Conductivity profile measurement for steam point detection in pulp refiners

Purpose and goal

The projects objective was to develop a prototype for measuring the conductancy profile in the grinding zone in HC pulp refiners. The aim was to see at which point along the radius that the vaporization occurs. During the time of the project we have developed and installed measuring equipment at UPMs mill in Kaipola, Finland. And we have made measurements where we see that the steampoint moves along the radius. The equipment has been developed further to be more like the original plan with sensors recessed into the segments and and will be installed to a mill in Sweden in May 2016.

Expected results and effects

The result so far can be summarized with: - We can see a good correlation between conductance and the amount of dilution water added to the pulp. - We see slow changes in conductance values, mainly after a start of production, that we can´t derive from a changed gap or a changed amount of added water. - We have a correlation between gap and conductance when we have lower impedance values. The results are so promising that the trials will continue even after the end of the project with the goal to develop a commercial product for the detection of the steam point in pulp refiners.

Planned approach and implementation

Two versions of a prototype have been developed to measure conductance and temperatures in five positions along the radius in a refiner at UPMs mill in Kaipola, Finland. They have been installed in booth a first and a second stage refiner. We have made trials with controlled changes in process parameters such as dilution water and gap and data from normal operation were logged and analyzed continuously. The prototype has been developed further into a ´ruler´ with 10 measuring points for conductance and temperature integrated into a grinding segment. These trials will start in May 2016.