Management of Wet End Chemistry Online Measurements and Mill Results

Demand for more cost-effective paper making while keeping the quality targets is today the main challenge for a papermaker. More sophisticated concepts for chemical treatments of stock are developed. Online measurements like consistencies, charge, pH, conductivity and turbidity have become everyday tools to solve these challenges in today's papermaking. Retention can be controlled by stabilizing white water consistency by changing retention polymer flow. This is still the cornerstone of a stabile wet end and its performance can be quarantined by sustaining optimum chemical environment for retention polymers. Optimum chemical environment can be created by measuring charge in all the process stages, where any change to chemistry can be introduced. In thick stock the target for good sample is a fines fraction including dissolved and colloidal material. Finally the white water charge at paper machine must be measured to guarantee runnability of the paper machine. White water is natural point of sample - it includes fines (and all dissolved and colloidal material) and can be reliably measured by streaming current technique. The other important benefit measuring charge in short circulation is good correlation with central roll release angle and at tissue machine with creping actions. This paper presents certain on-line measurements for key parameters concerning colloidal and interfacial chemistry and proven control results. Results are based on paper mill tests. We have proved that both retention and charge control are needed in efficient papermaking.