric construction of the knife set of grinding machines allows to purposefully predict its use for various modes of the grinding process in the production of certain types of finished products. The research results can be used in the design of new types of headsets, their manufacture and operation.