The RecuDry system consists of two modules: A Recu module and a condensation module. In the Recu module, the drying air is saturated by means of circulation and reheating until the optimal saturation point is reached. A partial current of this high-energy air is fed into the condensation module. The contained energy (that is predominantly latent) is pre-heating the fresh air for the condensation module. By means of an air-air heat exchanger, most of the input energy is recovered which guarantees highly efficient drying.

Next to energy saving ratios of 35 up to 55 %, the special features of this system are significantly reduced exhaust air streams and emissions. The extent of energy saved mainly depends on two determining parameters: on the one hand, the size of the relevant drying surface, and on the other hand the outer temperature. In case the latter drops, energy saving increases since air preparation is only marginally dependent on recirculation air. The heating medium used is water glycol.

In Gruvön, Stora Enso Timber is producing an annual output of 370,000 m3 of lumber and 150,000 m3 of further processing goods. Sawing by-products are used for pellets production with a production volume of 100,000 t/yr. The system in Gruvön has a wood chip output of 10 t/h with a water evaporation rate of 8.75 t/h. It reduces the water content of the woodchips from about 50 % to 10 % – and all this on a length of 45 m.

The long-established Bavarian company draws on experience made with installing over 400 belt dryer systems already. Every year, 5 million t are dried on Stela dryers for pellets production.

Cover: The new drying system of Stora Enso in Gruvön/SE

Source:
Holzkurier from 28.06.2018, edition 26