Wet Line Extension Reduces VOCs from Softwood Drying

Abstract

VOC emissions from drying softwood oriented strand board (OSB) or sawdust increase with decreasing particle size, and with increasing oven temperature and airflow rate. Particle size is related to surface area, an increase of which preferentially dries out the surface. Similarly, drying at high temperature or under high airflow depletes surface moisture. The optimum drying strategy from the perspective of reducing VOCs should minimize temperature imbalances and moisture gradients within the flake in order to reduce dry spots. Since surface dry-out will impede the movement of water to the surface, its onset should be delayed. Hence, the wet line should be maintained at the surface for as long as possible to keep the furnish evenly wet during drying.

Reducing VOC Press Emission from OSB Manufacturing

“…Therefore, they concluded that keeping temperatures below 160°C should lead to lower VOC emissions. It was also found that increasing flow rate increases VOC emissions 10 . This was attributed to surface drying.…”

“…They also suggest that only a portion of the potential VOCs available for release are lost during drying. A study 10 of the effects of particle size, temperature and flow rate on VOC emissions (from softwood flakes) was conducted. It was found that emissions increased with decreasing particle size, which means that removal of fines reduces emissions.…”

“…It was found that emissions increased with decreasing particle size, which means that removal of fines reduces emissions. This emission decrease is due to the fines drying out quickly and experiencing higher temperatures 10 . The authors also found an increase in VOCs at 160°C 10 .…”

“…This emission decrease is due to the fines drying out quickly and experiencing higher temperatures 10 . The authors also found an increase in VOCs at 160°C 10 . This was believed to be due to α-pinene having a boiling point of 156°C.…”

Low VOC drying of lumber and wood panel products. Progress report Number 9 [January 1999]

“…The mill was interested in alternative means of making measurements and sent samples of fiesh flakes to the Institute of Paper Science and Technology for analysis. These samples were wrapped, stored cold, and dried in a 130°C tube furnace equipped to monitor total hydrocarbon emissions (Banerjee et al, 1998). The results of laboratory analyses fiomthe first two year's samples demonstrated that the VOC concentrations varied by as much as 500% @om -300 pg/g to 1500 g/g on a wet basis), as shown in Figure 1.…”