Substantiation of the design parameters of a sectional screen for a drum-type wood chipping machine

Abstract

The production of wood chips for the pulp-and-paper, wood-based panel, and bioenergy industries requires ensuring stable granulometric composition (stable particle-size distribution) of the product. A promising direction for improving chip quality is the optimization of screening systems in drum wood chippers. The aim of this study is to develop a mathematical model of the interaction between wood chips and the screen and to substantiate its rational design parameters. The study was conducted using the methods of solid-body motion mechanics, mathematical modeling, and experimental testing. A mathematical model of the impact interaction between wood chip particles and the screen was developed, taking into account the kinematic parameters of particle motion and the physical and mechanical properties of the material. A relationship for determining the number of sections of a stepped screen was derived, and the patterns governing particle movement within the inter-drum space were established. The influence of the number of screen sections and the radial distance between the screen and the drum on the efficiency of wood chip sizing has been experimentally investigated. It was found that the use of a sectional screen improves the separation of substandard particles and the fractional composition of the output product. The optimal parameters are 11 screen sections and a radial spacing of 15 mm. Under these conditions, the proportion of the substandard fraction is 8–15%, whereas for a plate-type screen it is 25–32%. The obtained results may be used in the design and modernization of drum wood chippers.