chemical & process engineering ‘engineering from molecules’ airlift loop bioreactors with...
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Chemical &ProcessEngineering
‘Engineering from Molecules’
Airlift loop bioreactors with fluidic oscillator drive microbubbles
Will Zimmerman Professor of Biochemical Dynamical SystemsChemical and Process Engineering, University of Sheffield
with Jaime Lozano-Parada and Hemaka Bandulasena, PD research associateswith Kezhen Ying and James Hanotu, doctoral students
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Outline
• Why and how microbubbles?
• ALB concept
• Performance studies
• Steel stack gas trials
• Advantages for microbial and mammalian cell ALBs
• Sterilization: Ozone plasma microreactor in the lab
• Prototype designs
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Why microbubbles?
• Faster mass transfer -- roughly proportional to the inverse of the diameter• Flotation separations -- small bubbles attach to particle / droplet and the whole floc rises
Steep mass transferenhancement.
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
The Fluidic oscillator
Mid Ports
Inlet
Outlets
Linked by a feedback Loop
What is it?
No moving part, Self-excited Fluidic Amplifier.
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Fluidic oscillator makes microbubbles!
• 20 micron sized bubbles from 20 micron sized pores• Rise / injection rates of 10-4 to 10-1 m/s without coalescence: uniform spacing/size• Watch the videos!
Same Diffuser
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Relatively large coalescent and fast rising bubbles
Production of Mono-dispersedUniformly spaced, non-coalescent Microbubbles
Gas Inlet
Gas Inlet
Conventional Continuous Flow
Oscillatory Flow
Chemical &ProcessEngineering ‘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.
• 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 microalgae.
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Construction
Body / side view
Top with lid
Inner view:Heat transfercoils separatingriser /downcomer.
Folded perforated Plate -bubblegenerator.Replaced bySuprafilt 9inch diffuser
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Growing algae in the lab
Internal of the ALB
The gas separator section links the riser to the downcomer at the top, permitting gas disengagement and recirculation of fluid. Consequently, this drives a flow from the top of the riser to the bottom.
Dunaliella salina
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Gas Dissolution
Day 10
Day 3
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Biomass ConcentrationAlgal biomass / bioenergy production (~30% extra biomass from CO2 microbubble dosing for only 1 hour per day).
Chemical &ProcessEngineering ‘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 metrecube design with0.8 m2 square ceramic microporousdiffusers.
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Features
From the other experiments,
Microbubbles formed from fluidic oscillation draw 18% less electricity than the
same flow rate of steady flow forming larger bubbles. 1.5-2 bar gauge pressure
needed.
3-4 fold better aeration rates with ~300-500 micron bubbles, up to 50 fold
larger with 20 micron sized bubbles
Very low shear mixing is possible at low injection rates (rise rate 10-4 m/s )
From the air-lift loop bioreactor performance,
Microbubbles dissolve CO2 faster and therefore increase algal growth.
Microbubbles extract the inhibitor O2 produced by the algae from the liquid so
that the growth curve is wholly exponential.
Algal culture with the fluidic oscillator generated bubbles had ~30% higher
yield than conventionally produced bubbles with only dosing of one hour per
day over a two week trial period.
Bioenergy could become a more attractive option in the recycling of the high
concentration of CO2 emissions from stack gases (ongoing field trials).
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Ozone Kills and mineralizes!
Ozone dissolves inwater to producehydroxyl radicals
Hydroxyl radical attacks bacterial cell wall, damages it by ionisation, lyses the cell (death) and finally mineralises the contents.
One ozone molecule kills one bacterium in water!
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Microfluidic onchip ozone generation
Our new chip design and associated electronics produce ozone from O2
with key 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).
3. Recently discovered strong irradiation in UV “killing zone” of ~300 nm.
4. Operation at atmospheric pressure, at room temperature, and at low voltage (170V, can be mains powered).
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Plasma discs
• 25 plasma reactors each with treble throughput over first microchip
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Dosing lance assembly
Axial view of the old lanceWith 8 or 16 microdisc reactors
New lance = 70 microdisc reactorsQuartz for UV irradiation
Chemical &ProcessEngineering ‘Engineering from Molecules’
‘Engineering from Molecules’
Consequence
• Our low power ozone plasma microreactor can be inserted into the microporous diffusers to arrange for ozone dosing on demand in an ALB, for sterilization or other uses.