Spectroscopic studies of wood-drying processes

Area of Science:

• Spectroscopy
• Laser technology
• Materials science

Background:

• Accurate monitoring of wood drying is crucial for quality control and preventing defects.
• Traditional moisture meters may not provide detailed insights into the free water evaporation phase.
• Non-intrusive techniques are desirable for in-situ monitoring of material processes.

Purpose of the Study:

• To demonstrate a non-intrusive method for detecting water vapor and oxygen in scattering media using wavelength-modulation diode laser spectroscopy.
• To apply this technique for monitoring the wood drying process.
• To correlate spectroscopic signals with the evaporation of free water and the drying stages.

Main Methods:

• Utilized wavelength-modulation diode laser spectroscopy at 980 nm for water vapor and 760 nm for oxygen detection.
• Exploited the sharp absorption features of free gases compared to broad material features.
• Performed measurements during the wood drying process to analyze gas concentrations.

Main Results:

• Successfully detected water vapor and oxygen non-intrusively in wood during drying.
• Observed a distinct signal falloff for water vapor and a plateau for oxygen indicating complete free water evaporation.
• Identified a significant increase in the ratio of optical absorption signals at 980 nm and 760 nm, correlating with the end of free water evaporation.

Conclusions:

• The demonstrated laser spectroscopy technique provides valuable, complementary information to commercial moisture meters for wood drying.
• The method can precisely identify the point of complete free water evaporation in wood.
• This technique offers a promising approach for real-time, non-intrusive monitoring of drying processes in various materials.