Experiences from the PDU
Mats Galbe
Department of Chemical Engineering
Lund University
Process Development Unit (PDU)
 PDU: lab and process equipment
o Research in bench-scale, i.e., max size 100 litre
fermentor vessel
 National facility placed at Lund University,
mainly financed by the Swedish Energy Agency
o Commissioned work for companies and universities
o Internal research
Purpose of a
Process Development Unit
Research
Increased know-how
Tests of new ideas
Create models…
• Lab scale
Development
Test of process configs.
Optimisation
Products & By-products
•
PDU
•
Pilot scale
Verification
Evaluation
Test of methodology
Final optimisation
Data for scale-up
•
Industrial scale
Process Development Unit (PDU)
Steam pretreatment unit
10 litre reactor
160 - 230 °C
Impregnation with H2SO4
or SO2 or other catalysts
Main purposes
Hydrolysis of hemicellulose
Improve the enzymatic
hydrolysis of cellulose
Success: A number of units
constructed & sold
Pretreatment unit (small)
•4-litre capacity
•Jacket for less
heat losses
•Improved control
of temperature
•Surface-coated
flash-off vessel
Implemented
in large reactor
Steam pretreatment or
acid hydrolysis?
What do we actually mean?
o Steam pretreatment renders a material suitable for
further processing (e.g, by enzymatic hydrolysis)
 With or without catalyst (acid or base)
o Acid hydrolysis (strong or dilute) ideally produces
monomers that can be used without further treatment
Dilute-acid hydrolysis
• Dilute-acid hydrolysis:
– Concentrations typically less than 2%
– Temperatures 180-220°C
– Residence time usually < 15 min
– One- or two-step hydrolysis
– Advantage: rather fast and simple
– Drawback: results in degradation products -> may be
difficult to ferment
• Pentose sugars -> furfural
• Hexose sugars -> HMF, formic and levulinic acid
Acid hydrolysis of spruce
One-step at two temperatures
30
Glucose [g/100g]
Mannose [g/100g]
Xylose [g/100g]
25
Total C6 Sugars
Glucose [g/100g]2
20
Mannose [g/100g]2
Xylose [g/100g]
Total C6 Sugars
[g/100g DM]
15
10
5
0
2.6
2.8
3
3.2Combined Severity3.4
3.6
3.8
4
By-products in one-step acid hydrolysis
using a temperature profile
8
HMF [g/100g]
7
Furf ural [g/100g]
R² = 0.9756
Acetic acid [g/100g]
6
Levulinic acid [g/100g]
Formic Acid [g/100g]
Expon. (Levulinic acid [g/100g])
5
Expon. (Formic Acid [g/100g])
R² = 0.9413
4
3
2
1
0
2.6
2.8
3
3.2
3.4
3.6
3.8
4
Steam pretreatment
• Addition of a catalyst during pretreatment
• Milder conditions than in acid hydrolysis
– Acid results in hydrolysis of the hemicellulose
• H2SO4, H3PO4, SO2
– Alkali mainly oligo- and polymers
• NaOH, NH3
– Enzymatic hydrolysis (SHF) or simultaneous
saccharification and fermentation (SSF)
Different materials behave…
…differently
Agricultural materials
– Wheat straw
– Corn stover
– Sugar cane bagasse
– Sorghum (sweet/fibre)
– Arundo donax
– Rice straw
– Hemp
– Barley straw
– Paja Brava
 Forest materials
o Spruce
o Pine
o Poplar
o Cypress
o Salix
PDU – International partner
•Borregaard, Norway: Steam pretratment
•Chemtex, Italy: SSF, steam pretreatment
•Cargill, Germany: Steam pretreatment
•Mitsui Engineering & Shipbuilding, Japan: SSF
•Nagurjana Hills, India: SSF
•NBE Sweden: Hydrolysis, analysis, fermentation
•SGCC (State grid of China): Project and cooperation
Currently
•SEKAB: SSF, analysis
building full- •Taurus: Pretreatment and fermentation
scale plant in •…
Italy
•CTH
•KTH
•Brazil-EU: Partner in Cane Biofuel
•NILE (EU): SSF, pretreatment (Partner)
•University of Florida
•University of Georgia
•National Renewable Energy Labs (NREL), USA
•…
High-WIS applications
(WIS: Water-Insoluble Solids)
• High WIS is good…
– Potentially higher sugar concentrations
-> Higher ethanol concentrations
-> Less energy requirements
• …(or is it?)
– Increased viscosity
• Higher inhibitor concentrations
• Less available liquid
-> unfriendly environment
• Heat transport affected!
• pH control initially difficult
• OPTIMISATION!
Higher dry-matter concentrations
o Terrafors (originally for
solid-state fermentations)
o Difficult to control pH
o Mixing less efficient with
increased liquefaction
High-WIS hydrolysis quick tests
Rotating with steel balls
for mixing
High-WIS (SHF or SSF)
Test of equipment
First test of enzymatic
hydrolysis of spruce
100
Concentrations (g/L)
90
80
70
60
50
40
30
Cellobiose
Glucose
Xylose
Galactose
Arabinose
Mannose
20
10
0
0
24
48
Hydrolysis time (hours)
72
96