Desorption of yellow-poplar in superheated steam

Although drying in superheated steam has certain theoretical advantages, drying conditions in superheated steam dryers must be controlled in order to prevent defects in rapidly drying lumber. Accordingly, equilibrium moisture contents (EMCs) of yellow-poplar were determined by desorption in pure, superheated steam circulated in a new sorption apparatus at temperatures of 120?, 140?, and 160?C and pressures up to 5 atmospheres. The three resulting isotherms, reflecting EMCs at different partial vapor pressures, showed the moisture content (MC) of wood to be controllable below about 12 percent. Isotherms were lower with increasing temperature. At higher temperatures, there was a measurable loss of wood substance, apparently because of thermal decomposition. The EMCs reported here basically verify extrapolations from values reported in the literature.

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