Characteristic drying curves for cellulosic fibres

The tray drying of cellulosic fibres from citrus fruits has been studied here, for hot air drying at dry-bulb temperatures from 40–80 ◦C, a wet-bulb temperature of 40 ◦C, and a cross-stream air velocity of 1.3ms−1. It appears that a single characteristic drying curve may be adequate to describe the drying behaviour of the fibres, whether the fibres are mixed with water or with hibiscus extract. The amount of hindrance to moisture movement seems to be small relative to many other materials, and the characteristic curve has the approximate form f =Φ0.5. Comparison of the characteristic curve with the normalized drying rates measured by previous workers suggests that the characteristic curve remains applicable for sugar beet fibres dried in hot air over a wider range of temperatures, from 130 to 183 ◦C. The importance of the basic cellulosic component in the fibres in controlling the drying behaviour may explain the absence of any significant difference between the normalised drying rates for sugar beet fibres and those for citrus fibres. In the context of drying the fibres by other methods, including spray drying, compared with the tray drying used here, the absence of substantial additional hindrance to the movement of moisture caused by the extract (compared with water) may be useful.