Bioprocess and Biosystems Engineering

, Volume 33, Issue 4, pp 485–493 | Cite as

Reactor scale up for biological conversion of cellulosic biomass to ethanol

  • Xiongjun Shao
  • Lee Lynd
  • André Bakker
  • Richard LaRoche
  • Charles Wyman
Original Paper

Abstract

The absence of a systematic scale-up approach for biological conversion of cellulosic biomass to commodity products is a significant bottleneck to realizing the potential benefits offered by such conversion. Motivated by this, we undertook to develop a scale-up approach for conversion of waste paper sludge to ethanol. Physical properties of the system were measured and correlations were developed for their dependence upon cellulose conversion. Just-suspension of solid particles was identified as the scale up criterion based on experiments at lab scale. The impeller speed for just solids suspension at large scale was predicted using computational fluid dynamics simulations. The scale-up strategy was validated by analyzing mixing requirements such as solid–liquid mass transfer under the predicted level of agitation at large scale. The scale-up approach enhances the prediction of reactor performance and helps provide guidelines for the analysis and design of large scale bioreactors based on bench scale experimentation.

Keywords

CFD SSF Scale up Solids suspension Cellulosic biomass 

List of symbols

[C]

Cellulose concentration (g/L)

[Cb*]

Cellobiose concentration in interface (g/L)

[Cb]

Cellobiose concentration (g/L)

[CE]

Cellulose–enzyme complex concentration (g/L)

[I]

Solids concentration (g/L)

[X]

Xylan concentration (g/L)

ap

Particle surface area per volume (m−1)

CpL

Liquid heat capacity [J/(kg K)]

D

Impeller diameter (m)

DaM

Damkoeher number

ΔT

Temperature difference between tank inner surface and bulk liquid (°C)

dp

Particle diameter (m)

ε

Power per mass on liquid or turbulent kinetic energy dissipation rate (W/kg)

Eth

Ethanol

ϕ

Solids loading (g/L)

hi

Heat transfer coefficient in inner tank surface [W/(m2 K)]

k

Thermal conductivity [W/(m K)]

k(x)

Conversion dependent rate constant of cellulose hydrolysis (h−1)

kr

Reaction constant (s−1)

kt

Turbulent kinetic energy (m2s−2)

kSL

Solid–liquid mass transfer coefficient (m/s)

Mk

Mass transfer rate (g/(L s))

Mr

Reaction rate, g/(L s)

μL

Liquid viscosity (cp)

N

Operating impeller speed (s−1)

Njs

Just-suspended speed at large scale (rpm)

Njs0

Just-suspended speed at small scale (rpm)

P

Power (W)

Pjs

Power for just solids suspension (W)

ρave

Average density for reactor content (g/L)

\( {{\uprho}}_{{{\text{H}}_{ 2} {\text{O}}}} \)

Water density (g/L)

ρL

Liquid density (g/L)

Po

Power number of impeller, 1.5 for the marine impeller

Pr

Prandtl number

ρS

Solids density (g/L)

Q

Total heat of production by reaction (J)

r

Rate of reaction or heat production (g/(L s)) or (J/g)

Re

Reynolds number

S

Tank wall surface area (m2)

Sc

Schmidt number

Sh

Sherwood number

σ

Quality of solids suspension as defined in Eq. 3

T

Large scale tank diameter (m)

T0

Small scale tank diameter (m)

τB

Mixing/blend time (s)

tr

Characteristic reaction time (s)

V

Tank volume (m3)

VF

Volume fraction

\( w_{{{\text{H}}_{ 2} {\text{O}}}} \)

Amount of water added to flask (g)

wS

Weight of solids sample added to volumetric flask (g)

x

Conversion

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Xiongjun Shao
    • 1
  • Lee Lynd
    • 1
  • André Bakker
    • 2
  • Richard LaRoche
    • 3
  • Charles Wyman
    • 4
  1. 1.Thayer School of Engineering at Dartmouth CollegeHanoverUSA
  2. 2.ANSYS, Inc.LebanonUSA
  3. 3.DEM SolutionsLebanonUSA
  4. 4.Chemical and Environmental EngineeringUniversity of California RiversideRiversideUSA

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