L. Csoka, A. Iskalieva B.M. Yimmou, M. Horvath, P. Takats, G. Grozdits

Cleaning and Modifying Wheat-Straw Pulps with Inert Gas Ultrasonification

2011 FPS 65th International Convention

P. Takats, G. Grozdits

University of West Hungary, Inst. Wood & Paper Technology, Sopron, Hungary and Louisiana Tech University, Ruston, LA, USA

lcsoka@fmk.nyme.hu

Objective

• EU FP7 „SONOPULP” project - sonication of natural fibres and agro-wastes

• Create a new technology for pulping annual plants – less energy and chemicalsplants – less energy and chemicals

• Zero waste perspective• 6 countries: Spain, Netherland, Germany,

Austria, Belgium and Hungary• 5 WPs: raw materials to LCA and biogas

production, WP2 presented here

• Cavitation: is the formationof empty cavities in a liquidby high forces and the immediate implosion of them

Introduction

immediate implosion of them – Can be generated: acoustically and

hydrodynamically

Pressure of the liquid < Vapour pressure of the liquid

• 93 different chemical reactions• OH radicals, H2O2 formation• Chemical – physical effects

Introduction

• Wheat straw: screened by 5 mm hole screen• Pre-treatment in alkaline solution• Ultrasonic (batch, 150W, 50W/cm2,20 kHz) and

hydrodynamic (continuous)digestion (different consistency)

Materials and methods

• In case of ultrasonic digestion: argon, krypton and xenon inert gases has been applied

• Evaluation of yield and tensile properties

• Theoretical background

Materials and methods

= 2

2

4 dtVd

rp

πρ

(Strasberg, 1956))

Rd R

dt

dR

dtp

RdRdt R

pl

i( ) ( ) ( )2

223

21 4 2

+ = − − −

∞ρ

µ σ

100

150

200

250

300

350

400

450

500

Radius (micrometer)

-400000

-200000

0

200000

400000

600000

800000

1000000

Bulk Pressure (atm)

radius (micrometer)adiabatic phase starts hereBulk liquid Pressure (atm)

( ) ( )

−+−

−+++−+−

−++= παωξωπαω

ξπαωωξπαω

ξρtt

Rtt

RRr

p bb cos(cos(1)sin(cos(12 2

2

0

02

0

00

����( )

rfπρPγ

p0

21

3 ∞=21

00

321

= ∞

ργ

πP

fR

Bubble size distribution

0

10

20

30

40

50

0 40 80 120

160

200

240

280

320

360

400

Bubble size (10-6 m)

% No. of bubbles

R0(avg) =57.82 µm No. of Bubbles =41120

0

50

100

0 10 20 30 40 50 60

Time (microsec)

-800000

-600000

• Bubble dynamics model gives:Instantaneous value of:

- Radius

- Bubble wall velocity - Bubble wall acceleration

Results

- Bubble wall acceleration

- Pressure inside the bubble

h

d

3

22

38

cf

ρµπ

cIpa ρ2=

AW

I =

( ) 01

0

=

−∇ qpn

ρ

Results

Lignin content [%]7

8

9

10

11

9.4BC - before cookingW-US - without ultrasound treatmentAr - ultrasound with argon combinationKr - ultrasound with krypton combinationXe - ultrasound with xenon combination140, 210, 280 - ultrasound treatment with different water-fiber ratio

Yield: 50-70% in case of hydrodynamic device

40-50% in case of acoustic ultrasound device

Samples

Lignin content [%]

0

1

2

3

4

5

6 5.4

3.7

1.20.8

2.4

4.24.8

BC W-US Ar Kr Xe 140 210 280

Results

38.645.62 46.17 49.39

42.3

28.7

20

30

40

50

60

Tens

ile in

dex

0

10

1hs2hs

3hs4hs

5hs

HdC+Sommerville

Samples

Tens

ile in

dex

Results

Changes of tearing index Changes of tensile index

Results

OCH

R-COOHCOOC

O

OH

H

OCH3

COOR

COOH

COOOOOC

ROOCOOR

Increased:

carboxyl, conjugated carboxyl, phenolic OH, aromatic CH, aromatic esters

Oxidative degradation of lignin

Conclusions

• Agro-wastes, straws, stalks can be converted to valuable raw material for the paper industry

• 50-70% yield can be generated• Tensile properties acceptable• Tensile properties acceptable• Oxidative lignin degradation• Less energy and chemicals• Environmental friendly process• No wastes generated

Thank you for your attention!