Flatbed Dryer Design2

DESIGN OF MECHANICAL FLAT - BED DRYER ASSUMPTIONS:

500 24 15

Initial Palay Weight, Wi : Initial Moisture Content, Mci : Final Moisture Content, Mcf:

Kgs. % %

Drying Properties: Atmospheric Air:

70 % 20 °C 68 ºF

Relative Humidity: Temperature:

Abs. Humidity, H: Enthalpy, E: Abs. Volume, Va:

Inlet Air:

Outlet Air:

42 °C 107.6 ºF

0.01 Kg./Kg dry air 11 Kcal/Kg. 0.91

0.01 Kg./Kg dry air 16.1 Kcal/Kg. cu.m./kg.

1.) Calculate for the Water Removed: Ww = Wi - Wi(1-Mci)/(1-Mcf)

52.94 Kgs. of Water

at 8 hours drying operation:

6.62 Kgs./hour

2.) Calculate air volume required to remove the water from the grain: G = Ww/(H2-H1)

1,408.01 Kgs./hour

Q = G*r

1,278.47 cu.m./hr.of dry air 0.36 cu.m./sec.of dry air 751.90 cu.ft./min.of dry air

3.) Calculate the Heat energy required: q = G(E2-E1)

7,180.85

Kcal/hr.

4.) Calculate/Determine the amount of fuel to Dry the Palay @ 14% MC for 8 hours. Sr

Fuel

Approx heating value Kcal/Kg Natural State

A

Dry State

Fuel Reqt. Kg/8-hr.

BIOMASS

1 2 3 4

Wood

1500

3500

Cattle dung

1000

3700

Bagasse

2200

4400

Wheat and rice straw

2400

2500

5

Cane trash, rice husk, leaves and vegetable wastes

3000

3000

Coconut husks, dry grass and crop residues

3500

7

Groundnut shells

4000

4000

8

Coffee and oil palm husks

4200

4200

9

Cotton husks

4400

4400

Peat

6500

6500

6

10 B

16.41 15.53 13.06 22.98 19.15

3500

16.41

14.36 13.68 13.06 8.84

FOSSIL FUELS

1 2 3

Coal

5500

Coke

6500

Charcoal

7000

10.44 8.84 8.21

75 % 25 °C 77 ºF

4 5 6

Carbon

8000

Fuel oil

9800

Kerosene and diesel

10000

7 8 9 10 11

Petrol

10800

Paraffin

10500

12

Bio gas(Kcal/cu mtr) (12 kg of dung produces 1 cu. Mtr gas)

Natural gas

8600

Coal gas

4000

Pressure Drop

860

7.18 5.86 5.74 5.32 5.47 6.68 14.36 66.80

Kw/8-hr.

128.85

kgs. of dung (e.g.swine manure, etc) reqd.

5350

5.) Calculate the Drying Bin dimension:

Air Flow Pressure Rate per Area of a drop per unit Area of Drying Bin Foot depth Drying Bin, Required: of Grain, Ph: Q: CFM/sq.ft.

12.50 14.00 17.00 21.00 24.00 28.00 30.00

Inches, Water

3/16 1/4 5/16 6.5/16 1/2 5/8 10.5/16

Square Foot of Grain

60.15 53.71 44.23 35.80 31.33 26.85 25.06

Drying Bin dimension

Width,m.

1.50 1.50 1.50 1.50 1.50 1.50 1.50

Length, m.

3.73 3.33 2.74 2.22 1.94 1.66 1.55

1.) Calculating the Moisture Ratio: MC, %:

24.00

MR = (MC - Mce)/(Mci-Mce)

1.00

MR = e^(-x)(t^y)

-0.52

Where:

0.59

x = 0.026 - 0.0045h + 0.01215T Y = 0.013362 +0.194h - 0.000177h^2 + 0.009468T

2.) Calculating the Drying Time: td = M/V(ha-hea)

3.30 Hours

t0.5 = td/Y

0.25

DM = V*Cp*t0.5*(Tdh-Twa)/Ln/(Mco-Mce)

0.52 13.12