The perfect combination

Thanks to strong investments in its drying capacity, Rubner Holzindustrie today puts 38,000 tons per year less water on the road than five years ago. Energy savings were only one of many reasons why the company opted for two Dynamic 1003 PREMIUM progressive kilns and ten 1306 PRO fresh air exhaust kilns from Mühlböck.

Located in Rohrbach an der Lafnitz, Rubner Holzindustrie is convinced that lumber drying is one of the most important production steps in the sawmill, where a lot can be gained, but just as much can be lost. “We understand that high-quality lumber drying is the basis for excellent products downstream for us and our customers. In addition, we don't want to haul water around unnecessarily because of the implications in logistics and fuel costs,” explains Managing Director Albert Weissensteiner.
With this in mind, the company decided to invest massively in lumber drying with a round wood cut of 370,000 m3/year. “Since we wanted to dry a lot of side-cut products that always have the same dimensions, the only solution for us was a progressive kiln,” says Technical Manager Rene Karner and adds that they were also talking to other suppliers besides Mühlböck.
In Austria, the Upper Austrian drying specialists are primarily known for energy-saving fresh air / exhaust air kilns, but have also been successfully implementing progressive kiln projects for several years, for example in Germany, North America, Scandinavia, and the Baltic States. At Rubner Holzindustrie, Mühlböck converted ten existing kilns from different manufacturers to a joint control system several years ago and has been supporting them ever since.

The first in Austria
The fact that Rubner invested in Austria's first Mühlböck progressive kiln in 2017 was mostly down to the Type 1003 heat recovery system. “Back then, thermal energy was a bottleneck at our location. In light of the high energy prices right now, we are doubly happy to have opted for this energy-saving solution,” Weissensteiner emphasises. Specifically, Rubner Holzindustrie ordered a Type Dynamic 1003 Premium progressive kiln with pre-, main and after-drying zone. Interestingly, the entire thermal energy required for pre-drying is sourced from the main and after-drying zones. There is no need for additional energy. This allows for the energy-efficient operation of the system – Mühlböck estimates the energy savings potential at up to 50 % compared to traditional systems, depending on application.
“Immediately after its launch, the progressive kiln returned good results,” the person responsible for drying, Manual Schlögl, reports. Above all, he values the great cooperation with Mühlböck: “Of course, the system had to be adapted and optimised at first, but Mühlböck’s team and in particular its Project Manager Christian Grilz were always looking for solutions and were also able to find them quickly.” That's why Rubner Holzindustrie didn't wait long and ordered another progressive kiln of the same type with an equal 30,000 m3 annual performance in 2019. This system, however, has less buffer zones at the end of the dryer as it had to be adapted to space limitations.

Quiet kilns
In 2022, ten Type 1306 PRO fresh air / exhaust air kilns were installed in two stages. “Thanks to these, we can now dry more lumber than we cut and additionally provide us with an optimum mix of flexibility and capacity,” says Weissensteiner, who estimates the location's drying capacity at 270,000 m3 per year, happily. The thermal energy required for this is sourced from an equally new biomass cogeneration plant, the power mostly from a 2.4 MWp solar power system.
Mühlböck equips its Type 1306 PRO units with an active supply and exhaust air system. In contrast to conventional systems, all of the air heated by the heat exchanger is used for drying. This results in energy savings of up to 25 %, depending on outside temperature and batch. Another important topic was noise insulation. “In order to best protect our local residents from noise emissions, we have implemented everything that is necessary and sensible to do so,” says Weissensteiner. In addition to the sound-insulating elements installed by Mühlböck at all supply and exhaust air openings, this also includes a noise barrier at the entire rear of the kilns (see picture above). Since noise pollution has become an increasingly important issue for Mühlböck in recent years, the Upper Austrians have developed a pool of measures from which customers can draw depending on their requirements.

Promises kept
Only a few weeks after the latest kilns were commissioned, Rubner Holzindustrie is very happy with Mühlböck’s overall performance. “All deadlines were kept and the values in terms of drying time, energy requirements and quality, were met or exceeded,” says Schlögl and Weissensteiner adds: “Even though our investments in this field are now complete, Mühlböck will remain an important partner for us in the future.”