Opportunities for Membrane Distillation
Stephen Gray Institute for Sustainability and Innovation
College of Engineering and ScienceVictoria University
[email protected], San Diego, 28th August, 2015
How does membrane distillation compete with reverse osmosis?
• Low energy?– RO ‐ 1 ‐ 4 kW.h/m3
– MD ‐ >200 kW.h/m3
– MDs energy is mostly thermal energy
– Can we get thermal energy from otherwise wasted sources and minimise the electrical energy?
Zhang et al, Desalination, 232 (2013) 142‐149
Need applications with a heat source!
Conventional Distillation & energy HX recovery
Membrane Distillation @ VU
• Modelling of MD
• Applications– RO Brine (ZLD)
• GWMWater/WQRA• NCEDA/Siemens/CSIRO/Osmoflo• CSG ‐ NCEDA/Uni Wollongong/Osmoflo/AGL
– Industrial Water• Power Station (Smart Water/WQRA/CWW/GWMWater)• Textiles (Australian Textile Mills, AusIndustry)• Dairy streams
– Product Recovery• Acid recovery for minerals industry• Ammonia Recovery
Camacho et al., Water, 5 (2013) 94‐196
Factors affecting DCMD flux and Energy Efficiency
Counter flow Co‐flow
Hot Flow
Cold Flow
THi
THO
TCi
TCO
Hot Flow
Cold Flow
THi
TCi
THO
TCO
QH QH
QCQC
Membrane Length
Membrane Properties
Mass & Energy BalanceMass TransferKnudsen‐molecular diffusion transition mechanism (water vapour pressure in pores low => ӿA = PA/P)
Membrane mass transfer characteristicsf(porosity, tortuosities, thickness)
Driving force across membrane = f(temp, pressure)
Resistance in pore = f(pressure and partial pressure in pore)
Zhang et al., Journal of Membrane Science, 349, (2010) pp 295‐303Zhang et al., Journal of Membrane Science, 369, (2011) 514‐525Zhang et al., Journal of Membrane Science, 387‐388 (2012), 7‐16Zhang et al., Journal of Membrane Science, 442 (2013), 31‐38
Energy Balance
Function of local Nu number (ie. Nu changes with position along membrane as temp changes)Welty, Wicks Wilson and Rorrer (1984)Phattaranawik et al, JMS, 187 (2001) 193‐201
Vapour transport
Membrane characteristicλmembrane = λair.ε+ λsolid(1‐ε)
MD Models• Model needs to predict performance for each application making use of the heat available (compressibility)
• Direct Contact Membrane Distillation
• Air Gap Membrane Distillation
• Hollow Fibre Vacuum Membrane Distillation
Ahmad et al., AMTA Membrane Technology Conference, February 25‐28, 2013, San Antonio, TxAlsaadi et al., Journal of Membrane Science, 445 (2013) 53‐65
Zhang et al., Journal of Membrane Science, 434 (2013) 1‐9Zhang et al., Journal of Membrane Science, 442 (2013), 31‐38
Zhang et al., Journal of Membrane Science, 349, (2010) pp 295‐303Zhang et al., Journal of Membrane Science, 369, (2011) 514‐525Zhang et al., Journal of Membrane Science, 387‐388 (2012), 7‐16Zhang et al., Journal of Membrane Science, 442 (2013), 31‐38
Zhang et al., Journal of Membrane Science, 369, (2011) 514‐525Zhang et al., Journal of Membrane Science, 387‐388 (2012), 7‐16Zhang et al., Journal of Membrane Science, 442 (2013), 31‐38Dumée et al., Desalination, 323 (2013), 22‐30
Integration of Membrane Distillation
• A compact, easy to operate thermal desalination system• Low cost materials• Integrates well with industry heat• Using low grade waste heat source
A. Hausmann, et al (2012), Chemical Eng J, v211‐212 p378‐387
Power Plant Demonstration
Seawater
IX Regenerant3000 mg/L TDS
Parameter IX resin regenerant effluent
pH 7.7TOC (mg/L) 5.5TIC (mg/L) 208
Ammonia (mg/L as N) 38Total Dissolved Solids
(mg/L)3490
Calcium (mg/L) 7.1Iron (mg/L) 0.2
Potassium (mg/L) 14Magnesium (mg/L) 4.4Phosphorus (mg/L) <0.1
Zinc (mg/L) <0.1Silica (mg/L)* 19
Boiler Circulation Pumps – 30‐38C
Membrane Distillation ‐ Industrial
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Production rate (L/hr)Specific flux (x10 L/hr/m2/Pa)%Recovery
Trend of production rate, specific flux and water
recovery.
Dow et al, Membrane distillation of industrial wastewater, AWA Ozwater 11, Adelaide, 2011, 9‐11 May, paper 218
Dow et al, Power station water recycling using membrane distillation – A plant trial. Ozwater, AWA, 8‐10 May 2012, Sydney
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g/L)
Total Nitrogen (mg/L)
Total Inorganic Carbon (mg/L)
Total Dissolved Solids (mg/L)
Permeate water quality
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TDS (x1000 mg/L)
Conductivity (mS/cm)
Reject salt concentration
17% drop in flux over 3+ months
Membrane Distillation –Industrial
• Fouling was manageable
• Low heat efficiency but sufficient heat to treat all power plant water
• Similar low grade heat available at other industrial sites (survey of 6 industries)
3rd Demo ‐ Textile Wastewater
• Objectives– Test bench different membranes and pre‐treatments
– Trial MD on site– Test membrane cleaning– Assess integration with site waste heat
Noel Dow1, Jesus Villalobos Garcia2, Leslie Niadoo2, Nicholas Milne1, Jianhua Zhang1, Stephen Gray1, Mikel Duke11Institute for Sustainability and Innovation, College of Engineering and Science, Victoria University, Melbourne, Australia
2Australian Textile Mills, Wangaratta, Australia
Noel Dow
Jesus Garcia
Mikel Duke
Setup – Pilot Trial• Australian Textile Mills, Wangaratta• DCMD pilot plant developed by Victoria University
• Membranes– Option 1: scrim‐backed PTFE 0.1 µm pore size (Chang‐qi, China)– Option 2: Hydrophilic laminated PTFE (Australian Textile Mills)
• Step 1: choose membrane
6.4m2 module
Condensate return line
Air cooler (+cooling water)
Results – Membrane Comparison
Option 2:Laminated PTFE
• Flux: 17 L/m2/h
• Not tolerant to surfactants
• Flux: 5.2 L/m2/h• >80% water
recovery• Worked well
with surfactants
Option 1: Standard PTFE
Results ‐ Pretreatment
• Pre‐treatments greatly reduced wetting (Approx 50% TOC reduction)• Non‐biological not ‘perfect’ and wetting eventually occurs
– Risk of wetting due to process upsets
• Biological treatment more reliable pilot trial– Combine with fractionation on hot cycle to
capture surfactants
Water Source Permeate EC rise rate (µS/cm/hr)
Untreated water 300
50% Diluted 20
Foam Fractionation 10
Ozonation 24
Fenton Oxidation 16
Biological Treatment (Anaerobic + aerobic) 2
• Plant productivity, flux and temperatureResults – Pilot Trial
Hot water pump installed
Factory closed
Factory closed and CIP testing:Caustic CIP effective
Integration into Textile Process• Boilers for steam generation – 4 x 6 MW
– 1 or more boilers always working– Waste heat available at 50‐60˚C; 0.19 MW thermal energy
• MD thermal requirements– With internal heat recovery = 250 kWh/m3
– DCMD no heat recovery = 1,200 kWh/m3
• Insufficient heat available for treatment of full flow (1 ML/D)
Wastewater
High DOC, low salt (<500 mg/L)60% total flow
High salt (4,000 mg/L)40% total flow
RO MD
MD
Results – Integration AssessmentScenario 1 (all MD)
Scenario 2 (RO+MD)
MDHigh EC effluent
Clean water
Brine
ROMD
R = 90%
R = 90%
R = 99% 3.3 kL/day
• MD with heat recovery = 3.4MW (55% boiler)
• Not enough waste heat• Need to use additional energy
from boiler325 kL/day
Assessment:
325 kL/day Brine
33 kL/day
Clean water
Brine
3.3 kL/day
322 kL/day
High EC effluent
• MD with heat recovery = 0.3 MW (5% boiler)
• MD without heat recovery = 1.5 MW (24% boiler)
• Current waste heat source = 13% of MD capacity (no heat recovery)
29 kL/day
293 kL/day
• Viable options for MD if used with RO to treat textile wastewater
• Heat recovery MD design takes small amount of energy from current boiler
• ATM undertaking MBR trials for pretreatment before RO –MD
• Opportunity with other textile mills
Outcomes – MD Options
Conclusion• Need models to design Membrane Distillation process for
specific site locations and available waste heat sources
• Integration into industrial process needs to be considered; available waste heat is sometimes sufficient for low thermal efficiency membrane distillation but not always
• Membrane distillation cannot complete with RO but can compliment RO treatment as industry moves to zero liquid discharge
• Fouling and wetting can be management with correct pre‐treatment or selection of membranes
• Challenge is integration into site processes
Many thanks to:
Tony Fane ‐ Singapore/UNSWEmile Cornelissen ‐ KWR, The NetherlandsMike Dixon ‐ Alberta WaterSMARTLinda Zou ‐Masdar Institute of Science & TechnologySuzana Periera Nunes ‐ KAUST Matthias Wessling ‐ RWTH AachenNeil Palmer ‐ NCEDA/MurdochSophie Leterme ‐ FlindersNamita Choudhury ‐ UniSASheng Dai ‐ Adelaide UniHiep Le ‐ Osmoflo, SAMikel Duke ‐ Victoria UniAndrew Groth ‐ Evoqua Water TechnologiesDharma Dharmabalan ‐ Tasmania WaterHuanting Wang ‐Monash UniversityHo Kyong Shon ‐ UTSManh Hoang ‐ CSIROPierre Le‐Clech ‐ UNSWMatthew Hill ‐ CSIROAaron Thornton ‐ CSIRO
Join our 2016 Organising Committees in beautiful Adelaide, South Australia
Four outstanding plenary speakers confirmed
Benny Freeman Menachem Elimelech Xiao‐Lin Wang Sandra Kentish
5‐8 December, 2016Adelaide