Tackling Water Shortage by using
Solvent Extraction for Efficient
Desalination
Kary Thanapalan, Vivek Dua
Centre for Process Systems Engineering, Chemical Engineering Department
University College London
Presentation Outline
 Introduction
 tackling water shortage
 Conclusions
Introduction
• Water is essential for life.
• Inadequate water supply leads to water poverty
• Tackling water shortage
• Desalination methods
Introduction
Seawater
Desalination
Potable water
• High capital cost of equipment and
operating cost*
• Required final product quality
Tackling water shortages
Water distillation technologies
• Two technologies
 Thermal methods
 membrane separation process
Popular distillation methods:
Multiple Effect Distillation (MED)
Multi-Stage Flash (MSF) distillation
Vapour Compression (VC)
Reverse Osmosis (RO)
Tackling water shortages
Objective: Tackling water shortages to overcome
water poverty with minimum energy consumption
Problem Statement
GIVEN
 Seawater feed
 minimum purity level for the desired product
DETERMINE
 Production of more potable water with respect to purity, energy
efficiency and cost
Tackling water shortages
Solvent Extraction based Efficient Desalination
(SEED) system
 Energy efficient
 Less expensive to operate
 Can use low-grade of waste energy for desalination
 SEED is a more sustainable option
Tackling water shortages
Way ahead: Model-based optimization
Model based optimization can assist in making
assessment about energy efficiency, cost analysis etc.
Developed a mathematical model that can be used
for optimization of the process
Flow-sheet of the SEED process
Flow-sheet of the SEED process
Optimisation model
Objective function:
min f  x   
x
Subject to:
h x   0
g x   0
Variables: here the optimal values of variables
representing flowrates, temperatures etc.
h x   0
g x   0
x
Equality constrains- governed by each of the subsystem
Models equations
Inequality constrains – specifications of the operation
Of the system
Optimisation model
Inequality constrains
g x   0
F1w
:
9534 m 3 / hr  F1w  13166 m 3 / hr
F1s : 45.4 Kg / hr  F1s  177 Kg / hr
F1A : 0.038 Kg / hr  F1A  0.043 Kg / hr
p
:
6P
F
T8
:
10109 m3 / hr  F6pP  10350 m3 / hr
298K  T8  330K
Results
The optimisation of the energy consumption of the SEED process is carried
out w.r.t. the base case of the process presented in Lazare (1982)
Process
Energy used
Potable water
SEED
1.45  107 W
1603 m 3 / hr
Lazare(1992)
1.058  10 W
1578 m 3 / hr
8
Model based optimization based approach allows the evaluation of the
SEED system performances without the need of real plant implementation
in the development stage.
Reducing cost & time along the design stage and test
Conclusions
 Water poverty can be addressed by economically viable methods for
water desalination
 SEED process is the alternative to the traditional desalination process
 Energy consumption and total cost of the SEED process is much lower
than the traditional desalination process
 SEED process can use low-grade of waste energy for desalination,
which is not readily possible for other traditional desalination
technologies
 SEED a more sustainable option and model based optimization can
assist in making such assessment and exploring further option for
energy efficiency
Thank you!!