Studies of Wood and Wood Handling

Studying wood can provide insights that are crucial to answering several important questions in the pulp and paper industry, one of which is whether it is possible to introduce new wood species into production while maintaining the desired properties of the resulting pulp.

At RISE, we conduct extensive investigations of different wood materials to evaluate their suitability for pulp production. Our analyses focus on the chemical composition and structural quality of the wood, allowing us to assess its economic viability in relation to production costs and the resulting pulp quality.

We also investigate the processability of the wood, including its chippability and ease of handling during mechanical processing. These factors are evaluated in terms of their impact on the efficiency of operations and the quality of the final pulp product. An important part of our research involves characterising the mechanical and physical properties of the resulting pulp and paper, such as tensile strength and bulk density.

Our drip-feed chipper is designed to produce high-quality wood chips with precisely controlled dimensions. Before being used in laboratory experiments, the chips undergo careful characterisation, including assessments of size distribution, geometric shape, moisture content and chemical composition.

RISE has developed a standardised and well-established protocol that enables objective and comparable evaluations of different wood handling systems. By following this protocol, we can systematically analyse and compare performance, energy efficiency and functionality between different solutions. This provides manufacturers, suppliers and users with a reliable basis for decision-making when choosing or further developing wood handling technologies.

Optimising Debarking for Cost and Quality

Debarking studies play a crucial role in optimising the balance between cost efficiency and product quality, using both proximity to processing facilities and specialist expertise. Identifying the most efficient debarking method can lead to significant cost savings. For example, in a plant with an annual timber expenditure of SEK 1 billion, a reduction in timber losses of just 1% can yield savings of around SEK 10 million. In addition, consistent processing of heterogeneous wood sources contributes to improved pulp quality by promoting a uniform fibre mix.

A typical debarking study starts with the selection of about 200 logs from different lots. To minimise the impact of damage caused by felling or transport, a segment is cut from each log for analysis. Then bark and sapwood are removed to determine bark content, dry matter, bulk density and log diameter.

The logs are then mechanically debarked in a rotating drum, where samples are taken to evaluate wood loss, residual bark content and overall debarking efficiency. Drum residence time is assessed by applying a visible colour marker to a group of 100 logs and following their path through the system. As larger and heavier logs tend to leave the drum more quickly, it is important to carefully select a representative sample to ensure robust and accurate analysis.

The insights gained from these studies form the basis for adjustments to the operating parameters of the drum and optimisation of the wood mix, improving both process efficiency and product quality.

Optimising Wood Blending in Pulp Production

Understanding how different wood species interact with production processes and affect the quality of the final product is crucial for informed raw material choices. A key question is how much of a particular wood species can be mixed without degrading the pulp quality, which requires well-balanced mixing ratios for optimal performance and resource efficiency.

Chip size also has a major impact on pulp properties - it affects fibre structure, strength and processing efficiency - so it is important to evaluate it to maintain quality and uniformity.

In the RISE pilot boiling plant, up to six wood species or chip fractions can be processed separately in a single boiling cycle. This allows detailed studies under controlled conditions. After defibration, we evaluate yield, kappa number, viscosity, rejects, chemical composition and physical properties. Chip thickness is particularly critical in power boiling due to its impact on impregnation.

This is followed by bleaching trials to evaluate bleachability, strength and optical properties. The RISE customised refiner and pilot paper machine allows for further analysis of paper properties, supporting a comprehensive material assessment.

As wood prices fluctuate, interest in studying wood mixtures continues to grow. Mixtures of eucalyptus with birch or aspen, for example, require careful control to ensure quality. In Europe, species such as poplar, oak and beech are also important. Where wood chips are not available, we process logs in-house, allowing robust testing of new raw materials.