You have several bleaching stages, why don’t you use them?

ABSTRACT
I was discussing whether a mill should control to a constant CEK# (the post‐Eop stage
kappa number) or allow it to vary between some range. This is how my co‐worker answered the
question to make his point. This is one of the many things Kari Lampela taught me in his own
unique way through many years of working with him. I remember him quite fondly and many
things that he taught me, especially after his unfortunate passing earlier this year. This paper
will discuss some methods and reasons to adjust the CEK# or bleach load target going into the
D1 stage to better control a bleach plant. This method can be utilized to rebalance the chemical
usage across the bleaching stages, rather than always loading the front end to get as much
bleaching as possible. This method uses model predictive control to automatically adjust the
post‐Eop stage targets according to the limits of the final bleaching stage(s) and ultimately allow
you to reduce your overall bleaching cost to its minimum level.
This paper will discuss the pros and cons of running to a constant mid bleach plant target
versus allowing it to control between a minimum and maximum level. A stable CEK# does not
always indicate a well‐controlled or efficient bleach plant. This paper will explain the logic
behind that statement and discuss how each bleach plants CEK target range should be
established.
Finally, the CEK level can be measured several ways. Traditional lab testing, online
analyzers, or inline sensors can be used to determine its level. This paper will discuss the pros
and cons of each method. 

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