Kari Hyll at Innventia defended the doctoral thesis: "Image-based quantitative infrared analysis and microparticle characterisation for pulp and paper applications" on 12 February. The project involves how to improve thermographic process analysis and characterisation of fines and fillers.
Using image-based measurement methods we are able to both analyse a greater proportion of the paper web on the machine and obtain morphological information about the particles in the stock. When it comes to measurements of the paper web, there are many benefits of using infrared thermography, which gives a temperature image of the web. However, to obtain accurate measurement values using this technology, a material property known as emittance must be known.
In the doctoral thesis work, Kari Hyll measured the emittance of fibre-based samples and investigated how it is affected by various factors that are relevant at a mill, e.g. moisture and temperature. One application was implemented where accurate temperature measurement values are essential, namely calculation of thermal energy during deformation of paper. When it comes to measuring the particles in a stock, fibre analysers have not been able to detect many fines and filler particles due to a limited image resolution.
"I have evaluated new instruments with better resolution and shown that they enable us to obtain new information about fines and filler. I have also devised and evaluated a method for differentiating between fines and filler in a mixture, something that no current instrument can do," says Kari.
The conclusion presented by Kari in their thesis is that thermographic applications requiring more exact measurement values can now be employed, fines and fillers can be measured with better resolution and a potential method for distinguishing between fines and fillers has been developed.
Kari's supervisors are Lars Mattsson, Production Engineering, KTH Royal Institute of Technology, and Hannes Vomhoff, Research Manager at Innventia.
"Evaluation and implementation of new measuring methods is a central element of Innventia's research activities, and consequently we will derive great benefit from Kari's results. For example, they will facilitate quantitative analysis of process variations with the aid of thermography. In the future we plan to link the analysis directly to the quality control system on a board machine," says Hannes Vomhoff.
The work has primarily been carried out at Innventia, in collaboration with KTH Production Engineering, which is the department that Kari has been associated with.
For more information, please contact:
Hannes Vomhoff, Innventia, +46 (0) 8 676 74 88, This email address is being protected from spambots. You need JavaScript enabled to view it.