Manipulated Osmosis Applied to
Evaporative Cooling Make-up Water –
Revolutionary Technology
Peter Nicoll
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Osmosis
(Forward osmosis, manipulated osmosis)
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Defined as the movement of water across a selectively permeable membrane driven by the difference in osmotic pressure
Not a new technology
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Trees use it
Plants use it
First patents – 1960’s
Under‐exploited
In recent years much more interest in it both academically and industrially – dedicated sessions at conferences and first papers presented at IDA Perth 2011
Wide variety of applications; desalination, concentration, dilution, power generation, pre‐
treatment etc
Key issues; membrane availability, concentration polarisation (low flux), back diffusion
Simple Flow Diagram
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Evaporative Cooling
Water consumed as a result of evaporation, blowdown and drift losses
Process widely used across the world; power stations, industrial processes, air conditioning, district cooling etc
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Make‐up water typically of high quality and in Middle East region majority is provided by desalination
District cooling plants typically consume 9 litres/hr per ton of
refrigeration – massive increase in capacity forecast with corresponding significant requirement for suitable make‐up water Deployment of evaporative cooling (a ‘green’ process) currently inhibited by water scarcity
Use of treated sewage effluent for make‐up increasing but problematic
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7
1,200
Cooling capacity (m tons/hr)
6
5
1,000
Installed district cooling capacity (m tons/hr)
800
4
600
3
400
2
200
1
0
0
2003
2006
2008
2009
2013E
(F&S
2009)
2015E
(NALCO
2010)
2015E
(MEED
2006)
Source: Nomura Code, NALCO. Forecasts from MEED, Nalco and Frost & Sullivan
Water consumption 000 m3/day)
Implied water demand (000 m3/day)
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Forward Osmosis Applied to Evaporative Cooling
Conventional
Cooling System
Cooling System
incorporating FO make-up
(cooling water as osmotic agent)
Make-up via
forward osmosis
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Key Points
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8
RO w ith ERT
7
RO no ERT
6
Manipulated Osmosis
Manipulated Osmosis (OA
recovery)
5
kWh/m 3
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Radically lower power consumption compared with reverse osmosis (88% ‐ 40%, typically 50%)
Low fouling propensity of forward osmosis process
Osmotic agent based on a non toxic commodity chemical
FO membranes resistant to oxidising biocides
Blowdown recovery system retains osmotic agent and cooling water chemicals –
reduced chemical costs and environmental impact compared to conventional process
4
3
2
1
0
0
10,000
20,000
30,000
40,000
50,000
Feed Water TDS (mg/l)
0.6
RO Pow er Cost
RO Pow er Cost
w ith ERT
MO Pow er & OA
Cost
0.5
0.4
Cost US$/m3
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0.3
0.2
0.1
0
0
10,000
20,000
30,000
40,000
Feed Water TDS (mg/l)
Assumptions detailed in paper
50,000
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Demonstration Plant
Demonstration / test plant housed in 20’
container
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Requires a source of raw water (seawater, brackish water, TSE), drain, power and heat load
FO membrane pre‐
treatment
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Currently located at Sohar Industrial Port, Oman (seawater feed)
Operational since July 2010
Multi‐media pilot filter columns
Air scour
Backwash
Flocculant dosing
Antiscalant
Calcium hypochlorite dosing
Packaged cooling tower
Heat exchanger
Membrane Support Systems
Blowdown recovery system (retains osmotic agent)
Plant can be easily moved to test sites
100
90
80
70
System Volume (%)
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60
50
System
Volume Falls
Due to
Evaporative
Introduction
Cooling
of OA to
without
FO
Makeup
Membranes
40
System Volume
Steady due to MO
30
Permeate Makeup
20
10
0
09:00
10:00
11:00
12:00
13:00
Time
14:00
15:00
16:00
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Input from forward osmosis desalination
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Core forward osmosis technology well proven – plants operating since 2008
Significant operating experience gained on high fouling seawater –
conventional SWRO plant required frequent chemical cleans at Al Khaluf
Modern Water plant’s FO membranes have never required chemical cleaning
FO process is robust and reliable
100 m3/day FO based seawater
desalination plant, Al Khaluf, Oman
Process container, Al Khaluf, Oman
18 m3/day FO based seawater
desalination plant, Gibraltar
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Other advantages
Can utilise a wide range of feedwaters
from seawater to treated sewage effluent
• Process can be easily retrofitted to an existing installation
• Osmotic agent inhibits growth of Legionella
pneumophila (Modern Water undertaken detailed laboratory work) – minimising the use of oxidising / non oxidising biocides
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Legionella
(source CDCP)
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Hurdles for adoption
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The process appears to be radically different from conventional approach – yet membrane processes are widely known
The cooling tower industry is split between chemical suppliers and equipment suppliers – little incentives for radical change by either group
In GCC countries existing district cooling plants have a pass through cost arrangement for power and water –
so no incentives for significant opex cost reduction
Demonstration plant
DESALINATION: SUSTAINABLE SOLUTIONS FOR A THIRSTY PLANET │ SEPT. 4-9, 2011
Conclusions
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Energy consumption at least 50% less than reverse osmosis based make‐up system
Robust, fouling resistant core forward osmosis based process – in use since 2008
A simple solution for the production of high quality make‐up water from a variety of raw water sources
A water substation process displacing the use of valuable desalinated water A “disruptive technology” –
significantly lowering costs and extending applicability of evaporative cooling