Thesis shows infrared radiation quickens paper drying

P&PC staff
May 31, 2018
By P&PC staff
May 31, 2018 – A new thesis shows that infrared radiation shortens the drying process of paper production.

The drying process is responsible for much of the energy used in the paper machine, especially with premium tissue products such as toilet and kitchen towels. The dewatering is then performed by through air drying technique (TAD) which provides better absorption and softness. The new thesis now shows that supplied energy via infrared radiation increases the drying rate and reduces the need for fossil fuels. Consequently, premium products could be produced with less environmental impact and at lower cost.

Titled Through Air Drying - Thermographic Studies of Drying Rates, Drying Non-uniformity and Infrared Assisted Drying, Aron Tysén's thesis has investigated parameters related to drying rate and non-uniformity in through air drying. The measurements showed that the air flow through the samples varied with grammage and pulp type, where softwood pulp demonstrated much higher permeability compared to hardwood pulp. At low grammages, relevant to tissue, no connection was found between the amount of air flow and the drying rate.

“Because the air is the process’ medium for energy transport, it means that we have encountered some form of bottleneck for how quickly we can dry with room-tempered air," Tysén said. "I could then get past the bottleneck by adding energy via infrared radiation and thus achieving higher drying rates."

According to Tysén, IR technology could also be used to characterize the drying process with any paper-based product. Within the framework of his doctoral thesis, he developed a thermographic method that makes it possible to determine spatial local drying times with high resolution.
 
“With the right infrared camera, one should be able to see the drying behaviour of individual fibres in the sheet,” he said.
 
Now, Tysén has begun a new role at RISE as senior research associate, but with continued focus on process variability.
 
“Infrared radiation is an interesting method that we will look into in several different projects, including the Vinnova co-financed project 'Online variability analysis of the total production of paper and board for process optimisation' and the program areas 'Tissue products and processes' and 'Product Variability and Advanced Analytics in Papermaking' within the Bioeconomy Research Program 2018-2020," Paul Krochak, director paper technology at RISE, said.
 
Tysén defended his dissertation on May 22 at Karlstad University. The study was performed as part of the Industrial Graduate School VIPP (Values Created in Fibre Based Processes and Products) at Karlstad University, with the financial support of the Knowledge Foundation.

RISE is a Swedish Research Institute and innovation partner.

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