Multivariate analysis of seasonal pulp quality variations in a TMP mill

Pulp & Paper Canada T 230 105:10 (2004) ❘ ❘ ❘ 35 wood were interrupted at night or on weekends. Wood supplied to the chippers at this time of year was therefore largely fresh and the age of logs in inventory was generally low. Beginning in the fall, the inventory of cut wood was built up both in the mill’s wood yard and in roadside piles in the woodlands. In winter, this inventory of fall-cut wood made up a larger portion of the supply to the chippers, increasing to 100% of the feed during the spring thaw when logging roads were impassable and fresh wood was unobtainable. Wood supplied to the chippers at this time of year came largely or entirely from inventory, and the age of the logs from inventory was typically higher than during the summer and fall months. Wood age and species were thus both seasonal variables, with species being easier to quantify since the age of individual roadside piles was not recorded. Chips were saved in storage bins with maximum residence times of a few hours; there were no chip piles. Chips were therefore fresh when refined, and chip age did not vary seasonally. Following washing and steaming, chips were refined in the TMP plant. After screening, rejects were mixed with rejects from paper machine screening and cleaning operations, then processed in the rejects refining system. After further screening and cleaning, accepts from the rejects system were mixed with accepts from the mainline refiners at the disc filters. Following bleaching with hydro-sulphite, the pulp was mixed with excess paper machine white water in a blend chest. Pulp properties reported here were obtained from samples taken at this chest, and thus represent a composite of the entire TMP plant diluted with a certain amount of white water and fibre which has been rejected by the paper machine screens, then re-refined in the rejects system.