Off-grade in Celgar NBSK pulp has been an intermittent problem since 1998. In order to fully understand the cause of the problem, more than 170 dirt specks in Celgar off-grade pulp were collected over a 4 month period starting in 2005. Each individual sample was characterized using preliminary chemical testing. More detailed analytical methods were used on selected samples. This work was able to positively identify slime (biofilm) as the cause of off-grade in more than 70% of the samples examined. Prior to this work, it was not possible to clearly distinguish between slime and pitch during pulp grading at the mill, and off-grade from slime was frequently classified as pitch.rnA simple routine test was implemented to allow graders to clearly distinguish between pitch and slime.rnNitrogen isotope analysis was used to show the source of slime (biofilm) in individual dirt specks. This is the first time that this has been reported in the pulp and paper industry.rnAdditional analytical methods used include SEM/EDS, FTIR-microscope and glycoside composition analysis.
展开▼
