Validation of crill measurements in a high-yield pulp refining process for improved fines material control

Abstract

Abstract In high-yield pulp (HYP) refining, fine material is created by peeling action on the fibre surface. This fine material is usually characterized using conventional camera technology and image analysis. The smallest particles, the crill, also created in the refining process are too small to be visible in a camera image, and are therefore measured using light sources in the UV and IR wavelength spectrum. This research sought to determine whether the crill could be characterized in the presence of large fines material in a HYP refining process, and the results indicated that the larger fines material had little impact. In addition, the variation in crill measurements declined as the fibre treatment increased and remained low and stable during an extended period. Due to the great need to monitor and control pulp processes using rapid online measurements, cost-reduction actions at mills running close to specification targets put high demands on the measuring devices characterizing the production. The outcome of this study enables the use of the crill method to improve our knowledge of fibre treatment and its contribution to fibre adhesion in complex refining processes. Finally, combining conventional camera technology and the crill method could improve the overall fines material control.