Chemical & Process Engineering ‘Engineering from Molecules’ Airlift loop bioreactors with fluidic oscillator drive microbubbles Will Zimmerman Professor of Biochemical Dynamical Systems Chemical and Process Engineering, University of Sheffield with Jaime Lozano-Parada and Hemaka Bandulasena, PD research associates with Kezhen Ying and James Hanotu, doctoral students

Chemical & Process Engineering ‘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 & Process Engineering ‘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 transfer enhancement.

Chemical & Process Engineering ‘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 & Process Engineering ‘Engineering from Molecules’ Fluidic oscillator makes microbubbles! 20 micron sized bubbles from 20 micron sized pores Rise / injection rates of to m/s without coalescence: uniform spacing/size Watch the videos! Same Diffuser

Chemical & Process Engineering ‘Engineering from Molecules’ Relatively large coalescent and fast rising bubbles Production of Mono-dispersed Uniformly spaced, non-coalescent Microbubbles Gas Inlet Conventional Continuous Flow Oscillatory Flow

Chemical & Process Engineering ‘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 & Process Engineering ‘Engineering from Molecules’ Construction Body / side view Top with lid Inner view: Heat transfer coils separating riser /downcomer. Folded perforated Plate  -bubble generator. Replaced by Suprafilt 9inch diffuser

Chemical & Process Engineering ‘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 & Process Engineering ‘Engineering from Molecules’ Gas Dissolution Day 10 Day 3

Chemical & Process Engineering ‘Engineering from Molecules’ Biomass Concentration Algal biomass / bioenergy production (~30% extra biomass from CO 2 microbubble dosing for only 1 hour per day).

Chemical & Process Engineering ‘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 m 2 square ceramic microporous diffusers.

Chemical & Process Engineering ‘Engineering from Molecules’ Weather Day Light intensity, kLux Weather 24h Mean Temperature, o C Mean Temperature during process, o C Gas Flow rate, l/min Bioreactor Temperature, o C CO 2 inlet Temperature, o C Algae growth, μg/ml 27/04/ /04/ /04/ /04/ /05/ /05/ /05/ /05/ /05/ /05/ /05/

Chemical & Process Engineering ‘Engineering from Molecules’ Overall growth dynamics

Chemical & Process Engineering ‘Engineering from Molecules’ Probing operation

Chemical & Process Engineering ‘Engineering from Molecules’ Pseudosteady operation

Chemical & Process Engineering ‘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 bar gauge pressure needed. 3-4 fold better aeration rates with ~ micron bubbles, up to 50 fold larger with 20 micron sized bubbles Very low shear mixing is possible at low injection rates (rise rate m/s ) From the air-lift loop bioreactor performance, Microbubbles dissolve CO 2 faster and therefore increase algal growth. Microbubbles extract the inhibitor O 2 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 CO 2 emissions from stack gases (ongoing field trials).

Chemical & Process Engineering ‘Engineering from Molecules’ Ozone Kills and mineralizes! Ozone dissolves in water to produce hydroxyl 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 & Process Engineering ‘Engineering from Molecules’ Microfluidic onchip ozone generation Our new chip design and associated electronics produce ozone from O 2 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 & Process Engineering ‘Engineering from Molecules’ Plasma discs 25 plasma reactors each with treble throughput over first microchip

Chemical & Process Engineering ‘Engineering from Molecules’ Dosing lance assembly Axial view of the old lance With 8 or 16 microdisc reactors New lance = 70 microdisc reactors Quartz for UV irradiation

Chemical & Process Engineering ‘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. One potential use is providing a non-equilibrium driving force for biochemical reaction / biomass growth by breaking down extracellular metabolites secreted by microorganisms to minerals (CO2, H2O, nitrates, phosphates etc.) by UV-ozone providing a strong oxidizing environment in situ.