Interview with Ulla-Britt Mohlin of Innventia

10 February 2010

Interview with Ulla-Britt Mohlin of Innventia, a speaker at Refining and Mechanical Pulping conference

Q: Please tell us how the Eurofex project started and its objectives
In our present pilot plant, the stock preparation had become a limiting factor when we wanted to evaluate different raw materials or different components of a pulp in order to optimize the fibre use in different positions in the sheet, utilizing for example multilayer forming. The common procedure in any pilot plant is to prepare the pulp batch-wise before the actual paper machine trial. In the case of combining refining and fractionation this could take days. In addition to a laborious procedure, this approach has another drawback - the refined pulp looses some of the refining effect due to agitated storage. This makes studying the papermaking process in a relevant manner difficult. A research grant to update our paper machine facility with mainly a flexible stock preparation plant, sized to fit the production on the paper machine, was obtained from the Knut and Alice Wallenberg Foundation. The new stock preparation plant allows us to use different fractionation combinations of screens - hydrocyclones and refiners to tailor the pulp to be used in paper making. It will also allow us to evaluate a larger integration between stock preparation and the approach flow to the PM and at last but not least any unwanted effects of storage that would change the pulp quality in an uncontrolled way can be avoided. With this addition, the EuroFex system becomes more like a real paper machine and will allow for much more relevant studies. For example we can study how to use the fibre resources in the best way and how that may be affecting the efficiency of the papermaking process. Furthermore, the extension of the pilot plant will also allow us to investigate future concepts for paper making where stock preparation operations will be directly integrated in the wet end of the paper machine.

Q: Your talk is titled 'inside an LC refiner', what have been the most surprising results of your research?
The work I will discuss will cover observations from high speed imaging of the flow of fibres in the refining gap. This is the first time, as far as I know, this has been done in a fully loaded LC-refiner. The reference in this area is the study by Fox, published in the early 1980s. He used a plexiglass refiner running at 0,1 % consistency with quite a large gap. Our results confirm most of his observations, but also suggest different mechanisms for the stapling of fibres to the bar edge and for the flow patterns in the grooves. The most surprising result is probably that at high loadings of the refiner very few fibres are seen at the bar edge or between the bars.

Q: How is fibre engineering technology changing the way the industry approaches refining?
Refining is a very cost effective way to change the properties of the fibres that will probably still be around for a long time. The combination of refining and chemical/enzymatic treatments will maybe in the future extend the property span that can be obtained. Most fibre treatments cannot compete cost-wise with LC-refining.

Q: What elements of the conference are you looking forward to this year?
To meet with friends and colleagues. Energy aspects of the process are always important to take into consideration.