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Abstract

Formation of pitch and sticky deposits through the destabilisation of colloidal material present in paper manufacture
continues to be a challenge in improving machine efficiency in newsprint manufacture from a furnish comprising
thermo-mechanical pulp (TMP) and recycled fibre (RCF), and in an environment where water usage efficiency is at best
practice. Findings from laboratory studies that have investigated colloid structure, impact of multiple and multi-valent
cations, pH, temperature, shear and dissolved organic matter on Pinus radiata extractive colloid stability have been
used , along with observations of process conditions in Norske Skog’s Albury mill to determine which properties are
most important in maintaining colloid stability.
Developments in our understanding of wood extractive colloid structure have led to an explanation as to why pitch
deposition is more likely during summer months. A parameter called the “ester to acid ratio” has been shown to
exhibit both short and long-term trends when applied to process stream extractive levels. This greater propensity for
deposition during summer months is exacerbated by elevated soluble calcium levels during summer time. Dissolved
organic wood polymers also affect colloid stability and their behaviour is further modified by the presence of soluble
calcium. More stable colloids are obtained under conditions of neutral pH, avoidance of downward temperature
shocks and avoidance of shear forces.

Item Type:	Article
Authors/Creators:	Richardson, DE and Lee, R and Stack, KR and Lewis, T and Garnier, G
Keywords:	Pitch deposits, colloid stability, wood extractives, resin acids, fatty acids, glycerides, TMP, recycled fibre, newsprint manufacture.
Journal or Publication Title:	Appita Journal
ISSN:	1038-6807
Additional Information:	Copyright 2012 Appita Journal
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