Using the refining zone temperature profile for quality control

Paper in proceeding, 2007

To achieve good quality control in TMP refining, relevant information about the process is needed. In this paper, the refining zone temperature profile has been studied to investigate if this information can be used to stabilize the pulp quality. The studied system is a commercial RTS primary refiner at Hallsta Paper mill. The response of the temperature profile was examined and compared with the pulp quality disturbances after both the first and second stage. The disturbances in the radial position of the temperature peak were found to be strongly correlated with the disturbances in freeness and mean fiber length. Based on these results, a new control strategy was designed to keep the peak position constant by changing the inlet pressure. This new control strategy decreased the freeness disturbances compared to the mill's normal strategy, and analysis suggests that the disturbances could be further reduced by including also the maximum temperature in the control concept. The potential of improvement in terms of reduced standard deviation of CSF was estimated to 11% or more. The comparison indicates that temperature parameters are better than the commonly used specific energy when it comes to predicting and reducing these quality disturbances.