Technical information

Country: Sweden
Model: TC Continuous kiln, 1 unit
Capacity: > 100,000 m³/year (≈ 3.5 MMBF/year)
Commissioning: 2013

Bollsta sawmill is one of SCA Timber’s five sawmills and is located in Bollstabruk, Kramfors Municipality, in Västernorrland County.

Nearly 100,000 m³ (≈ 42.4 MMBF) of lumber are dried in the TC kiln each year. Primarily 25 mm (≈ 1 inch) side boards of pine, but the record-fast drying times and high flexibility have also led Bollsta to dry smaller dimensions in the unique facility, which was commissioned in 2013.

A Tailor-made solution

The kiln is the result of SCA Timber’s specific needs and conditions. When Bollsta decided in 2011 to increase the sawmill’s capacity from 450,000 m³ (≈ 190 MMBF) to 525,000 m³ (≈ 223 MMBF), Valutec was tasked with mapping the existing kilns, logistics, and the type of lumber to be sawn. The conclusion was that the new drying capacity should focus on drying 25 mm (≈ 1 inch) pine side boards down to a final moisture content of 18%.

The solution was a transverse circulation (TC) continuous kiln – a model particularly well suited for large volumes of side boards. To meet the desired capacity, it was equipped with no fewer than ten drying zones. The annual capacity at delivery was calculated at 86,000 m³ (≈ 36.4 MMBF) of the chosen dimension, but the final yearly output reached 100,000 m³ (≈ 42.4 MMBF) after fine-tuning.

Efficient drying

The shortest drying times used for 25 mm (1") side boards down to a moisture content of 18% have been just 20 hours – a Swedish record. Thanks to these record-fast drying times and the high flexibility, the kiln has also been used for smaller dimensions, even though the thickest timber in the batch governs the overall drying time.

Dimension changes have been handled efficiently thanks to the automatic climate control in each zone and the straightforward handling for forklift operators, who, through smart logistics and careful load management, have contributed to smooth dimension changes.

Meeting quality requirements

A common benchmark for high drying quality is that the moisture content variation within the timber – the standard deviation – should be less than 10% of the final moisture content. For a target moisture content of 18%, this means a value lower than 1.8%. Results from the TC kiln in Bollsta show standard deviations ranging between 1.2 and 1.5 percent.

“That’s an important factor. Low moisture variation allows us to work with more precise dimensions that suit both planing and optimized sawn timber yield,” says Niclas Larsson.

Close collaboration on development

SCA Timber and Valutec have established a long-term partnership on issues related to lumber drying. An important part of the delivery to Bollsta was the establishment of a joint development steering group.

“We always want to find ways to refine our kilns at customers’ sites, and this is a great example of collaboration on shared development challenges,” says Robert Larsson, CEO of Valutec. From SCA Timber’s side, the collaboration involves staff from the Bollsta sawmill as well as other mills within the group. Valutec continuously develops upgrades for the Valmatics control system software, while SCA Timber’s personnel carry out tests whose results are then analyzed and discussed together.

“It’s a really strong collaboration, allowing us to improve our processes and make the best possible use of our kilns,” says Niclas Larsson.

Why SCA chose Valutec

When SCA decided to expand capacity at its Bollsta facility – investing in a new boiler, an upgraded saw line, and increased kiln capacity – Valutec was entrusted with delivering the channel kiln along with six additional batch kilns.

“We have had very good experiences with previous deliveries from Valutec, and it was easy to place our continued trust in them,” said Katarina Levin, Sawmill Manager.