8. MECHANICAL DESIGN OF PROCESS EQUIPMENTS
1. MECHANICAL DESIGN OF ROTARY DRIER
1. Flight design:
Number of flights = 3 x D. = 3 x2.09
=6.27 ≈ 7 flights are required using lip angle of 45°.
Radial height is taken as 18 of diameter, Radial height = 2.098
= 0.2615m.
2. Thickness of dryer:
Let x be the thickness of drier. Mild steel can be used since it can withstand temperature up to 200°C.
Density = 7688.86kgm
3
. D
2
– D
1
= 2x. Volume of mild steel =πD
2 2
4 - πD
1 2
4 x L
=πD
1
+2x
2
4 - πD
1 2
4 x L = πDLx.
Weight of dryer = π x12.24 x2.09 x x x 7688.86 = 0.626 x10
6
x kg. Assume holdup = 0.2
Volume of drier filled with material = πD
2
L x0.2 4
= π x2
2
x12. x0.2 4
= 7.53 m
3
.
Weight of material at any time = 7. 53 x 1049.2 = 11219.7 kg.
The dryer is supported over two-tension roll assemblies, 20ft apart. It is uniformly distributed load.
Maximum bending moment = WL8 = M. M = 0.626 x10
6
x8 + 11219.7 9 x12 = 0.939 x10
6
x + 16829.5 We know that
M = f xZ. Z = π xD
2 4
– D
1 4
32D
2
. = 0.785x
3
+ 12.59x
2
+ 67.31x.
f = 1800psi. Take factor of safety = 5.
f = 3.6 x10
5
lbft
3
. = 1.75767 x10
4
kgm
2
. Thus M = f xZ on simplification becomes,
1.38 x10
6
x
3
+ 22.13 x10
6
x
2
+ 113.264 x10
6
x – 0.819 = 0
x = 15 mm
3. Diameter of the feed pipe:
Feed rate =10417+212.9= 10629.9 kghour Density of feed = 1410 kgm
3
Hence volumetric feed rate = 10629.91410 = 7.534 m
3
hr Assuming the velocity of air = 150 mhr , for chute inclination of 60
Cross-section of feed chute = 7.53 150 = 0.050 m
2
Diameter of feed chute = √ C.S.A. x4 π = √ 0.050 x 4 π = 0.252 m
4. BHP to drive the drier:
BHP = r x 4.75 x d x w + 0.1925 x d x w + 0.33 w 1000 Where,
w= weight of the drier + weight of the material + weight of the insulation.
w = π x12 x2 x 0.01 x 7688.86 + π 4 x 2
2
12 x0.1 x1410 w = 28.65.65x 10
3
kg
HP of blower: Temperature of atmospheric = 30
C Humidity in air= 16743. 89 kg min = 915. 5 ft
3
min Volume of this air , Q = 279.05 29 x 22. 4 x 303 298
= 219.9 m
3
min = 718.9 ft
3
min
HP of blower = 0.000157 x Q x head developed by water = 0.000157 x718.9 x10
=1.2 hp
5. HP of exhaust fan
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