Page 336 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Packed Towers 325

1 .O
0.8
0.6
0.5
- 0.4
6 0.3
-
P 0.2
-
m
0
*
2
!3 0.1
c
0.08
8 0.06
0.05
0.04
5 0.03
ul
p! 0.02
a
0.01
0 500 1000 1500 2000
10 20 30 40 50 100 150
Boil-Up Rate, pounds per hour per square foot
Flow Rate, percent of flood
A B
Figure 9-50. HETP and pressure drop data for a typical distillation system. Packing: equivalent to X-200 (8 strands), stainless steel. System:
methylcyclohexane and toluene. Reflux Ratio: 100%. Column Diameter: 18 inches. Packed Height: 5 feet. Used by permission: ACS Industries,
Inc., Separation Technology Division, Bull. B-129 (1 992).
3. Using an available HETP value for a specific Type X sure drop should be calculated for each foot of packing,
or S packing to convert to a column of different diam- or less, adjusting the load. This particularly applie, to vac-
eter, use the “rough” correction factors in Table uum columns or tall columns at high pressures. Maximum
9-36C. These factors recognize that larger diameter heights of a packed section in a column should be deter-
columns have more uneven liquid distribution. When mined after consultation with the manufacturer.
no HETP values or data are available, it is suggested
to use the approximation developed for S-100 pack- Pressure Drop (Estimated):
ing. Estimating HETP:
Use Figure 9-49 to estimate column pressure per foot of
HETP = [0.18 + po,55]/[l.2S + (3.15/Ro.“)] (9-65) packing height referenced to liquid load as percentage of
maximum flood load. For varying load, perhaps *‘LO%-
where. HETP = height equivalent to a theoretical vacuum systems and varying latent heats in the column,
plate/tray/stage, ft calculate the pressure drop for each foot of packing or
p = liquid viscosity, CP less; this requires adjusting the percentage load in each
R = liquid rate, gal/hr/ft2
calculation.
If p is less than 0.30 cp, use 0.52 in place of the p0.55 term. Koch Sulzer Structured Packing [I 001
To convert an available HETP value for a given system
and column diameter to a different packing in the same This packing is woven wire mesh with the following char-
series (X or S) , assume HETP is inversely proportional to acteristics as reported by the manufacturer/licensee [ 1001 :
the specific surface (consult manufacturer for this detail).
HETP of about 7 in., even at low liquid and vapor
HETP2 = HETPl (SS1/SS2) (9-66)
loads.
where 1 and 2 = two different wire mesh packings Efficiency essentially independent of column diameter.
Capacity and pressure drop characteristics superior to
For highly varying vapor loads through the column, the best commercially available mass transfer devices.
pressure drop may be estimated for differences in latent Specific pressure drop of 0.2 mm Hg per theoretical
heats from one point in the column to another, the pres- tray