Heat Pump Dehumidification During the Curing of Flue-Cured Tobacco

A study was conducted in order to investigate the incorporation of dehumidification into the curing cycle of flue-cured tobacco. Multiple cures of cultivar K326 flue-cured tobacco were made over three harvesting seasons. Tobacco from the same source and stalk position was cured in a barn coupled to a heat-pump-dehumidifier and, for comparison, in a conventional barn heated with an open flame propane furnace. In the heatpump barn, dehumidification was applied during the lamina and stem drying phases, but not during the coloring and color-drying transition phases of the curing cycle. During successive cures of each season, modifications were made in the operation of the heatpump barn in order to improve performance. A procedure for curing with dehumidification was developed. Dehumidification was found to automatically raise temperature and reduce humidity, causing a set in lamina color. Tobacco cured in the heat-pump barn was found to have at least comparable quality with that cured in the conventional barn as determined by standard chemical analyses and USDA grade. There was a significant reduction of Tobacco Specific Nitrosamines (TSNA) in the tobacco cured in the heatpump barn as compared with tobacco conventionally cured. A short burst of high temperature heat was effective in finalizing stem drying in the heat-pump barn. Dehumidification constituted only 26.8 percent of the total energy use in the heat-pump barn.