B.Tech Thesis Presentation

Dehydration of tert-Butyl Alcohol by Extractive
Distillation: Experimental and Simulation Studies
School of Mechanical and Building Sciences,
VIT University, Vellore - 632014
Dr. G. S. Nirmala
Project Guide
Dr. B. Satyavathi
Project External Guide
Principal Scientist
CSIR-IICT
Ashish Singh (11BCH0003)
Debiparna De (11BCH0016)
MEE499

Challenges in TBA dehydration
2
MEE 499 PROJECT WORK, School of Mechanical and Building Sciences
Azeotrope of
TBA at 0.8824 wt
fraction at
temperature of
79.91 °C at 101.3
kPa
•Conventional distillation fails to break the azeotrope
•Advanced separation technique is necessary
•A novel and efficient extractive distillation technique is adopted in the present study
which is termed as “Saline Entrainer Extractive Distillation”

• Selection of suitable salt and solvent as entrainer with low environmental impact for
dehydration of TBA.
• Gathering and determination of phase equilibrium data for TBA-water-entrainer and
its constituent binary systems at 94.9 kPa.
• To determine the optimal entrainer concentration needed for distilling TBA-water
azeotropic mixture , designing a feasible and economic column with low energy
consumption.
• Economic evaluation of the system proposed in terms of energy and total annual
cost.
3
Objectives of the Project

Saline Entrainer Extractive Distillation (SEED)

Entrainer Selection
Salt
Entrainer
Screening

Residue Curve Map (RCM) topology for
Solvents
6
Ternary Map (Mole Basis)
TBA
( 82.4 7 C)
WA TER
( 100 .02 C)
TEG(2 88.3 8 C)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
79.98 C
TBA
( 82.4 7 C)
WA TER
( 100 .02 C)
EG( 19 7.08 C)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
79.98 C
TBA
( 82.4 7 C)
WA TER
( 100 .02 C)
GLYCEROL( 287 .71 C)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
79.98 C
TBA
( 82.4 7 C)
WA TER
( 100 .02 C)
DMSO( 19 0.74 C)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
79.98 C
TBA
( 82.4 7 C)
WA TER
( 100 .02 C)
TETRA -01 (3 29.3 3 C)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
79.98 C

Pseudo Binary Vapour-liquid
Equilibrium Curve for Entrainers
7
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
x(TBA)
y(TBA)
Triethylene Glycol
Glycerol
Dimethyl
Sulfoxide
Tetraethylene
Glycol
Ethylene Glycol
TBA-H20
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
x(TBA)
y(TBA)
Glycerol
Glycerol+MgI2
Glycerol+MgCl2
Glycerol+NaCl
TBA-water
The solubility of the salts were checked in the selected solvent experimentally from lower to
higher temperatures by slowly increasing the concentrations of salt from 1% to 10%.

Experimental System Selected
 TBA+ water+Glycerol+MgCl2
 The phase equilibrium data was generated which is vital for further design
of continuous system.
 The experiments were carried out in a modified Othmer type ebulliometer .
 Vapor samples collected were analyzed for TBA mole fraction by using gas
chromatography.
8

Schematic Experimental Setup
9
1. Othmer ebulliometer , 2. Salt loading port, 3. Heating cum magnetic plate, 4. Condenser,
5. Sampling port, 6. Thermostat, 7. Voltage regulator, 8. Heating tape, 9. Temp. indicator,
10. Vacuum pump, 11. Trap, 12. Pressure regulator, 13. To manometer

Binary VLE Combinations
10
Thermodynamic
Modeling and
consistency
(ENRTL)
Binary
Interaction
Parameters
Helps in thermodynamic
modeling of ternary and
quaternary system

Electrolyte NRTL interaction parameters
used in this work
11

Experimental Validation for Multicomponent
VLE
TBA+Water+Glycerol TBA + Water+Glycerol+MgCl2
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
x(TBA)
y(TBA)
Est. x-y NRTL
TBA-water
Exp. x-y
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
x(TBA)
y(TBA)
Exp. Gly+MgCl2
Exp. Glycerol
S/F = 0.5, MgCl2=10%
Est. ENRTL
TBA-water
Est. NRTL

Schematic Representation of continuous
SEED
13

Experimental Setup of continuous
SEED
14

Preliminary continuous SEED profile
15
Variation in TBA composition in the distillate Exp. vs Simulations observations

Simulation Process Flow Sheet
16MEE 499 PROJECT WORK, School of Mechanical and Building Sciences
1-Azeotropic feed 2- Mixed saline entrainer 3- Pure TBA Distillate 4- Saline Entrainer+Water
5- Pure Water Distillate 6- Saline Entrainer bottoms 7- Saline Entrainer Recycle 8- Solvent
Entrainer 9- Salt Feed

Process Simulation Basis and Analysis
 A Rad-Frac Column is used as the basis for simulating both the dehydrating and regenerating
column.
 The basis for simulation was 100kmol/hr of azeotropic TBA (saturated liquid).
 The entrainer flow was taken as 50kmol/hr at 70o
C.
 Other initial input values were:
 Number of theoretical stages: 20
 Entrainer stage: 3
 Azeotropic Feed stage: 16
 Reflux Ratio: 0.5
 Sensitivity Analysis was carried out using response surface methodology analysis by varying
two conditions and observing the effect on a single design parameter.
17

Effect of azeotropic Feed Stage and number
of Theoretical Stages
18
Effect on Distillate Composition Effect on Reboiler Duty

Effect of Saline Entrainer Feed Stage and
Reflux Ratio
19

Effect of Salt Concentration in the Solvent
20

Effect of Saline Entrainer Feed Temperature
21

Optimized Operating Conditions Results
Obtained For Both the Columns
22
Operating Variables C1 C2
Feed Flow (kmol/h) 100 87.75
Entrainer Flow (kmol/h) 50 --
Distillate Flow (kmol/h) 62.250 38
Molar fraction of TBA in distillate 0.9999 --
Azeotropic Feed Temperature (ᵒ
C) 30 127
Entrainer Temperature (ᵒ
C) 70 --
Molar Reflux Ratio 0.6 0.6
Number of Theoretical Stages 20 10
Azeotropic Feed Stage 14 5
Entrainer Feed Stage 3 --
Entrainer to Feed Ratio (E/F) 0.5 --
MgCl2 Concentration (g/ml solvent) 0.05 --
Condenser Duty (kW) 1008 718
Reboiler Duty (kW) 1495 1286

Sequential Linear Iterative Optimization

Process Economics for SEEDC
24

Optimization of S/F ratio for SEEDC

Optimization of feed stage location for
SERC
26
▲NSER = 8; ■: NSER = 10; ● NSER = 12

Optimized process flow sheet for TBA
water azeotrope separation

Break down of TAC at optimized conditions
(TAC $1000/year)
28

29

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