Renewable packaging materials ‑ Impregnation depth measurements for pulping industry using synchrotron

This is a project within the Treesearch collaboration. The goal is synchrotron measurement for validation of a prototype pilot for on-site sulphonation measurements. The pilot is supposed to be further developed by Valmet AB for BillerudKorsnäs AB as end user. These measurement will also increase the knowledge about energy efficiency and quality stability of the defibration process of CTMP pulp.

Sulphonation mapping measurements is possible using low energy XRF imaging at NanoMAX. Air absorption can be avoided by using a plastic helium gasbag. The goal for spatial image resolution is 200 nm. Scanning of a 100x100 μm area is necessary to be able to image single wood fibres.

Potential

The main goal of this project is to enable prototype development of a pilot on-site XRF measurement equipment. A crucial part is validation of data in synchrotron infrastructure. The benefit for the partner companies is increased knowledge concerning improvement of energy efficiency and quality stability of the defibration process of CTMP pulp. This project will provide:

• Sulphonation mapping measurements of high quality for wood chips, which will increase the process knowledge
• Validation of the pilot prototype, to evaluate the usability of the pilot for on-site measurements.
• The project outcome will generate basis for decision if the project partner Valmet AB should continue develop the pilot for final mounting at the BillerudKorsnäs site.

Increasing demands to replace plastics in packaging material with renewable, easy to recycle and compostable materials needs better fundamental scientific understanding of pulp and paper manufacturing systems. High yield pulping (HYP) processes, such as CTMP, are increasingly interesting for packaging material as well as manufacturing of hygiene paper.

In order to separate the wood to individual fibers with a minimum amount of electricity, it is necessary to soften the lignin. The lignin is softened by means of a combination of sulphonation at high pH and elevated temperatures in the preheater and in the refiner, where the fiber separation occurs. It is challenging to create a process technology that gives an even distribution across the wood chips of the sodium sulphite (Na2SO3) containing liquid used for impregnation. In order to improve the impregnation technology, it is valuable to measure the sulphonation degree on a detailed level. In addition, a more even distribution of sulphonation can have a good potential to reduce energy demand in chip refining of CTMP pulp.

The purpose of this proposed project is to validate and compare our XRF lab results obtained from thin paper sheets (thickness 10-25µm) of CTMP pulp. Obtained results from our newly built laboratory-based setup of XRF imaging system are needed to be validated at synchrotron before the final pilot lab setup for pulp industries (proposed at Valmet and Billerud Korsnäs) to be used as a tool for process optimization and process control in order to save energy.

In order to obtain the scanning image of the individual fiber, the focal spot size of the beamline should be less than 20 μm to obtain a high-resolution image. Therefore, we will apply to conduct XRF imaging measurements at NanoMAX. As alternative, we will also apply for the ID21 beamline at ESRF and for the I08 beamline I08 at Diamond.

The method developed within the project could become useful in pulp and paper industry in the future. In a word, to find the possible way of Na and S even distribution could help reduce specific energy demand and improve process control. Research on how sulphonation influence shives content indicate an electric energy reduction potential of 200 kWh/t corresponding to an energy saving potential of 200 GWhel/year, as Swedish CTMP- production is about 1Mt/y.