effect of pre-steaming and impregnation on the eucalyptus pulp cooking yield 23082010

7/25/2019 Effect of Pre-steaming and Impregnation on the Eucalyptus Pulp Cooking Yield 23082010

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Effect of pre-steaming and impregnation on the eucalyptus pulp cookingyield

24.08.2010

Arauco StoraEnsoOlli Joutsimo Mats Nasman


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Contents1 Introduction ................................................................................................. 3

1.1 Limitations with laboratory cooking studies ........................................... 32 Objective of the work................................................................................... 4

3 Background................................................................................................. 4

3.1 Effect of pre- steaming on liquor penetration......................................... 53.1.1 Effect of wood dryness on steaming and chip size ......................... 6

3.2 Chemical Impregnation ......................................................................... 63.3 Effect on cooking temperature and pulp yield ..................................... 103.4 Effect on alkali profile .......................................................................... 113.5 Effect on uniformity and point of defibration ........................................ 123.6 Mill experience .................................................................................... 13

3.6.1 Tres Lagoas.................................................................................. 133.6.2 Varkaus ........................................................................................ 133.6.3 Effect of fresh wood on impregnation efficiency and cooking rejectamount 14

4 Conclusion ................................................................................................ 15

5 Recommendations .................................................................................... 16

6 Experimental Part...................................................................................... 166.1 Pretest at RCK .................................................................................... 16

6.1.1 Methods........................................................................................ 166.1.2 Results.......................................................................................... 176.1.3 Conclusions .................................................................................. 19

6.2 Cooking with and without impregnation, Scitech study........................ 196.2.1 Raw material and cooking conditions ........................................... 206.2.2 Results.......................................................................................... 21

7 Conclusions............................................................................................... 24

8 Recommendations .................................................................................... 25

9 References................................................................................................ 26


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1 Introduction

The wood impregnation is affected by the wood humidity, which is dependenton the climate conditions and the degree of debarking of the wood. Theimpregnation efficiency will depend on the impregnation time, pressure and presteaming of wood. The level of impregnation will affect the cooking result i.e.amount of reject generated and cooking yield and will have important financialeffect of the pulp production. The objective of this brief study is to determine theeffect of impregnation on the cooking results in one vs. two vessel cookingsystem. Other objective is also to determine effect of wood moisture content onthe impregnation time in order to gain the sufficient level of cooking yield.

1.1 Limitations with laboratory cooking studies

Generally the laboratory cooking is very uniform because of following factors:The chip pre steaming in the laboratory is usually also very effective and willevacuate all the air from the chips effectively and therefore ensure perfectimpregnation. The impregnation in laboratory vessels with circulation usuallyyields to very efficient impregnation result because there will be no canalization,which would inhibit heat and liquor transfer. The heat uptimes before reaching

the cooking temperature after impregnation in the laboratory are generally verylong and therefore ensure even more efficient impregnation. The effectivecooking circulations without canalization will ensure a homogenous cookingresult.

Table 1. The differences between laboratory and actual process.


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The above mentioned factors make it challenging to study this subject inlaboratory.

2 Objective of the work

The objective of this brief study is to firstly give summary of recent studiesrelated to pre-steaming, impregnation and effects on cooking results, secondlyin the experimental part determine the effect of impregnation on the cookingresults in one vs. two vessel cooking system. Other objective is also todetermine effect of wood moisture content on the impregnation time in order togain the sufficient level of cooking yield. The results are expected to showweather one vessel cooking system is feasible and if the chip dry-matter has

any impact on the need of impregnation. The aim is to provide sufficientinformation so that the cooking process can be designed based on the probablewood dry matter content.

3 Background

The alkali wood impregnation implies the penetration of liquids, diffusion ofchemical reagents and also chemical reactions and swelling.

The penetration of liquors is affected by the air trapped inside of the woodchips, which can be removed efficiently by pre-steaming. What is sufficient timeand conditions of pre-steaming are dependent on the specific features of thewood capillaries. In practice, however, complete removal of air may be difficultto achieve, even by applying optimal steaming conditions and long steamingtimes. The specific features of the wood capillaries can limit the removal of air.Some air cannot be removed because the pressure gradient at the end of pre-steaming is insufficient to overcome the surface tension forces at the liquid-airmenisci that block the air passage. In addition, some air can be trapped withincapillaries, which are sealed by extractives, or within the blind pores /1, 2/.

In the phase of diffusion of regents and reaction products are transportedbetween impregnation liquor and wood material. In this phase the reaction ofacetyls, acidic groups and peeling reaction of the hemicelluloses. Thedeacetylation is the main reaction involved in the impregnation and isresponsible for the main consumption of the alkali. On the other and the alkalialso modifies the local ion transportation capacity and it has been shown thatthe diffusion in the hardwood transverse direction is strongly affected by thealkalinity /3, 4/.


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3.1 Effect of pre- steaming on liquor penetration

The principal reason for the chip pre-steaming is preheats the chip fromambient temperature to 100 - 120 C and remover the air in the wood voidspaces and capillaries. This removal operation is important in order to achieveuniform penetration of impregnation liquor into wood chips. with cooking liquorduring the impregnation stage of pulping. The liquor penetration time is affectedby the pre-steaming time and temperature. Zanuttini /1/ has shown that 5minutes of steaming eucalyptus chips is sufficient for obtaining complete liquidpenetration with pressurized impregnation (6 bar). Malkov /2/ has presented theeffect of steaming temperature (steaming time 6 minutes) on the penetrationdegree and time, shown in the Fig. 1.

Fig. 1. Effect of steaming temperature on water penetration into heartwoodchips Steaming: 6 minutes; Penetration: 85 C and 5.3 bar; Chip dimensions:25x15x8 mm /2/.

The Fig. 1 shows that the penetration of liquor into the chip can be almostperfect even after 6 minutes of steaming time in the laboratory environment.

However it is not likely to achieve similar situation in the mill cooking processenvironment. It can be considered that the steaming time have to be at least 6minutes at 120 oC degrees in order to have 95% penetration degree and in the

mill environment the time should be most probable at least doubled.


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3.1.1 Effect of wood dryness on steaming and chip size

The wood chip moisture content affects the steaming time required to evacuateair from the chips. In the Fig. 2 is shown the effect of different steaming on theliquor penetration of the chips with different dryness contents.

Fig. 2. The effect of steaming on the amount of floating chips. /5/

The Fig. 2 clearly shows that the steaming time is important for the air removalof the chips. Higher dryness content of the chips is also demanding moresteaming. In the mill environment it has to be also considered that the dryness

of the chips will vary and the variation in dryness will increase the chip sizedistribution in chipping which will further increase the need for pre-steaming /6/.

3.2 Chemical Impregnation

The concept of chemical impregnation describes the diffusion of chemicalsthrough the cell wall. It has been shown that for eucalyptus pulping an extendedimpregnation stage in modified craft cooking leads to more efficientdelignification /7/. This leads to lower alkali consumption and higher yield /8/.For the alkali impregnation /9/ the impregnation takes only place by diffusionacross the cell wall. During this diffusion process the alkali is consumed mainlyby the deacetylation reactions. During the chemical impregnation the advancingfront separates the growing swollen outer zone from the intact inner zone of thechip /9/. The diffusion of the alkali is dependent mainly on the alkaliconcentration and diffusion time. This ion diffusion capillarity is significantlyincreased when pH is increased from 12 to 13. At room temperature, alkalinityhas a strong effect on the ECCSA (Effective Capillary Cross Sectional Area),particularly when the pH is elevated from 12.5 to 13.5. However, it has beenalso shown that there is a steep elevation of ECCSA is at pH 10.5 at 90oC./10/.


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In the Fig. 3 is shown the effect of concentration of Na and NaOH on theadvance of the concentration front (in the chip thickness direction, presented asmicro meters) in fresh eucalyptus wood.

Fig. 3. The effect of concentration of Na and NaOH on the advance of theconcentration front in fresh eucalyptus wood at 20 and 55min/3/.

From the Fig. 3 can be concluded that without pre-steaming of the fresh woodeucalyptus chips needs to be impregnated at least 55min in order to have theconcentration front at the middle of the 4mm thick chip. The effect of the pre-steaming at different alkali concentrations with dry and fresh wood arepresented In the Fig. 4 /3/.


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Fig. 4. The effect of the pre- steaming at different alkali concentrations with dryand fresh wood /3/. Front position is the position of chemical impregnation frontas a function of time into chip thickness direction.

From the Fig. 4 can be obtained that the in the perfect liquor flow conditions thefresh eucalyptus wood chip with pre-steaming, chemical impregnation front willreach middle of the 4mm thick chip in approx 30 min /3/.

In Fig. 4.1 it is shown how the impregnation front (impregnation front position is

the point physically in the chip thickness direction at which the concentration ofthe hydroxyl ion starts to increase) is dependent on surrounding concentrationand impregnation temperature/10/. The most important factor is theconcentration. The impregnation is normally done in the range 0.5N to below0.25 N at 100-110 C in the digester systems available for MdP. From the figureit is possible to see that it will demand at least about 30 minutes for the diffusinghydroxyl ions to reach the centre of the 4.4 mm thick chip /10/.


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Fig. 4.1 This figure shows after which time the impregnation front reaches themiddle of a chip piece with the thickness of 2.2 mm. The differentconcentrations are [OH-] /10/. Steaming applied, impregnation pressure: 0.6MPa,

In the Fig. 5. is shown how the kappa number after cooking is affected afterdifferent impregnation time /5/. It is clearly shown that the homogeneityexpressed as a lower kappa number achieved after the same cooking processis improved with both applied steaming and applied impregnation time.

Fig. 5. The effect of the pre- steaming and different impregnation time on thecooking homogeneity expressed as achieved kappa no after cooking /5/.


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55,0

55,5

56,0

56,5

57,0

57,5

58,0

17 18 19 20 21

%

+ 2

.

20 . 30 .

10 .

Fig. 6. The effect of the pre- steaming and impregnation time on screened yieldafter cooking in the same cooking conditions. /5/

There is some scattering in the rejects amount/kappa no for the differentimpregnation times but the difference between impregnation and noimpregnation is clear. The higher yield is obtained with impregnation.

3.3 Effect on cooking temperature and pulp yield

The shortening of the retention time in the system will increase the cookingtemperature need (h factor need) with a few degrees due to the lesshomogeneity of the cook without doing any impregnation. On top of this thecooking temperature will also be higher due to the fact that the first cookingzone will be run at a lower cooking temperature than in the 2nd cooking zone. Areasonable estimate of the cooking temperature increase is 2-3 C.

In Fig. 7 is presented the yield gain when cooking at 140 C to 145 C

compared to 160-165 C was 0.5-1.0 %. The results were compared at similarresidual alkali levels /11/. The effect of the cooking temperature has also beenshown by Gomide and Mcdonough /12/.


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48

49

50

51

52

53

54

55

56

57

12 13 14 15 16 17 18

Kappa no.

Yield%

E.grandis high temp.

E.grandis low temp.E.globulus high temp.

E.globulus low temp.

E.nitens high temp.E.nitens low temp.E. from China high temp.

E. from China low temp.

Scan. birch high temp.Scan. birch low temp.

Fig. 7. The cooking yield is shown for different raw materials at different cookingtemperatures (cooking time 240(low temp.) or 50 min. (high temp.), L/W 4.0)

3.4 Effect on alkali profile

It is well known that the eucalyptus wood in general is sensitive to higher alkaliconcentrations.

In the two vessel system which includes the impregnation vessel the alkali

charge is divided to 3 points: chip feed, digester top and to CD1. This results inan even alkali profile without any high peaks in the alkali concentration.

In the one vessel case the alkali charge is made to 2 points: chip feed and CD1.This results in a higher alkali (30-40 g/l NaOH) concentration in the digester topat a temperature of 145-150 C vs the case with impregnation (15-20 g/l NaOH).

At this temperature already the cooking has started which leaves little space forthe alkali to diffuse into the fibers since it will be consumed in deacetylation anddelignification reactions. This is detrimental from cooking homogeneity point ofview. The higher alkali charge in addition to the relatively high temperature as

well will have an effect on the yield, especially the retention of thehemicelluloses.


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3.5 Effect on uniformity and point of defibration

The effect of shorter retention times are shown to effect reject amountsignificantly. The shorter the retention time is in the system the lower is thedefibration point of the eucalyptus pulp. (defibration point = kappa number atwhich the reject amount starts to increase sharply) /13/.

In the Fig. 8 is shown the yield curve at normal cooking kappa no, 16-19 issteep and with Extended Impregnation Cooking (EIC) system. Only a differencein 0.5 units as max cooking kappa target makes a big impact on yield /13/.

Fig. 8. In these figures 1 and 2 the reject and screened yield is shown forEucalyptus urograndis cooked with and without impregnation before cooking.


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3.6 Mill experience

3.6.1 Tres Lagoas

We do not have any extensive report from the Tres Lagoas mill. The installeddigester system is a one vessel steam phase digester similar to the suggestedone vessel digester for MdP project. However the SE/Arauco/MdP team hasbeen visiting the mill. The mill said to be running on lower kappa number targetthan expected and this of course have an impact on the yield in the mill.

The information from the visit is that the kappa target was 16-17 instead of thedesign 18. The reject amounts were 0.3% knots and 0.5% shives. The reasonsfor the high reject levels were said to be the lack of impregnation and dry

wood/15/.

3.6.2 Varkaus

In Stora Enso Varkaus mill it has been tested to run with and withoutimpregnation vessel on birch (simply by running with different chip levels in theimpregnation vessel). The impregnation times were 5, 30 and 60 minutes

It was very clear that the reject amount increased with less or no impregnation

see Table 2.

Table 2. Effect of impregnation time on the reject amount at Varkaus mill.

Full= impregnation vessel full of chipsInt. = half filled impregnation vesselMin = empty impregnation vesselWD = wet disintegration

In order to reach even close to the same kappa number level the cookingtemperature was increased by 7.8 C resulting in an H-factor increase from 429to 740 /11/.

From the Varkaus mill study can be also concluded that the alkali consumption

was higher compared at the same kappa number level and the bleachability of


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the pulps with shorter impregnation time was greatly deteriorated. The resultsare shown in Table 3.

Table 3. The effect of impregnation on the alkali consumption and bleachability.

3.6.3 Effect of fresh wood on impregnation efficiency and cooking rejectamount

From the literature can be also found that when fresh wood is used in the millenvironment increases the impregnation efficiency. This yields to lower alkaliconsumption and cooking homogeneity is increased /16, 17/. Therefore, when

dry wood is used the importance of the sufficient impregnation time forhomogenous cooking result is even greater.


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4 Conclusion

Based on the material reported above the following can be concluded about theprocess effects when the impregnation vessel is excluded from the digestersystem

Cooking without impregnation:

- There is no sufficient time for proper chemical impregnation, which willlead to inhomogeneous cook.

- Inhomogeneous cook will result in higher reject amounts and though

lower overall yield. Also there is an obvious risk with having shivescontamination in the finally bleached pulp.

- The inhomogeneous cook may cause decrease of the kappa targetkappa number compared to the level originally intended. This alsodecreases yield and increases in white liquor demand. At kappa levelsbetween 15-19, the yield curve is steep i.e. 0.5% is gained inyield/increased kappa unit.

- The risk of inhomogeneous cook increases with different euca speciescooked in a mix. This risk increases when the impregnation is excluded

from the process as well as with increased dryness of the wood.

- The alkali profile is affected when excluding the impregnation vessel,which means that higher alkali concentration at relatively hightemperature is needed for the same kappa level. This decreases cookingyield, especially the hemicelluloses retention is decreased.

- Clear evidence from the Varkaus mill clearly shows the detrimentaleffects of excluding the impregnation.

Especially in the case of Montes del Plata when wood is debarked at theplantations and the storage is prolonged the wood will be dry, which will impairthe impregnation efficiency. Further this emphasizes the importance of goodimpregnation efficiency.

In the operation of Montes del Plata during the first 10 years differentEucalyptus species will be cooked as a mixture, which will increase theimportance of proper impregnation in order to reach high yield and homogenouscooking result.


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5 Recommendations

- Based on the findings from the literature it can be concluded that the

recommendation is to keep the impregnation vessel as a part of thedigester system.

6 Experimental Part

The experimental part of impregnation study consists of pretest made in theStoraEnso research centre in Sweden and study made in Scitech laboratories inFinland.

6.1 Pretest at RCK

A pretest was done at RCK laboratory in order to see if the testing could bedone with the equipment available.

6.1.1 Methods

Veracel chips were used as raw material. Dry chips was used, ca 90% dryness.The chips size distribution was as shown in table 4.

Table 4. chips size and thickness distribution.Thickness distribution Size

distribution

%-weight %-weight

>10mm 0 >dia.45mm 0

8mm 0 //8mm 0,5

6mm 9,6 Dia.13mm 76,6

4mm 42,6 Dia. 7mm 21,3

2mm 44,3 Dia. 3mm 1,4


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Table 5. (conditions 1st cook/2nd cook, if only 1 condition is presented thesame was used in both cooks)

+

. 1 . 2

1

.

2

,

10 10

5/ 5/

, 45 45, (10 ) 120

45 (15/20

)

120(10/8

)

/ 4 4,5 3 4,5 3

, % 8,9 6,8/6,3 1,6 15,7/14,7 1,6/2,1., 105 154/152 154/152 140/144 156,5/154

650/550 650/550

, % 31,6 31,6

The residual alkali was measured with SCAN N30:85 and rejects as gravimetricevaluation with 0.15 mm slots.

6.1.2 Results

The shives contents of the pulps were at very low level and no difference couldbe seen between two cases.

The total yield was also on the same level for the two cases (Fig. 8).


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5051

52

53

54

55

56

57

5859

60

15,5 16 16,5 17 17,5 18 18,5

%

45

. ( 1520

)

Fig. 8. Yield versus kappa number.

The achieved kappa number after a certain H-factor was lower in the case whenimpregnation was used (Fig. 9). The difference was however small.

15,5

16,0

16,5

17,0

17,5

18,0

18,5

540 560 580 600 620 640 660

45

. ( 1520

)

Fig. 9. Achieved kappa number at certain H-factor.


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6.1.3 Conclusions

In RCK laboratory it is difficult to show any difference between the two casesbecause of:

o The heating up time in the non impregnation case was 15-20min.During this time already impregnation is taking place

o The circulation flow could not be reduced as much as expectedwhich resulted in a short liquor circulation retention time, ca 3minutes (but anyway lower than normal)

Further can be also concluded that:- Reject and yield were at the same levels- Indications on that the achieved kappa level in the impregnation case is

lower at the same H-factor (more homogenous)

6.2 Cooking with and without impregnation, Scitech study

After discussions taking into account the previous test and other knowledgeavailable it was decided to try to study the impregnation in a larger circulationdigester which allows the cooking to be done with 5.8 kg OD chips. Thiscirculation digester is a jacketed circulation digester that allows a circulationflow of 3 l/min which corresponds to a circulation liquor retention time of 8.7 minat a L/W of 4.5 m3/Bdt. This is almost 3 times less circulation than the

circulation that was possible to keep at RCK laboratory. The heating up timewas between 16-19 min (including white liquor fill for the non impregnationcase). The laboratory study provider was SciTech in Rauma, Finland.


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6.2.1 Raw material and cooking conditions

The chips samples were prepared in Uruguay (Latu) before they were sent toFinland. The chips were dried before shipment and the dry content was 93% formix 2 and 91% for mix 3 (analyzed at Scitech).

The chips dry content was adjusted to 80% before the cooking experimentswere done. This was done by rewetting and conditioning in plastic bags. Thesteaming for 10 minutes further reduced the chip dryness to 71% for bothmixes.

The raw material mixes was according to table 6.

Table 6.E. globulus E. dunnii E. grandis Other

MIX 2 50% 20% 20% 10%MIX 3 25% 70% 5% -

The chips size distribution was analyzed according to the SCAN-CM 40:94method and the results are shown in table x.

Table 7.>45 mm >8 mm

slot>13 mm > 7mm > 3 mm < 3 mm

Mix 2 0.2 4.0 63.6 29.4 2.5 0.2Mix 3 0.0 2.5 57.6 35.6 3.9 0.2

The cooking conditions are presented in table 7. The alkali charge was split to 3dosage points in the impregnation case: Impregnation/cook zone 1 /cook zone2. In the non impregnation case two dosage points were used: cook zone 1/cook zone 2. Alkali charges were set to achieve the target residual alkali levels.Table 8.

% 35

, 10

( )

40

6

/ / 4

. 105

/ 68


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45

6

/ / 4,5

. 145

/ 68

120

6

/ / 3,5

.

/ 68

The residual alkali was measured with SCAN N30:85 and rejects as gravimetricevaluation with 0.15 mm slots.The rejects were analyzed on 0.2mm slotsscreen.

6.2.2 Results

Alkali consumption

The alkali charge had to be increased with 0.2% EA NaOH on wood for themixes cooked without impregnation in order to keep the residual alkali withingiven frame. However when calculating the alkali consumption based on thecharges, liquor mass balance and residuals there is a difference in alkaliconsumption only for mix 2. The difference is about 0.4% EA NaOH, see Figs.10 and 11.

141516171819202122

150,0 155,0 160,0 165,0

Kappano.

consumed NaOH kg/Bdt wood

Montes del Plata

M2, with imp.

M2, no imp.

141516171819202122

145,0 150,0 155,0

Kappano.

consumed NaOH kg/Bdt wood

Montes del Plata

M3, with imp.

M3, no imp.

Fig. 10. Alkali consumption for mix 2. Fig. 11 Alkali consumption for mix 3.

The kappa number s achieved after a certain H-factor showed no differences formix 2. The results for mix 3 were also too close to each other in order to draw

reliable conclusions (Figs 12 and 13).


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14151617181920

2122

250 350 450 550

Kappano.

H-factor

Montes del Plata

M2, with imp.

M2, no imp.

14151617181920

2122

250 350 450 550

Kappano.

H-factor

Montes del Plata

M3, with imp.

M3, no imp.

Fig. 12. Achieved kappa no vs H factorfor mix 2.

Fig. 13. Achieved kappa no vs H factorfor mix 3.

Reject

The reject levels were on the same level on the achieved kappa numbers in thelower range. On the highest kappa number for mix 2 the rejects were higher forthe case without impregnation, see Figs. 14 and 15.

In general the shives content are on a high level for both mixes.

0,0

0,2

0,4

0,6

0,8

1,0

1,2

10 15 20 25Shives%onwood

Kappa no.

Montes del Plata

M2, with imp.

M2, no imp.

0,0

0,2

0,4

0,6

0,8

1,0

1,2

10 15 20 25Shives%onwood

Kappa no.

Montes del Plata

M3, with imp.

M3, no imp.

Fig. 14. Shives content for mix 2. Fig. 15 Shives content for mix 3.

Yield

When analyzing the yield results one has to remember that no impregnationliquor was circulated to the cooking. This means that for the impregnationcooking it is actually a hemicelluloses extraction phase and this does not applyfor the non impregnation case. For mix 2 there is no difference between theimpregnation/non impregnation case, in practice this means that yield actually is

be higher when the results are equal.


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The yield of mix 3 is on a higher level than mix 2. At lower kappa levels for mix3 it seems like the no impregnation case gives higher yield. This result can beexplained with hemicelluloses extraction and dissolution because of higher

cooking time to lower kappa numbers. However the same can be stated as withmix 2 when the results are equal in practice the yield is higher with theimpregnation option.

The total yields are shown in Figs. 16 and 17.

Fig. 16. Total yield for mix 2. Fig. 17. Total yield for mix 3.

The screened yields are found in Figs. 18 and 19.

Fig. 18. Screened yield for mix 2. Fig. 19 Screened yield for mix 3.


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7 Conclusions

No or small differences could be noticed in this studyo Higher alkali consumption when running without separate

impregnation for mix 2.o If the impregnation liquor would have been recirculated the yield

with impregnation would have been higher.

Main reasons why results did not show similar results as found in literature andwhich were expected:

o No recirculation of the impregnation liquorno hemicelluloses

precipitationdecrease in yieldo Steaming has been obviously near to perfecto Heat up time too long compared to mill caseo Even though the circulation flow in the digester was reduced with

2/3 compared to the pretest levels used in the RCK laboratory itwas not possible to achieve reliable results.

In the end we must take into account thato There will be variations in the raw material flow in the mill resulting

in non uniform process performance Variations in wood species Variations in chip humidity Variations in chip quality and size Variations in steaming of the chips

o Separate impregnation will improve the process result duringoperations in such conditions

o Existing results from mill trials and mill experience supports thefact that separate impregnation is giving favorable process results(see literature report)

o

Impregnation vessel enables a possibility to further optimize thealkali profile for both yield and quality reasons


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8 Recommendations

It is obvious that this subject is difficult and very demanding to be studied inlaboratory in order to obtain differences, at least when applying steaming onnormal chip sizes.

Due to this, the above conclusions and the conclusions made in the literaturestudy our recommendation is to keep the impregnation vessel in the scope ofthe project Montes del Plata.


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9 References

1. Inalbon M.C., M. Citroni, V. Marzocchi,C. Pieck , M. Zanuttini.Impregnationof eucalyptus and pine wood in alkaline pulping processes.Effects ofsteaming and pressurized impregnation. ABTCP 2004.

2. Malkov, S., Tikka, P., Gullichsen, J. (2002) Towards complete impregnationof wood chips with aqueous solutions. Part 4. Effects of front-endmodifications in displacement batch kraftpulping. Pap. Puu. 84:526530.

3. Zanuttini, M., Citroni, M., Mocchiutti, P., Inalbon M.C. Alkali impregnation of

hardwood chips. Tappi Journal 2(2005) pp. 28-30.

4. Inalbon M.C., Mussati, M. C., Zanuttini, M., Experimental and theoreticalanalysis of the alkali impregnation of eucalyptus. Ind. Eng. Chem. Res. 48,4791-4795, 2009.

5. Internal Stora Enso report. 1243e.

6. man, M., Sderstam, G., Comparison of stored green wood raw materials.Pap. Puu 83(2001)11 pp. 50-57.

7. Silva, F., Maciel, P., Silva, M., Peixoto, M. Implentacao de uma eficienteetapa de impregnacao na pulpacao kraft de eucalipto 14-17, Oct., ABTCP2002,.

8. Weipang, B., Lucia, L., Tappi J., 2(3):32(2003)

9. Stone, J., Green, H., Pulp and Paper Mag. Can. 59(1958)10 pp.223.

10. Inalbon M.C., Zanuttini, M., Citroni, M., Mocchiutti, P., Experimental andtheorethical analysis of the alkali Alkali impregnation of eucalyptus wood.Ind.Eng. Chem. Res,48(2009) pp. 4791-4795.

11. Tolonen, L., Hiltunen, E., Helttunen, J., Sixta, H. Effects of impregnationtime on hardwood kraft pulp characteristics and papermaking potential amill study. APRIL 2010 | TAPPI JOURNAL

12. Gomes, F. and T. J. McDonough (2002). "Lo-solids pulping of eucalyptus:effect of production rate." O Papel(January): 69-81.


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13. H Wedin, M Ragnar, M Lindstrm, accepted for publishing in NPPRJ,Extended impregnation in the kraft cook-an approach to improve the overallyield in eucalypt kraft pulping

14. Gustavsson, C. (2006). On the interrelation between kraft cooking conditionsand pulp composition. Stockholm, KTH. Doctoral thesis.

15. Notes from SE/Arauco/MdP team visit to Tres lagoas mill, PB

16. Oman M., Soderstam G., Comparison of stored and green wood rawmaterial. Paperi ja Puu. 83(2001):1,50.

17. Metsateho Markku Mkel, raportti 071, 2001 Varastoinnin vaikutuskuitupuuhun j asen merkitys sellun valmistukssessa 15p.

effect of pre-steaming and impregnation on the eucalyptus pulp cooking yield 23082010

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