Refining Control and the Prediction of Pulp Properties by Direct Measurement of Both the Number and Severity of Fiber Impacts..., 1997 Process Control, Electrical & Info. Conference Proceedings

In 1979 Brenholdt discovered the presence of transient voltages on the surfaces of refining elements in pulp and wood chip refiners. These voltages give rise to transient electric currents in the frame of the refiner. In 1987 a pioneer patent was issued describing means for detecting these currents and using them for optimum control of the refining process.

In a recently completed research project, means were developed for characterizing these currents in terms of the number, N, and severity, S, of fiber impacts. It was found that these parameters agreed with many of the theories concerning N and S and their significance in determining the outcome of the refining process.

Ratios developed from these parameters were found to correlate well with important papermaking properties of the pulp produced; e.g. freeness, strength, fiber size, etc. It was also found that these ratios track plate wear and indicate the occurrence of the critical gap. All of these observations were found in both pulp and wood chip refining.

A significant aspect of the patented sensor is the fact that it is constructed entirely of solid state components and does not require penetration of the stock flow piping or the refiner.