1. CHEE 4401 DRYING u we are primarily concerned with drying wet porous solids (granules) u important in ensuring proper moisture content  low enough to prevent product degradation and ensure good powder flow, but high enough to provide good tablet properties

2. CHEE 4402 u General process heated air

3. CHEE 4403 u drying is a result of simultaneous heat and mass transfer u mass is transferred as a result of  diffusion  capillary flow u drying rate is determined by T, gas flow rate, humidity of gas

4. CHEE 4404 definitions u psychrometry  determination of the vapor concentration and carrying capacity of drying gas u wet bulb T u dry bulb T u relative humidity (RH) u moisture content

5. CHEE 4405 Psychrometric Chart

6. CHEE 4406 Example u using psychrometric chart, determine the relative humidity and moisture content in the air if the wet bulb T is 35 C and the dry bulb T is 50 C.

7. CHEE 4407 Types of Dryers

8. CHEE 4408 Tray/Truck Dryers u Static - Bed  common

9. CHEE 4409 Drying Time profile drying behavior for static bed

10. CHEE 44010 Fluidized Bed

11. CHEE 44011 Spray Dryer

12. CHEE 44012 Drying Equations u Tray/Truck Dryers  constant rate drying stage only l parallel flow over a static bed l perpendicular flow through a bed

13. CHEE 44013 Drying Equations u Fluidized beds and spray driers  use correlation for flow past an individual spherical particle

14. CHEE 44014 Example Wet granules (density = 1.5 g/cm 3 ) are spread onto a screen at an amount of 10 kg/m 2 of screen. The bed porosity is 45% and the wet granules have an average diameter of 300  m. Air at 60C(dry bulb) and a wet bulb temp of 25 C is passed through the bed at a velocity of 0.15 m/s. How long will it take to dry the granules from 20 to 10 % moisture? The critical moisture content of the granules is 9 %.