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

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.

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

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

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

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

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

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

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

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

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

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

Data

Time, min Wind Velocity, m/s Temp, °C Dew Pt, °C %RH Ws, g 98.3 7.2   98.3 7.2 1187.567 5 2.8 101.9 34.6 5.5 1169.46 10 3 106.7 36.6 4.7 1149.3 15 3.1 105.5 25.5 4.6 1123.38 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 1045.32 35 0.6 106.1 33.8 1023.79 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

Treatment of Data

Determination of Weight of Dry Solids X*=0 gwater/gdrysolids Average final weight: 0.971424 kg 0 = (AveFinalweight – Qave)/ Qave Q = 0.971424 kg

Total Moisture Content E, Mass of Empty Tray = 0.255 Q, Mass of Bone dry Sand = 0.971424 Ws, Mass of Tray with Sand @ θ=5 = 1.169 kg W = mass of moisture / mass of bone dry solid W = (Ws-E-Q)/Q W= 0.27639 kg moisture/ kg dry sand

Table 2. Data Gathered and Calculated Time, min Ws, g W X 1187.567 0.301658 5 1169.46 0.276388 10 1149.3 0.248252 15 1123.38 0.212077 20 1094 0.171073 25 1070 0.137578 30 1045.32 0.103133 35 1023.79 0.073085 40 1005.7 0.047838 45 990.46 0.026568 50 978.88 0.010407 55 974.5 0.004294 60 971.87 0.000623 65 971.46 5.12E-05 70 971.4 -3.3E-05 75 971.41 -1.9E-05 Table 2. Data Gathered and Calculated

Rate of Drying By Graphical Differentiation of W vs θ θ=5 Ra = (W/θ) Ra = (0.276389/5) Ra= 0.055277616 kg moisture/ minute-kg dry sand

Table 3. R by graphical differentiation of W vs ɵ Time, min W Ra 0.301658 5 0.276388 0.055277616 10 0.248252 0.024825196 15 0.212077 0.014138463 20 0.171073 0.008553651 25 0.137578 0.005503105 30 0.103133 0.003437774 35 0.073085 0.002088145 40 0.047838 0.001195948 45 0.026568 0.000590408 50 0.010407 0.000208137 55 0.004294 7.80713E-05 60 0.000623 1.03898E-05 65 5.12E-05 7.87285E-07 70 -3.3E-05 -4.65214E-07 75 -1.9E-05 -2.48114E-07 Table 3. R by graphical differentiation of W vs ɵ

Figure 2. Total Moisture vs Time

Rate of Drying By Computing the Slope of curve W vs θ R = - (dW/dθ) R = - (0.248252 – 0.276389)/(10-5) R= 0.005627 kg moisture/ minute-kg dry sand

Figure 3. Drying Rate vs Free Moisture

Mass Transfer Coefficient Xc = 0.103133 T= 105.5 deg C %RH= 4.6 Ps @ 105.5degC= 124.233 kpa 0.046 = Pa / 124.233 kpa Pa = 5.62959 kpa H = Pa / (101.325 – Pa) H=0.05977 Hs = (Ps / (101.325 – Ps)) *(18/29) Hs = 3.3661 K = Rc/(Hs-H)*A K =0.000197

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

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