Defibration mechanisms and energy consumption in the grinding zone – a lab scale equipment and method to evaluate groundwood pulping tools

Abstract

Abstract Groundwood pulping is a process that employs large machines, making them difficult to use in research. Lab scale grinders exist, but even though they are smaller, the sizes of the grinding stones or segments make them cumbersome to exchange and tailor. This study presents a method and an apparatus for investigating the detailed mechanisms and the energy requirements behind the fibre separation process. A well-defined grinding tool was used at three different temperatures to demonstrate that the equipment can differentiate levels of energy consumption and defibration rates, confirming the well-known fact that a higher temperature facilitates defibration. It is also shown how the equipment can be used to study the influence of grinding parameters, exemplified by the effect of temperature on the way fibres are separated and the character of the produced fibres. A key feature of the equipment is the use and evaluation of small grinding surfaces, more readily designed, produced, evaluated and studied. This reduces both the cost and time necessary for testing and evaluating. At the same time, a technique to produce well defined grinding surfaces was employed, which is necessary for repeatability and robust testing, not achievable with traditional grinding stones.