Summarizing the knowledge of today in the area of refining theory.
There are today proposals for hypotheses that explain differences between various refining techniques or the ways the industry choose to run refiners, but the development is still mainly based on trial and error as long as the measurement systems are not developed enough to be able to test the hypotheses.
The purpose of this project is to summarize existing literature and to describe what happens in refiner zones based on hypothesis proposals, both developed in the project as well as based on descriptions occurring in the industry.
A literature review focusing on refining theory is being compiled. In addition, an analytical/numerical comparison between different refining models and how well they can predict e.g. refining intensity, is carried out. Experts within all participating companies are to be interviewed about their hypotheses of which they, either consciously or unconsciously, base their control strategies and systems (DCS, etc.) on. The interviews are to be summarized and evaluated in an article.
At the moment, literature describing flow of pulp in refiner gaps are being scanned and summarized. The review is focused on studies where models were developed, e.g., where equations describing the flow of pulp, the forces acting on the pulp, etc. are given. However, also literature describing refining mech¬anisms on a smaller scale (fibre level) is referred to.
The work on an analytical/numerical comparison between how well the different models can predict variables like refining intensity, pulp consistency or residence time has just been started. This will be a challenging part of the subproject since the suggested models are so different in character (and what variables they include).
A set of questions to be used for the interviews has been developed and tested on several experts in the field of mechanical pulping. Starting now, in April, interviews/discussions will be carried out at SCA Ortviken, Stora Enso Kvarnsveden, Norske Skog Saugbruks, Holmen Braviken, SCA Östrand (CTMP) and Stora Enso Skoghall (CTMP). After the visits to the mills the answers or topics of discussions will be summarized. After all the interviews have been completed the plan is to compile an article (a live-review) based on the interviews. It will be interesting to see if there is an overall agreement regarding for example control strategies or if there are totally different opinions.
Together, the literature review, the live-review and the analytical/numerical comparison between models will serve as a mapping of the theories we have today regarding what happens in the refiner gaps during production of mechanical pulp.
The mapping will be filed as the “accumulated basic refining zone knowledge level 2010” (Accurefizone 2010). This compilation should then be updated when new knowledge is achieved – through the force and mass distribution measurements that will be carried out in subprojects 1 and 2 and other process advances that will be made within “Filling the gap” during the project period.