Bleach Plant Benchmarking and the Sequence Kappa Factor Flaw

Abstract
Sequence Kappa Factor is often used as a metric to compare the performance of bleach plants operating
at different “Kappa to Bleach” values. However, this metric has a flaw. The denominator “Kappa to
Bleach” skews the data causing mills operating at a lower “Kappa to Bleach” to “appear” to have a
relatively high chemical consumption.
The alternative is to compare bleach plant performance relative to a benchmark value at the same “Kappa
to Bleach”. To this end, a benchmark/model based on published laboratory data was developed that
calculates a theoretical Total Active Chlorine consumption as a function of “Kappa to Bleach” at a given
TAC/(ΔKappa) in the bleach plant brightening stage(s). The model also predicts the optimal
DEo(p) Kappa and DEop Kappa Factor for a specific “Kappa to Bleach”. The benchmark is linear with
respect to “Kappa to Bleach” and has a positive y-intersect.
Published laboratory data was plotted against the model. The data validated the model and showed no
difference between SWD and HWD nor conventional and oxygen delignified pulp. The 2013 PAPTAC
Bleaching Study data (TAC vs “Kappa to Bleach) was plotted against the model. The slope of the
regression equation of the PAPTAC data was almost identical to the model. The y-intercept was higher
which is attributable to commercial vs laboratory operations (e.g., losses due to carryover). The data
clearly showed that mills operating at a lower “Kappa to Bleach” are generally as efficient relative to the
benchmark as mills operating at a higher “Kappa to Bleach”.
The Sequence Kappa Factor Flaw
Figure 1 is from the 2013 PAPTAC Bleaching Study. When using the Sequence Kappa Factor to
segregate mills into Hi/Lo relative chemical consumption the dominant parameter is “Kappa to Bleach”. 

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