Equilibrium Moisture Content Relations and Drying Control in Superheated Steam Drying

Proper control of EMC conditions is of importance in any wood seasoning process. Conventional EMC charts for wood are limited to temperatures below 212?F. The author presents a chart which gives relative humidities and EMC values as functions of dry and wet bulb temperatures at normal atmospheric pressure up to a dry bulb temperature of 300?F. The usual practice in high temperature drying requires heating of the charge in a saturated atmosphere to prevent drying until the wood has become thoroughly heated to 212?F. Then the dry bulb temperature is increased to a value corresponding to the desired EMC while maintaining 100 percent steam content. After the charge has become partially dry, the EMC may be lowered by further increasing the dry bulb temperature. Often, however, the kiln vents are opened to admit some air and thus lower the wet bulb temperature while keeping the dry bulb temperature constant.

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