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Composition of Methanol-Water Batch Distillation. September 20, 2005. Prepared by: Jason Hixson Don ScottMichael Hickey. Objective. Determine the composition of liquid methanol-water binary system at equilibrium based on temperature in a distillation column. - PowerPoint PPT Presentation
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Composition of Methanol-Water Batch Distillation
Prepared by: Jason Hixson Don Scott
Michael Hickey
September 20, 2005
Objective
• Determine the composition of liquid methanol-water binary system at equilibrium based on temperature in a distillation column.
Vapor-Liquid Equilibrium Diagram
Antoine Equation
*ln m
Bp A
C T
*,m wp Vapor Pressure in mmHg of methanol and water.
T is the absolute temperature
A, B, and C are constants.
*ln w
Bp A
C T
Antoine Constants
• Are calculated using using the known temperatures and vapor pressures from Perry’s Chemical Engineers Handbook.
p*(mmHg) T(C )1.00 -44.005.00 -25.30
10.00 -16.2020.00 -6.0040.00 5.0060.00 12.10
100.00 21.20200.00 34.80400.00 49.90760.00 64.70
p*(mmHg) T(C )1.00 -17.305.00 1.20
10.00 11.2020.00 22.1040.00 34.0060.00 41.50
100.00 51.60200.00 66.50400.00 83.00760.00 100.00
WaterMethanol
Antoine Constants
•Arbitrary values are then chosen for A, B, and C giving an incorrect vapor pressure.
•Excel solver is then used to find values of A, B and C for both methanol and water which gives the correct pressure.
*,ln m w
Bp A
C T
METHANOL A 18.5875B 3626.5500C -34.2900
WATER A 18.3036B 3816.44C -46.13
* ** * (1 )* *total m m m m w wP x p x p
Van Laar’s Model
Gamma correction factors for non-ideal system.
2
exp[(1 )
mm
m
AAx
RTBx
2
exp[(1 )
ww
w
AAx
RTBx
Gamma Correction Factor
Ideal Gas Constant = 1.987 cal/K*g-mol
Temperature (K)
A and B are constants
, *
*
*m
m actualm m
y P
x p , *
*
*w
w actualw w
y P
x p
Using data from Perry’s where P is 760 mmHg the constants A and B can be calculated using solver in Excel
T (C) xa ya100 0 096.4 0.02 0.13493.5 0.04 0.2391.2 0.06 0.30489.3 0.08 0.36587.7 0.1 0.41884.4 0.15 0.51781.7 0.2 0.57978 0.3 0.665
75.3 0.4 0.72973.1 0.5 0.77971.2 0.6 0.82569.3 0.7 0.8767.5 0.8 0.91566 0.9 0.95865 0.95 0.979
64.5 1 1
GivesVAN LAAR A= 585.6215111LIQ MODEL B= 375.733096
Raoult’s Law
** /a a a totaly x p P
Vapor Liquid
Set Up
Xa yA T(C) T(K) pA (mmHg) pB (mmHg) G A CALC G B CALC P DIF0.020 0.133 96.591 369.751 2384.780601 672.2824004 2.114262724 1.000486141 760 0.001905382
•Set arbitrary temperature = (Pcalc-Pactual)
Use Solver to minimize DIF cell by changing T(C).
METHANOL- WATER
65.000
70.000
75.000
80.000
85.000
90.000
95.000
0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.000
xm, ym
Tem
per
atu
r (C
)
Liquid
Vapor
VLE Diagram
Composition Calculation Using WFIT Program
0.38652+0.39727*B2-0.012737*B2^2+0.00013528*B2^3-(0.00000048036)*B2^4)+1%
Reboiler Composition vs TimeTime Vs Composition
0
5
10
15
20
0 10 20 30 40 50 60 70 80 90
Time (minutes)xM
eth
ano
l (%
)
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
5
10
15
20
0 10 20 30 40 50
Time (minutes)
xMet
hano
l (%
)
Initial xm: 23% Initial Vm: 16.86 L
Tray # 12 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
510
15
20
2530
35
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xM
eth
an
ol
(%)
Tray # 11 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 10 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 9 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 8 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 7 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 6 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
10
20
30
40
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 5 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
05
10152025303540
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 4 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 3 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0
1020
30
40
5060
70
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 2 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Tray # 1 Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Reflux Composition vs Time
0% Reflux75% Reflux 2500 W
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50 60 70 80 90
Time (minutes)
xMet
han
ol
(%)
Time Vs Composition
0102030405060708090
100
0 10 20 30 40 50
Time (minutes)
xMet
han
ol
(%)
Collected 1.69 L Collected 6.38 L
Conclusions
• At 0% reflux the amount of distillate collected was larger than 75% reflux.
• At 75% reflux the purity of methane was a much higher quality.
• If quality is more important then a high reflux percentage is needed.
• If quantity and timeliness is more important then a low reflux is needed.
QUESTIONS?