Control of the Accumulation of Non-Process Elements in Pulp

230 Pages·2001·12.41 MB·English

DoEAD/13441
Control of the Accumulation of Non-Process Elements in Pulp
Mills with Bleach Filtrate Reuse: A Chemical Equilibrium
Approach to Predicting the Partitioning of Metals In Pulp Mill
and Bleach Plant Streams
Final Report - 07/24/1996 - 06/30/2000
W. J. Frederick, Jr.
A. W. Rudie
G. W. Schmidl
S. A. Sinquefield
G. L. Rorrer
M. L. Laver
W. Yantasee
D. Ming
August 2000
Work Performed Under Contract No. DE-FC07-961D13441
For
U.S. Department of Energy
Assistant Secretary for
Energy Efficiency and Renewable Energy
Washington, DC
By
Oregon State University
Corvallis, OR
The Institute of Paper Science and Technology
Atlanta, GA
PROCESSED FROM NW’ AVAILABLECOPY
DOEIID113441
CONTROL OF THE ACCUMULATION OF NON-PROCESS ELEMENTS IN PULP
MILLS WITH BLEACH FILTRATE REUSE: A CHEMICAL EQUILIBRIUM
APPROACH TO PREDICTING THE PARTITIONING OF METALS IN PULP MILL
AND BLEACH PLANT STREAMS
FINAL REPORT
07/24/1 996 – 06/30/2000
W. J. Frederick, Jr.
A. W. Rudie
G. W. Schmidl
S. A. Sinquefield
G. L. Rorrer
M. L. Laver
W. Yantasee
D. Ming
August 2000
Work Performed Under Contract No. DE-FC07-961D 13441
Prepared for the
U.S. Department of Energy
Assistant Secretary for
Energy Efficiency and Renewable Energy
Washington, DC
Prepared by
Oregon State University
Corvallis, OR
The Institute of Paper Science and Technology
Atlanta, GA
DISCLAIMER
This repott was prepared as an account of work sponsored
by an agency of the United States Government. Neither
the United States Government nor any agency thereof, nor
any of their employees, make any warranty, express or
implied, or assumes any legal liability or responsibility for
the accuracy, completeness, or usefulness of any
information, apparatus, product, or process disclosed, or
represents that its use would not infringe privately owned
rights. Reference herein to any specific commercial
product, process, or service by trade name, trademark,
manufacturer, or otherwise does not necessarily constitute
or impiy its endorsement, recommendation, or favoring by
the United States Government or any agency thereof. The
views and opinions of authors expressed herein do not
necessarily state or reflect those of the United States
Government or any agency thereof.
DISCLAIMER
Portions of this document may be illegible
in electronic image products. Images are
produced from the best available original
document.
Control of the Accumulation of Non-Process Elements in Pulp Mills
with Bleach Filtrate Reuse: A Chemical Equilibrium Approach to
Predicting the Partitioning of Metals In Pulp Mill and Bleach Plant
Streams
Final Report
W.J. Frederic~ Jr., A,W. Rudie, G.W. Schmidt and S.A. Sinquefield
The Institute ofPaper Science and Technology
I
G.L. Rorrer, M.L. Laver, W.Yantasee, and D. Ming
Oregon State University
August 2000
A Summary Report
Ofthe Project
Work Performed Under Contract DE-FC07-961D13441
Prepared for
The U.S. Department ofEnergy
OffIceofIndustrial Technologies
Washington, D.C.
Prepared by
Oregon State University
Corvallis, OR
The Institute ofPaper Science and Technology
Atlanta, GA
-. *
TABLE OF CONTENTS
PREFACE
L EXECUTWESUMMARY.......*.*......**.*.......*....*..*...*.**.......................***.......1
l
A Introduction
B. TheMetalsBindingCRPacityofDHsolvedOrganicMatterinBlack
LiquorandBleachFiltrates
C. Stabiity ConstantsforMetalComplexesWithDbNOlvedOrgakdcM@fer
D. TheMetalsBiiding CapacityofWoodI?@ fibers
E. SorptionEquMbriumConstantaforMetalswithWoodPulpN&n’s
F. ThermodynamicPropertiesandActivityCoefficientsforInorganicSpecies
G. ChemicalEquilibriumModeling
E FieldDataforMetalIonsinFtdpingLiquorStreams
I L EvaluationoftheChemicalEquilibriumModel
LL MuMcompo~ InorgauicSolutions
X2. AqueousFiber-MetalIonSystems
L3. AqueousFiber-MetalIon-D~solvedOrganicSystems
J. StatusofModelingCapabilityandRemainingNeeds
IL INTRODUCTION*..**.*.*.,...****...*.... 8
l ...............0.. .*. **. *.......*..* ..........*** ..........
InteractionofMetalswithDbsolvedWoodOrganics
A
B. InteractionsofMetalswithPolpFibers
C. DatabaseofThermodynamicProperties
D. EvaluationofVolubilityCalculations
E. TechnologyTransfer,ResultsD~emination, andFinalReport
IIL CHARACTERIZATIONOFDISSOLVEDMATTERINTCFBLEACHPLANT
FILTRATESAMPLES.....*.*..*.*.*...........***...*..*...................*.....**.*........*....12
l
A Clwacteriaticaofliltrate Samples
B. ChamwtwiaationofDissolvedOrganicMatter
B.1. CharacterbmtionofDissolvedCarbohydratesbyTLC
B.2. CharacterizationofDissolvedWoodExtractiveainFiltratesbyTLC
C. CharacterizationofDissolvedLii by=C-NMR
(X. CharacterizationofAidrichLigninby0 C-NMR
C.2. CharacterizationofFWrataLigninbyuC-NMR
Iv. COMPLEXATIONOFMETALIONSWITH
DISSOLVEDORGANICS.**.........*,..............*................0.................***....*....21
A PrecipitationofaPolymer
B. ExperimentalApproach
c. IlataAnalysis
D. Resalts
v. CHARACTERIZATIONOFPULPFIBERS................................... ..............30
l
A Pulp samples
B. FkmctionalGroupContentofPulpSamples
C.. NPEMetalFrofdeainPldp%unpk%
Cl. NPEMetalsAdytii Method
C*ZNPEMetalProfilesinPulpBeforeAcidWashing
C.3. NPEMetalProfilesinPulpAfterAcidWashing
C.4. NPEProfflesinPulpAfterASd WashingandIonExchange
VL CHARACTERIZATIONOFBINDINGOFMETAL10NS
T()PULPFIBERS........................................ .*............*.* .......................*36
l
IL MetalIonAdsorptionIsothermsonWoodPulp
AA Single MetalIonAdsorptionMeasurements
A.2. AdsorptionIsothmn Database
z&3 IonExchangeCharacteristicsofMetalIonAdsorptionontoWoodPulp
&4. FreundIichAdsorptionIsothermParameters
zL5. CorrelationofMetalIonAdsorptiontoWoodPulpConstituents
B# MetalIonAdsorption Kinetics onWoodPulp
c. Multi-ComponentMetalIonAdsorptionExperiments
Cl. Comp&itiveMetalIonAdsorptionMe&umments
C.2.CompetitiveAdsorption of Two MetalIonsonWoodPalp
versuspH
THERMODYNAMIC’PROPERTIEASNDACTIVITYCOEFFICIENTSFOR
INORGANICSPECIES.........*..*.*....*...*.**.*...... ..*****......*..*..*..*****..**.*.1*0..4 ‘
l
k DevelopmentofaDataBaseforInorganicIons
Ii EstimationMethods
B.1.ThermodynamicProperties
B.1.a. Eti”mationofFreeEnergy
B.1.b. EstimationofIonEntropiesandHeatCapacities
B.2. ActivityCoefficients
B.2.& EstimationofActivity CoefflcientaforStrongElectrtdytes
B.2.b. EstimationofActivityCoefficientsforNeutralSpecies
B.2.c Estimationofpitzer IonInteractionParameters
FIELDANDLABORATORYDATAMETALIONSINPULPINGLIQUOR
STREAMS........................*..**................................*.....**...*................139
A Objectives
B. SummaryofResults
c. Methods
D. SampleLocations
E. ResultsstudDiscussion
F. Alkali-SolubleNon-processElements:K$l, Al,Si
G. Alkali-insolubleNonprocessElements: BXCa,Co,Cu,Zn,F%Mg,Mn,P
E Alkali-solubleProcessElements:N%S
L RemovalEfficiencies
Ix EVALUATIONOFTHEINORGANICSPECIESDATABASEFORPREDICTING
TEESOLTJBILITYOFINORGANICCOMPOUNDSINAQUEOUSPULPMILL
STREAMS.......................................*.....*.**1.61
IL MajorSpeciesinGreenandWhiteLiquor
B. Non-ProcessElementsIn Moderate toHighIonicStrength Media
C, Mill Data
x ORGANOMETAL EQUILIBRIUMCALCULATOR..........................**.*.....176
A ModelConcept
R BasisandConstraints
C. OrganometalComplexation
Cl. BindingSitesforOrganomctalComplexation
C.2. StabilityConstants
C.3. MassBaIauceandElectricalNeutralityConstraints
C.4. Cakuiationprocedure
D. IonExchangeofMetalIonswithWoodPulpFibers
D.1. IonExchangeofMctaiIonswithWoodPulpFibers
D.2. IonExchangeEqtilbrium Constants
Chapter I. Executive Summary
A. Introduction
The overall goal of this project was to develop fundamentale,xperimentally based methods for
predicting the volubility oforganic and inorganic matter andtheir interactions in recycled effluent
fkomH,pi.dp milk and bleach plants. This included: characterizing the capacity of.wood pulp
and dissolved organic matter to bind pxhl ion$ developing a thermodynamic database of
properties neededto describe the solubil~”of rnorganic matter mpulp mill streaqs, incorporation
ofthe database into equilibrium calculation software for predicting the volubility ofthe metals of
inte~ and evaluating its capability to predict the distribution ofthe metals betw-’pulp fiberi,
inorganic precipitates, and solution.
This chapter summarizesthe results ofthe work performed.
B. The Metals Binding Capacity of Dissolved Organic Matter in Black Liquor and Bleach
Ftitrates
The soIubility of metals in pulp mill streams, especially alkaiine streams, is increased when
metals cxxpplexwith soluble organic matter. One objective of this work was to quantify the
fi,mctionalgroup content of organic matter found in pulp mill and bleach plant streams. Chapters
II contains results obtained by fkwtionating the dissolved organic solids in black liquor and
bleach filtrates obtained from a totally chlorine free @CF) bleached kraft pulp mill. Additional
data, obtained inthis study and fromthe literature are reported in Chapters IV and X. The results
are summarized mthis section.
Only the filtrates from brownstock washing stages contained detectable quantities of lignin. The
total hydroxyl content per mass of krdt lignin remained essentially constant through brownstock
washing. However, the distribution ofhydroxyl groups shifted through the brownstock was@ers,
toward a higher percentage of hydroxyl groups as aliphatic groups, while the percentage as
phenolic hydroxyl groups decreased. Filtrates from oxygen delignification and subsequent
bleaching stages contained no detectable lignin. The average phenolic hydroxyl content fix lignin
degradation products flom black liquor was determined to be 3.12+0.44 mmol phenolic hydroxyl
groups per g lignin. This corresponds to a molecular weight of 320=!=4g6/mole phenolic hydroxyl
sites. There isno significant trend ofphenolic hydroxyl cuntent with pulp kappa number over the
range 12to 34.
‘Ilweeextractive compounds, quercet@ dihydroquercetin and catechin were also identified inthe
filtrates upstream ofthe oxygen delignii-kation stage. All contain phenolic hydroxyl groups.
Polysaccharides were found in fdtrates horn all stages except the third peroxide bleaching stage.
No monosacc~des were found infiltrates from any ofthe stages.
The work reported in this chapter was done with bleach plant filtrates tiom a TCF bleach plant.
We would expect kraft lignin to be present in at least the earlier bkaching stages from ECF and
conventional bleach plants. We would also expect the la-aftlignin to become more degraded with
increasing bleaching with a reduction in its phenolic hydroxyl content. These remain to be
verified.
C. Stability Constants forMetal Complexes With Dissolved Organic Matter
Another objective ofthis work was to quant@ the complexation equilibrium between metal ions
and dissolved organic matter. Chapter IV summarizes the experimental methods developed and
employed in measuring the equilibrium (stability) constants for complexes of metal ions with
dissolved organic matter. Stability mnsbnts are reported for fbur metal ions (@a,Ca,Mg, Ni).
The values of log (K) for phenolic hydroxyl groups (and other oxygen donor ligands) with a
sties of m~ ofien corre~ we~ Withthe values”of log (&-) for the me m&d& Thk
methcd was modified for metals ccmpkxing wih lign~ degradation products in black liquor, by
using liganda otherthan OH. as the reference. The log (Q’s for black liquor correlated very well
with the log (Q’s for pyridine-2,6-dicarboxylic acid and nitriletiracetic acid. Since there is a
large database of formation constants fbr these two chelating reagents, these correlations can be
used for edrnating formation constants forNPEs that werenot evaluated inthis project.
Polysaccharides form much weaker oomplexes with metal ions than do organics that contain
phenolic hydroxyl groups. However, in filtrates where kraft lignin or extractives are abse@
polysacoharide complexes with metals may account for a significant fkaction of the total
dissolved metals.
I). The Metals Binding Capacity ofWood Pulp Fibers
Pulp fibers bind metals via ion exchange with hydrogen ions (or other metals) on carboxylic acid
andphenolic hydroxyl sites. A significant fktion of most metals input with wood are sorbed or
precipitated on the pulp fibers and carried into the bleach plant. The acid bleach stages remove
the metals, replacing them with hydrogen ions. In alkaline bleach stages, the metals are resorbed
or reprecipitated onthe fibers.
k this study, pulp samples were obtained from aTCF bleached pulp mill for use m metal sorption
studies. Pulp samples were obtained from the brownstock washers and fkomthe various bleach
stage washers. Each pulp sample was analyzed for Kappa number, carboxylic acid and phenolic
hydroxyl conteng using standard analytical methods. The carboxylic acid content of the pulp
decreased modestly asthe bleaching sequence moved fromthe brownstock to third peroxide stage
(P3), whereas the phenoiic hydroxyl group content decreased tc nearly zero by stage P3.
Unbleached brcwnstock pulp contained carboxylic acid and phenolic hydroxyl groups in
approximately in equal amounts, whereas the fidly bleached (P3) pulp contained only carboxylic
acid groups. l%ese results are rncluded in Chapter V.
Correlationa were developed for the carboxylic acid content and phenolic hydroxyl content of
soilwood wood pulp fibers (see Chapter X). These correlations can be used to estimate the total
metal binding capacity of softwood pulp fibers. The verj limited data available fix hardwood
pulps suggests that the correlations may not apply forhardwood pulps.
l%e amounts of metals sorbed or precipitated on the pulp samples were measured for the as-
receved pulps (after washing with ion-flee water), after acid washing, and after acid washing and
ion exchange with various metals (see Chapter V). The as-received pulps contaiued mainly Ca,
Mg, and Na (-100-1000 mg of each metal per kg of pulp), and smaller quantities of Al, B%Fe,
K, ~ and Zn (-2-50 mg of each metal per kg of pulp). No other metals were present at levels
above their detection limits. Acid washing removed -90Y0 of each metal. Ion exchange of the
2
acid-washed pulps with sodi~ calcium ornickel ion finther reducedthe content of other sorbed
metals.
Thetotal metal sorption capacity ofpulp fibers ~ nearly neutral pH is essentially the same asthe
content of carboxylic acid groups onthe pulp fibers, when compared as chemical equivalents. At
pH greaterthan 8.5,the phenolic hydroxyl groups begin to dissociate and contribute to binding of
metals.
E. Sorption Equilibrium Constants forMetals with Wood Pulp Fibers
Sorption isotherms for Ba, C% CA Mu, Na, Ni, Pb, and Zn with three brownstock pulps, one
oxygen delignified pulp, and one filly bleached pulp were measured at neutral pH and 25, 50,
and 75”C. Allmetal ion adsorption isotherms were performed on Calcium-exchanged pulp in order
to provide a common basis fbr ion exchange equilibrium coefficients. The results are reported as
Freundlich isotherms (see Chapter 6). Selectivity coefficients for ion exchange equilibrium were
also extractedfromthe data fromthis studyandthe literature(fix M%seeChapter X).
The order ofaf6nity ofmetal ionsfir woodpulp fibersat25°Cis:
pb>Ni>fi>cd>~>~>Mg>~>Na
Metals had a higher aflhity fir unbleached brownstock pulp than bleached EOP and P3 pulps.
Sorption of all metals decreased with increasing tempemture from 25 to 75”C. At 25”C,the total
equivalents of metal sorbed exceededthe total available so@ion sites (carboxylic acid groups) by
up to 100%. At 75”C,the measured sorption capacity was the same as the available carboxylic
acid sites. The measured sorption capacity for metal ions on 02deliguified and fidly bleached
pulps was closer to 1 equivalent metal/equivalent -COOH than were the values tir brownstock
puips.
The competitive adsorption versus pH of two metal ions, sodium and talc@ was also
measured. Two pulps were used, an unbleached brownstock and a fidly bleached pulp.
Measurements were made at 25°C over the pH range 2.5-11. Below pH 2.5 no metal ion
adsorption occ~ and the pulps remained in the hydrogen-exchanged form. For the fidly
bleached pulp, at pH 4.5 and above, the adsorption of both Na and Ca leveled off and remained
constat with increasing pH. However, fbrthe unbleached brownstock pulp,the adsorption ofboth
Na and Ca continued to increased from pH 4.5 to pH 11, reflecting the increasing availability of
phenolic hydroxyi groups as adsorption sites. About twice as much Calcium adsorbed as Sodiq
when compared relativeto the concentrations ofCalcium and Sodium ions msolution.
Adsorption kinetics were measured fbrthe adsorption of Bariuq Cadmi~ and Manganese ions
on Calcium-exchanged brownstock pulp at 25”C. Adsorption/desorption kinetics were also
measured at 25 and 75”C, for Nickel ions dimlacin~ Calcium on brownstock Dulm and for
Calcium ions (Ca+2)on Sodium-exchange~ ~ly br=ched pulp at 25°C. A&o~on was
complete within 10-30 minutes in all experiments. Temperature, initial metal concentration, and
the specific metal being adsorbed didnot have any significant effect onthe adsorption kinetics.
F. Thermodynamic Properties and Activity Coeffkients for Inorganic Species
Various commercial software packages are available that can calculate the distribution of metals
and other species in aqueous solutions at equilibrium. The more difficult component to acquire
canbethe thermodynamic properties and activity coefficient parameter databases required forthe
3