Page 365 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Mixing of Liquids 333

,5 3. Determine impeller speed:
20
- Number on Curve is Sea le
...
>
....... � Ratio of Impellers, D2 /D1 N =N ( DI )(2x- l)/x (5- 80)
-
Q. 10 � ,, 2s ls 0 2
' �
• ' ' '
wv
eN ' ''
eu; 5 \.. � ,\ 4. Determine power using x and compare with step 5
:,-
-'a "2 \ below:
OE l\\
> Cl) l�
c.
=' 2 "'
:::, .!::! (5-81)
.. Cl)
••
-�
A. Cit
.. :;1.0 �
-.
•...J ...... --..
� 0.7 .............. ._ 5. Determine tank volume:
0. ,, .......... ----
- 0.5 "� r-, 2
0
- � ........ 3
.s
a
a: 4 (5- 81A)
� 5
0.6 0.7 0.8 0.9 1.0
Mixing Correlation Exponent, 1

Figure 5-41. Scale-up relation for power, volume, and mixing slope. and substitute in step 2, solving for P2.
By pennission, Rushton, J. H. and Oldshue, J. Y., Chem. Engr. Prog.,
V. 49, No. 4, 1953, p. 161 [20]. For a scale up of impeller diameters of 2, D2/D1 = 2,
Table 5-7 illustrates the changes to be expected. Such
scale up has been found to be guite reliable.
lines as given in Figure 5-40. It should be determined
on anv system not considered dimensionally similar
or otherwise applicable to cases shown in Table 5-6
or Table 5-7.
In-line, Static or Motionless Mixing
Maintaining (h 0) 1 = (h h on scale-up:
0
For dimensionally similar systems [l 6]: This mixing device contains no moving parts, is rela-
tively simple, and its cost can be guite reasonable when
compared to mechanical driven mixers.
1. Determine from experimental data the Reynolds Static or motionless mixers are a relatively new devel-
number exponent for the system, or use information
in Figure 5-40 if the systems of Table 5-8 can be con- opment and have proven to be effective for many specific
sidered similar, use proper coefficients and solve for and valuable process applications. Although useful for a
wide range of viscosity fluids, some of the units have per-
outside film coefficient, h 0.
formed exceptionally well in the mixing of molten poly-
mers. This type of unit is particularly useful in _liguid-lig-
2. Referring to Figure 5-41, read the new approximate
horsepower per unit volume ratio for the.exponent uid mixing, although some units can be de � 1gn_ed � or
solid-liquid dispersion and for gas-gas and gas-h9md mix-
x and the impeller ratio, D2/D where D2 is the larg-
1,
er impeller diameter. Calculate: ing/ dispersion. Some units are also reported sm_table f?r
solid-solid blending. The three commonly applied units
are from Chernineer (Kenics U.S. Patent 3,286,992),
f,) Ratio from curve, Figure 5- 41 (5 - 79) [Dow Chemical, U.S. Patent 3,168,390]) and Koch Engi-
( � ) / ( Charles Ross and Son (lnterfacial Surface Generator,
2 1
neering Co. (Sulzer Bros. ofWinterthur, Switzerland, U.S.