Hot water extraction of wood

Hot water extraction of wood and extract purification

FuBio JR2 WP1

Petri Kilpeläinen, Johanna Tanner

Finnish Forest Research Institute

FuBio JR2

Research partners

• Research organisations – Aalto University, Aalto

– Finnish Forest Research Institute, Metla

– Lappeenranta University of Technology, LUT

– University of Helsinki, UHe

– University of Jyväskylä, UJy

– VTT Technical Research Centre of Finland, VTT

– Åbo Akademi University, ÅA

• Industrial partners – Andritz

– Kemira

– Metsä Group

– Stora Enso

– UPM-Kymmene

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The aim

•To get fundamental knowledge of pressurized hot water extraction (PHWE)

•To extract hemicellulose and lignin from sawdust

To produce polymeric, water soluble hemicellulose

Lignin as by-product

Extracted sawdust is processed to novel pulps

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Rawmaterials and pre-treatment

Separation and purification

Products

Refined products

Wood - Spruce sawdust

- Birch sawdust

PHWE

- Lab scale, METLA, ÅA

- Pilot scale, METLA, VTT

- Supercritical, Aalto

Delignification

- Lab scale, Ujy

- Pilot scale, VTT

Concentration

- Ultrafiltration, LUT

Hydrolysis

- Enzymatic, UHe

- Acid, ÅA

Purification

- EtOH precipitation, LUT,

METLA

- Oxidation, ÅA

Acidification

- METLA

Monosugars High Mw

hemicelluloses Lignin

Fuels Barriers Composites Pulp

Extract

High Mw Low Mw

Black liquor

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METLA

ÅA

VTT

Aalto

Extraction temperatures

• Viscosity, diffusivity and dieletric constant of water changes at higher temperatures

• pH scale changes as pKw value of water changes

Gas

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Lab scale

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Batch extraction of fine spruce sawdust

• Accelerated solvent extraction (ASE) 350, Zr-type cell

• Temperature: 150-180

C

• Solvent: distilled water

• Liquor/Wood ca 4/1

• Pressure: 10 MPa

• Fine fraction 0.05-0.1 mm of ground spruce sapwood

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TDS of extracts obtained at different temperatures (particle size 0.25-1.0 mm vs fine fraction 0.05-0.1 mm)

Ethanol precipitated polymeric GGM from extracts obtained at different temperatures (particle size 0.25-1.0 mm vs fine fraction 0.05-0.1 mm)

Possible to obtain polymeric hemicellulose at lower temperature with fine fraction

180

C Max yield

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PHW flow-through extraction of birch sawdust with pH buffer

• 10 g a.d. of birch sawdust

• 50 ml extraction vessel

• Temperatures 160-180

C

• 50-70 Bar

• 30 min extraction

• 4 ml/min flow rate

• 0.1 M acetate buffer

• pH 4.0, 4.2 and 4.6

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Molar mass of xylan increases with (pH 4.0) buffer

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

24 29 34 39 44

RID

Retention time, min

NO BUFFER

160°CMw 18.8 kDa

170°CMw 2.1 kDa

180°CMw 1.1 kDa

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

24 29 34 39 44

RID

Retention time, min

BUFFER

160°CMw 14.2 kDa

170°CMw 4.8 kDa

180°CMw 3.9 kDa

Decreasing molar mass Decreasing molar mass

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Oxygen-alkali delignification of PHW extracted sawdust

• Pulp yields were lower after PHWE combined with oxygen-alkali cook

• Less lignin was dissolved since some lignin was dissolved during PHWE

0

10

20

30

40

50

60

70

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30 60 90 120 150P

ulp

yie

ld, %

of

ori

gin

al d

ry

wo

od

Cooking time, minutes

Spruce sawdust

PHW extracted sawdust

• Spruce and birch PHW extraction residues were cooked for 30-150 min at 170

C

• Liquor to wood ratio 5L/kg

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Supercritical water treatment

• Target: Dissolution of crystalline cellulose in near- and supercritical water

• Produce cello-oligomers from cellulose

• Minimizing sugar losses by applying a short reaction time

Cellulose Dissolved poly- and oligomers

Glucose Degradation

products

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Cellulose dissolution in subcritical and supercritical water

Short reaction time t < 1 s

Long reaction time t > 1 s

Microcrystalline cellulose (MCC), Pre-hydrolyzed Kraft pulp (PHK), Alkaline treated (mercerized)

Cellulose precipitate after 0.2 s treatment

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Modeling

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Modeling of PHWE

• Objective: Develop a model for the degradation of birch in a percolation reactor.

• Previous PHWE study for batch reactor (Borrega et al. 1) .

• Models were fitted to describe the degradation of lignin, xylan and glucan.

• How do the parameters obtained from the batch experiments fit the new data from percolation cooks?

Schematic diagram of the flow-through percolation reactor and associated

elements used for the hot water extractions of wood.

1. Borrega, M., Nieminen, K., and Sixta, H. (2011). “Degradation kinetics of the main carbohydrates in birch wood during hot

water extraction in a batch reactor at elevated temperatures,” Biores. Technol. 102(22), 10724-10732.

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Model

• It is assumed that the hot liquor moves as a plug flow

• Initially the reactor only partly filled with hot liquor – the reactions occur only in the hot section.

• Once a wood component has been dissolved, it stays in the reactor only for a short time before it is washed out and cooled down – less further reaction products than in a batch reactor.

• Partial differential equations describe the time developments of the various products 0 10 20 30 40 50 60

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

% o

.d.w

Time (min)

0 50 100 150 200

0

1

2

3

4

5 Glucooligosacharides (GOS)

Glucose

Hydroxymethylfurfural (HMF)

Other degradation products (Dp)

% o

.d.w

Time (min)

200

C

Batch

Flow-through

Flow rate 100

ml/min

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Average Mw GGM content of the PHWE extract mg/g

Temperature (

C)

Flo

w r

ate

(l/m

in)

1

2

3

4

6

5

150 160 170 180 155 165 175 185 150 160 170 180 155 165 175 185

Temperature (

C)

1

2

3

4

6

5

14

6 250

10

50

150

Modeling flow-through PHWE of spruce sawdust utilizing Modde (partial least squares method)

• A combination of low PHWE temperature and low flow rate dissolves highest molecular mass GGM, but with lower yield

• The model can be used to choose process conditions for PHWE in order to produce desired GGM properties

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From lab to pilot scale

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Example of stepwise batch PHWE process of spruce sawdust in a semi-pilot scale (30 l vessel) extraction

0

1

2

3

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5

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9

10

160 °C/40 min 170 °C/60 min 180 °C/3 h washing at50 °C/30 min

Avera

ge M

w o

f sp

ruce

saw

du

st

extr

act

(kD

a)

• Stepwise PHWE dissolved GGM with high average Mw in the 1st step. The Mw was clearly

decreased in the 2nd and 3rd steps.

• PHWE processes in VTT’s 30 l extraction vessel are reproducible, when looking at e.g. average

molecular mass of the extracts in the first two steps of the two separate processes

2-step PHWE

3-step PHWE

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Pilot scale (300 L) extraction

vessel

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Results Spruce Birch

Sawdust weight o.d. [kg] 53 kg 73 kg

Time when collected [min] 15 – 30 min 30 – 45 min 15 – 35 min 35 – 55 min

pH 4.4 3.7 3.9 3.8

Hemicellulose yield [wt%] 4 wt% 7 wt% 3 wt% 6 wt%

Mw [kDa] 13 kDa 8 kDa 14 kDa 8 kDa

PHWE flow-trough extraction examples in pilot scale • Spruce at 170

C

• Birch at 160

C with pH 4.0 buffer

– pH stabilization during extraction

• Extracts to ultrafiltration and purification

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Lignin from pilot scale extraction

•Extracted sawdust was cooked with soda-aq to remove lignin

•Solution was acidified to precipitate sulfur free lignin

•Lignin was purified to remove inorganics

•Purified lignin was used to make biocomposites

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Separation and purification of extracts

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Recovery of high molar mass hemicelluloses in pilot scale

• High shear rate CR-filters • Commercial, hydrophilic 10 kDa regenerated cellulose membrane (Alfa Laval) • 60

C, 2 bar, rotor velocity 9.5-13.8 m/s

CR-350

FeedPermeate

Concentrate

Filter cassette

Drainage support

Membrane

FeedPermeate

Concentrate

Filter cassette

Drainage support

Membrane

From Metso Paper

Operation principle:

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Ultrafiltrations can be done continuously without losing filtration capacity

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Extract can be concentrated and molar mass (Mw) of hemicellulose increases during extraction

• Possible to achieve the TDS

and Mw of hemicellulose required for film manufacturing

• Increase in TDS content and Mw of hemicellulose have a clear effect on capacity

• Filtration capacity with spruce extracts higher than with birch extracts

• Birch extracts need further purification to obtain better filtration results

Three different birch extract filtrations

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Summary

•Fundamental knowledge obtained to up-scale system from lab to pilot scale

•Possible to extract polymeric, water-soluble hemicellulose from spruce and birch

•Produced lignin can be utilized to make biocomposites

•Purification and concentration of hemicelluloses can be done continuously with ultrafiltration

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Acknowledgements

Aalto

Lasse Tolonen

Marc Borreca

Herbert Sixta

Metla

Petri Kilpeläinen

Sanna Hautala

Johanna Tanner

Veikko Kitunen

Olli Byman

Teemu Tikkanen

Zhiqiang Li

Kaisu Leppänen

Hannu Ilvesniemi

LUT

Mari Kallioinen

Elsi Koivula

Tuomas Nevalainen

Mika Mänttäri

Uhe

Maija Tenkanen

Ujy

Joni Lehto

Raimo Alén

VTT

Marjatta Kleen

Tarja Tamminen

ÅA

Andrey Pranovich

Risto Korpinen

Jan-Erik Raitanen

Chunlin Xu

Jarl Hemming

Jens Krogell

Henrik Grénman

Tapio Salmi

Stefan Willför

Kemira

Marcus Lillandt