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Kraft Recovery-

The effect of sodium sulfideon the equilibrium of thecausticization reactionJohnC. Ransdell andJosephM. GencoGradu ate assistant and professor of chemical engineerin g, Dept. of Chemical Engineering,Un iver sity of M aine, Orono, Me. 04469

ABSTRACT The causticizing reaction equilibrium was studiedexperimentaly.In the &raftcausticization reaction, sodium bydroxide isregenerated y solid calcium hydroxide reacting with aqueous sodiumcarbonate solution in the presence of sulfide and other ions.0 ,15 , nd 30 .The data could be explained in terms of athermodynamic mode4 the basis for which is an estimation for the activitycoefficients o r C0:- and OH- ions in strong electrolytes. The current work.extends the theoretical model to include the effect of the sulfide ion.A set ofion interaction parameters and the thermodynamic equilibrium coefficientwere obtained from the equilibrium data. Causticization efficiencies can beobtained based on the use of the model with the experimentally determinedparametm

Fifty-eight causticization qerimentswereperformed at sulfidity levels of

KEYWOORDSCausticizingChemicalrecoveryKraft liquorsKraft pulpingSodiumhydroxideSodium sulfideThermodynamics

In the kra f t pulping process , thechemical recovery step of causticiza-tion is utilized to regenerate sodiumhydroxide. The causticization reac-tion is an exchange of hydroxide ionfrom slaked lime with carbo nate ionin solution.

In the causticization reaction, anequil ibrium exists that depends prim-arily on the cationic sodium concen-tratio n of th e solution and secondarilyon the tempera ture . Pressure haslittle effect on the thermodynamicequi l ibr ium because l iquid-phasereaction occurs (1, 2 ) .The extent of the conversion ofsodium carbonate to sodium hydrox-ide in the process is important inreg ard to the efficient operatio n of thekraft recovery operation. It is desir-

able to obtain as low a level of carbon-ate ion as possible in the w hite liquo rsolution. T he causticizin g efficiency,E, is given by the relationship dis-cussed by Hough 3):

constant calculated in concentrationuni t s , K, , was the same for bothcarbon ate solutions, with and withoutsodium sul f ide . This equi l ibr iumconstant is calculated as:E = 100 [NaOH y [NazCOs ] (2) K = [OH-]'/ [CO;] (3)

whe re [Na OH] is defined as the The units for [OH- ] and [c03'- ] a resodium hydroxide concentration in moles per liter of solution.the w hite liquor less the concentration Lindberg and Ulmgren 1 , Z )deter-of sodium hydroxide in the green mined the effects of the major vari-l iquor and [Na~ C03 is the concentra- ables of con centratio n, composition,tion of sodium carbona te in the green and temp eratu re on the causticizationliquor. equilibrium . The theoretical equili-brium constant for the reaction wasRelated research expressed in terms of activity coeffi-cients. The activity coefficients wereConsiderable early work has beenpublished on causticization of sodiumc a r b o n a t e (4-11). Rydin and co-workers ( 1 2 ) tudied th e effect of lim equality on the equilibr ium. Kojo 13-1 5 ) concluded that the equilibrium

assumed to be independent of thesolution com position, provided theconce ntration s of in ert cations Na'and K, with opposite signs to thereactants OH- an d CO: rem ainedconstant in a medium of high totalAugust 1991 Tappi Journal 169


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concentration. They concluded thatthe ca t ion concen t ra t ion was thepa ram ete r of greatest influence on themagnitude of the equilibrium con-stant and that tem perature had l i tt leeffect.Lindberg and Ulmgren were ableto f i t their data accurately to thefollowing emp irical equation:

*82

log K, = 2.95 - 0.62 x ( [Na' + [K' 1) (4)The presence of hydrosulfide ( H S )had no effect on the equi l ibriumconstant but was shown to have asligh t effect on the de gree of caustic-izing as a result of the increase in thetotal cation concentration.

ThermodynamicconsiderationsGenco and Daily proposed a semiem-pirical model for the causticizationreaction, based on the fundamentalthermodynamic equations governingchemical equilibrium in electrolyticsolutions 16 , 17). For this reaction,the thermodynamic equilibrium con-s t an t , K(T), is given by the rela-tionship:

,

In K r ) = In [K. T ,X ) x mZoH -/ co3== AG /R T (5)whereK.(T, X ) = activity coefficient constantmOH = [OH- ] expressed inmolality units of g moles/

1000g watermcos= + [CO;. expressed inmolality units of g moles/

1000g waterT = temperatureR = universal gas constant.

In Eq. 5, A G O is the Gibbs freeenergy charge for the react ion if itoccurs in the stan dard sta te. The unitsused to describe the equilibrium arearbitrary. The units of molality areoften used because the concentrationterm s ar e independent of th e solutiondensi ty . Using molal i ty uni ts , theequilibrium constant, Eq. 3 becomes:K, = mZoH-/cog= (6)

Based on this fundamental relation-ship, Daily and Genco 1617 ) sed thework of Pitz er an d eo-workers 18-21)170 August 1991 Tappi Journal

to quantify an estim ate for the activitycoefficient con stant K,(T, X ) , in whichA rep rese nts th e ionic composition ofthe system. Daily and Genco estab-lished the basic relationship of Eq. 7for describing the equilibrium condi-tion for the causticization reaction.

See Equations 7-11.In this model, m and x a r e t h emolalities and valences of the majorionic species in solution-that is, thesodium, hydroxide, carbonate, andbisulfide ions.A is the Debye-Huckelparameter given by Pytkowicz 22)for water a t 100C (A' = 0.4603), ands a constant for the P itzer equations0= 2.0). The functionsf: gl(l), and

g2(4 ar e calculated from the value ofthe ionic streng th, I , by Eq. 11.The model has six para meters; thethermodynamic equilibrium constant,K(T), and the Pitzer ion interactionparameters pt:l , Ct:l, pB3 oH-, p*,',ll,co=,P*N aliHS-, which describe he interactionof' ion pairs. For example, the parame -ter p::) is used to describe thermody-namic interaction of cationic sodiumion with anionic carbonate ion andan ion ic hydroxy l ion . The Pi t zerparameters ar e s imilar to second andthird virial coefficients used for des-cribing the thermodynam ic propertiesof gases and vapors.The pra ctica l value of Pitzer's w orkis that it permits a n analytical expres-sion to be written for the activitycoefficient constant K,( T,X)and thusgives the prop er theoretical form forthe causticization equilibrium equa-tion (Eq. 7). Thus, one does not havetc i resort to f i t t ing an arbi t rary em-pirical equation. Theoretically, he sixunknown para mete rs in the model canbe determine d from a n analysis of theproduct reaction an d a l inear regres-sion analysis, since the model equa tionis l inear in the six unknown param e-ters.Daily and Genco studied the caus-ticization reaction for pure sodiumcarbonate 17).They solved for five ofthe unknown p aram eters in the modelby the method of linea r least squa res.In this analysis, the quantity Y wasest imated from the experimental dataand the calculated function 2fy.

See Equation 12.Because their experiments wereperformed in the absence of sulfide

ion, they om itted the reaction param e-t e r p HS- w h i ch d es c r i b e s t h einteraction of sodium ion with bisul-fide ion.Not al l of the parameters werefound to be statistically significantwhen the equi l ibrium data were f i t tothe model. Rather, for the causticiza-tion of pu re NaZC03 with Ca(OH)2, aprincipal component analysis reducedthe number of parameters to two.These two parameters were In K(T)and P*( )N, +. The reduced form of themodel is given by Eq. 13 17).See Equation 13.

where the thermodynamic equi l ibri -um constant In K(T) and the Pi tzerparameter p*('ha + had the values 7.27and -0.193, respectively.ObjectiveOur objective in this work was toexperimental ly determine the effectof sulfide ion on the causticizationequilibrium . We wished to extend themodel proposed earlier (16, 17) toinc lude the ef fec t o f su l f ide ion .Another goal was to determine thePi tzer parameter &$ HS-, describinginteractions of sodium with bisulfideions.ResultsThe apparatus , experimental proce-dure s, and m ethod of estima ting theequilibrium coefficients K, and K,are summ arized in the experimentalprocedures sect ion. Detai ls of theexperimental procedures and a sum-mary of the data are presented else-where 23,24). austicization efficien-cies were calculated from E q. 2.The values for In K, (Eq. 3 ) wereobtained from an analysis of the d at afor causticization solutions at equili-brium . The values of th e ter m In K,for 15 and 30 sulfidity 23)werecombined with values obtained at 0sulfidity by Daily (24).All t he da tawere compared to values obtainedfrom the empi r i ca l model (Eq . 4)suggested by L indberg and Ulm grenI , @ .All of the experimental da ta areshown in Fig . 1, ogether with the lineproposed by Lindberg and Ulmgren.F i g u r e 2 isa gr ap h of the equilibriumconstan t In K, plotted ag ainst sodiummolality, for th e total set of 58 caus-


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1. In K vs. total sodium ion concentration, showing model line ofLindberg 2. In K vs. total sodium for O , 15%, and 30% sulfidity

5.5

5.0

4.5C- 4.0

3.5

L

- 0015% I30%3.0 I J0.5 1.5 2.5 3.5 4.5 5.5TOTAL SODIUM, g moleslL

f i e

4.5 .EYC- 4.0

3.5

Sulfidlty015%30%

3.0 I0.5 1.5 2.5 3.5 4.5 5.5TOTAL SODIUM, g m o l e d l

ticization expe rime nts havin g sulfid-ities of 0%,E ,nd 30 .Discussion: treatmentofexperimentaldataLeast square d y s i sA leas t squares analys is was per-formed on the data using the SAS'statistical analysis system co mputerprogram 25).Values for the modelparam eters w ere numerically calcu-lated over the entire data set of 58

causticizations an d a re given in TableI. Unfor tuna te ly , the s ign i f i cancelevels of the six unknown p ara me terswere determined to be low. Thisdetermination was made by estimat-ing the confidence limits or stan darderr or on the model coefficients usingt h e SAS com pute r p rogram . T heconfidence levels on the six coeffi-cients ar e though t to be low becausethe independent parameters in themodel are not truly independent of

each other but vary in a colinearmanner. Thus, it is difficult to esti-mate all six coefficients directly fromthe causticization reaction equilibri-um and come out with narrow confi-dence l imits . Rather , each of thecoefficients would have to be deter-mined in independent experimentsand then combined in Eq. 7 to predic tthe causticizing equilibrium.Principal componentanalysisHere, the model may be simplified

August 1991 Tappi Journal 17


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1. Least squares estimation of the equil ibrium model coefficients and the eigenvalues obtained by principal component analysisLeast sq uares analysis Principal component analysis

Standard Principal CumulativeParameter Value error co mm nen t Eigenvalue contrib utionIn K(T) 7.94 f1.26 4.50734 0.75122pig 0.910 k0.664 2 0.8 0.89948fl;:, HS- 3.52 f5.57 3 0.56241 0.99322C -0.0701 f0.0535 4 0.03943 0.99979Na+flirJgH- -4.71 f5.76 5 0.00125 ooooop (1) -12.1 f15.7 6 0.00001 oooooNa+,Cog

( 17, 23). The diagnost ic techniqueterme d the pr inc ipa l componentanalysis was used to examine theinfluence of each parameter on thesolution of th e mod el.The eigenvalues for the principalcomponents of the model are su mm ar-ized in Table I . For three of thep r i n c i p a l co mp o n en t s , t h e e i g en -values are s ignificant . The eigen-values of the fourth principal compo-nent is below 1 f the eigenvalue ofthe f i rs t principle component . Forstatistical significance, differences inma gnitu de between t he eigenvalues ofeach of the pa ram eters would need tobe low. A low difference between theeigenvalue for the first componenta n d e a c h s u b s e q u e n t c o m p o n e n twould indicate th at the a ddition of thesubsequent component was signifi-ca nt in the solution of th e mo del.For the d ata set, the significance ofthe fourth and subsequent principalsis low. Therefore, based on the princi-pal componentanalysis for the da ta set,the number of model unknowns andcoefficients should be redu ced to threein order to eliminate the potential forover-specifying he model. Statistical-ly, any three of the model coefficientscan be chosen to f i t he da ta, and a goodfit would be obtained. How ever, basedon physical-chemical considerations,we chose the eq uilib rium coefficient InK(T) and the Pitzer parameters &and &. : SH .Following our ear ly results ( 17) forcausticizing pure sodium carbonate,t h e r ed u ced mo d e l eq u a t i o n w aschosen to be:

See Equation 14,172 August 1991Tappi Journal

where gz I ) , and I are given in Eqs.8, 10, and 11 and AO= 0.4603 and= 2.0.The solution of the reduced modelis given in Table I1 for the com pletedata set of 58 causticizations, includ-i n g t h e s t an d a rd e r ro r s f o r e achparameter. These s tandard errors a relow in relation to the value of theparameters . Note that the s ignifi -cance levels of these values ar e high.LJsing the best-fit parameters fromTable 11,values for the va riable In mcan be obtained direct ly from themodel equation as a function of thesodium molality and the sulfidity.Values of In K m determined by the useof the m odel are plotted as curves inFig. 3, together with the experimen-tal data points.Estimation of causticizingefflciencyThe term causticization efficiencyhas been used frequently to describethe quality and degree of the caustic-ization reaction. The m odel, as devel-oped, can be utilized to determineequilibrium values for the causticiza-tion efficiency, given the total cationconcentration of the solution and itssulfidity

= (TTA/31) X 23 (15)mHs- = x sulfidity)/2 (16)

sulfidity = [Na2S /AA (17)whereTTA = total titratable alkali, g as

N a ~ O / k g= NaOH + NazS NaC03

/z NaZS03

II Estimation of the revised equi l ibr iummod el coefficients and associated errorsStandardParam eter Value errorf0.0209

-0.163 3~0.00589

[NaZS ] = concentration of sodiumsulfide, g as NazO/kg.

AA = active alkali, g as NazO/kg= N a O H + N a z S

In Eq. 16, i t i s assumed that thehydr olysis of the sulfide ion is com -p le te , accord ing to the fo l lowingreaction (2 6 ) :S= HzO SH-+OH- (18)

The electrical neutrality conditionfo r t h e s y s t em can b e u s ed a s aconstraint:

The causticizing efficiency can beestimated by solving simultaneouslyEq. 6 for the equilibrium coefficientK, and Eq. 19 for the concentration


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3. In K vs. total sodium for 0%, 15%, and 30 sulfidity and the r educ ed equilibrium mod el

:::.038-._ -.- 3.0EYE-

0 Sulfldlty- model

4.03.5 . 0 SuHldky-model

5.5, 1

TOTAL SODIUM, g m o ld kg TOTAL SODIUM, g m o ld kg TOTAL SODIUM, g mo le/kg

4. Caustic ization effic iency vs. total titratable alkali for 0 , 15%, and 30% sulfidity data and the r educ ed equilibrium model

85

. 15 Sulfidity- model55 85 115 145 17 25 55 85 115 145 175

TOTAL TITRATABL E ALKALI, as NazO/L TOTAL TITRATAB LE ALKA LI, as Na,O/L TOTAL TITRATABL E ALKALI, as NazO/L

of car bon ate ion,mco; to get Eq. 20:See Equation 20.

In the solution, values for the sodi-um and bisulfide molalities must begiven to determine a valu e of K, usingthe model equat ion, Eq. 14. Thehydroxide molality can then be de ter-mined using Eq . 20. Once the valueof the hydroxide molality is known,the carbo nate molality may b e calcu-lated from Eq. 19.For this system at equilibrium:

( m H ' - mHS- + 2 C O ; )E = OH- - WLHC)/ (21)

TTA = [NaOH] + [NazCOs] + [NazS] (22)Figure 4 present p lots for theequilibrium causticizing efficienciesdetermined experimentally and byuse of the model equation. As thesegraphs show, the model equations

r e p r e s e n t t h e e x p e r i m e n t a l d a t aextrem ely well.ConclusionsSulfidity has a n effect on the equili-brium coefficients K, and K,. Withsulfide ion added to green liquor, thereaction is somewhat suppressed, andthe equ ilib rium coefficient (K, or K,)is lower. This less active reactionresults in less carbonate ion beingconverted to the solid form and lesshydroxyl ion being formed.The unknown parameters in thethermodynamic model were evaluat-ed from the composition data deter-mined for the reaction at equilibrium.However, the statistical significanceof the six unknown parameters waslow. Th e model equation is thought tobe over-specified in relation to thequality and size of the d at a set and the

fact that the independent variables inthe model vary colinearly.With int erpreta tion of a principalcomponents analysis of the da ta an dthe model, the equilibrium modelequation was reduced to three un-known parameters and coefficients.This reduced model, Eq. 14, f i t s thedata set well, and the significance ofthe unknown model parameters ishigh. The model equation can be usedto predic t the equilib rium causticiza-tion efficiency, given only the sodiummolality an d sulfidity.Experimental method*PPSodium carbonate solutions havingvario us levels of sodium su lfide werereacted with calcium hydroxide in acons tant- temperature, s t i r red- tank,batch reactor at 100C (Fig. 5 ) . The

August 1991 TappiJournal 173


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f 111. Example of results of causticization product analysis at 30% sulfidityRun

Molar concentration, g moleslLNa+ OH' COS HS- lnK, Densit%kglL

Conc. ofwater,kg H20ILMolal concentration, m oleslL

Na+ OH- Cog' HS- l n K m3935312725483438

1.72812.19492.66463.09883.45103.97114.52144.9962

1.44921.81252.17332.46002.72003.04843.35163.6000

0.011 210.0337140.0614540.0902420.1204920.1830680.2606820.337273

0.24670.31500.36830.45830.49000.55670.64830.7217

4.874.584.344.214.123.933.763.65

1.0681.0871.1041.1181.1311.1531.1731.189

0.99450.99330.98990.98440.98200.98050.97500.9688

1.73772.20982.69173.14803.51444.05044.63735.1571

1.45721.82482.19542.49912.76993.10913.43763.7159

0.0162100.0339420.0620800.0916770.1227040.1867160.2673730.315943

0.24810.31710.37210.46560.49900.56780.66490.7449

4.884.594.354.224.143.953.793.68

reaction vessel was constructed fromstainless steel and h ad a volume of 1.2L. The reactor was sealed to 15 psigwith Teflon block covers.Reaction access and mixing wereprovided by a sealed ap erture an d asealed b earin g assembly in the cover.An in-line Teflon filter 10 pm) anda stainless steel heat exch anger w ereutilized in removing the produc t andcooling.The temperature within the reactorwas measured using a stainless steelthermocouple and a data logger. Thetemperature was controlled by im-mers ing the reac t ion vesse l in aconstant temperature bath of 100Ccomposed of 60 glycerin and 40water.C h e m i d pteparationand product analysisCausticizing reactions we re conduct-ed with sodium carbona te and sodiumsulfide solutions with concentrationsranging from 1.5to 5.25 g moles Na'/L, increased stepwise in increm ents of0.25 g moles/L. T he reac tants were ofr eag en t ch emi ca l g r ad e . Ca l c i u mhydroxide was added in the reactionsequence in a n excess of 125% of th eamount required to stoichiometricallyc o n v e r t all of t h e c a r b o n a t e t ohydroxide.The reac t ion p roduct s -sod iumhydroxide, sodium carbonate, andsodium sulfide-were analyz ed usin gthe titration analysis techniques des-cribed in TA PP I Test Method T 624,Scandinavian SCA N-N 2:63 27), andelsewhere (28). The carbonate ionconcentration determined from titra-tion results is considered a less accu-rate representation of the tru e valuetha n values obtained by the gravim et-ric or conductivity techniques. There-fore, the carbon ate ion concentration174 August 1991Tappi Journal

5 Design of the basic causticizing apparatus

Se t t l i n gzon;

C o n s ta n t - t emp e r a tu r e b a th (100C)

was also determine d using gravimet-ric techniques described in TAPPIT 624.Experimental procedureFor causticizations, distil led, deio-nized w ater and sodium sulfide solu-tion were added to the reactor. Toprevent oxidation of the sodium sul-fide solution, the solution was storedunder a nitrogen atmosphere. Gran-ular sodium carbonate was added tothe reactor, and the reagents were

mixed a t 100C for 15 min. Calciumhydroxide was added, and the reactorwas sealed for a minim um causticiza-tion period of 2 h. For an additional2-h period without mixing, the calci-um carbonate and hydroxide solidsw ere a l l o w ed t o s e t t l e p r i o r t osampling.Estimationof he equilibriwncoefficientsThe ion concentrations were convert-ed to molalities, given the solution


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dens ity by the following equations:mi = c;/ P . 4 s (23)[HzO ] = p s - CJ (24)C. = [NaOH MW,,oH

+ [CaCO, MWc.cos+ [NaHS 3MWN~HS (25)

wheremi = molality of species i moles/kg

solventCi = concentration of i moles/L of

solutionps = density of the solution, kg/LMW = molecular weight.

Table I11 i l lustrates the experi-men ta l d a t a f o r t h e ca se o f 30sulf idity. The equilibrium constantsK, and K, were estimated from theconcentrations or molalities for hy-droxyl and carbonate ions. Solutiond en s i t i e s we r e measu r ed u s in g aMetler /Paar DMS 35 density meter .lJLiterature cited1. Lindberg, H., and Ulmgren, P., J. PulpPaper Sci. 9(1): TR-7(1983).2. Lindberg, H. and Ulmgren, P., 1985International Recovery ConferenceProceedings, TAPP I PR ESS , Atlanta,p. 329.3. Hough, G., Chemical Recovery in theAlkal ine Pulping Process, TAPPI

PRESS , Atlanta, 1985, p. 201.4. Lunge, G. and Sch mid,J., Berichte derDeutschen Chemischen Gesellschaft,18: 3 286( 1885).5. Goodwin. L. F.. J. SOC. hem. Ind. 45:360T ( 1926).Chem. Ind. 45: 362TU 926).6. Goodwin, L.F. and Sills, J. L., J. SOC.7. Olsen, J. C. and Direnga; 0. G., Ind.Eng. Chem. 33(2): 204(1941).8. Hugher, G. B., Herndon, L. K., andWi t h row, J. R . , P a p e r T r a d e J.TS(Feb. 26): 105(1942).9. Kobe, K. A. and Wilkinson, J. A., Ind.Eng. Chem. 45(2): 307(1953).10. Littman, F. E. and G aspari , H. J., Ind.Eng. Chem. 48(3): 408(1956).

11. Rothbrock, C. W., Tappi 41:241A(1958).12. Rydin, S., Haglund, M., and Mattsson,E., Svensk Patterstid. 80(2): 54(1977).13. Kojo, M., Paperi Puu 61: 244(1979).14. Kojo, M., Paperi Puu 61: 701(1979).15. Kojo, M., Pap eri Puu 61(8): 515(1979).16. Daily, C. M. and Genco, J. M., Ther-modynamics of the kraft causticizingreaction, paper presented at the 1986AIChE Meeting, Session No. 81, Ad-vances in Chem ical Recovery Technol-ogy, P a r t 11, AIC hE, New York, 1986.17. Daily, C. M. and Genco, J. M., Ther-modynam ic model of the kr af t caustic-

izing reaction, J. Pulp Paper Sci . ,paper submitted for publication, 1991.18. Pitzer, K. S., J. Physical Chemistry77(2): 268(1973).19. Pitzer, K. S. and Mayorga, G., J.Phys i ca l Chemi s t ry 77(19):2300( 1973).20. Pitze r. K. S. and Kim. J..J.Am. Chem..SOC.6( 18): 5701( 1974).21. Pitzer, K. S., Activity Coefficients inElectrolyte Solutions, Vol. I (R. M.Pytkowicz, Ed.), CRC Press, BocaRaton, 1979, Ch. 27, p. 157.22. Pytkowicz, R. M., Activity Coefficientsin Electrolyte Solutions, Vol. I , CRCPress, Boca Raton, Fla., 1979.23. Ransdell, J.,Ef fec t of sulfide ion on thekraft causticizing reaction, M.S. the-sis,University of Maine (Dec. 1989).24. Da ily, C. M., A thermodyn amic modelof the kraf t caust icizing react ionequ ilibrium , M.S. thesis, University ofMaine (Dec. 1987).25. SAS User 's Guide: Statist ics, SASInstitu te, Inc., Ca ry, N.C., 1985.26. Teder, A. and Tormund, D., SvenskPapperstid. (16): 607( 1973).

27. SCAN-N 2:63, Svensk Papperst id .66( 18): 727( 1963).28. Causticizing, Pulp and Paper Manu-facture-the Pulping of Wood, Vol. 1,2nd edn. (R. G. MacDonald, Ed.),McGraw-Hill, New Y ork, 1969, p. 532.The a uthor s w ish to e xpre s s the i r s inc e rea ppre c ia t ion to the U.S. National ScienceFoundation for the financial support of this work.Received for rev iew Ju ly 2, 1990.Accepted Dec. 7,1990.P r e se n t ed a t t h e T A P P I 1 9 90 P u l p i n gConference.

H RSTAINLESSSTEEL PIPING,FITTINGSANDACCESSORBFOR THE PULPAND PAPERThird Edition. A project of theMaintenance & MechanicalEngineering Committee of theTAPPI Engineering Division.Establishes recommendedspecifications for corrosionresistant pipe, tube, fittings andaccessories for the pulp andpaper industry. Covers themanufacture and fabrication ofcorrosion resistant pipe, tube,fittings and accessories whichconform to uniformrecommendations which millpersonnel can use as a guidefor purchase and installation.Includes a laboratory corrosionresistance data chart and anInternational Standard (SI)factors for conversion ofcustomary units.1986.28 pp., 812 x B 1soft-coverOrder Number: 01 01 R133TAPPI Members: $30.12;l i s t : $44.95

TAPPI PRESS Pub lic atio n SalesTechno logy Parkl Atl anta P.O. Box 105113Atl anta, GA 30348.51 13 1-800-332-8686August 1991TappiJournal 175

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Reator de Cal - Como Calcular