Impregnation of eucalyptus and pine Impregnation of eucalyptus and - - PowerPoint PPT Presentation

Impregnation of eucalyptus and pine Impregnation of eucalyptus and pine wood in alkaline pulping processes. wood in alkaline pulping processes. Effects of steaming and pressurized Effects of steaming and pressurized impregnation impregnation

Inalbon M.C., M. Citroni, V. Marzocchi, Inalbon M.C., M. Citroni, V. Marzocchi,

• C. Pieck ,
• C. Pieck , M. Zanuttini
• M. Zanuttini

FIQ FIQ -

• UNL

UNL Santa Fe Santa Fe -

• Argentina

Argentina

Chip Impregnation for pulping Chip Impregnation for pulping

A proper A proper Penetration of liquids Penetration of liquids Diffusion of chemicals Diffusion of chemicals Both are necessary for optimal efficiency of: Chemical pulping Chemical pulping Chemimechanical pulping Chemimechanical pulping

Uniformity Uniformity

The uniformity of the impregnation The uniformity of the impregnation the uniformity of the chemical the uniformity of the chemical treatment in the first stage of pulping treatment in the first stage of pulping the homogeneity of the pulp obtained the homogeneity of the pulp obtained determines determines Is essential for Is essential for

Distribution of kappa number of a kraft softwood pulp Gr Grá áfica de fica de malkov malkov

foto foto Fluorescencia Fluorescencia

Kappa Kappa number number

• f
• f

individual individual fiber fiber

Malkov, et al Malkov, et al

Fluorescence Fluorescence – – kappa number kappa number

Flourescence on kraft fibers Flourescence on kraft fibers

Yue Liu, Tappi J. 82(9), 1999 Yue Liu, Tappi J. 82(9), 1999

The Malkov work shows: The Malkov work shows:

• A fairly broad distribution of

A fairly broad distribution of kappa of the softwood kraft pulp. kappa of the softwood kraft pulp.

• Distribution can be notably

Distribution can be notably reduced when a proper reduced when a proper impregnation is applied impregnation is applied

Benefits of a proper wood Benefits of a proper wood impregnation in a kraft pulping impregnation in a kraft pulping

In general it is shown in the literature that In general it is shown in the literature that it can lead to: it can lead to:

• Increase in pulping yield

Increase in pulping yield

• Reduction in cooking time

Reduction in cooking time

• Reduction in bleaching chemical

Reduction in bleaching chemical

The alkaline impregnation The alkaline impregnation phenomenon is complex. phenomenon is complex. It implies It implies: :

• Air removing

Air removing

• Penetration in the longitudinal direction

Penetration in the longitudinal direction

• Diffusion in all directions.

Diffusion in all directions.

• Chemical reactions and wood swelling

Chemical reactions and wood swelling

• Chemical modification of wood. Alkali

Chemical modification of wood. Alkali diffusion coefficient is changed diffusion coefficient is changed

Issues not considered in the literature Issues not considered in the literature

Chips treated with alkali shows a Chips treated with alkali shows a impregnation front impregnation front

The size of the intact core reduces with time. The size of the intact core reduces with time. Situation depends on the wood and treatment Situation depends on the wood and treatment conditions. conditions.

Alkali impregnation of hardwood in Alkali impregnation of hardwood in transverse direction transverse direction For poplar For poplar (Zanuttini et al., JPPS 2003)

(Zanuttini et al., JPPS 2003) and

and for eucalyptus wood for eucalyptus wood (Zanuttini et al., Holz

(Zanuttini et al., Holz un Roh, 2003), un Roh, 2003), it was shown:

it was shown: At temperatures below 100 At temperatures below 100 o

• C,

C, impregnation is a reactive diffusion impregnation is a reactive diffusion process. process.

Consumption could be as high as 6.0 % NaOH / wood Consumption could be as high as 6.0 % NaOH / wood

• Deacetylation is the main reaction and is the

Deacetylation is the main reaction and is the main responsible for alkali consumption. main responsible for alkali consumption.

0,00 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 Stoichiometric consumption Original wood 50

• C

70

• C

90

• C

ACETYLS (%) CONSUMPTION ( g NaOH / g wood )

Mechanism Mechanism At low temperature, it was shown that: At low temperature, it was shown that: During impregnation, a reactive front During impregnation, a reactive front is established which separates an is established which separates an intact inner zone from a reacted and intact inner zone from a reacted and swollen outer zone. swollen outer zone.

Pre Pre-

• steaming and pressurized

steaming and pressurized impregnation impregnation

• Presteaming rapidly heats the wood and the

Presteaming rapidly heats the wood and the steam produced inside chips is useful to steam produced inside chips is useful to displace the air displace the air (Malkov et al 2000).

(Malkov et al 2000).

• When chip is immersed in liquid under

When chip is immersed in liquid under pressure, a high liquid uptake takes pressure, a high liquid uptake takes place place (Malkov et al. 2000)

(Malkov et al. 2000)

• Presteaming stage and pressurized

Presteaming stage and pressurized impregnation impregnation should be considered should be considered for a for a impregnation analysis impregnation analysis

In this paper: In this paper: The pattern of the pressurized alkaline The pattern of the pressurized alkaline impregnation is analyzed: impregnation is analyzed: Profiles of: Profiles of:

• alkali

alkali concentration concentration

• alkali content

alkali content

pine and eucalyptus pine and eucalyptus wood wood

pre pre-

• steamed wood

steamed wood

• liquid content

liquid content

• acetyls content

acetyls content It is shown that the level of impregnation It is shown that the level of impregnation can be predicted for given operation can be predicted for given operation conditions conditions

Experimental Experimental

Cubes from eucalyptus wood Cubes from eucalyptus wood

Outer Zone Outer Zone Inner Zone Inner Zone

Cubes Cubes

Impregnation Impregnation experiences experiences

A Weverk digester: A Weverk digester:

• Steaming of wood

Steaming of wood samples by the samples by the liquor vapor liquor vapor

• Pressurization by

Pressurization by Nitrogen Nitrogen

Positions of Weverk digester during Positions of Weverk digester during impregnation impregnation

Despresurización

N2

Wood Wood Samples Samples

Pressure Pressure relief relief

Procedure stages Procedure stages

1) 1) Preheating of liquor at 100 Preheating of liquor at 100 o

• C

C 2) 2) Load of samples (under the digester cover) Load of samples (under the digester cover) 3) 3) Heating, air relief and steaming Heating, air relief and steaming 4) 4) Immersion in the liquor Immersion in the liquor (Position 2) (Position 2) and and pressurization up to 6 Bar (N pressurization up to 6 Bar (N2

2)

) 5) 5) Treatment under digester rotation Treatment under digester rotation 6) 6) Relief of digester (wood submerged in the liquid). Relief of digester (wood submerged in the liquid). Flash in wood was avoided Flash in wood was avoided (Position 1) (Position 1) 7) 7) Opening of digester and immersion of cubes in Opening of digester and immersion of cubes in liquid Nitrogen by 2 hours. liquid Nitrogen by 2 hours. 8) 8) Store at freezer temperature. Store at freezer temperature.

Slicing of treated cubes Slicing of treated cubes

Wood Wood sample is sample is still frozen still frozen Slices are weighed, and chemical analyzed Slices are weighed, and chemical analyzed

Tangential Tangential face of face of impregnated impregnated wood wood

1 cm

1 cm 1 cm Wood vessels Wood vessels

Chemical Chemical analysis of analysis of slices slices

• Titration

Titration

• Drying

Drying

• Acetyl content by

Acetyl content by GC chromatography GC chromatography

Results Results

Results Results

• Profiles in radial direction

Profiles in radial direction

• For Eucalyptus and Pine

For Eucalyptus and Pine

• Liquid content of the internal

Liquid content of the internal zone of the wood zone of the wood

as a function of the position from de as a function of the position from de interphase interphase

Eucalyptus Eucalyptus – – 15 minutes 15 minutes

2 4 6 8 10 12 0.0 0.5 1.0 1.5 2.0

POSITION FROM THE SURFACE (mm)

ALKALI (g NaOH / L) ALKALI (g NaOH / kg) ACETYLS (x10) LIQUID (x5 g water/g) REACTION ZONE INNER ZONE REACTION ZONE OUTER ZONE

ACETYLS ALKALI

Eucalyptus Eucalyptus – – 30 minutes 30 minutes

2 4 6 8 10 12 0.0 0.5 1.0 1.5 2.0 2.5 3.0

POSITION FROM THE SURFACE (mm)

ALKALI (g NaOH / L) ALKALI (g NaOH / kg) ACETYLS (x10) LIQUID (x5 g water/g) REACtION ZONE OUTER ZONE REACTION ZONE INNER ZONE

ACETYLS ALKALI

Latewood of Latewood of pine pine

2 4 6 8 10 12 0.0 0.5 1.0 1.5 2.0 2.5

POSITION FROM THE SURFACE (mm)

ALKALI (g NaOH / L) ALKALI (g NaOH / kg) ACETYLS (x10) LIQUID (x5 g water/g) REACTION ZONE OUTER ZONE REACTION ZONE INNER ZONE

ALKALI ACETYLS

Mechanism of the chip Mechanism of the chip impregnation impregnation

Spent liquor penetration Liquor penetration and reaction Liquor diffusion and reaction

Liquid content inside wood Liquid content inside wood

0.7 0.7 2.5 2.5 0.75 0.75 1.3 1.3

Liquid Liquid Content Content (g / g wood) (g / g wood)

Late Late-

• wood

wood Early Early-

• Wood

Wood Central Central Exterior Exterior Pinus Pinus elliotti elliotti Eucalyptus Eucalyptus grandis grandis

Prediction of the impregnation level Prediction of the impregnation level

0.2 0.4 0.6 0.8 1 1.2 1.4 10 20 30 40 50 Time (min) Chemical Impregnation (mm)

The chip The chip half half-

• thickness

thickness distribution distribution Fraction of Fraction of impregnated wood impregnated wood

Prediction Prediction

If the speed of moving front is If the speed of moving front is know, the level of impregnation know, the level of impregnation can be predicted can be predicted

Conclusions (1) Conclusions (1)

n n Steaming (5 minutes) and pressurized

Steaming (5 minutes) and pressurized immersion (6 Bar) can complete the immersion (6 Bar) can complete the liquid penetration liquid penetration

n n Initially alkali does not reach the core a

Initially alkali does not reach the core a chip chip

n n The chemical impregnation:

The chemical impregnation: reaction reaction and diffusion and diffusion A front of the impregnation is always A front of the impregnation is always established. established.

Conclusion (2) Conclusion (2)

The time needed for chemical The time needed for chemical impregnation (time in which the impregnation (time in which the front reaches the center of the front reaches the center of the chip) can be predicted for a given chip) can be predicted for a given wood and treatment conditions wood and treatment conditions

The end The end