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Multivariate analysis of seasonal pulp quality variations in a TMP mill

Pulp & paper Canada, 2004-10, Vol.105 (10), p.35-39

2005 INIST-CNRS ;Copyright Southam Business Communications, Inc. Oct 2004 ;ISSN: 0316-4004 ;EISSN: 1923-3515 ;CODEN: PPCADD

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  • Title:
    Multivariate analysis of seasonal pulp quality variations in a TMP mill
  • Author: BROWNE, T ; MILES, K ; MCDONALD, D ; WOOD, J
  • Subjects: Applied sciences ; Brightness ; Energy consumption ; Exact sciences and technology ; Paper chemicals ; Paper, paperboard, non wovens ; Polymer industry, paints, wood ; Printing properties ; Properties and testing ; Pulping ; Quality control ; Wood ; Wood. Paper. Non wovens
  • Is Part Of: Pulp & paper Canada, 2004-10, Vol.105 (10), p.35-39
  • Description: Data for this study was supplied by an Eastern Canadian TMP newsprint mill. During the period covered by the data, pulp was made from logs chipped onsite. The log supply was nominally a mix of 60% balsam fir and 40% black spruce, although spruce consumption levels varied seasonally from 35% to almost 50%. Throughout the months following the end of the spring thaw, fresh wood deliveries to the mill gate were generally directed to the chippers, with excess going to an onsite log pile. The pile served to ensure a constant supply to the mill when deliveries of fresh 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, J.R.] 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. It is clear that high brightness pulps occur during periods of high spruce consumption as shown in Fig. 6, and in the factor loadings for Factor 1. It could be suggested that spruce pulps are inherently brighter, thus requiring lower levels of bleaching chemicals to maintain a minimum brightness level, but this is inconsistent with reports showing fresh fir can be as bright as fresh spruce [(7)]. We prefer to suggest that brightness loss during storage for either spruce or fir is reduced during the period when coincidentally, spruce content is high, in this case the cold weather period. This would explain the apparently counter-intuitive result that lower rates of bleach addition yield higher brightness pulps, as seen in Fig. 6 and 8. Factor 1 thus models the effect of wood freshness on brightness, and implies that improved wood freshness (due to shorter storage times, lower storage temperatures, etc.) will improve brightness and reduce bleach chemical consumption. It is a measure of brightness retention or brightness potential of the wood. When the wood allows more energy to be put into the pulp, freeness can be reduced without increasing the level of fibre cutting. The result is higher energy use leading to well-fibrillated, collapsed fibres, reduced fibre cutting, and therefore higher tear at higher freeness. Wood quality for a given species is extremely variable [(8)], and can be due to any number of factors, such as seasonal changes in wood quality, geographic location of wood cutting operations, wood temperature during debarking or chipping, genetics, etc. These variable wood properties have an influence on the ease of application of energy in a refiner and on the resulting pulp properties [(9)], in a manner consistent with the loadings making up Factor 2. Factor 2 thus models the ease with which energy can be applied to the wood.
  • Publisher: Don Mills, ON: Southam
  • Language: English
  • Identifier: ISSN: 0316-4004
    EISSN: 1923-3515
    CODEN: PPCADD
  • Source: ProQuest Central
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