The Effect of Wood Alignment on Wood Grinding – Part 1: Properties of Pulp and Fines Revealed in the Grinding Mechanism

Abstract

In industrial wood grinding, logs are pressed against a rotating stone, with the logs and fiber axis parallel to the axis of the stone. The objective of this study is to clarify how the wood alignment affects the process and pulp properties. In this research, wood blocks were fed into a laboratory grinder with various alignments in relation to the surface of the grinding stone. The effects of the alignment on the properties of the pulp and the amount and quality of fines were measured. A grinding mechanism was proposed. The results show that the pulp quality is very sensitive to the angle between the stone surface and the log. In gentle refining, the fiber structure is loosened by fatigue before it is bent on the surface; pressure pulses produce fibrillar material, and fibers develop toward having good bonding ability. In forced grinding, the process is "violent", and the fiber wears and becomes crushed immediately on the surface into small particles with low bonding ability.

Dry grinding of waste wood fiberboard: Theoretical and practical aspects affecting the resulting fiber quality

“…Such fibres have a large specific surface area, and are therefore capable of forming cohesive bonds and improving the structure of boards. Fine fibres, Group B fibrilplasm, and Group A mehlstoff have a small specific surface area, and act as a filler, increasing the sheet density to a certain extent (Chistova 2010;Zyryanov 2012;Heinemann et al 2016;Saharinen et al 2016).…”

Use of mechanically ground lignocellulosic native fines (LF) in the all-cellulosic composite filaments: fines properties and plasticizers

“…The lignocellulosic native fines (LF) were produced by utilising a custom-made W-stone grinder at VTT in accordance with the procedure presented earlier (Saharinen et al 2016b). The custom grinder comprises a special grinding stone with a serrated grinding surface.…”

“…The fibre orientation of the wood blocks was parallel to the shaft of the grinding stone. The angle used ensured that the fibres in the wood blocks disintegrated into fine particles instead of disintegrating from the cell wall (Saharinen et al 2016b). With the given operational conditions, the wood was ground to a micrometre scale LF with a yield of 90%.…”

“…Recently, a W-stone grinding method, which is a low-cost approach to producing fine lignin containing fibrillated cellulose material directly from wood and which retains all the chemical components of wood, was introduced (Saharinen et al 2016b). W-stone grinding is based on the perpendicular grinding of native wood with a W-shaped rotating stone in water (Saharinen et al 2016a).…”

Investigating tool engagement in groundwood pulping: finite element modelling and in-situ observations at the microscale

“…The orientation of the wood with respect to the stone axis has been shown to influence the character of the produced fibres, with higher degrees of shorter fibres and fines when the angle between the stone axis and the wood structure increases (Beath 1958;Heinemann et al 2016;Saharinen et al 2016). Such angular alignment is also possible to influence using designed tool surfaces.…”