Page 349 - Chemical Process Equipment - Selection and Design

312 SOLID-LIQUID SEPARATION
so 1
I I
I
z
60 CT 0 40
I
.
u1
v
40 2 F30
d
I f
L
20 = a 20
fl
10
10
Time, minutes 0
0.5 1.0 1.5 2.0 2.5
WASH RATIO
(a) (b)

32
I I

ap 30
c
I
I
I-
W
28
0
W
3
I
8 26
W
4
3
DRY TIME - MIN.

Figure 11.3. Laboratory test data with a vacuum leaf filter. (a) Rates of formation of dry cake and filtrate. (b) Washing efficiency. (c) Air flow
rate vs. drying time. (d) Correlation of moisture content with the air rate, pressure difference AP, cake amount WIb/sqft, drying time
Od min and viscosity of liquid (Dahlstrom and Silverblatt, 1977).

EXAMPLE 11.3 speed in rph and the drum diameter:
Rotary Vacuum Filter Operation
A TiO, slurry has the properties cake thickness = 0.01 m = -5 C
PJl- E) A
200 v,
~-
-
-
c = 200 kg solid/m2 liquid, 4270(0.4) A '
ps = 4270 kg/m3,
/A = 0.001/3600 N hr/m2,
a= 1.6(E12) m/kg (item 4 of Fig. 11.2), wash liquid = pore volume
E = 0.6. = O.Ol(0.6) = 0.006 m2 m2.
With the pressure difference in bar,
Cloth resistance is Rf = l(E10) m-l. Normal peripheral speed is
about lm/min. Filtering surface is 1/3 of the drum surface and ~- 105AP,
d(V/A) -
washing surface is 1/6 of the drum surface. The amount of wash dt (0.001/3600)[1010 + 160(1010)V/A]
equals the pore space of the cake. The cake thickness is to be - 36APb
-
limited to 1 cm. At suitable operating pressures, find the drum 1 + 160V/A.