HYDRODYNAMIC MIXING INSIDE THE TUBULAR PHOTOBIOREACTOR : PREDICTION OF ALGAL CELL TRAJECTORY pathlin

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HYDRODYNAMIC MIXING INSIDE THE TUBULAR
PHOTOBIOREACTOR PREDICTION OF ALGAL CELL
TRAJECTORY (pathline)AND LIGHT REGIME PARAMETERS

• ing. tepán Papácek (e-mail papacek_at_alga.cz)

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OUTLINE

• Algal biotechnology basics
• State-of-the-Art of PBR design
• Algal suspension flow description
• (by CFD)
• Irradiance history record of an individual cell
• Light regime parameters
• Photosynthetic response measurements
• Concluding remarks

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Algal biotechnology basics (1/2)

• Cell (Algae Cyanobacteria, photosynthetic
  factory PSII, )
• Algal suspension
• (state variables density, viscosity, pH,
  temperature, dissolved oxygen, diss. CO2,
  nutrients, cell concentr., averaged PFD, etc. )
• Products (biomass, high value or bioactive
  compounds)
• Geometric form of the bioreactor (cylindrical
  tank, column, rectangular, tubular, annular,
  flat-panel, etc.)
• PBR design parameters operating conditions
• (total photic volume, max. PFD - irradiances,
  conditions of light use i.e. light regime
  parameters, pumping device, flow rate,
  cultivation regime batch, continuous,
  semi-cont., etc.)
• Measurement Control (on-line measurement or
  state estimation, control based on .)

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Algal biotechnology basics (2/2)
10 mm
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Photosynthetic microorganisms
Algae Chlorella, Scenedesmus, Cyanobacteria
Pediastrum duplex, Anabaena sp., Phormidium sp.,
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Introduction to photosynthesis Physical
approach (1/2)
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Introduction to photosynthesis Biotechnological
approach (2/2)

• Three-state model
• PSF - photo-synthetic factory, X1 open,
• X2 closed,
• X3 inhibited,
• X1X2X31
• Growth
• X2 Me
• Me-maintenance

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• State-of-the-Art of PBR design
• Principal design parameters operating
  conditions
• total photic volume (V), S / V ratio (S -
  illuminated surface), pumping device, flow rate,
  incident irradiance (I), light regime parameters
  ( Iav, L/D cycles,...), cell concentration (X),
  etc.

Laboratory flat-panel PBR At the Institute of
Microbiology, Academy of Sciences, Trebon,
Czech Republic

• Photic volume
• 1 panel 15 Litres
• (30 canals of 1.2 m length, section 30x13 mm)
• Light energy intensity
• 150 W m-2

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Annular PBR, IFREMER, Nantes, France (annular
light chambers photic volume 100 L, max.
irradiances ? )
( from A. Muller-Feuga, 2002)
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Novel solar tubular PBR in Academic and
University Center, Nove Hrady, Czech Republic

• Photic volume
• 50 Litres (24 m of tubes i.d. 48 mm)
• Total volume
• 60-70 Litres
• Mean axial flow velocity
• 0.4 m/s, Re 10 000
• Light / dark cycles
• (t l )g 60 s , (t d)g 20 s
• Max. irradiances
• 7000 m E m-2s-1

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PBRs OPERATING CONDITIONS
Incident Light (PFD,)
Culture concentration
( from Grobelaar, 2000)
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Process productivity P mXV

• X biomass concentration g/L
• specific growth rate (dX/dt 1/X) day -1
• V total volume of PBR L

Having a good (optimal) light regime to maximize
m
2 antagonists phenomena
The increase of the culture concentration X
improves P (but reduces the light depth of
penetration)
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Hydrodynamical (radial) mixing
more efficient use of light
improvement of mass transfer characteristics
process productivity increases!
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Different existing solutions for mixing
improvement

• Static mixers
• (Ugwu, Ogbonna Tanaka, 2002), see fig. 1,
• Flow invertors
• (Zitny, 2002), see fig. 2,
• Swirling flow
• (Muller-Feuga, 2002).

Fig. 1
Fig. 2
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OUTLINE

• Algal biotechnology basics
• State of the Art of PBR design
• Algal suspension flow description (by CFD)
• Irradiance history record of an individual cell
• Light regime parameters
• Photosynthetic response measurements
• Concluding remarks

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NavierStokes equation Since 1840 modelling the
flow motion of a viscous compressible fluidFor
an incompressible Newtonian fluid
Mass conservation or continuity equation div
u N.u 0 in W Where u is the velocity of
the fluid, p is the pressure, r is density, f is
the external force field per unit volume and m is
the dynamic viscosity. Boundary u 0
on dW1 Initial conditions u f (xi , t
) on dW2 Fluid properties m is
time-varying (fluid is non-Newtonian),
two-phase flow (particle-fluid
suspensions), three-phase flow
(particle-gas-liquid) Particle properties buoyanc
y, gravitaxis, phototaxis.
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Numerical Solution of N-S eq. system (1/2)

• Computational Fluid Dynamics (CFD)
• Finite Element / Volume Method (FEM/FVM),
• Lattice-Boltzmann method (LBM), ...
• Commercial software
• FLUENT (based on FVM), ...

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Numerical Solution of N-S eq. system (2/2)

• Turbulent fluid motion
• Reynolds-Averages Approach (RANS)
• vs. DNS (Direct numerical simulation)
• Kolmogoroffs turbulence theory Diameter of
  smallest eddies 10-4 m, 10 grids points for an
  eddy gt DNS is impractical
• Turbulence models
• RANS (time-averaged N-S eq.) k- e, RSM,
• LES (Large Eddy Simulations) time averaging is
  applied only to the eddiest smaller than

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CFD solution of the algal suspension flow-field
in PBR cross section (by Fluent)
Desired result algal cell trajectories
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Numerical solution should be verified e.g.
using PIV - Particle Image Velocimetry (other
accessible experimental technique is Chlorophyll
Fluorescence Measurement)
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OUTLINE

• Algal biotechnology basics
• State of the Art of PBR design
• Algal suspension flow description
• (by CFD)
• Irradiance history record of an individual cell
• Light regime parameters
• Photosynthetic response measurements
• Concluding remarks

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Light distribution inside the algal suspension
(tube flat-panel cross sections)
I
II
III
I
II
III
Zone I PFD gt (photoinhibition) Zone II
PFD (interval) (photolimitation) Zone III
PFD lt (darkno grown zone)
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Computational Fluid Dynamics (Lagrangian Flow
Description gt particle path / trajectory)
Radial mixing
Light Shear stress conditions (Residence Time
Distribution, Light/Dark cycles, shear
stress,...)
Photosynthetic response (photoinhibition and
photolimitations processes, specific growth rate,
final culture concentration in batch cultivation)
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Coupling Irradiance field and Algal cell
trajectory gt Light history record for an
individual cell with an initial position in
Xi i 1,,100,..
Irradiance - PFD (photon flux density)
I
II
III
t
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Light/dark cycles, periods, frequencies during
one main period T - one passing through
PBRglobal dark time in one circulation (t d
)gglobal time spent in illuminated section of
PBR (t l )gfraction of circulation time spent
in illum. section (t l )g / T
PFD
(t d )g
(t l )g
(t d )g (t l )g T
I
II
III
t
T
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Residence Time Distribution - Histogramsfor an
individual cell and t lt (t l )g
Sample relative frequency of time spent by one
cell in the respective zone
For cell X3
For cell X2
For cell X1
III
II
I
II
III
PFD
I
PFD
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Residence Time Distribution - Histogram for
whole algal culture and t lt (t l )g
Sample relative frequency of time spent by whole
culture in the respective zone
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Histograms ( probability density curves) of time
interval spent in respective zone without
interruption
Sample relative frequency of time interval spent
in the resp. zone without interruption
For zone III
For zone II
For zone I
t mean III
t
t mean II
t mean I
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OUTLINE

• Algal biotechnology basics
• State of the Art of PBR design
• Algal suspension flow description
• (by CFD)
• Irradiance history record of an individual cell
• Light regime parameters
• Photosynthetic response measurements
• Concluding remarks

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Photosynthetic Response (1/2)

• Photosynthetic response to light/dark cycles in
  small cultivation systems (deterministic flashing
  or intermittent light experiments Kok, 1953
  Philips Myers, 1954 Nedbal Grobelaar, 1996
  Wu Merchuk, 2001) higher PE
• Photosynthetic response to flashing effect of the
  local mixing in large cultivation systems
  (probabilistic phenomenon), i.e. photosynthetic
  response to different
• light regime parameters

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Photosynthetic Response(2/2)

• PBRs sensitivity to changes of light regime
  parameters (e.g. to ratio of iluminated/non-illum
  inated section, etc.)
• Optimal conditions for biomass production
  (maximum values of specific growth rate or
  maximal diurnal productivity)
• Optimal residence time of the culture in the PBR
  illuminated section
• Ratio of illuminated / non-illuminated section
• Optimal mean value of Time spent in each specific
  section without interruption.

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CONCLUDING REMARKS

• Many different approaches to PBR design Light
  condition description in PBR still exist after 50
  years of RD (incident light, average light,
  light regime parameters) gt a vast area for
  RD
• Multidisciplinary, multilevel and multiscale
  problems... Theoretical, numerical and
  experimental analysis should be complementary
  tools !
• 4 steps to describe Light condition in PBR
  modelling
• - Light field description,
• - Flow-field description,
• - Microalgae path (trajectory) calculation
• - Local Global characteristics of the light
  use (i.e. Light regime).
• Just proposed methodology of PBR design
  Numerical simulation aiming to find
• PBR optimal design operating parameters
  directly without scaling-up a laboratory PBR!

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Thanks for your attention

• A za podporu a konzultace dekuji kolegum z
  VÝZKUMNÉHO CENTRA FOTOSYNTÉZY a MBÚ Trebon, Dr.
  Karlovi Peterovi (CVUT Praha), Dr. P. Strasákovi
  (Techsoft Praha), Dr. P. Polachovi a Dr.
  M.Schusterovi (koda Výzkum s.r.o.) a kolegum z
  KMO, FM TU Liberec.