| Summary: | The presence of unreacted lime (free lime) in the lime mud can cause many problems in the chem - ical recovery operation of kraft pulp mills. There are currently no standards for free lime determination. Conventional methods used in mill laboratories require extensive preparations and give inconsistent and some - time erroneous results. A systematic study was performed to determine if zeta potential, a dispersion characteristic of the lime mud and liquor slurry, can be used to indirectly indicate the amount of free lime in the lime mud. Lime mud with differ - ent free lime contents was produced in the laboratory by causticizing green liquors with lime at different liming ratios. The results show that zeta potential changes from negative to positive when the free lime in lime mud exceeds a critical value. This unique characteristic enables a rapid detection of free lime. This work was conducted as part of the research program on “Increasing Energy and Chemical Recovery Efficiency in the Kraft Process - III”, jointly supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and a consortium of the following companies: Andritz, AV Nacka - wic, Babcock & Wilcox, Boise, Canadian Kraft Pulp, Carter Holt Harvey, Celulose Nipo-Brasileira, Clyde-Bergemann, DMI Peace River Pulp, Eldorado, ERCO Worldwide, Fibria, FP In - novations, International Paper, Irving Pulp & Paper, Kiln Flame Systems, Klabin, WestRock, StoraEnso Research, Suza - no, Tembec, and Valmet.
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