Virkestorkning i vandringstorkar

The aim of this project has been to develop a computer based simulation model for the timber drying process in progressive kilns and to use this model for an analysis of the process, with special emphasis on energy and cost efficient drying. The software, TorksimLC, is based on the same principles as our corresponding models for batch kilns. In this way direct comparisons between different drying methods can be made. TorksimLC includes both the single stage and the both common types of two stage progressive kilns. The software has been verified and validated based on experimental results from drying tests in full scale. The model accuracy has been shown to be comparable to the accuracy of the corresponding models for batch kilns. It is judged that this accuracy is sufficient for industrial analyses at the sawmills. The analysis of the drying process has clearly shown that the temperature level, at which the drying is performed, has an utmost importance regarding both the energy consumption and the drying costs. Even a small increase in the temperature level has a positive effect. A comparison of different types of dryers has shown that two stage progressive kilns are more cost efficient than single stage kilns, although the energy consumption is about the same. Compared to batch kilns the progressive kilns require longer drying times but both the energy consumption and the drying costs are clearly lower. The progressive kilns have a good potential for both energy and cost efficient timber drying. Progressive kilns can not in all respects replace the batch kilns, but it seems that this potential is not fully utilised today. Key words: progressive kiln, timber drying, simulation, energy consumption, drying costs