京都大学 / 新制・課程博士 / 博士(農学) / 甲第24661号 / 農博第2544号 / 新制||農||1098(附属図書館) / 学位論文||R5||N5442(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 矢野 浩之, 教授 和田 昌久, 教授 今井 友也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Pulp and paper mills are being placed under increasing pressure to maximise the use of the biomass being processed for pulp, and move towards integrated biorefineries (IFBRs), where a diverse range of products can be produced and not just pulp exclusively. Extracting hemicelluloses prior to the pulping process could increase the profitability of the mills as the hemicelluloses could be used to produce a number of additional products. Hemicelluloses are a plant polysaccharides with the most abundant hemicellulose in hardwoods being xylan, with xylose being the primary monosaccharide constituent of xylan. The majority of pulps produced in the Southern Hemisphere are done with hardwoods as feedstock, typically with the Kraft process. The attraction of the concept of extracting hemicellulose prior to pulping is further augmented by the fact that hemicellulose is underutilised in the Kraft process. In the Kraft process the hemicellulose is dissolved during pulping and burned along with lignin for the production of energy, however, hemicellulose has about half the heating value when compared to that of lignin. The main objective of this study was to find a pre-extraction method that is effective in releasing xylan from Eucalyptus grandis, the most important hardwood feedstock used for pulping in the Southern Hemisphere. The method also needs to be practical in terms of integrating it into the Kraft process and should have a minimal effect on pulp yield and subsequent paper qualities. Xylan extractions from E. grandis as feedstock were carried out with white liquor, green liquor and NaOH. Green liquor is the dissolved smelt originating from the recovery boiler in the Kraft process and consists mainly sodium carbonate and sodium sulphide. White liquor’s principal components include sodium hydroxide and sodium sulphide and is used in the digesters during the pulping stage of the Kraft process. NaOH is a make up chemical used in the Kraft process. These chemicals were chosen since they are all already present within the Kraft process. The suitability of these chemicals as xylan extraction methods is further bolstered by the fact that their alkalinity may actually reduce chemical usage in pulping. This provides scope for integration of hemicellulose extraction into Kraft pulping without implementing major changes to the existing industrial process. Moreover, alkali chemicals for pre-extraction allow for minimal effect on resulting pulp and paper. In terms of the extracted product, the alkaline conditions provided by these chemicals create conditions that are suitable for a high degree of polymerisation of hemicelluloses. Xylan pre-extracted chips from selected extraction conditions were subjected to varying pulping conditions, to replicate pulp yields and properties obtained with untreated E. grandis chips when using conventional pulping. Handsheets were also produced from the pulps produced under the highest pulp yield conditions, and these were tested for pulp quality properties. Furthermore, mass balances were performed to gauge the impact that hemicellulose pre-extraction would have using green liquor, white liquor and NaOH on the sodium and sulphur balances of the mill. From the extractions performed, the highest fraction of xylan recovered was 15.15% w/w utilising 2M NaOH, at 120°C for 90 minutes extraction time. This was followed by white liquor extraction at 13.27% w/w utilising 20% AA at 140°C for 90 minutes. Green liquor extraction produced the lowest xylan recovery at 7.83% w/w with 2% TTA and 160°C with an h-factor of 800. The residues from selected extraction conditions were utilised for these pulping optimisation experiments. Selected extraction conditions used for further pulping included 2% TTA and 160°C for green liquor, 20% AA and 120°C and 140°C extraction temperature for white liquor, as well as 2M concentration and 120°C for NaOH. The highest yielding pulping conditions were achieved with a 35% reduction in pulping chemicals and 45 minutes pulping time in combination with green liquor pre-extraction, while for pulping combined with white liquor pre-extraction a 50% reduction in chemicals and 30 minute pulping time was preferred. For pulping subsequent to NaOH pre-extraction a 75% reduction in the NaOH dosage and a 45 minute pulp time was preferred. All pulp steps were performed at 170°C. Unbeaten handsheets produced from the selected pulping conditions for white liquor and green liquor extracted chips showed similar physical properties (burst, tear, tensile indices) when compared to the control (pulps from non-extracted chips). However the greater quantity of xylan removed from cellulose fibres with NaOH extraction, resulted in pulps with lower xylan contents, which affected the burst and tear indices of the handsheets formed from these pulps. An increase in tear, while a reduction in the burst index, was observed for the pulp produced from NaOH extracted chips. It was concluded that although white liquor and NaOH extraction allows for greater xylan recovery, the large chemical expenditure associated with these methods will impose significant cost impacts on the existing Kraft process. From mass balances performed, green liquor xylan extraction due to its lower alkalinity, will be more forgiving in terms of additional make up chemical costs. It also allowed for minimum effect on both the pulp and paper quality, thus making it the most practical of the pre-extraction methods. However, whether the additional make chemicals required for the green liquor extraction method will be justified by the quantity of xylan extracted will only be answered by a thorough economic assessment, which was not in the scope of this project. / AFRIKAANSE OPSOMMING: Pulp- en papiermeule word onder toenemende druk geplaas om die gebruik van die biomassa wat vir pulp verwerk word, te maksimaliseer, en om te beweeg na geïntegreerde bioraffinaderye, waar ʼn groot verskeidenheid produkte vervaardig kan word, en nie slegs uitsluitlik pulp nie. Die ekstraksie van hemisellulose voor die verpulpingsproses kan die winsgewendheid van die meule verhoog, aangesien die hemisellulose gebruik kan word vir die vervaardiging van verskeie bykomende produkte. Hemisellulose is ʼn plantpolisakkaried, met xilaan as die hemisellulose wat die oorvloedigste in hardehout gevind word, en met xilose as die primêre monosakkaried-bestanddeel van xilaan. Die meerderheid van die pulp wat in die Suidelike Halfrond geproduseer word, word met hardehout as voerstof gedoen, tipies met behulp van die Kraft-proses. Die aanloklikheid van die konsep om hemisellulose voor verpulping te win, word verder versterk deur die feit dat hemisellulose in die Kraft-proses onderbenut word. In die Kraft-proses word die hemisellulose tydens verpulping opgelos en saam met lignien verbrand vir die opwekking van energie, maar hemisellulose het egter ongeveer die helfte van die verhittingswaarde van dié van lignien. Die vernaamste doelstelling van hierdie studie was om ʼn pre-ekstraksiemetode te vind wat xilaan doeltreffend van Eucalyptus grandis, die belangrikste hardhout-voerstof wat in die Suidelike Halfrond vir verpulping gebruik word, kan vrystel. Die metode moet ook prakties wees met betrekking tot integrering met die Kraft-proses, en dit moet ʼn minimale uitwerking op pulpopbrengs en gevolglike papiergehalte hê. Xilaan-ekstraksie uit E. grandis as voerstof is uitgevoer met wit loog, groen loog en NaOH. Hierdie chemikalieë is gekies omdat hulle reeds in die Kraft-proses teenwoordig is. Die geskiktheid van hierdie chemikalieë as xilaan-ekstraksiemetodes is verder ondersteun deur die feit dat hul alkaliniteit moontlik chemiese verbruik in verpulping kan verlaag, wat ruimte vir die integrasie van hemisellulose-ekstraksie in Kraft-verpulping laat sonder om grootskaalse veranderinge aan bestaande nywerheidsprosesse te implementeer. Alkali-chemikalieë vir preekstraksie lei boonop tot ʼn minimale uitwerking op resultante pulp en papier, terwyl die alkalitoestande, met betrekking tot die geëkstraheerde produk, toestande skep wat geskik is vir ʼn hoë mate van polimerisasie van hemisellulose. Uit die ekstraksies wat uitgevoer is, is die hoogste fraksie xilaan gewin deur die gebruik van NaOH teen 15.15% w/w met 2M NaOH, teen 120 °C vir 90 minute ekstraksietyd. Dit is gevolg deur witloog-ekstraksie teen 13.27% w/w met die gebruik van 20% AA teen 140 °C vir 90 minute. Groenloog-ekstraksie het die laagste xilaan-winning teen 7.83% w/w met 2% TTA en 160°C met ʼn h-faktor van 800 voortgebring. Houtspaanders wat aan xilaan-pre-ekstraksie met groen loog onderwerp is, het pulp met kappanommers en opbrengste soortgelyk aan dié van nie-geëkstraheerde spaanders voortgebring toe die chemiese lading met 35% verlaag is, in verhouding tot dít wat vir niegeëkstraheerde spaanders gebruik is. Xilaan-pre-geëkstraheerde spaanders met wit loog het ʼn 50%-vermindering in verpulpingschemikalieë gelewer in verhouding tot houtspaanders wat aan konvensionele verpulping onderwerp is. Die chemiese reduksie van groen loog was minder as dié van wit loog weens die laer alkalilading wat tydens hemisellulose-ekstraksie voor verpulping gebruik is. Vir witloog-ekstraksie kon pulpopbrengste gehandhaaf word, alhoewel pregeëkstraheerde spaanders met wit loog ʼn neiging getoon het om pulp met laer kappanommers voort te bring. Alhoewel pulp wat uit houtspaanders gemaak is wat aan NaOH-ekstraksie onderwerp is, gelei het tot ʼn 75%-vermindering van NaOH gebruik in verhouding tot dié van konvensionele verpulping, is verwag dat geen NaOH benodig sou word nie, aangesien die houtspaanders reeds tydens xilaan-ekstraksie aan 2M NaOH blootgestel is. Voorts, in die literatuur is verpulping uitgevoer ná 2M NaOH-ekstraksie sonder dat die toevoeging van NaOH tydens verpulping nodig was [61]. Handvelle is vervaardig uit die pulp wat in die hoogste pulpopbrengs-toestande vervaardig is, en dit is vir pulpgehalte-eienskappe getoets. Die verpulpingstoestande met die hoogste opbrengs is bereik met ʼn 35%-vermindering van verpulpingschemikalieë en 45 minute verpulpingstyd in kombinasie met groenloog-pre-ekstraksie, terwyl vir verpulping met witloogpre- ekstraksie ʼn 50%-vermindering van chemikalieë en 30 minute verpulpingstyd verkies is. Vir verpulping ná NaOH-pre-ekstraksie is ʼn 75%-vermindering van die NaOH-dosis en 45 minute verpulpingstyd verkies. Alle verpulpingstappe is teen 170°C uitgevoer. Ongeklopte handvelle vervaardig uit die gekose verpulpingstoestande vir witloog- en groenloog- geëkstraheerde spaanders het soortgelyke fisiese eienskappe getoon (bars-, skeuren trek-indeks) in vergelyking met die kontrole (pulp uit nie-geëkstraheerde spaanders). Die grootste hoeveelheid xilaan is egter uit sellulose vesel met NaOH-ekstraksie verkry, wat gelei het tot pulp met laer xilaaninhoud, wat die bars- en skeur-indeks van die handvelle wat uit hierdie pulp vervaardig is, beïnvloed het. ʼn Toename in die skeur-indeks, met ʼn afname in die bars-indeks, is waargeneem vir die pulp wat uit NaOH-geëkstraheerde spaanders vervaardig is. Die gevolgtrekking is gemaak dat alhoewel witloog- en NaOH-ekstraksie groter xilaanwinning moontlik maak, die groot chemiese uitgawe geassosieer met hierdie metode ʼn aanmerklike koste-impak vir die bestaande Kraft-proses inhou. Groenloog-xilaanekstraksie sal, weens die laer alkaliniteit, meer geskik wees met betrekking tot die koste van bykomende aanvullende chemikalieë. Dit hou ook ʼn kleiner uitwerking op die pulp- en papiergehalte in, wat dit dus die praktieste van die pre-ekstraksiemetodes maak. Of die bykomende chemikalieë nodig vir die witloog- en NaOH-ekstraksies egter geregverdig kan word deur die hoeveelheid xilaan wat gewin is, kan slegs deur ʼn deeglike ekonomiese assessering beantwoord word, wat nie binne die omvang van hierdie projek geval het nie.

<p>Chemical pulp fibres from wood are commonly used in products associated with packaging as well as with printing and writing. The prevalent way of liberating fibres is by subjecting wood chips to Kraft cooking. This process has a history of almost 130 years and should be both well described and well established. However, new products and new applications that use fibres as an important renewable resource make it all the more important that the properties of fibres be controllable. The properties of wood fibres are influenced by their carbohydrate composition which, in turn, is dependent on the cooking conditions used. This thesis studies the degradation and dissolution of the different carbohydrates during Kraft cooking and summarizes the results in kinetic expressions.</p><p>Industrial wood chips from Norway spruce (Picea abies) were cooked at a high liquor-to-wood ratio in an autoclave digester at varying concentrations of hydroxide ions, hydrogen sulphide ions and sodium ions as well as varying temperatures. The pulps were analysed for carbohydrate composition, kappa number, content of hexenuronic acid and the pure cellulose viscosity, i.e. only the cellulose content in the pulp sample was used for calculating the viscosity. Kraft cooking of Eucalyptus urophylla and Eucalyptus grandis was also studied, using industrial liquor-to-wood ratios, to examine the relationship between hexenuronic acids and the amount of xylan in the pulp samples.</p><p>For Kraft cooking of Norway spruce it was found that an increase in the concentration of hydroxide ions increased the rate of dissolution of the carbohydrates and the degradation of the cellulose degree of polymerization (DP). However, measured at a kappa number of 30, it is seen that a low hydroxide ion concentration can lower the carbohydrate yield and the pure cellulose viscosity dramatically. The hydroxide ion concentration not only affects the rate of dissolution but also the amount of xylan that reacts in the slower, final phase. Both cellulose and hemicelluloses were found to be affected by the hydrogen sulphide ion concentration. The dissolution of cellulose and hemicelluloses at varying sodium ion concentrations was found to be affected in different directions. The effect of sodium ion concentration on the DP was found to be dependent on the method of evaluation. The pulp viscosity was found to be affected twice as much by the sodium ion concentration than the pure cellulose viscosity was. For Kraft cooking of hardwood it was found that a high xylan yield not always is synonymous with a high hexenuronic acids content.</p>

Chemical pulp fibres from wood are commonly used in products associated with packaging as well as with printing and writing. The prevalent way of liberating fibres is by subjecting wood chips to Kraft cooking. This process has a history of almost 130 years and should be both well described and well established. However, new products and new applications that use fibres as an important renewable resource make it all the more important that the properties of fibres be controllable. The properties of wood fibres are influenced by their carbohydrate composition which, in turn, is dependent on the cooking conditions used. This thesis studies the degradation and dissolution of the different carbohydrates during Kraft cooking and summarizes the results in kinetic expressions. Industrial wood chips from Norway spruce (Picea abies) were cooked at a high liquor-to-wood ratio in an autoclave digester at varying concentrations of hydroxide ions, hydrogen sulphide ions and sodium ions as well as varying temperatures. The pulps were analysed for carbohydrate composition, kappa number, content of hexenuronic acid and the pure cellulose viscosity, i.e. only the cellulose content in the pulp sample was used for calculating the viscosity. Kraft cooking of Eucalyptus urophylla and Eucalyptus grandis was also studied, using industrial liquor-to-wood ratios, to examine the relationship between hexenuronic acids and the amount of xylan in the pulp samples. For Kraft cooking of Norway spruce it was found that an increase in the concentration of hydroxide ions increased the rate of dissolution of the carbohydrates and the degradation of the cellulose degree of polymerization (DP). However, measured at a kappa number of 30, it is seen that a low hydroxide ion concentration can lower the carbohydrate yield and the pure cellulose viscosity dramatically. The hydroxide ion concentration not only affects the rate of dissolution but also the amount of xylan that reacts in the slower, final phase. Both cellulose and hemicelluloses were found to be affected by the hydrogen sulphide ion concentration. The dissolution of cellulose and hemicelluloses at varying sodium ion concentrations was found to be affected in different directions. The effect of sodium ion concentration on the DP was found to be dependent on the method of evaluation. The pulp viscosity was found to be affected twice as much by the sodium ion concentration than the pure cellulose viscosity was. For Kraft cooking of hardwood it was found that a high xylan yield not always is synonymous with a high hexenuronic acids content.

Xylan is the main hemicellulose in birch, eucalyptus, and most other hardwood species. During kraft pulping a series of chemical reactions and physical processes involving xylan takes place. The processes studied here are the following: dissolution, degradation, redeposition onto the fibres, side-group conversion, and cleavage of side groups off the xylan backbone. The side group in native xylan consists of methylglucuronic acid, which is partly converted into hexenuronic acid during kraft cooking. Hexenuronic acid affects the pulp in terms of increased brightness reversion and reduced bleachability. The kinetics of the side-group cleavage and conversion reactions were studied using various analytical tools. The study revealed that the most common methods for methylglucuronic acid quantifcation can be signifcantly improved in terms of accuracy. A modifcation and combination of two of the methods was suggested and evaluated. In order to minimise the hexenuronic acid content, a common suggestion involves the use of a high cooking temperature. The kinetic study found that the degree of substitution of pulp xylan is only slightly affected by temperature, and that the observed effects are likely to be more associated with the xylan content of the pulp than with the hexenuronic acid content of the xylan. For the dissolved xylan, however, the degree of substitution indicated a high temperature dependency for birch kraft cooking. By collecting black liquors at different stages in the cook, different molecular properties of the dissolved xylan was obtained. The liquors were charged at later parts of the cook, making the dissolved xylan to reattach to the fibres. Depending on the molecular properties of the added xylan, the tensile strength properties of the produced paper were improved. These improvements in paper properties were correlated to the molecular behaviour of the added xylan in solution. / QC 20100702

Abstract Quality and economical requirements have raised evident need and interest in the industry to further develop continuous kraft cooking. A Kappa number, representing the cooking degree, is one of the few quality measures of cooking, and usually the only one measured on-line. Cooking degree is mainly controlled by temperature, chemical charge, and cooking time. Cooking conditions strongly depend on the packing degree of a chip column in the digester. At the same time, the packing of a chip column is affected by the cooking degree of chips. A typical problem is that the conditions and cooking degree in the process are not known. To achieve better control, more information about the cooking process is required. The aim of this thesis has been to more accurately describe the cooking conditions and phenomena in the digester scale. Conventional and Downflow Lo-Solids™ continuous cooking processes, producing both softwood and hardwood pulp, were investigated. Information achieved from measurements, and physical and chemical models describing chip scale phenomena, were utilised. Kappa number modelling was based on the use of an optimised and on-line adapted Gustafson's model. Modelling over grade change situations was accomplished by smoothly adjusting the model parameters as a function of temperature change profiles. Real-time profiles of cooking chemicals, temperature, and lignin and carbohydrates contents of chips within the processes were modelled. These real-time profiles were utilised in the modelling of the chip column's packing degree in the conventional process. Based on the developed models, blow-line Kappa numbers of both processes were predicted. By exploiting the prediction results, a new control strategy for the Kappa number was developed. In the strategy, set points for chemical charge and cooking temperature are iteratively solved by using only the developed prediction models of the blow-line Kappa number. It was shown that the modelled profiles of wood components and cooking chemicals can give new information regarding the continuous cooking processes. The modelling results are feasible in control purposes, and they also can support the operators' work. In the new control strategy, compared to the widely used H-factor based control, chemical concentrations can be more precisely taken into account.

The technique to produce pulp has improved and become more complex throughout the years. The purpose of pulping is to liberate the wood fibers and it can be done in two ways, either by chemically or mechanically separating the fibers. This thesis will focus on the commonly used kraft pulping process for eucalyptus and especially on the impregnation stage and how it affects kappa number and alkali consumption. This is done by studying the alkali charge, impregnation time and temperature for the impregnation stage while maintaining constant cooking parameters. This project has shown that the impregnation temperature affects the alkali consumption more than the impregnation time. A correlation between alkali consumption in the impregnation and the kraft cook was seen. When the consumption is high in the impregnation stage, a lower consumption was observed in the cooking stage. / Tekniken för framställningen av trämassa har utvecklats och blivit mer komplex genom åren. Massaframsställningens syfte är att separera träfibrerna ifrån varandra vilket kan utföras på två sätt, antingen på kemisk eller mekanisk väg. Denna studie kommer att fokusera på den beprövade sulfatkokningen och då i synnerhet hur impregneringssteget påverkar kappa numret och alkali konsumtion. För att uppnå detta studeras basningen för alkalin, impregneringstid och temperatur under impregneringen samtidigt som de övriga parametrarna hålls konstanta. Detta projekt har visat att impregneringstemperaturen påverkar alkali konsumtionen mer än tiden den impregneras. Andra studier som exempelvis Weiping Ban and Lucian A. Lucia 2003 och Joni Lehto &amp; Raimo Alén 2013 har har också påvisat denna relation mellan alkali konsumtion och impregneringstemperaturen. Denna studie har även visat en alkali konsumtionstrend mellan impregneringen och sulfatkoket. När konsumtionen är hög under impregneringen så är den lägre i koket.

The effect of xylan from different plant species on tensile properties of spruce pulp was studied. Xylans from spruce, birch, wheat straw and rice husks were mixed with the fresh white liquor and added at the later stages of separate kraft cooks, in exchange of the black liquor removed from the system at that time. Results show that xylans, from rice husk, wheat straw and birch, gave stronger pulps. However it was only possible to attach small quantities of xylans onto the fibers. Moreover, pulps containing birch and rice xylan were easier to beat than the other pulps in the study.

This thesis summarizes the outcome of work performed withthe objective to contribute to the knowledge and development ofthe kraft cooking process using spectrophotometricinterfaces. In kraft cooking, it is desirable to maximize the removal oflignin in the cook without loss of pulp strength. Theselectivity can be improved by exchanging some of the hydrogensulfide ion in the white liquor for polysulfides. Paper Ipresents a spectrophotometric method for in-line monitoring ofthe electrochemical production of polysulfide using anATR-probe for the UV-Vis range. A linear relation existsbetween the ATR-probe response and the concentration ofabsorbing species. Thus the process can be followed by simplemonitoring of a few wavelengths. A spectrophotometric monitoring system using a durableNafion ionomer membrane interface for continuous on-linemeasurement of sulfide and dissolved lignin during kraftcooking has previously been developed by our group. In paperII, the permeation of low molecular weight anions from liquorshaving high ionic strengths through a membrane in Na+ form hasbeen studied. A general relation between penetration and ionsize approximated by molecular weight has been established. Thepenetration of different anions can be explained as a diffusionthrough the winding membrane channels. Further the differentanions transport independently without being interfered by thesample matrix. In light of this validation, we applied the membraneinterface to the determination of anthraquinone-2-sulfonate(AQ-S) in alkaline pulping liquor. In paper III, a simple andrapid spectrophotometric method was developed and implementedon real samples. Interferences from other compounds penetratingthe membrane were minimized by reduction of the penetrated AQ-Sand measurement at 520 nm. This method is quick and can be usedon-line. Further, we extended the method to determination ofanthraquinone (AQ) in pulping liquor (paper IV). Although AQ isregarded as insoluble, it was found that the apparentsolubility of AQ in alkaline solutions increases considerablyin the presence of lignin, reaching 0.14 g/L at 90 oC. Thismakes the calibration of AQ possible. Time-resolvedmeasurements of dissolved AQ in 3 kraft-AQ pulping processeswere performed. The results show that the membrane has great potential aspart of a selective interface in applications where theconcentrations of small anions are to be monitored in mediawith high ionic strength. Keywords: Kraft cooking, On-line, Sulfide, Lignin,Polysulfide excess sulfur, Anthraquinone-2-Sulfonate (AQ-S),Anthraquinone (AQ), Nafion Membrane, UV-Vis, ATR-probe,Spectrophotometric.

<p>This thesis summarizes the outcome of work performed withthe objective to contribute to the knowledge and development ofthe kraft cooking process using spectrophotometricinterfaces.</p><p>In kraft cooking, it is desirable to maximize the removal oflignin in the cook without loss of pulp strength. Theselectivity can be improved by exchanging some of the hydrogensulfide ion in the white liquor for polysulfides. Paper Ipresents a spectrophotometric method for in-line monitoring ofthe electrochemical production of polysulfide using anATR-probe for the UV-Vis range. A linear relation existsbetween the ATR-probe response and the concentration ofabsorbing species. Thus the process can be followed by simplemonitoring of a few wavelengths.</p><p>A spectrophotometric monitoring system using a durableNafion ionomer membrane interface for continuous on-linemeasurement of sulfide and dissolved lignin during kraftcooking has previously been developed by our group. In paperII, the permeation of low molecular weight anions from liquorshaving high ionic strengths through a membrane in Na+ form hasbeen studied. A general relation between penetration and ionsize approximated by molecular weight has been established. Thepenetration of different anions can be explained as a diffusionthrough the winding membrane channels. Further the differentanions transport independently without being interfered by thesample matrix.</p><p>In light of this validation, we applied the membraneinterface to the determination of anthraquinone-2-sulfonate(AQ-S) in alkaline pulping liquor. In paper III, a simple andrapid spectrophotometric method was developed and implementedon real samples. Interferences from other compounds penetratingthe membrane were minimized by reduction of the penetrated AQ-Sand measurement at 520 nm. This method is quick and can be usedon-line. Further, we extended the method to determination ofanthraquinone (AQ) in pulping liquor (paper IV). Although AQ isregarded as insoluble, it was found that the apparentsolubility of AQ in alkaline solutions increases considerablyin the presence of lignin, reaching 0.14 g/L at 90 oC. Thismakes the calibration of AQ possible. Time-resolvedmeasurements of dissolved AQ in 3 kraft-AQ pulping processeswere performed.</p><p>The results show that the membrane has great potential aspart of a selective interface in applications where theconcentrations of small anions are to be monitored in mediawith high ionic strength.</p><p>Keywords: Kraft cooking, On-line, Sulfide, Lignin,Polysulfide excess sulfur, Anthraquinone-2-Sulfonate (AQ-S),Anthraquinone (AQ), Nafion Membrane, UV-Vis, ATR-probe,Spectrophotometric.</p>