High Precision, In-Mill Measurement of Zeta Potential Distributions of Stocks and Furnish Aids Alkaline Performance, 1991 Papermakers Conference Proceedings

Zeta potential distributions of alkaline papermachine stocks and furnish have been measured by the Doppler Electrophoretic Light Scattering Analysis (DELSA) technique in six major mills to assess colloidal charge conditions which impact papermaking performance. Charge variations in stocks are more critical to performance on the alkaline side because of the diminished role of alum as a cationic coagulant. We have found that significant stock charge distribution variations result from pulp washing variations, inherent pulp type differences, and from variation in white water/fresh water ratio used to mine pulp. Approach system charge distribution variations are also affected by broke recycle rate. Large pH gradients through the system may lead to deposits. Small fluctuations in furnish charge (difficult to detect by other methods) have been seen to lead to retention upsets and breaks. An around-the-mill zeta potential distribution analysis is strongly recommended to provide early warning of system changes which could result in poor sizing, holes, breaks and excessive broked reels.