Distillation Column Specifications
The The colu column mn spec specif ific icat atio ions ns were were foun found d usin using g exte extens nsiv ivee anal analys ysis is and and are are summarized summarized in the following following table. To find these specification specifications, s, many variables were found and calculated. calculated. The liquid density density and vapor density were found in AlcoDens a progr program am foun found d in the the inte intern rnet et that that repor reporte ted d the the dens densit itie iess to be 59.12 59.124l 4lb bm/ft3 and 0.5438lbm/ft3, respectively. Using the sizing notes found found Peters & Timmerhaus2, p. 779781, the velocity was estimated to be 3.1ft/s from the following equation:
Vnf
=
0.3
ρ l
- ρ v
ρ v
=
3.1137 ft / s
=
0.9490 m / s
Assuming 60% of flooding, Vn = 0.6Vnf = 1.8682ft/s =0.5694. The volumetric flow rate rate was calculated to be 137.184 m3/hr which is equivalent to 2.2864ft3/s. The area area of the column is 4.015454 m2 , as calculated from the following equation: equ ation: . An
V =
v
2.2864 =
.5694
=
4.015454 m2
The downcomer is assumed to occupy 10% of the cross sectional area of the column column.. Thus, Thus, the column column area becomes becomes 4.015454 m2 /.9= /.9= 4.46161 4.46161m2, m2, which which is asso associ ciat ated ed with with a downc downcom omer er area area of 0.401 0.40154 5454 54 m. The The colu column mn cons consis ists ts of 20 trays,.which was computed from McCabe-theile Method, shown below.
Graphical Representation 1 0.9 0.8 0.7
Assumed Equilibrium Curve Series1
0.6 y0.5
Line for Ymax
0.4
RL 0.3 0.2 0.1 0 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
x
Also, according to the sizing notes, 5 feet on the bottom and 5 feet on the top are added to the total column height. Thus, the column height is found to be 19 m from the following expression: 20*.8m/tray + 1.5+1.5= 19 m. The column diameter is found by using the following equation for the area of a circle: .
D
4( 4.46161 ) =
=
2.3834 m
π
The duties of the condenser and the reboiler were obtained from from energy balances done previously. Qr= 25,901,591.28 BTU /day and Qc= 12, 937,234.57 BTU /day An effective active area of a distillation tray for an area calculated at 60% flooding is 70% of the tray area, not including the downcomer. Therefore, the active area for the distillation trays is 0.7Ac = 0.7*4.46161m2 = 3.23127 m2 A sieve tray is an inexpensive, efficient means of achieving separation, and is comparable in effectiveness to bubble cap and valve trays at low flooding levels and hole areas of less than 14% of the total active area. Because separation increases as hole size
decreases, provided flow is not restricted, the holes were assumed to be 2% of the total active area. This gives a hole diameter of 4.4 inches according to the following calculations. 0.02*3.23127 m2= 0.0646254ft2 per hole 0.0646254ft2 = 1/4πd2 d = (0.0646254ft2 *4/π)1/2 = 0.286851m Table 1. Distillation Column Specifications
Tray Spacing
.8 m
Type of Trays
Valve
Flooding
60%
Velocity
0.9490 m / s
Column Area
4.46161m2
Column Diameter
2.3834 m
Column Height
19 m
Area for Downcomers
0.4015454 m, 10% of Column Area
Pressure Drop per Tray
0
Condenser Duty
- 12, 937,234.57 BTU /day
Reboiler Duty
25,901,591.28 BTU /day
ref http://www.cbu.edu/~rprice/lectures/distill7.html
