Chemical &
Process
Engineering
Energy efficient microbubbles for aeration, flotation and
other uses: wastewater aeration, dispersed air flotation,
ozone dosing,
digester/algal growth/carbon capture.
Will Zimmerman
Professor of Biochemical Dynamical Systems
Chemical and Biological Engineering, University of Sheffield
and Technical Director, Perlemax, Ltd.
with Dr Hemaka Bandulasena and Dr Jaime Lozano-Parada,
with Mr Kezhen Ying and Mr James Hanotu
and special thanks to Professor Vaclav Tesar, Dr Buddhi Hewakandamby, and
Mr Olu Omotowa (all formerly University of Sheffield researchers).
‘Engineering from Molecules’
Outline
• Why microbubbles: mass transfer and flotation
• Wastewater aeration
• Potential for replacing dissolved air flotation
• Algal growth / carbon capture / wastewater plant
integration => target energy positive and CO2 neutral
• Ozone
• Fluidic electricity generator
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Why microbubbles?
Steep mass transfer
enhancement.
• Faster mass transfer -- roughly proportional to
the inverse of the diameter
• Flotation separations -- small bubbles attach
to particle / droplet and the whole floc rises
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Fluidic oscillator
Fluidic oscillator
No moving parts switching
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Pilot scale: Experimental design
Suprafilt layout for 30m^3/h
Chemical &
Process
Engineering
Master-slave amplifier system
for fluidic oscillator
‘Engineering from Molecules’
‘Engineering from Molecules’
Energetics: Power
consumption
Oscillatory flow draws less power than steady flow at the same throughput!
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Visualization study
and
Frequency analysis
With Oscillator
Chemical
&
Without
Oscillator
Process
Engineering
‘Engineering
Molecules’
With Oscillator, Master (small)
shutfrom
completely
‘Engineering from Molecules’
Frequency of oscillation depends on feedback loop and air
throughput
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Aeration: DO profiles, clear
water
Blow-up
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Delay time and dosage
1
D
T
Chemical &
Process
Engineering

T
0
C dt
‘Engineering from Molecules’
‘Engineering from Molecules’
Summarized findings
• Visualization study
• Oscillation frequency
• power consumption: with maximum value of 18%
reduction at the best aeration configuration.
• Clear water dissolved oxygen study: 3-4 fold better
dosage at 83% of the design volumetric flow rate.
• Pilot plant trial with UU in planning stages
• SBR planned next in Rosslare – two basins with
automatic control.
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Potential for dissolved air
flotation (DAF) plant
•
Potentially eliminate recycle flow and saturator load (90-95% electricity cost)
•
Uses blowers not compressors/saturators (much lower capital)
•
Cheap materials for retrofit with fluidic oscillators introduced in the plumbing
and manifolds to diffuser bank for dispersal.
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Microporous diffusers
Fine mist of bubbles rising from Micropore
Technologies Metallic membrane diffuser
Chemical &
Process
Engineering
Median: 47 microns
‘Engineering from Molecules’
Standard deviation: 20 microns
‘Engineering from Molecules’
20 micron sized pores
Field trial campaign
Microporous
diffuser
Growing algae
with microbubbles
• Agreed with UU and AWS and AECOM Design Build (Brenda
Franklin) to trial the technology in a single DAF cell at Padfield
• 12m2 of surface area available for microporous diffuser insertion for
retrofit. Unit instrumented to measure performance and to be
outfitted with visualization equipment.
• Tune performance in operating parameters – chiefly air throughput
rates, water flow rate (~cm/s) and oscillation frequencies.
• Model data from performance studies for engineering design
parameters (number of plate diffusers, placement, flow rates).
• Gain operational experience – identify potential problems, risks,
failure modes -- to plan maintenance regime.
• Assess CAPEX and OPEX requirements
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Ozone plasma microreactors
• How ozone disinfects in water solutions.
• The ozone plasma microreactor in the lab
• How to get the ozone off the chip? Microbubbles!
• Prototypes
• Field trial campaign
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Ozone Kills!
Ozone dissolves in
water to produce
hydroxyl radicals
One
ozone
molecule
kills one
bacterium
in water!
Chemical &
Process
Engineering
Hydroxyl radical attacks bacterial cell
wall, damages it by ionisation, lyses the
cell (death) and finally mineralises the
contents.
‘Engineering from Molecules’
‘Engineering from Molecules’
Ozone plasma microreactor in the lab.
Upper plate
Electrical connection
Electrodes
Fibre optics
Chipholder construct
Lower plate
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Microfluidic onchip ozone generation
Emission UV-Vis spectrum
of exit gas with clear O3
signature. Analysis
suggests 30% conversion at
temperature 350K.
Our new chip design and associated electronics produce ozone from O2 with two
key economic features:
1. Low power. Our estimates are a ten-fold reduction over conventional ozone
generators.
2. High conversion. The selectivity is double that of conventional reactors (30%
rather than 15% single pass).
Additionally, it works at atmospheric pressure, at room temperature, and at low
voltage (170V, can be mains powered).
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Plasma disks
• 25 plasma reactors each with treble throughput over
first microchip
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Dosing lance prototypes
New lance = 70 microdisc reactors
Quartz for UV irradiation
Axial view of the old lance
With 8 or 16 microdisc reactors
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Corporation cock assembly
Ball valve
External assembly.
Chemical &
Process
Engineering
‘Engineering from Molecules’
Valve control to
toggle for flow/no
flow
‘Engineering from Molecules’
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Dual ozone-UV prototype design
New lance = 70 microdisc reactors
Quartz for UV irradiation
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Potential markets
• Water purification (municipal)
• Waste water – organics removal
• Waste water – disinfection before release
• Sterilization (medical, biotech, pharmaceutical)
• Distributed / remote / portable water purification
• Ventilation system sterilization
• Gas analysis (ozonolysis) and sensors
• Biomass treatment and biofuels co-products
Planning trials with UU (priority substances) and AWS
Chemical
&
(pesticide
removal)
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Air lift loop bioreactor design
Schematic diagram of an internal ALB with
draught tube configured with a tailor made
grooved nozzle bank fed from the two
outlets of the fluidic oscillator. The
microbubble generator is expected to
achieve nearly monodisperse, uniformly
spaced, non-coalescent small bubbles of
the scale of the drilled apertures.
Chemical &
Process
Engineering
• Journal article has won the 2009
IChemE Moulton Medal for best
publication in all their journals.
• Designed for biofuels production
• First use: microalgae growth
• Current TSB / Corus / Suprafilt grant on
carbon sequestration feasibility study on
steel stack gas feed to produce
‘Engineering from Molecules’
‘Engineeringmicroalgae.
from Molecules’
Construction
Top with lid
Inner view:
Heat transfer
coils separating
riser /downcomer.
Folded
perforated
Plate m-bubble
generator.
Replaced by
Suprafilt 9inch diffuser
Body / side view
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
ALB for algae growth
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Results
4.00
Fluidic Oscillator
Day 7
Without Fluidic
Oscillator
3.50
Chlorophyll Content
(μg/ml)
8.4
8.2
8
7.8
7.6
7.4
7.2
7
6.8
6.6
6.4
6.2
With Fluidic
Oscillator
Without Fluidic
Oscillator
3.00
pH
2.50
2.00
1.50
1.00
0
15
30
Time (minutes)
45
60
0.50
0.00
1
Chemical &
Process
Engineering
3
4
5
7
8
9
10 11
Time (days)
Rapid pH drop
Potential licensee for carbon
Sequestration organic chemistry
Best poster 6th Annual bioProcessUK
Conference, Nov 2009, York.
2
30% higher relative growth rate with only
60 minutes per day dosing
TSB / Corus / Suprafilt project for
continurous dosing.
‘Engineering from Molecules’
‘Engineering from Molecules’
Current programme of field trials
• Corus: steel plant algal culture
• Aecom: separation/harvesting
• Air lift loop bioreactor development
for biofuels
Approximately
1 cubic metre
cube design with
0.8 m2 square
ceramic microporous
diffusers.
Chemical &
Process
Engineering
‘Engineering from Molecules’
‘Engineering from Molecules’
Prospects for process integration /
intensification for WWTW flowsheet redesign
Anaerobic digestor:
Key concept: Microbubble
dosing will be cheap,
but allow access to all
process gases.
CO2 dosing and CO2/CH4
stripping
Accelerates biochemistry
CHP provides CO2 for
Anammox process
algal growth
Stage 1 Aerobic (air
Result: Accelerate biochemistry
dosing)
of all processes by reactive
extraction. Influence
Stage 2 Anaerobic CO2
production by nutrient dosing
dosing and CO2/N2
rate. Grow algae for biomass /
stripping
biofuel. Sequester CO2.
Chemical &
Process
‘Engineering from Molecules’
‘Engineering Provide
from Molecules’ O2.
Engineering
Potential microbubble markets
• Dispersed air flotation for solids removal in water and
wastewater (achieved target bubble size, 20 microns)
• Wastewater aeration (partner YW, 18% energy reduction,
3-fold higher dosing rates on retrofit)
• Algal biomass / bioenergy production (partner Corus,
>30% extra biomass from CO2 microbubble dosing)
• Wastewater treatment processes integration and
intensification: aeration, digestion, de/nitrification, algal
growth. Targets: smaller footprint; carbon and energy
neutral!
• Ozone dosing from a plasma microreactor dosing lance
• Air lift loop bioreactor development for biofuels
•Chemical
Heterogeneous
chemical and bioreactor engineering,
&
Process
‘Engineering from Molecules’
gas-lift oil recovery, ‘Engineering
oil-water
separations, heat
transfer
from Molecules’
Engineering
More Acknowledgements
• TataSteel: Bruce Adderley, Mohammad Zandi and more.
• Suprafilt: Graeme Fielden, Jonathan Lord, and Hannah
Nolan
• Micropore Technologies: Mike Stillwell
• HP Technical Ceramics: Tim Wang
• AECOM DB: Brenda Franklin, Ben Courtis, Hadi Tai, Yen
Chiu
• Yorkshire Water: Martin Tillotson, Ilyas Dawood
• UoS: Jim Gilmour, Raman Vaidyanathan, Simon Butler,
Graeme Hitchen, Adrian Lumby, Stuart Richards, Clifton
Wray, Andy Patrick
• Yorkshire Forward, TSB, EPSRC, SUEL, Perlemax
Chemical &
Process
Engineering
‘Engineering from Molecules’
• Royal Society Brian ‘Engineering
Mercer
Award,
EPSRC
fromInnovation
Molecules’