09 Presentación 3 ICEP 2007 Modelling impregnation.ppt ... · 3,5 4 0 500 1000 1500 2000 Position...

Inalbon Ma. CristinaInalbon Ma. Cristina,, Zanuttini MZanuttini M., Marzocchi V.., Marzocchi V.

ITCITC--FIQFIQ--UNLUNL

Mussati M.Mussati M.

INGARINGAR

Santa FSanta Fe, ARGENTINAe, ARGENTINA

MODELING of the ALKALINE MODELING of the ALKALINE

IMPREGNATION IMPREGNATION

of EUCALYPTUS CHIPS. of EUCALYPTUS CHIPS.

REACTIONS and ION TRANSPORTREACTIONS and ION TRANSPORT

id29577156 pdfMachine by Broadgun Software - a great PDF writer! - a great PDF creator! - http://www.pdfmachine.com http://www.broadgun.com

KRAFT

PROCESS

STEAMINGSTEAMING IMPREGNATIONIMPREGNATION

(105 (105 �� 120 120 ººC)C)

COOKING COOKING (165 (165 ººC)C)

Degree of impregnation

A proper impregnation leads to a more homogeneous pulp

A narrower kappa number distribution of the individual fibers can be obtained (Malkov et al. 2003).

Incomplete impregnation leads to:

Uncooked rejects (Gullichsen 1995).

Pulping yield (Gullichsen et al 1992, 1995).

Pulp strength (Gullichsen 1995).

Pulp bleachability (Malkov 2002).

Wood direction of interest

� The critical dimension for alkali

impregnation is the chip thickness

9 % NaOH/wood 9 % NaOH/wood

95 95 ººC C

30 min30 min

Partially impregnated chipPartially impregnated chip

Chip thickness: critical dimension

TangentialTangential

RadialRadial

transverse wood directionstransverse wood directions

Steaming stage and pressurized

impregnation : consequences

If wood has an acceptable permeability:

Steaming rapidly displaces the air from the chip.

Under these conditions, for eucalyptus wood, we have shown that:-Wood results almost saturated with liquid-No evidence of alkali inside wood was found(Inalbon y col. 2005).

A good steaming

+

pressurized impregnation

High liquid uptake

(Malkov et al 2001).

Liquor penetrationand reaction

Spent liquorpenetration

Chip

Liquid reaches the core of the chip

but alkali does not

Assumption

Impregnation (in thickness direction) is

considered:

- Isothermal process

- A diffusion process in wood saturated

with liquid (penetration has finished)

Chemical reactions

� a) Deacetilation.

� b) Acid groups neutralization or

hydrolysis of their esters.

� c) Peeling.

The deacetilation is the main reaction:

It accounts for most of the alkali consumption

(Zanuttini et al, 2003).

It can be taken as indicative of the wood

swelling produced by the alkali treatment

(Zanuttini et.al, 1999).

Chemical reactions consequences

� Alkali consumption (5 � 6 % on wood) � Chemical species

Mobile ions: a) Sodium +b) Hydroxide -c) Acetate -

Fixed: a) Acetyl groupsb) Non ionic acid groupsc) Ionized acid groups -

For the modeling we need:

� Kinetics of reactions

� Diffusion properties of each ion

Kinetics of reactions

a) Deacetylation

For the eucalyptus wood under study we made an experimental kinetic analysis :

Slices of wood (350 ìm) were treated under� different alkali concentrations� at 20º, 45º and 90 ºC.

Deacetylation kinetics

� Obtained expression:

53.1)()( 09.2 OHCAcetylsCkAcetylsR

TR

EAk T exp.)(

The k�constant follows the Arrhenius law:

Hydroxil concentrationCOH - :

Acetyl concentrationCAcetyls :

Specific rate constantk :

Temperature (ºK)T :

Relative activation energyE / R :

Arrhenius constant A :

Acid groups reactions

These reactions represent an additional alkali consumption (1 % NaOH on wood)

Assumption:

We consider them as coupled to deacetylation reaction (they have the same reaction rate)

Acid groups neutralizationAcid groups neutralization

Ester hydrolysisEster hydrolysis

Ion diffusion coefficients

� The concept of effective capillary (Stone 1957)allows considering for each ion

Diffusion

coefficient

in wood

Ion diffusion

coefficient in the

liquid mediumEffective Capillarity

(the same for all ions)

can be obtained

from literatureValues Di

0 can be

interpolated in temperature

using the Nernst-Einstein

equation (ui : ion mobility)

Di = EC. Di0

Di0

Di0 = ui.R.T

Effective capillarity

� We developed a method different from that used by Stone (1957):

Method:

Slices of wood (400 m) a low mass and

thermal diffusion

restriction

The evolution of electrical conductivity through slices,

was followed using laboratory conductivimeter

Electrical

conductivityIon diffusion

EC determination

Slices were placed between electrodes of the

conductivimeter cell

The slice was considered as a series The slice was considered as a series electrical circuit with the solutionelectrical circuit with the solution

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

7 8 9 10 11 12 13 14

pH

Eff

ec

tiv

e c

ap

illa

ry

20ºC-60 min

20ºC

EffectiveEffective CapillarityCapillarity vs. vs. pHpH

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

7 8 9 10 11 12 13 14

pH

Eff

ec

tiv

e c

ap

illa

ry

20ºC-60 min

45ºC-60 min

20ºC

45ºC

T



0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

7 8 9 10 11 12 13 14

pH

Eff

ec

tiv

e c

ap

illa

ry

20ºC-60 min

45ºC-60 min

90ºC-60 min

90ºC

20ºC

45ºC

T


0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

7 8 9 10 11 12 13 14

pH

Eff

ec

tiv

e c

ap

illa

ry

20ºC-60 min

45ºC-60 min

90ºC-60 min

Stone, 25ºC, 24 hs

90ºC

20ºC

45ºC

T

0

0,05

0,1

0,15

0,2

0,25

0,3

0,0 1,0 2,0 3,0 4,0

Acetyl content (%)

Eff

ec

tiv

e c

ap

illa

ry

pH 12

20ºC

EffectiveEffective CapillarityCapillarity vs. vs. AcetylAcetyl contentcontent

0

0,05

0,1

0,15

0,2

0,25

0,3

0,0 1,0 2,0 3,0 4,0

Acetyl content (%)

Eff

ec

tiv

e c

ap

illa

ry

pH 12

pH 13

20ºC

Effective Capillary vs. Acetyl contentEffective Capillary vs. Acetyl content

0

0,05

0,1

0,15

0,2

0,25

0,3

0,0 1,0 2,0 3,0 4,0

Acetyl content (%)

Eff

ec

tiv

e c

ap

illa

ry

pH 12

pH 13

pH 13.5

20ºC


0

0,05

0,1

0,15

0,2

0,25

0,3

0,0 1,0 2,0 3,0 4,0

Acetyl content (%)

Eff

ec

tiv

e c

ap

illa

ry

pH 12

pH 13

pH 13.5

pH 14

20ºC


EC depends on:

- Concentration of alkali

- Temperature

- Time

EC EC dependsdepends onon::

-- TemperatureTemperature

-- DeacetilationDeacetilation degreedegree

An empiric equation of Capillarity as a function

of acetyl content and temperature was used for

modeling

EC = EC = f(Acf(Ac, T), T)

Ac : Acetyl content T : Temperature

Modeling

i

iiii

i

i RxRT

cFDz

x

cD

xt

c

DiffusionInteraction

between ions

Chemical

reactions

For each chemical species we consider:

Diffusion coefficient of � i�Di :

Position from the external interphasex :

Time t :

Molar concentration of � i � specieci :

Where:

Differential equations system

Reaction rateRi :

Electric potential :

Faraday constantF :

Charge number of � i �zi :

It involves 9 differential equations and 9 variables

in space and time:

6 chemical species concentrations

Deacetylation rate

Effective Capillary

Electrical potential

ResultsResults

Na+

Co

ncen

tratio

n(m

ol/

l)

Position (cm)

Co= 0.5 M; T=110ºC; 15 minutes

ResultsResults

Co

ncen

tratio

n(m

ol/

l)Co= 0.5 M; T=110ºC; 15 minutes

Position (cm)

OH-

Na+

ResultsResults

Co

ncen

tratio

n(m

ol/


Position (cm)

AcetylsOH-

Na+

ResultsResults

Co

ncen

tratio

n(m

ol/


Position (cm)

Acetate

AcetylsOH-

Na+

Co

ncen

tratio

n(m

ol/


Position (cm)

AG

Acetate

AcetylsOH-

Na+

ResultsResults

nrAG

ResultsResults

Co

ncen

tratio

n(m

ol/


Position (cm)

AG

Acetate

AcetylsOH-

Na+

nrAG

Model vs. Experimental Data

0,25N; 105ºC; 5 minutes

0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000

Position (microns)

Con

tent

(%

on

woo

d)

acetyls exp

0.25N ; 105ºC; 5 minutes



0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000

Position (microns)

Con

tent

(%

on

woo

d)

acetyls

acetyls exp



0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000

Position (microns)

Con

tent

(%

on

woo

d)

acetyls

acetyls exp

Na+ exp




0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000

Position (microns)

Con

tent

(%

on

woo

d)

acetyls

Na+

acetyls exp

Na+ exp




0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000

Position (microns)

Con

tent

(%

on

woo

d)

acetyls

Na+

acetyls exp

OH- exp

Na+ exp




0

0,5

1

1,5

2

2,5

3

3,5

4

0 500 1000 1500 2000

Position (microns)

Con

tent

(%

on

woo

d)

acetyls

OH-

Na+

acetyls exp

OH- exp

Na+ exp



C0: 0.25 N; 110ºC

1 min

Acetyl Groups

OH-

C0: 0.25 N; 110ºC

5 min

C0: 0.25 N; 110ºC

10 min

C0: 0.25 N; 110ºC

15 min

C0: 0.25 N; 110ºC

20 min

C0: 0.25 N; 110ºC

25 min

C0: 0.25 N; 110ºC

30 min

C0: 0.25 N; 110ºC

35 min

C0: 0.25 N; 110ºC

40 min

C0: 0.25 N; 110ºC

50 min

C0: 0.25 N; 110ºC

70 min

C0: 0.25 N; 110ºC

90 min

Application

For a given wood and set of conditions: For a given wood and set of conditions:

�� A sequence like this can give a criterion A sequence like this can give a criterion

to take a decision regarding the extent of to take a decision regarding the extent of

impregnation stageimpregnation stage

0

0,02

0,04

0,06

0,08

0,1

0,12

0,14

0,16

0,18

0,2

0,22

0 10 20 30 40

Time (minutes)

Po

sit

ion

(c

m)

105ºC-0,25N

Front Position vs. Time

Chip center

Inter-phase

0

0,02

0,04

0,06

0,08

0,1

0,12

0,14

0,16

0,18

0,2

0,22

0 10 20 30 40

Time (minutes)

Po

sit

ion

(cm

)

105ºC-0,25N

105ºC-0,5N


0

0,02

0,04

0,06

0,08

0,1

0,12

0,14

0,16

0,18

0,2

0,22

0 10 20 30 40

Time (minutes)

Po

sit

ion

(c

m)

105ºC-0,25N

105ºC-0,5N

105ºC-1N

0,25 N1 N 0,5 N


0

0,02

0,04

0,06

0,08

0,1

0,12

0,14

0,16

0,18

0,2

0,22

0 10 20 30 40

Time (minutes)

Po

sit

ion

(c

m) 105ºC-0,25N

105ºC-0,5N

105ºC-1N

110ºC-0,25N

110ºC-0,5N

110ºC-1N

Temperature

0,25 N1 N 0,5 N


0

0,02

0,04

0,06

0,08

0,1

0,12

0,14

0,16

0,18

0,2

0,22

0 10 20 30 40

Time (minutes)

Po

sit

ion

(c

m)

105ºC-0,25N

105ºC-0,5N

105ºC-1N

110ºC-0,25N

110ºC-0,5N

110ºC-1N

120ºC-0,25N

120ºC-0,5N

120ºC-1N

Temperature

0,25 N1 N 0,5 N


Speed of impregnation

� Model shows that a change in alkali concentration

from 0.25 M to 1.0 M speeds up impregnation more than an

increase in temperature from 105 to 120 ºC

Concluding Remarks (1)

This model allows the analysis of the effects

of impregnation variables such as :

external alkali concentration

temperature

time

chip thickness.

For a specific wood:

effective capillary

kinetic parameters

Should be experimentally verified before

the application of the model


Phenomenon: A reaction front is

established which moves to the interior of

the wood and separates an intact inner zone

from a reacted outer zone

The alkali profile differs from Sodium

concentration profile; the latter goes in the

front of the former


Besides the variables here analyzed, the model allows considering:

a) Additional ions such as sulfide; hydrosulfide, carbonate and others

b) Chip thickness distribution

c) Changes in external alkali concentration

including different alkali profiling scenarios

Deacetylation in biofuel production

Capillarity

1) to determine2) to promote it by deacetilation

Are useful to analize the effects of pre-treatments for fermentation processes

Deacetylation and Capillarity

Pretreatment

Fermentation

Biological treatment

Capillarity

Wood

� Thanks for your attention !

09 Presentación 3 ICEP 2007 Modelling impregnation.ppt ... · 3,5 4 0 500 1000 1500 2000 Position...

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