Download renewable desalination in qatar - US

RENEWABLE DESALINATION IN QATAR
US - Denmark Summer Workshop on Renewable Energy
August 21, 2013
Authors:
Magdalena Brum
Anthony Palavi
Tyler Lee
Rebecca Quinte
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Contents
1
Abstract
Acknowledgements (e.g. people who provided you with information important to your project)
Table of Contents
2.
List of Tables
3.
List of Figures
Table of Nomenclature
4.
Executive Summary (not more than 2 pages with representative graphic of results. Briefly
state conclusions.)
5.
Introduction and Problem Statement
6.
Background & literature review
6.1
Water Desalination in Qatar
6.2
Multi-stage Desalination
6.3
Reverse Osmosis
6.4
Integrated Solar Combined Cycle MED Desalination
6.5
Brine Waste
6.5.1 Alternative Use for Brine
6.6
7.
Methodology
8.
Results
Discussion and Conclusions
References (complete citations so anyone reading the report can also find the same reference you
used. Make sure all references included are cited in the report. If using a web url, give the date
of access in parenthesis.)
Appendix
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Abstract
By comparing different types of desalination this research’s objective is to find the
optimal method for desalting water in Qatar. There are three different types of desalination in
this study: multi-stage flash (MSF), reverse osmosis (RO), and Integrated Solar Combined Cycle
MED Desalination (ISCC MED). Researching the advantages and disadvantages of each method
of distillation and modeling the different types of desalination against each other with a baseline
output of fresh water the simulation should obtain an economical solution. An assessment of the
desalination plant’s discarded brine pollution is studied, and an economic solution to the wasted
brine in Qatar.
Executive Summary
Qatar is a country experiencing heavy strains on its energy and water supply, coupled with
increasing demand and significant environmental impact. To address these issues, its national
government has set targets to reduce electricity consumption by 20% and water consumption by
35% by 2030. This report will explore the use of multistage flash, reverse osmosis, and solar
energy desalination technologies for potential use in Qatar, as well as inspect how brine waste
from desalination can be utilized for salt production. A feasibility analysis will demonstrate the
different benefits and efficiencies of desalination systems and their waste product, brine, which
have the potential to help Qatar achieve its goals, alleviate expanding demand, and save the
country’s natural gas resources.
Desalinated water in Qatar is produced in natural gas-based cogeneration power plants (CHP)
that use either simple gas turbines cycle or combined cycles. These cycles generate electricity
and provide thermal energy (as steam) to a multistage flash (MSF) desalting system. MSF has
high-energy consumption (20 kWh/m3), so an alternative system for the MSF process should be
able to provide the same amount of fresh water and electricity than the current CHP plants.
Additionally, since on of the major factors affecting the choice of desalting system is the
consumed energy and its production cost, serious consideration should be given to the type and
cost of energy to be used. Based on a preliminary literature review, reverse osmosis (RO) and
solar energy (both integrated solar combined cycle based on concentrated solar power and solar
PV for electricity production) appear to be promising alternatives for MSF desalination.
Multi-stage flash distillation is one of the most trusted desalination techniques, but it has a highenergy consumption and outputs a large amount of brine for a small fraction of fresh water. In
Qatar, MSF has been chosen over other types of desalination because more reliable than other
desalination methods and it is unaffected by the high salt levels in the Persian Gulf. Most of the
desalination plants in Qatar are MSF with a CHP component.
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Reverse osmosis (RO) is currently the most energy efficient, reliable, and cost effective
technology for seawater desalination, becoming one of the most popular choices outside of the
Middle East for desalination plant type over the past two decades. In a salt water reverse
osmosis (SWRO) system, feed seawater at about 35ºC is pressurized to create a net driving
pressure across a semipermeable membrane, usually a robust thin-film composite membrane; a
brine waste is discharged at a minimum of 65,000 once the process is over. Despite SWRO’s
popularity, in the Gulf countries the accessibility of natural gas has made thermal desalination
the standard, despite the fact that the use of SWRO instead of thermal desalination technologies
in Qatar could reduce the country’s CO2 emissions from 3.564 to 0.891 million tons per year,
seawater intake from 8.4 Mm3/d to 3.6 Mm3/day, and brine discharge from 7.2 Mm3/d to 2.4
Mm3/day. RO is favorable to MSF since no heating or phase change is necessary (Karaghouli
and Kazmerski), overall recovery ratios are 30% to 50% (Karaghouli and Kazmerski), and RO
requires up to 4 to 7 kWh of electricity per cubic meter of water.
Solar energy can directly or indirectly be harnessed for desalination. Indirect solar desalination
methods involve two separate systems: the collection of solar energy, by a conventional solar
converting system, coupled to a conventional desalination method. In indirect systems, solar
energy is used either to generate the heat required for desalination and/or to generate electricity
that is used to provide the required electric power for conventional desalination plants such as
multi-stage flash (MSF) or reverse osmosis (RO) systems. Concentrating solar thermal power
technologies are based on the concept of concentrating solar radiation to provide hightemperature heat for electricity generation within conventional power cycles using steam
turbines, gas turbines, or Stirling and other types of engines. For concentration, most systems use
glass mirrors that continuously track the position of the sun. The four major concentrating solar
power (CSP) technologies are parabolic trough, Fresnel mirror reflector, power tower, and
dish/engine systems.
Brine is a waste product from desalinated water, and if not properly managed, could cause
environmental and sociological damage. It is a serious concern within the Persian Gulf, given
that Qatar alone possesses a desalination capacity of 300,000 cubic meters per day.
Additionally, the cost of brine disposal can range anywhere between 5% and 33% of the total
desalination system’s cost. In this report we have developed an Environmental Impact
Assessment (EIA) to present a brief overview about some key environmental effects that brine
waste has on the environment and its aquatic life, focusing on fossil fuel demand, desalination
pollutants, resultant thermal pollution, and quality of brine waste content. Moreover, as an
alternative to dumping, this report will examine the economic feasibility of table salt production
from brine waste, to be sold for commercial use.
To develop our feasibility analysis, we first decided to choose a plant with a capacity of 200,000
cubic meters per day. This was a number based on the average sized Qatar plant. After choosing
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this figure, we used an Excel-based software freely provided by the International Atomic Energy
Agency (IAEA), the Desalination Economic Evaluation Program (DEEP), which can be used to
analyze performance and cost of various types of plants. In regards to the MSF and RO plants,
the program had default features in place, with most of the technical data correlating with the
data we found in literature. The necessary economic parameters were developed from our own
calculations. We were also able to model a SE plant with a few adjustments to the default plants.
From this modeling, we found that as expected, both RO and IS MED show a significant
reduction in the fossil fuel requirement when compared to the BAU MSF plant. However, under
the described set of assumptions, RO appears to be a better alternative in terms of LCOE and
LCOW than ISCC MED, due to the significantly higher upfront costs of the solar array.
The two factors economies of scale and technology development can increase the future
competitiveness of the solar option. Since CSP plants are feasible above 50MW, which was the
size considered for this study, an increased CSP scale could decrease the effect on the levelized
costs of electricity and water. However, it is necessary to model such scenario in order to make
proper conclusions on the effects of solar array scale. Further technology development will
assist in lowering the cost of solar technology.
1. Introduction and Problem Statement
Qatar is facing substantial challenges relating to the management of water and energy resources.
Both resource systems are increasingly stressed by expanding demand (15% annual growth for
the last five years), diminished supply, and environmental degradation. Qatar’s national
government has announced plans to reduce electricity consumption 20% and water consumption
35% by 2030. Three-fourths of municipal water supply comes from desalinated seawater
obtained from a natural gas-based multistage flash (MSF) process, which is energy intensive and
costly. Thus, deploying a more energy efficient desalting system can help alleviate the water and
energy issue, while saving a significant amount of natural gas, the nation’s main source of
income.
Given these factors, the scope of this report will encompass a comparative analysis of the
environmental impact of MSF, reverse osmosis (RO) and integrated solar MED (IS-MED)
desalination technologies, under the assumption of equal outcomes of fresh water and electricity
production.
Additionally, production and disposal of brine waste is an integral part of the desalination
process. However, improper brine management adversely affects the marine environment and
organisms. An Environmental Impact Assessment (EIA) showed temperature spikes as large as
57°C at brine output plumes, chemical discharges and emissions of air pollutants from energy
inputs. Also, a proposal suggested using natural evaporation method to produce salt from brine
waste. Economic & market analysis showed in 2010 Qatar imported $24.5 million (usd) of salt;
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capacity feasibility showed Qatar has 12,580 sq km of open land for salt production. Therefore,
the proposal could potentially benefit the environment and diversify the business sector in Qatar.
2. Background & literature review
2.1
Water Desalination in Qatar
Qatar is producing about 150 million cubic meters of desalinated fresh water annually, which
accounts for approximately “three-quarters of the total water demand” of the region (Danoun,
2007). According to The World’s Water, an online resource with an invaluable collection of
water-related data tables, Qatar had about 560,764 cubic meters/day of total installed
desalination capacity between the years 1945 - 2004 (Danoun, 2007). Desalinated water in Qatar
is produced in natural gas-based Cogeneration Power Plants (CHP) that use either simple gas
turbines cycle or combined cycles. These cycles generate electricity and provide thermal energy
(as steam) to a multistage flash (MSF) desalting system, an energy-intense process.
The rapid economic growth in Qatar is leading to a substantial increase in electric power and
desalted seawater demands, which results in a significant stress on the environment due to fossil
fuel combustion and brine waste disposal. On one hand, natural gas combustion results in
emission of air polluting gases as well as CO2. On the other hand, concentrated brine discharged
from the desalination plants pollutes the marine and terrestrial environment. This brine has
higher temperatures than seawater and is mixed with chemicals such as chlorine. Thus, to protect
the environment and to make the DW more sustainable potable water source, renewable energy
and more energy-efficient desalting systems compared to MSF system should be used for
desalting seawater (Darwish 2012).
Since the BAU is to integrate desalination plants with a CHP plant, an alternative system for the
MSF process should be able to provide the same amount of fresh water and electricity than the
average CHP plants existing in the country. Based on a preliminary literature review, reverse
osmosis (RO) and integrated solar multi-effect distillation (IS-MED) appear to be promising
alternatives for MSF desalination in Qatar.
One of the main factors affecting the choice of desalting system is the consumed energy (thermal
or mechanical, or both) and its production cost. The energy cost represents a good portion of the
final desalted water unit cost, and thus serious consideration should be given to the type and cost
of the energy to be used. (Darwish 2012, Shatat 2013).
2.2
Multi-Stage Flash Desalination
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Figure [-_-]
In the MSF, brine is heated before being exposed to a low pressure causing its partial
evaporation by flashing in successive stages. In figure [-_-] it shows that when pressure goes
down the boiling temperature also decreases. This property is fundamental of MSF and aids in
the distillation process. Each state of MSF has lower pressures in each stage. The flashed vapor
is condensed in a condenser mounted in the upper part of each stage where the brine is primarily
pre-heated. The brine is finally heated in a brine heater before entering the first stage for partial
evaporation by flashing. The brine is moved from one stage to the next to conserve the heat.
Distillation of seawater is the oldest method of retrieving fresh water from salt water. It has been
known for thousands of years. Distillation is when water is heated up and changed into steam
from liquid leaving behind other particulates and additives like salt. Currently, the majority of
desalination is distillation specifically MSF because of two reasons the scalability and it's
independence from salt content (Young 1971). Most of the desalination in the world is done in
the Middle East where the seawater salinity levels are high.
One major flaw of MSF desalination is that its brine output is one of the highest in desalination
technology. For every cup of water you will get six cups of brine as well. The amount of brine
that’s released from the MSF plant is still pretty diluted, and most MSF plants release the used
brine back into the seawater input (Veerapaneni 2007). MSF(multi stage flash) desalination only
has a brine 1.2 times the amount as seawater, but other desalination methods like reverse osmosis
might have brines with greater parts per million of salt than MSF desalination.
Thermal multistage desalination in the Persian Gulf isn't affected by the high salinity levels of
the sea water which has around 45000 parts per million of salt. Average seawater salt content is
35000 ppm. Reverse osmosis is more expensive when the salinity content of the water is higher.
Desalinating brackish water like sea water found in the Baltic Sea, which has around 7000 ppm
of salt, is more favorable for reverse osmosis because the lower the salt content the more
efficiently the RO can run. MSF distillation has a high energy demand and runs almost
independently of how much ppm of salt there is in the water (Probstein 1973). The amount of
water processed is proportional to the energy used. However, the downside to being unaffected
by salt ppm is that the same energy needed to desalinate seawater with a content of 45000 ppm
and 7000 ppm is relatively the same (Veerapaneni 2007).
One of them main requirements of MSF is a heat source. Most of the heat needed for a MSF
plant comes from an electricity generating turbine. The steam is transported from the gas turbine
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plant to the desalination plant. In places like Saudi Arabia and other Middle Eastern countries it
made sense to use combined heat and power for desalination. Ten megawatts of gas turbine
power can help produce 1 million gallons of fresh water a day with a MSF plant (Reuther 2000).
The needed heat for a MSF plant can be subsidized with heat that is produced when making
energy. This makes a MSF plant more efficient and cuts down the cost.
Source: Al-Karaghouli (2009)
MSF require heat at 70-130°C and use 25-200 kWh/m³,
2.3
Reverse Osmosis
Reverse osmosis (RO) is currently the most energy efficient, reliable, and cost effective
technology for seawater desalination (K&K). Over the past two decades, the majority of
desalination plants worldwide have utilized RO technology, and there are many future plants that
will incorporate the technology as well. However, in the Gulf countries, due to the accessibility
of fossil fuels, the standard is thermal desalination. Thermal desalination plants consume
significant amounts of thermal and electric energy, which involve significant greenhouse gas
emissions (Elimelech), seawater intake, and brine discharge; so significantly that the use of
SWRO instead of thermal desalination technologies in Qatar could reduce the country’s CO2
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emissions from 3.564 to 0.891 million tons per year, seawater intake from 8.4 Mm3/d to 3.6
Mm3/day, and brine discharge from 7.2 Mm3/d to 2.4 Mm3/day (Darwish).
In a salt water reverse osmosis (SWRO) system, feed seawater is pressurized to create a net
driving pressure across a semipermeable membrane. Once the feed water passes through the
membrane, it has been desalinated; the remaining feed water continues along the pressurized side
as brine. Reverse osmosis (RO) systems are composed of four main processes: pretreatment, a
relatively energy intensive process in which feed water is treated to protect RO membranes from
fouling; pressurization of feed water; separation, in which the membrane allows water to pass
through while retaining dissolved salts and discharging a portion of this brine; and posttreatment,
in which the desalinated product water undergoes pH readjustment and degasification, to be used
for drinking water or stored for later use (Karaghouli and Kazmerski).
Figure X. Schematic diagram of an RO system (Karaghouli and Kazmerski).
As such, the two most essential components of the system are the high-pressure feed pump and
the RO membranes (Karaghouli and Kazmerski). Most RO desalination plants use robust thinfilm composite membranes, and are capable of rejecting 99.6-99.8% of dissolved salts in
seawater feed. Composed of two different polymer layers that can be optimized separately, they
have higher intrinsic water permeabilities and are stable over a greater pH range than the first
commercially viable cellulose-based membranes; the different layers also yield higher salt
rejections and water fluxes. However, a disadvantage of thin-film composite membranes is that
they are prone to fouling; this negatively affects process performance (Elimelech and K&K).
Reverse osmosis is favorable to MSF since no heating or phase change is necessary (Karaghouli
and Kazmerski), but energy requirements increase with increasing salinity or water recovery
(Elimelech). Since the specific electricity consumption of the plant needs to be kept as low as
possible and overall recovery ratios are 30% to 50% (Karaghouli and Kazmerski), large-scale
SWRO plants use energy-recovery turbines that recover some of the pumping energy. RO
requires up to 6 kWh of electricity per cubic metre of water (depending on both processing and
its original salt content), and there is a thermodynamic limit on the energy demand for
desalination, so future research to continue to improve energy efficiency should have a strong
focus on pretreatment and posttreatment stages (Elimelech).
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2.4
Integrated Solar Combined Cycle MED Desalination
Solar energy can directly or indirectly be harnessed for desalination. When integrated with
conventional desalination systems, indirect methods are used. Indirect solar desalination methods
involve the collection of solar energy, by a conventional solar converting system, coupled to a
conventional desalination method. The solar energy is used either to generate the heat required
for desalination and/or to generate electricity that is used to provide the required electric power
for conventional desalination plants such as multi-stage flash (MSF) or reverse osmosis (RO)
systems. (Qiblawey 2008).
Concentrating solar thermal power technologies are the current choice in many countries in the
Gulf region 1 , thus the one to be consider for this analysis. These systems concentrate solar
radiation to provide high-temperature heat for electricity generation within conventional power
cycles using steam turbines. The best-known solar thermal desalination combination is solar
multi-effect distillation (MED) (Darwish, 2012). From an energy perspective, the main supply to
the desalination plant is a large thermal input, as well as some auxiliary electricity required for
pumping.
Figure 1 - Schematic diagram of solar-based MED
2.5
1
Desalination Process Waste: Brine
Shuaiba North in Kuwait, JabalAli and Ali in UAE.
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Brine is a waste product from desalinated water, and if not properly managed, could cause
environmental and sociological damage. Studies taken at various institutions around the world,
such as The Ocean Technology Group (OTG) at the University of Sydney, Australia, concur that
“using desalination as a water resource would have considerable environmental impacts to the
surrounding area including the ecosystems” (Danoun, 2007). Hence, this Environmental Impact
Assessment (EIA) intends to present a brief overview about some key environmental effects that
brine waste has on the environment. This EIA will be based on the following features: fossil fuel
demand and quality of brine waste content (salinity content, quantity output, temperature range).
Lastly, to avoid dumping in the ocean, table salt production from brine waste will be studied in
order to assess the economic feasibility for alternative uses for brine waste.
Salinity content in seawater plays an important role in the size and growth of aquatic organisms.
Any significant changes to salinity content could influence the life expectancy of aquatic
animals, their population density growth rate, and breeding of species (Danoun, 2007). Brine
waste is highly concentrated, containing double the salt concentration of input seawater (Ibrahim,
1987), with an estimated salinity content of 64-70 parts per thousand (ppt) (Danoun, 2007).
Given Qatar’s total desalination capacity of 300,000 m3/day, subsequent millions of tons of brine
are discharged into the Persian Gulf each year (Ibrahim, 1987).
Chemical discharges from desalination plants have been shown to greatly disrupt the aquatic life.
In 2008, the Institute for Chemistry and Biology of the Marine Environment (ICBM) at the
University of Oldenburg conducted an “Environmental impact and impact assessment of
seawater desalination technologies” which examined the effect desalination plants had on the
marine environment. These effects include chemical discharges into the ocean, emissions of air
pollutants from the energy demand of the processes. Some of the chemical materials found in
seawater used throughout various stages in the desalination process (e.g., blot clearing, cleaning
stages) include: Sodium hypochlorite (NaOCl), Ferric chloride FeCl3 or aluminum chloride
AlCl3, Sulfuric acid H2SO4 or hydrochloric acid HCl, Sodium bisulphate NaHSO3, Crystalline
acid EDTA (ethylenediaminetetraacetic acid) C10H16N2O8 and Citric acid C6H8O7 (Danoun,
2007).
Temperature changes also produce an impact on marine ecosystems. Brine discharge can act as a
catalyst for oceanic temperature changes, referred to as “thermal pollution,” where temperature
levels increase higher than the ambient ocean water temperature (Danoun, 2007). In areas of
thermal pollution, temperatures spikes can be as large as 57°C at the output of the plume
discharge (Danoun, 2007). Figure 4 shows difference of temperature in ocean waters and around
brine discharging stations at saltwater desalination plants. Considerable changes in temperature
are apparent, where the top graph shows higher fluctuations (between 10 and 40°C) in
comparison with mean oceanic temperatures.
Figure 4
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Source: Jenkins et al, 2005
Flora and fauna on both the macro and micro scales have been shown by marine biologists to
have been affected with regard to behavioral and life-cycle patterns from thermal pollution
(Danoun, 2007).
3. Methodology
This study will consider an average sized MSF plant producing both power and fresh water as
the business as usual (BAU) technology. Reverse osmosis and solar MED producing the same
amount of fresh water and electricity will be analyzed in terms of their inputs and production
costs and will be compared to the BAU.
The analysis will address the following research questions:
 Can RO and IS-MED technologies reduce the environmental impact of the desalination
sector in Qatar in terms of seawater and fossil fuel requirement for equal outcomes of
electricity and fresh water?
 How do LCOE and LCOW change with the technologies considered?
 What are the characteristics of the brine waste for each of the technologies considered?
 Is there an economically feasible alternative use of brine to avoid dumping it to the Gulf?
In order to select an appropriate size for the CHP desalination plants, the capacities of the newest
combined cycle desalination plants in Qatar were considered.
Table 1- Capacities of newest combined cycle desalination plants in Qatar
Plant
MW
MGD
MW/MGD
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name
RAF B
RL A
RL B
609
756
1025
33
40
60
18
19
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Based the above plants, the average plant capacity to be considered is:
Electric power - 950 MWe
Fresh water - 53 MGD = 200,000 m3/d
3.1
Desalination Economic Evaluation program (DEEP)
The Desalination Economic Evaluation Program (DEEP) is a tool made freely available by the
International Atomic Energy Agency, which can be used to evaluate performance and cost of
various power and water co-generation configurations (IAEA, 2007). The program allows
designers and decision makers to compare performance and cost estimates of various
desalination and power configurations. Desalination options modeled include MSF, MED, RO,
and hybrid systems, and power options include nuclear, fossil, and renewable sources. Cogeneration of electricity and water, as well as water-only plants, can be modeled. The program
also enables a side-by-side comparison of a number of design alternatives, which helps to
identify the lowest-cost options for water and power production at a specific location. Data
needed include the desired configuration, power and water capacities, as well as values for the
various basic performance and costing data. The DEEP performance models cover both the
effect of seawater salinity and temperature on recovery ratio and required feed water pressure.
3.2
Model assumptions
The basic model parameters used for the analysis are summarized in the tables below.
Table 2 - General modelling parameters
Parameter
Gulf seawater salinity
Gulf seawater
temperature
Natural gas price
Natrural gas CO2
emission coefficient
Value
45000ppm
30 C
3.368 $/mmBTU
53.1 kg
CO2/mmBTU
Source
based on average conditions for the Persian Gulf
(Kämpf 2006).
based on average conditions for the Persian Gulf
(Kämpf 2006).
based on international prices as of 8.16.2013
(Index Mundi)
EIA
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Table 3 - Technology-specific model parameters
3.3
Model flow diagrams
Using the parameters indicated above, the flow diagrams for the three technologies were
constructed.
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Figure 2 - MSF-CC Plant Flow Diagram
Figure 3 - RO-CC Plant Flow Diagram
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Figure 4 - IS-CC-MED Plant Flow Diagram
4. Results
4.1
Input comparison
The main parameters considered for the technology comparison, are the natural gas requirement
and the levelized costs of both electricity and fresh water. The table below summarizes the
results.
Natural Gas
(mmBTUX10^6)
LCOE ($/kWh)
LCOW ($/m3)
MSF-CC
72
0.052
5.35
RO-CC
68
0.052
4.14
IS-CC-MED
66
0.122
4.7
4.2
Cost distribution comparison
The relative cost share for the different plants is shown in the graphs below.
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Figure 5 - Comparative cost share between technologies
4.3
Alternative Use for Brine
Considerable amounts of brine waste are disposed of during the desalination process, especially
on a production scale of 150 million cubic meters per year of freshwater (Danoun, 2007).
Current brine disposal options for seawater desalination plants include: discharge to surface
water, wastewater treatment plants, deep well injection, land disposal, evaporation ponds, and
mechanical/thermal evaporation. Given the appropriate process, “brine can yield ... salt, sodium
chloride” (Ibrahim, 1987). Therefore, we are proposing the production of Crystalline salt from
brine waste, which could be sold for commercial use. In addition, we will present brief technical
and economical feasibility assessments of salt production from brine waste in Qatar.
Conventional methods for heating brine waste involve using thermal evaporation, which can be
an energy intensive process (Arnal, et al., 2005). Nevertheless, according to the Chemical and
Nuclear Engineering Department (CNED) at the Polytechnic University of Valencia, companies
located in areas with warm conditions can use environmental or “natural” evaporation methods
(Arnal, et al., 2005). One drawback noted with the natural evaporation method is that the process
requires “large earth extensions since the productivity of the process is quite low (around 4 L.m2 -1
.d )” (Danoun, 2007). However, Qatar has approximately 12,580.7 sq km (7,817.28 sq mi) of
arable and undeveloped land that could provide an adequate amount of open space for salt
production (Appendix D).
Economic considerations are also important assessments to make for this analysis. In general,
brine management and plant location are two essential factors to consider with saltwater
desalination. The cost of disposing of brine “ranges from 5 to 33% of total cost of desalination”
(Arnal, et al., 2005). Seawater desalination plants can easily dispose their brine into coastal
waters using “pipes or submarine emissaries,” whereas inland plants are limited with an
expensive and less-optimal set of options (Arnal, et al., 2005). However, Qatar does not have this
problem because the country is located near the ocean. Moreover, given their warm climate and
17
fresh-water production capacity of over 300,000 m3/day, Qatar is in a unique position with
regard to salt production from brine.
Qatar’s entry into the salt market could help domestic business development, attract
entrepreneurs and create jobs. Figure 5 shows that in 2010 Qatar imported $24,410,025 (USD) of
salt, including table salt. This figure is astounding because that same year millions of tons of
useful brine waste had been dumped back into the ocean. Equally incredible is the upward trend
behavior of the curve in Figure 5, showing significant increases in domestic salt import spending.
Figure 5
Multi-Stage Flash (MSF) desalination plants have larger capacity than other plants, such as
Reverse Osmosis or electrodialysis (Ibrahim, 1987), and a reject brine concentrate that is twice
that of input seawater. Given these considerations it would be highly beneficial for desalination
plants in Qatar to incorporate a sodium chloride recovery process into their MSF plants. This in
turn would enable Qatar to operate dual-purpose desalination plants. Since desalinated water
accounts for about “three-quarters of the total water demand” in Qatar (Danoun, 2007), dualpurpose or “mineral recovery plants” would cut the energy demand cost of single-purpose plants
below that of dual-purpose plants. In short, Qatar could completely replace their salt imports
with a self-sufficient, salt-producing industry.
Brine capacity estimates for Qatar have been calculated in the database belonging to the
International Desalination Association (IDA), World Congress. The brine discharge study by
IDA concerned brine discharge into the Arabian Gulf from desalination plants along the Arabian
coastline, which started from Kuwait to United Arab Emirates. Furthermore, the vast coastline
was divided into three groups: A, B, and C. Qatar belonged to Group C, which produced an
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estimated brine reject of 10 million m3/day and in year 2050 it will have increased to
approximately 26 million m3/day (Bashitialshaaer and Persson, 2011).
5. Discussion and conclusion
As expected, both RO and IS MED show a significant reduction in the fossil fuel requirement
when compared to the BAU MSF plant. However, under the described set of assumptions, RO
appears to be a better alternative in terms of LCOE and LCOW than ISCC MED, due to the
significantly higher upfront costs of the solar array.
Two factors can alter (increase) the future competitiveness of the solar option:
● Economies of scale - according to the literature, CSP plants are feasible above 50MW,
which was the size considered for this study. An increased CSP scale could have a
positive (decrease) effect on the levelized costs of electricity and water. However, it is
necessary to model such scenario in order to make proper conclusions on the effects of
solar array scale.
● Further development of the technology can decrease the cost of the panels or increase
their efficiency significantly.
For brine waste management, we recommend integrating mineral (sodium chloride) recovery
methods into the desalination process. The end salt product could then be sold in both
international and domestic markets as a commercial product. Also, since Qatar imports over
$24.5 million (usd) of salt each year since 2010 (World Bank, 2010), then salt production from
brine waste could turn the $24.5 million (usd) import cost into a surplus. Lastly, operation of
dual-purpose desalination plants would cut the energy demand cost of single-purpose plants
below that of dual-purpose plants.
Due to huge amounts of reject brine from Qatar desalination plants, in the order of 10 million
m3/day, the recovery of salt (Sodium Chloride) becomes feasible. Implementation of our
recommendation for producing commercial salt from brine waste in Qatar will create jobs and
diversify the business sector, supplement salt import costs of $24.5 million (usd), and operate
self-sufficient desalination plants.
Work Contributions
Magdalena Brum:
Anthony Palavi: Brine Waste, EIA, Problem statement & Recommendations (for brine)
19
Tyler Lee:
Rebecca Quinte:
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Appendicies
Appendix A:
Appendix B:
Appendix C: the U.S. Public Health Service considers water to be potable if it has a TDS of less
than 500 ppm (Probstein 1973).
Appendix D: Brine Waste
The World Bank reported that the percentage of Arable Land in Qatar was 1.1% of the total land
area (World Bank, 2010). The total land area in Qatar is approximately 11,437 km2 (4,416 sq
mi).
Hence: 11,437 x 1.1 = 12,580.7 km2
22