Microwave Drying of Wood Strands

Abstract

Characteristics of microwave drying of wood strands with different initial moisture contents and geometries were investigated using a commercial small microwave oven under different power inputs. Temperature and moisture changes along with the drying efficiency were examined at different drying scenarios. Extractives were analyzed using gas chromatography/mass spectrometry (GC/MS). The results showed that the microwave drying process consisted of three distinct periods (warm-up period, evaporation period, and heating-up period) during which the temperature, moisture change, and drying efficiency could vary. Most of the extractives were remnant during microwave drying. It was observed that with proper selections of power input, weight of drying material, and drying time, microwave drying could increase the drying rate, save up to 50% of energy consumption, and decrease volatile organic compound (VOC) emissions when compared with the conventional drying method.

Keywords:

• Microwave drying
• Wood strand
• Temperature
• Moisture content
• Energy efficiency
• Extractives

ACKNOWLEDGMENT

This work was supported by the USDA Wood Utilization Research Grant and the Tennessee Agricultural Experiment Station, Project #83. The authors thank colleague Chris Helton for his helpful assistance. The authors also thank Huber Engineered Wood LLC for providing experimental materials.

Notes

^a 147.9 mm long, 89.7 mm wide, 8.2 mm thick, initial moisture content = 95.7%.

^b 152.9 mm long, 87.4 mm wide, 7.0 mm thick, initial moisture content = 96.3%.

*Unit energy consumption.