How to use the DRYIT semi-continuous tray dryer
Practical Action
Figure 8: Section of a psychrometric chart to show specific volume of surrounding air
• Tray loading: = 75kg of material
• Initial Moisture content: = 90%
• Desired final moisture content: = 6%
• Total moisture in fresh material = 75 x 0.9 = 67.5 kg
• Total weight of bone dry material= 75 - 67.5 = 7.5 kg
• Moisture in dried product: = 7.5 x 0.06 / 0.94 = 0.5kg
• Moisture to be lost from material = 67.5 - 0.5 = 67kg
To calculate drying time
= Total moisture to be lost / Rate of moisture loss
= 67 / 16.66 = 4.02 hours
Drying time 4.02hours = 4hrs 1min
Hence after 4 hours it should be possible to dry 75kg of herbs to a moisture of 6% assuming
a pick-up factor of 50%.
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