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H20 Desalination – An Experience1
WATER DESALINATIONAND POWER PRODUCTION
An Experience Based Vision for the Future
BY
MOHAMMAD AK. AL-SOFI
H20 Desalination – An Experience2
WATER DESALINATION: An Experience Based Vision for the Future
There are three processes of thermal desalination:
Multi Stage Flash (MSF) is the workhorse of this industry for large and extremely large capacities of up to gegaliters, per day productions;
Multi Effect Distillation (MED) for medium capacities in mega liters per day productions; and
Vapour Compression Distillation (VCD) is suitable for capacities in kilo liters per day productions.
H20 Desalination – An Experience3
WATER DESALINATION: An Experience Based Vision for the Future
Other technologies are Sea Water Reverse Osmosis (SWRO)
Brakish Water Reverse Osmosis (BWRO);They are found suitable everywhere for medium to large capacities;Electro Dialysis (ED and with Reversal-EDR) is another permeation process;Both ED & EDR are found to serve small capacities particularly when industrial water is the prime requirement; andIn such cases, Ion Exchange Desalination (IED) that utilizes special resins could also be used.
H20 Desalination – An Experience4
WATER DESALINATION: An Experience Based Vision for the Future
For the future, the Arab World should spare no effort in developing other processes.
These are the combination of solar ponds heat recovery and solar distillation specifically for remote areas;Last yet quite valuable is a call for the development of stand-alone and/or combined hybrid applications; Such as the utilization of selective species separation membrane processes; &Concentrated efforts in such development are to be directed towards Ultra & Nano (UN) Filtration techniques.
H20 Desalination – An Experience5
WATER DESALINATION: An Experience Based Vision for the Future
Future work required to develop MSR are:
1. Unit capacity growth pattern;2. Process efficiency to maximize energy
utilization [Gain Output Ratio (GOR)];3. Intake design to maximize feed
utilization [Recovery Ratio (RR)];4. Capital (installation) cost per unit
output;5. On-stream factor, as expressed by
availability and reliability;
H20 Desalination – An Experience6
WATER DESALINATION: An Experience Based Vision for the Future
0.3 0.30.2
0.40.3 0.3
2.0
1.8
1.6
1.3
1.11.0
15
14
11
9
6
7
0.0
0.3
0.5
0.8
1.1
1.4
1.6
1.9
2.2
2.4
2.7
1954 1964 1974 1984 1994 2004
Cost in SR/kl($/kgal)
0.0
1.8
3.5
5.3
7.0
8.8
10.6
12.3
14.1
15.8
17.6
Unit Capacity in MIGDInstallation Costs - SR/L($/gal)
Treatment Cost Production Cost Installation Cost Unit Capacities, (M) MIGD
Figure 1: MSF Costs and Unit Capacity
H20 Desalination – An Experience7
WATER DESALINATION: An Experience Based Vision for the Future
10
25
40
24
20 20
50
40
10
5 4
21
42
63
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
1954 1964 1974 1984 1994 20040
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Number of Stages SD TC Frequency/Decade OL TC Frequency in hr/wk Gain Output Ratio "GOR"
Figure 2: MSF Number of Stages, Descaling Frequencies & GOR
H20 Desalination – An Experience8
WATER DESALINATION: An Experience Based Vision for the Future
6.Understanding of scaling potentials and prevention mechanism;
7.Corrosion resistant materials that are most suitable for seawater & desalination;
8. Electronic measurement, monitoring and control, i.e., instrumentation.
H20 Desalination – An Experience9
WATER DESALINATION: An Experience Based Vision for the Future
9. Mathematical modeling and simulations to prevent:a) Stage pairing;b) Mist carry-over; andc) Non-Condensable accumulation
through improved:i)Bundle design;ii) Vent off Take locationing; andiii) Reduction in vapour losses.
H20 Desalination – An Experience10
WATER DESALINATION: An Experience Based Vision for the Future
a) Reduce scale build up through:10. Demister design to:
i) Retard mist carry over through tighter sealing; and
ii) Simplify as well as affect expedient installation & removal.
i) Self draining configuration(s); andii) Insitu salt removal by distillate jet
flushing.b) Assembly/mounting techniques in
order to:
H20 Desalination – An Experience11
WATER DESALINATION: An Experience Based Vision for the Future
11. Staggered Venting, i.e.,a) Directional flow of non-
condensables and;b) Creation of counter flow of gases
around the bundles.N.B. This needs to be done in conjunction with item 9 above.
H20 Desalination – An Experience12
WATER DESALINATION: An Experience Based Vision for the Future
12. Hybrization/Integration
i) MSF/MECii) MSF/MEC feed
treatment (De-hardening/ Separation)
a) Process hybridization
H20 Desalination – An Experience13
WATER DESALINATION: An Experience Based Vision for the Future
b) Integrated Productioni) Simple Power Cycle(s), i.e., BTG
or GTG;ii) Combined cycle of
GTG/HRSG/STG; andiii) Variable back pressure, STG
design.
H20 Desalination – An Experience14
WATER DESALINATION: An Experience Based Vision for the Future
a) Analytical laboratory chemical equilibrium assessment to clearly understand where CO2 is being released in the process;
b) Prototype and pilot plant evaluation to verify the reality of the above analytical results; and
c) Stage-wise simulation & mathematical modeling to quantify off takes.
13. Carbon dioxide recovery improvements through:
H20 Desalination – An Experience15
WATER DESALINATION: An Experience Based Vision for the Future
1) Intake and Feed pretreatment systems.2) Better understanding and prevention of
membrane fouling and deterioration.3) Improving membranes for higher flux.4) Reduction of its multiple-flow streams.
SWRO has proved itself worthwhile in recent years, but needs further development in four areas, which are:
H20 Desalination – An Experience16
WATER DESALINATION: An Experience Based Vision for the Future
One basic upgrading requirement that MEC industry is to come up with is the design of larger thermal (steam) ejecto-compressors. In this respect, reference can be made to a proposal put forward for a 75 MGD2 (283.5 MLPD) MEC of 30 vertically stacked stages designed as a column.
2 MGD stands for Million US Gallon per day (approximately 3.78 liters per US Gallon)
The said design was based on multi ejectors and 6 parallel flow streams rather than larger components, since larger ejectors are still not available to the desalination industry.
H20 Desalination – An Experience17
WATER DESALINATION: An Experience Based Vision for the Future
Figure 3: Typical MEC
H20 Desalination – An Experience18
WATER DESALINATION: An Experience Based Vision for the Future
BACK PRESSURE TURBINE
EJECTORBOILER
FUEL
MOISTURESEPARATOR
HEATER # 2 HEATER # 1
CONDENSATE PUMP
DEAERATOR
MSF DISTILLERS
DUMPCONDENSER
BOILER FEED PUMP
GENERATORFLUE GASES
Figure 4: Typical Dual Purpose Process
H20 Desalination – An Experience19
WATER DESALINATION: An Experience Based Vision for the Future
U o
UBi Ui
UBo
Figure 5: Ultra Filtration
H20 Desalination – An Experience20
WATER DESALINATION: An Experience Based Vision for the Future
Figure 6: Nano Filtration
uo Ni
Nano Filtration
80% No
15%NRUBi
95%100%
5%
H20 Desalination – An Experience21
WATER DESALINATION: An Experience Based Vision for the Future
FeedTank
FeedTank
SWSWIntakeIntake
CFCFDualDual
mediamediaFine SandFine Sand
mediamedia
PumpPump
NF RejectNF Reject
ProductProduct
NF UnitNF Unit
B.BB.B
H.RJH.RJ4 HRC Stages4 HRC Stages
Brine Brine HeaterHeater
SW from MSF Rejection SectionSW from MSF Rejection Section
CWCW
DPDP
HPHPPumpPump
Booster PumpBooster Pump
PermeatePermeate
SWRO UnitSWRO UnitReject to MSFReject to MSF
D/AD/A
B.RB.R
MSF UnitMSF Unit
SWSW
RHRH
MUMU
RFRF
PRPR
RRRR
TRTR
NFNF
MSFMSFMM--UU
Figure 7: Schematic Flow Diagram of NF, SWRO and MSF
H20 Desalination – An Experience22
WATER DESALINATION: An Experience Based Vision for the Future
90*87*NRNR75+MSF+MEC+SWRO
88*85*NRNR72+MSF+MEC
86*83*NRNR69+MEC+SWRO
82*81*NR7868+MEC
8180NR7767+MSF+SWRO
8078NR7565+MSF
NANA54--3830--Power only
BTG (BP)
GTG-STG (BP)GTG-STGBTGGTGPROCESSES
NOTES:NA= Not Applicable NR = Not Recommendable* = Lower Back Pressure__ = Lower Heat Utilization due to Ambient Temperatures
This table shows that the scheme which is being heavily promoted these days; which is the combined cycle with desalination dual production schemes do not show as high energy (heat) utilization as Steam Cycle Back Pressure with desalination. It is felt that this stems out of higher efficiency fired boilers when compared to NRSG
H20 Desalination – An Experience23
WATER DESALINATION: An Experience Based Vision for the Future
Commercialization of Suggested and Innovative Schemes
1. Unconventional High Temperature MSF (HTF);2. Solar Energy Utilization, especially through Solar
Ponds;3. Utilization of Other Renewable Resources, such as:
Wind and Wave Energy;4. Electrically Induced Separation; 5. Ion Exchange (IED);
The future of desalination will very much depend on developmental work to reduce production cost. New frontiers are to be explored by spending time and money to check the viability of some of the following options of suggested and innovative processes such as:
H20 Desalination – An Experience24
WATER DESALINATION: An Experience Based Vision for the Future
6. Hydration;7. Freezing;8. Chemical Reaction, Salt Precipitation;9. Combined Membrane Processes of
Electro-Dylitic, Osmotic & Ion Exchange (ED, RO, IX);
10. Biodesalination, Anion/CationBacterial (oxi-re); and
11. Nuclear Energy Utilization.
H20 Desalination – An Experience25
WATER DESALINATION: An Experience Based Vision for the Future
Solar energy deserves further developmental work in a stage wise pattern. The proposed stages are:
1) Literature review; 2) Proposal development; 3) Mathematical analysis and modeling; 4) Prototype construction and analyzing of
results; and5) Development of pilot plant(s).
H20 Desalination – An Experience26
WATER DESALINATION: An Experience Based Vision for the Future
Few options of direct and indirect solar energy utilization.1. Multi-layered and convictive solar
stills.2. Humidification/De-humidification3. indirect utilization techniques 4. Solar ponds heat recovery for
conventional distillation of segregated versus integrated MSF/MEC process(es).
H20 Desalination – An Experience27
WATER DESALINATION: An Experience Based Vision for the Future
Figure 8: Proposed MSF Design Concept
H20 Desalination – An Experience28
WATER DESALINATION: An Experience Based Vision for the Future
Figure 9 Figure 10
H20 Desalination – An Experience29
WATER DESALINATION: An Experience Based Vision for the Future
Figure 11 Figure 12
H20 Desalination – An Experience30
WATER DESALINATION: An Experience Based Vision for the Future
Figure 13
H20 Desalination – An Experience31
Thank You
WATER DESALINATION: An Experience Based Vision for the Future
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