1. Tray Drier Bernal Kim, Geo Dela Cruz, Patrick Dolot, Max
Escoto, Ezekiel
Eugenio, Darwin

2. Objective
To determine the rate of drying of wet sand with a known surface area under constant drying conditions
To determine the mass transfer coefficient in the operation.

3. Theory
Drying
a unit operations, mass transfer process that is involved with the removal of water or a solvent by evaporation from a solid.
can be a batch operation or a continuous operation

4. Theory Batch Drying Continuous Drying
Drying under a specific one-time set of feed
Drying at constant conditions
Continuous Drying
drying of a continuous flow of solids and drying medium under variable conditions

5. Theory
X=W-X* (all in dry basis) Where: X = Free Moisture Content W = Total Moisture Content X* = Equilibrium Moisture

6. Theory 𝑅= 𝑄 𝐴 −𝑑𝑋 𝑑Θ Where:
𝑅= 𝑄 𝐴 −𝑑𝑋 𝑑Θ
Where:
R = drying rate or the Weight of moisture removed per time per Area
Q = Weight of dry solids
A = Area in direct contact with drying medium
X = Free moisture content
Θ = time

7. Figure 1. Drying Rate versus Free Moisture Content
Theory
Figure 1. Drying Rate versus Free Moisture Content

8. Theory 𝑅=𝑘′( 𝐻 𝑠 −𝐻) Where:
R = drying rate k’ = mass transfer coefficient
Hs = Humidity of liquid surface
H = Humidity of the main stream

9. Equipment / Materials Tray Drier (insert model here) Anemometer Sand
Tyler 20 mesh screen

10. Procedure A tray is measured for its weight and dimensions
Sand is sieved with a 20 mesh screen
The sieved sand is transferred into the tray, layered equally and then was weighed.
The tray drier was turned on then the temperature was set to 95oC

11. Procedure
After the tray drier reached the set temperature, preliminary conditions were measured using the anemometer
The sand was then wetted and then weighed again
The sand was put inside the tray drier

12. Procedure At every 5 minute interval:
Outlet air conditions were measured
Sand was weighed using a top load balance
This was repeated until constant conditions were met

13. Data

14. Time, min Wind Velocity, m/s Temp, °C Dew Pt, °C %RH Ws, g 98.3 7.2
98.3
7.2 5
2.8
101.9
34.6
5.5 10 3
106.7
36.6
4.7
1149.3 15
3.1
105.5
25.5
4.6 20
105.7
35.5
4.5
1094 25
1.6
107.3
35.7
4.4
1070 30
1.5
100.9
35.1
4.3 35
0.6
106.1
33.8 40
1.3
106.2
32.2
3.9
1005.7 45
0.4
105.8
29.7
3.2
990.46 50
103.9
23.7
2.7
978.88 55 1
100.1
17.9
2.1
974.5 60
1.1
99.5
13.9
1.7
971.87 65
0.8
102.3
7.6
971.46 70
1.8
97.6
5.8
971.4 75
95.6
2.4
971.41
Table 1. Raw Data

15. Treatment of Data

16. Determination of Weight of Dry Solids
X*=0 gwater/gdrysolids
Average final weight: kg
0 = (AveFinalweight – Qave)/ Qave
Q = kg

17. Total Moisture Content
E, Mass of Empty Tray = 0.255
Q, Mass of Bone dry Sand =
Ws, Mass of Tray with Sand @ θ=5 = kg
W = mass of moisture / mass of bone dry solid
W = (Ws-E-Q)/Q
W= kg moisture/ kg dry sand

18. Table 2. Data Gathered and Calculated
Time, min
Ws, g W X 5 10
1149.3 15 20
1094 25
1070 30 35 40
1005.7 45
990.46 50
978.88 55
974.5 60
971.87 65
971.46
5.12E-05 70
971.4
-3.3E-05 75
971.41
-1.9E-05
Table 2. Data Gathered and Calculated

19. Rate of Drying By Graphical Differentiation of W vs θ
θ=5
Ra = (W/θ)
Ra = ( /5)
Ra= kg moisture/ minute-kg dry sand

20. Table 3. R by graphical differentiation of W vs ɵ
Time, min W Ra 5 10 15 20 25 30 35 40 45 50 55
E-05 60
E-05 65
5.12E-05
E-07 70
-3.3E-05
E-07 75
-1.9E-05
E-07
Table 3. R by graphical differentiation of W vs ɵ

21. Figure 2. Total Moisture vs Time

22. Rate of Drying By Computing the Slope of curve W vs θ
R = - (dW/dθ)
R = - ( – )/(10-5)
R= kg moisture/ minute-kg dry sand

23. Figure 3. Drying Rate vs Free Moisture

24. Mass Transfer Coefficient
Xc =
T= deg C
%RH= 4.6
degC= kpa
0.046 = Pa / kpa
Pa = kpa
H = Pa / ( – Pa) H=
Hs = (Ps / ( – Ps)) *(18/29)
Hs =
K = Rc/(Hs-H)*A
K =

25. Conclusions
It is concluded that the tray dryer is not suitable for large operations
The rates of drying and mass transfer coefficient was determined by the data gathered in the experiment

26. Recommendations Use other types of feed to determine it’s capability
It is recommended that a holder for the anemometer is to be installed
Clean the tray dryer
Mittens for handling the tray
If possible a weighing scale is to be installed inside the dryer