Drying of timber in progressive kilns: Simulation, quality, energy consumption and drying cost considerations

Abstract

Progressive (semi-continuous) kilns for softwood drying are very common in Finland and Sweden and are used in some other countries too. A simulation program has been developed that covers all three types of this kiln. The program calculates the climate in the length direction of the kiln and moisture content, moisture profile, wood temperature, slicing test gap and stress development. Energy consumption and drying costs may also be determined. The temperature level is the most important parameter regarding kiln efficiency. Two-zone progressive kilns are found to be more efficient than single-zone kilns. Progressive kilns have lower energy consumption and drying costs than batch kilns. Experimental full-scale tests show that the timber quality from a progressive kiln is comparable to, or in some cases even better than, timber dried in batch kilns.

Keywords:

• Drying cost
• energy consumption
• progressive kiln
• simulation
• timber drying

*This is an extended and slightly modified version of a paper presented at the 15th International Drying Symposium in Budapest, 20–23 August 2006.

*This is an extended and slightly modified version of a paper presented at the 15th International Drying Symposium in Budapest, 20–23 August 2006.

Acknowledgements

The work presented in this paper has been financed by the Swedish Energy Agency, Valutec AB, WSAB Oy and Swedish sawmills, and this is gratefully acknowledged.

Notes

*This is an extended and slightly modified version of a paper presented at the 15th International Drying Symposium in Budapest, 20–23 August 2006.