United Arab Emirates University College of Engineering Chemical Engineering Department Graduation Project II

1
United Arab Emirates UniversityCollege of
Engineering Chemical Engineering
DepartmentGraduation Project II

• Designing an Effective Dehumidification Method to
  Produce Fresh Water From Air Faculty Advisor
  Dr. Ali AL Marzouqi

2
Outline

• Introduction
• Summery of Achievement in GP1
• Updated Background Theory
• Detailed Design
• Economical, Ethical and Contemporary Issues
• Project Management
• Conclusion and Way Forward

3
Introduction

• Problem Statement and Purpose
• Shortage of water.
• UAE the water resources have been depleted due
  to
• Increased tourism.
• Construction activities.
• Population growth 1.

Table1 Population for year 2008 and 2009
4
Major Productions of Fresh Water
Consumption of water produced by desalination
plants in UAE is 98 2
5
Desalination Plant Disadvantages

• High cost
• High energy consumption
• Environmental impacts

6
Project and Design Objectives

• Obtain fresh water from the atmosphere using an
  efficient and economic way.
• Selection criteria
• Cost
• Effectiveness
• Simplicity
• Safety
• Ethics
• Practicality for large scale operation
• Minimization of Environmental impacts

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Detailed Design Alternative
The proposed design for the air dehumidification
process to produce water is a modification of a
patent by a US inventor Richard J. Bailey 3
Figure 1 Schematic diagram for water production
system by Bailey
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Summary of Design Process
Figure 2 Schematic diagram of the proposed
dehumidification process.
10
Summary of achievements of GP1
Table 2 Comparison between different technologies
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Tasks

• The tasks required for GPII were as follows
• Design of a commercial-scale dehumidification
  unit.
• Mass and energy balance.
• Process flow diagram using HYSYS and Visio.
• Sizing.
• Material of construction/Cost.
• Instrumentation.
• Health, safety and environmental impact (HSE).
• Economic analysis and business plan.
• Reports and presentations.

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Material and Energy Balance

• Heat exchanger condense water vapor.
• Material balance
• and
• Liquid water condensed
• Air

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• Energy balance
• Air

• Water

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• Storage tank
• Material balance
• Valve
• 
  0

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• Pump
• Material balance
• Energy balance
• 
  
  0
• Power of the pump (kW)
• Head loss ?P/?w g
  
• Blower

16
Updated Background Theory

• Relevant literature for GP 2
• Weather conditions in the UAE including the
  humidity.
• Dubai 4
• Material of construction

Table 3 Dubai temperatures in summer
Summer June July August Average
Temperature (oC) 33.6 35.1 34.6 34
Relative Humidity () 51 54 56 54
Table 4 Dubai temperatures in winter
Winter December January February Average
Temperature (oC) 20 18.3 19.2 19
Relative Humidity () 64 63 63 63
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• Temperature of seawater at different depths of
  the sea5

Figure 3 Seawater temperatures at different
depths
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Environmental Issues for New Literature

• Decreasing the humidity of air.
• Rejecting heat to the seawater from the
  downstream.

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• Detailed Design

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Detailed Design

• Absolute Humidity
• Based on the average temperature and relative
  humidity obtained from Dubai forecasting for
  three months
• Table 5 Temperature, relative humidity and
  absolute humidity in summer and winter seasons
  4

Summer Winter
Temperature (oC) 35 19
Relative Humidity () 54 63
Absolute Humidity (g/m3) 21 11
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Detailed Design
Dew Point Temperatures
Table 6 Dew Point Temperatures
Summer Winter
Temperature (oC) 35 19
Relative Humidity 54 63
Dew Point Temperature (oC) 24 13
Figure 4 Dew-RH Chart 6
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Detailed Design
List of Process Variables

• The dehumidification process is affected by many
  variables. These variables can be adjusted and
  manipulated to achieve the highest water
  production.
• Table 7 List of Process Variables

Process Variables Process Variables
Temperature (Air Water) (oC) T
Air Mass Flow Rate (kg/hr) mA
Water Mass Flow Rate (kg/hr) mw
Air Mass Fraction y
Water Mass Fraction x
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Detailed Design
Design Criteria for the Process Variables
Table 8 Comparison between Middle East
Worldwide water production 7
Year 2006 Desalination Plants Water Production (m3 water/day) Average Water Production/Plant (m3 water/day)
Middle East 12 2,973,800 247,816
World Wide 41 7,040,823 171,727
Average capacity for plants in the Middle East is
higher than that of all plants worldwide. For the
purpose of our calculations a capacity of 200,000
m3/day, which is between these two average values
was used.
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Process Flow Diagram (PFD)
Air
5
4
w1
A1
8
3
1
2
Figure 5 PFD for air dehumidification unit
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Main Equipment Design (Manual Design)
Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications Table 9 Equipment Specifications
  VLV-100 P-100 VLV-101 VLV-102 E-100 VLV-103 B-100 V-100
Pressure Drop (kPa) 9.929 1013 9.929 0.0052   0.0062    
Heat Duty (kJ/hr)         16x106      
Power (kW)   1190         1502  
Overall heat Transfer Coefficient (kJ/hr.m2.oC)         60      
Head Loss (m)   103            
Area (m2)         27121   19.6  
?TLMTD(oC)         11      
Diameter (m)               10.8
Height (m)               12.2
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Main Equipment Design (Manual Design)

• Pipe Sizing
• Table 10 Pipe dimensions and properties
• Based on pipe limitations, the maximum flow rates
  for both seawater and air that could be achieved
  are 4.16x106 kg/hr

Maximum Velocity (m/s) 4.13
Maximum Diameter (m) 0.6
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Design in Hysys Program
Figure 6 Design of the dehumidification process
in Hysys program
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Comparison between Simulators including Hysys and
Detailed Manual Design
Table 11 Manual and Hysys design comparisons for
summer and winter seasons
Summer Summer Summer Summer
Equipments Parameters Manual Design Hysys Design
Pump Power (kW) 1190 1148
Heat Exchanger Heat Duty (kJ/hr) 5.80E07 1.30E08
Heat Exchanger Seawater flow rate (kg/hr) 2.00E06 4.20E06
Winter Winter Winter Winter
Equipments Parameters Manual Design Hysys Design
Pump Power (kW) 1190 1146
Heat Exchanger Heat Duty (kJ/hr) 2.70E07 3.70E07
Heat Exchanger Seawater flow rate (kg/hr) 5.00E05 4.20E06
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Bench Scale Design
Figure 7 Air Dehumidification Prototype
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Experimental Results for the Dehumidification
Prototype
Table 12 Experimental conditions
  Twater (oC) Tair (oC) Relative Humidity Air Flow Rate (m/s)
Run1 15 35 75 3.2
Run2 20 35 73 3.2
Run3 20 35 66 3.2
Run4 15 25 63 3.2
Run5 20 25 63 3.2
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Experimental Results for the Bench Scale Prototype
Figure 8 Condensed amount of water for the
experimental runs.
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Piping and Instrumentation Diagram (PID)
Figure 9 PID for the dehumidification unit
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Types of equipment (Heat Exchanger)
Table 13 Comparison of different types of heat
exchanger 8
Types Advantages Disadvantages
Extended Surface Heat Exchanger (Plate-Fin) - Increases heat transfer area lead to enhance heat transfer coefficient. -Economical. -Flexible withstand high pressure.
Tubular Heat Exchanger -Production in the widest variety of sizes and styles. -Flexible Expensive Small duties required.
Plate Heat Exchanger High heat transfer coefficient Having small gap between plates
Plate-Fin HE
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Types of equipment (Valves)
Table 14 Comparison of different types of valves
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Type of Valve Application
On-Off valve (Isolation valves) Allow or stop the flow
Non-return valves (Switching valves) Allow the fluid to flow only in the desired direction.
Throttling valves (Control valves) Regulate the flow, temperature, or pressure of the process.
Throttling valve
On-Off valve
Non-return valve
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Types of equipment (Pump)
Table 15 Comparison of different types of pumps
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Pump Type Function Further Classification Uses
Centrifugal Pump Uses a rotating impeller to increase the velocity of a fluid where it works by the conversion of the rotational kinetic energy, typically from an electric motor or turbine Axial-flow pumps Large masses of liquid, such as in evaporators and crystallizers
Positive Displacement Pump Operates by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump Reciprocating pumps Sludge slurry
Positive Displacement Pump Operates by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump Rotary pumps Liquid that does not contain hard and abrasive solids, including viscous liquids
Centrifugal Pump
Positive displacement Pump
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Types of equipment (Blower)
Table 16 Comparison of different types of
blowers 11
  Centrifugal Positive Displacement
Properties Have impeller that is typically gear-driven. Have Rotors that trap air and push it through housing.
Speed Rotate as fast as 15000rpm They turn much slower than centrifugal blowers (e.g. 3600rpm)
Advantages Can operate against high pressures. Suitable for applications prone to clogging.
Disadvantages Air flow tends to drop drastically as system pressure increases.  
Positive Displacement Blower
Centrifugal Blower
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Material of Construction (MOC)

• The dehumidification plant must be safe,
  completely free of any harmful contaminants,
  toxins and bacteria.
• All equipment must be protected from corrosion.
• Therefore it is important to choose the best and
  the safest material to be used in the
  construction of the dehumidification plant.

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MOC
Table 17 Comparison of different types of
stainless steel 12
Family Example Grade Advantage Limitations
Ferritic 410S 430 446 Low cost, moderate corrosion resistance good formability. Nominal corrosion resistance, formability, weldability elevated temperature strength
Austenitic 304 316 Good corrosion resistance cryogenic toughness. Excellent formability weldability. Widely available Work hardening can limit formability machinnability. Limited resistance to stress corrosion cracking.
Duplex 2205 Good mechanical strength. Very good pitting, crevice and stress corrosion cracking (SCC) resistance. Application temperature range more restricted than austenitics. More expensive, and less widely available than austenitics.
Martensitic 420 431 Low cost, hardenable by heat treatment with high hardness. Nominal corrosion resistance. Limited formability weldability.
Precipitation Hardening 17/4PH Strengthenable by heat treatment giving better toughness. Restricted availability corrosion resistance formability.
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• Economic Analysis

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Capital Cost of the Plant

• Total module cost for one unit 13
• Where is the capital cost (total
  module) of the plant
• is the bare module
  equipment cost which
• Bare Module cost
• Where FBM is the bare module cost factor
• is the purchase cost
  for base conditions.

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Table 18 Bare module cost calculation for each
equipment.
Equipment Heat Exchanger Pump Storage Tank Fan
Type Flat plate Centrifugal Vertical Axial Tube
MOC Stainless steel Stainless steel Stainless steel Carbon steel
K1 4.6656 3.3892 4.8509 3.0414
K2 -0.1557 0.0536 -0.3973 -0.3375
K3 0.1547 0.1538 0.1445 0.4722
  479,545 102,000 95,499 1,931,968
  1 1 0 -
  2.4 2.2 4 -
B1 0.96 1.89 - -
B2 1.21 1.35 - -
  3.86 4.86 8 1
  1,851,044 495,720 763,992 1,931,968
For the year 2001, total module cost is
5,950,414 For the year 2009, total module cost
is 7,983,183
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CAPCOST program results

• Table 19 Comparing the
  cost using equations and CAPCOST program.
• For the heat exchanger the specified heat
  transfer area was too large maximum is 1000 m2
  and in the process is 1300 m2.
• For the pump the specified power was too large
  maximum is 300 KW, and in the process is 1190 KW.
• For the storage the diameter (12.2m) is too
  large in the process.

Equipment Heat Exchanger Pump Storage tank Fan Total module cost
Bare module cost using equation 1,851,044 495,720 763,992 1,931,968 7,983,183
Bare module cost using CAPCOST program 2,960,000 1,540,000 141,000 1,890,000 7,706,580
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Manufacturing Cost of the Plant

• Cost of Manufacture (COM) Direct Manufacturing
  Costs (DMC) Fixed Manufacturing Costs (FMC)
  General Expenses (GE)
• DMC CRM CWT CUT 1.33COL 0.03COM
  0.069FCI
• FMC 0.708COL 0.068FCI depreciation
• GE 0.177COL 0.009FCI 0.16COM
• TC CRM CWT CUT 2.215COL 0.190COM
  0.146FCI depreciation

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Utilities cost (CUT) This is associated with
different heating or cooling media.
Table 20 Total cost of utilities
Power of the pump (KW) 1190
Cost of electricity (/KWh) 0.06
Cost of pump (/yr) 625,464
Power of the fan (KW) 2365
Cost of the fan (/yr) 1,243,044
Total cost of utilities (/yr) 1,868,508
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• Operating labor cost (COL)

Table 21 Operating labor costs
P 0
  3
  2.64
Operating labor per shift 4.5
Operating labor 12
Labor costs (/yr) 600,000
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Table 22 Cost of manufacturing
Fixed Capital Investment ,FCI 7,983,183
Cost of operating labor ,COL (/yr) 600,000
Cost of utilities ,CUT (/yr) 1,868,508
Cost of waste treatment ,CWT (/yr) 0
Cost of raw materials ,CRM (/yr) 0
COM (/yr) for one unit 6,171,556
COM (/yr) for 294 units 1.81 109
Table 23 Additional cost for the process
Maintenance cost (/yr) 399,159
Insurance cost (/yr) 79,832
plant overhead cost (/yr) 739,327
Development cost (/yr) 30,000
pipe cost (/yr) 399,159
marketing cost (/yr) 600,000
Total additional cost (/yr) for one unit 2,247,477
Total additional cost (/yr) for 294 unit 660,758,238
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Total Cost

• The total cost is equal to 2,470,758,238.
• Although the cost of this process seems high, it
  is less than the cost of producing water from
  desalination plant for the same capacity, the
  cost is 3,033,600,000.

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Cast Flow Analysis
Figure 10 Cash flow diagram for the project
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• Ethics
• Reducing the humidity may affect human health
  which may lead to dryness of the skin.
• Putting the plant near a community may scare the
  society.
• People have the right to know that
• No chemicals will be used.
• No harmful wastes will be dumped into the sea.

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• HAZOP
• The objective of HAZOP is to minimize the effect
  of unusual situation by
• Ensuring that the control and other safety
  systems are in place.
• Ensuring that people who use and operate can do
  so without risk of personal injury.

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HAZOP Study
Figure 11 Schematic diagram of the proposed
dehumidification process including streams numbers
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HAZOP Study
Table 24 HAZOP study for stream 1
Guide Word Deviation Cause Consequence Action
No No flow - Pump failure - Blockage in pipelines before the heat exchanger. - No water vapor condensation. - Less product. - Standby pump. - Standby pipe. - Remove blockage using chemicals. - Provide strainer.
Less Less flow - Pump efficiency decreases. - Partial blockage in pipeline. - Less product. - Standby pump. - Standby pipe. - Remove blockage using chemicals. - Provide strainer.
High High temperature - Pipe exposure to sunlight. - Less water vapor condensation. - Less product. - Pipe must be insulated.
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Table 25 HAZOP study for stream 2
Guide Word Deviation Cause Consequence Action
No No flow - Pump failure - Blockage in pipeline. - No product (absence of cooling water). - Pump heats up. - Back up pump. - Back up pipe. - Remove blockage using chemicals. - Provide strainer.
Less Less flow - Pump efficiency decreases. - Partial blockage in pipeline. - Less product. - Back up pump. - Back up pipe. - Use chemicals. - Strainer.
Low Low pressure - Pump efficiency reduces. - Cavitation. - Pump heat up. - Adding recycle stream before pump. - Back up pipe.
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Table 26 HAZOP study for stream 3
Guide Word Deviation Cause Consequence Action
No No flow - Blockage of tubes. - Backward flow of water which affect pump and header. - Tube damage due to high pressure. - Back up heat exchanger. - Clean tubes using chemicals.
Less Less flow - Partial blockage of tubes. - Backward flow of water which affect pump and header. - Tube damage due to high pressure. - Back up heat exchanger. - Clean tubes using chemicals.
High High temperature - High temperature of both inlet streams - Reject high temperature to seawater which affect marine environment. - Cooler before rejecting water to the sea.
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Table 27 HAZOP study for stream 4
Guide Word Deviation Cause Consequence Action
No No flow - Blower is not working. - Complete blockage in the line. - Less product. - Backup blower. - Backup pipe. - Remove blockage using chemicals.
Less Less flow - Blower efficiency reduces. - Partial blockage in pipeline. - Less product. - Backup blower. - Standby pipe. - Remove blockage using chemicals.
Low Low temperature - Weather condition during night/winter. - Less water vapor condensation. - Less product. - Put heater.
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Table 28 HAZOP study for stream 5
Guide Word Deviation Cause Consequence Action
No No flow - Blockage in the shell side. - No air in the inlet air stream. - Less product. - Backup blower. - Remove blockage in the shell side using chemicals.
Less Less flow - Low flow in the inlet air stream. - Fouling problem in the shell side. - Reduce product. - Separation will take longer time. - Use inhibitors for fouling problem. - Standby blower.
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Safety

• Safety should be the top priority of any design.
• The proposed process is considered to be a safe
  process since
• No use of harmful materials or part of the
  system.
• No use of chemicals.

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Conclusion

• A bench scale prototype was designed, constructed
  and tested.
• A large scale process was designed using Hysys
  program.
• The plant should be located near the sea.
• The effectiveness of the process was tested
  during the summer and winter seasons for Dubai
  condition.
• The results showed that during the summer, higher
  production rates are achieved due to higher
  temperature and relative humidity.

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Conclusion

• HAZOP study was performed and analyzed for the
  process and solutions were suggested for sever
  situations.
• Economic analysis was performed on the process.
• The cost of the plant is high (2,5 billion) due
  to the huge number of units that will be required
  to fulfill the required capacity.
• The dehumidification plant was less expensive
  than the desalination plant (3 billion) with
  less environmental impact

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Way Forward 

• The proposed process should be introduced to
  different related companies for investment in
  this technology.

61
References

• http//images.zawya.com/images/features/090519_uae
  _01.gif
• UAE's fresh water supply drying up, April 20.
  2010. http//www.watersolutionsme.com/Global/power
  _and_water/water/pdf/UAEsfreshwatersupplydryingup2
  0Apr10TN.pdf
• RJ. Bailey. Water production system for making
  portable water. Patent Application Publication,
  US 2007/0151262 A1, Jul.5, 2007
• Golden Sun Internet Consulting. Dubai Climate.
  http//www.goldensun.com. 1998
• Wikipedia the free encyclopedia. Ocean. Retrieved
  November 23, 2009.http//en.wikipedia.org/wiki/Oce
  an.
• Wikipedia the free encyclopedia. Dew point.
  Retrieved 17 May 2010. http//en.wikipedia.org/wik
  i/Dew_point
• Wangnick/GWI.2005.2004 Worldwide desalting plants
  inventory. Global Water Intelligence. Oxford,
  England.
• T.Kuppan. Heat Exchanger Design Handbook. CRC
  Press, 2001.
• M. Castier1, L.A. Galicia-Luna and S.I. Sandler.
  Modeling the high-pressure behavior. of binary
  mixtures of carbon dioxide alkanols using an
  excess free energy mixing rule. Brazilian Journal
  of Chemical Engineering. 2004
• Paresh Girdhar, Octo Moniz, Practical
  Centrifugal Pumps Design, Operation and
  Maintenance Elsevier, 2004.

62
References

• 11. Energy Efficiency Guide for Industry in Aisa.
  Electrical Enegry Equipment Fans and Blowers.
  UNEP 2006.
• 12. Aalco. Technical Information of Stainless
  Stell. 2008. http//www.aalco.co.uk/technical/stai
  nless.html
• 13. Richard Tuton/Richard C. Bailie/Wallace B.
  Whiting/Joseph A. Shaeiwitz, Analysis, Synthesis
  and Design of Chemical Processes, Second Edition,
  Text printed in the United States at Hamilton in
  Casleton, New York, November 2007.

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• Thank you for your attention

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Problems Faced

• Problems that were faced during this study are
  listed below
• Specific data about temperature of seawater at
  different depths were limited in the literature.
• The aim was to reach the same capacity of water
  from one desalination plant, which was a large
  capacity that required large number of units for
  realistic dimensions.