Marie Bäckström - Academia.edu (original) (raw)
Papers by Marie Bäckström
BioResources
This paper studies the impact of refining heterogeneity on paper property development and pressab... more This paper studies the impact of refining heterogeneity on paper property development and pressability. Three trials were performed in different refining equipment. The results showed that the strength development was due mostly to the water retention value (WRV) and the fiber straightness. Curly fibers require more energy to reach a given strength property. A heterogeneous refining, which in this case was performed by mixing less refined and highly refined pulps in different proportions, increased the energy requirement to reach a given tensile index or tensile stiffness index. The pressability of the pulps was not affected by the refining heterogeneity. At a given WRV, the pulp had the same solids content after dynamic pressing independent of the degree of heterogeneity.
KTH Royal Institute of Technology, 2020
Although the pulp and paper mill processes have been operational for long time there is still a n... more Although the pulp and paper mill processes have been operational for long time there is still a need to understand the unit operations in paper making and how they interact with the ingoing pulp material. This is crucial in order to fully utilize the potential of the wood as well as of the unit operations. In order to do that it is vital to have an understanding about the produced pulp fibres, how they are constructed and how they respond to different conditions of their environment. The aim of this work has been to clarify how the environment influences the refining efficiency of kraft pulps in terms of energy requirement and paper property development. The main hypothesis has been that the swelling of the fibres, due to their inherited polyelectrolytic gel nature, will not only affect the fibre as such but also the strength and properties of the fibre flocs that are mechanically treated between bars in the refiner and in this way affect the refining efficiency. The main focus has been to study how the chemical environment, in particular the initial fibre swelling, affects the refining efficiency. Therefore, the influence of counter-ions to the charged groups, the number of charged groups, electrolyte concentration, pH and rheological behaviour was studied. Additionally, the importance of fibre flocculation for the refining efficiency was investigated by chemical means, i.e. to chemically flocculate and deflocculate a fibre suspension just before entering the refiner and evaluate the refining efficiency. An investigation to clarify the importance of refining homogeneity was also performed. The work was performed both on a laboratory scale and in pilot scale using industrial refiners to ensure the validity of the results. The importance of the counter-ions to the charged groups on refining was demonstrated. When the counter-ions was sodium the refinability, defined as the required energy input to reach a certain WRV or tensile index, was reduced by up to 50%. The more energy-efficient refining of pulps in the Na+-form may be explained as a co-operation between a higher osmotic pressure in the fibre wall and the mechanical stress applied during refining, so called “electrostatic repulsion-assisted refining”. When mechanical forces are applied on the fibre and the fibre wall, the electrostatic repulsion forces due to the ionization act as an additional aid to increase the swelling, and this in turn helps to delaminate the fibre wall. This “electrostatic repulsion-assisted refining” also resulted in another type of external fibrillation of the fibres than that produced for the reference pulp in calcium form. The fibrils were very short and tiny. The improved refining efficiency could not be attributed to any rheological effect such as floc strength or floc size. The number of charges correlated to refinabiliy of the pulp material, but there has to be a balance between the number of charges and ultrastructure of the pulp fibre. If too many charges were introduced, the internal ultrastructure was eventually damaged, and no property development was obtained in the refining. The importance of refining heterogeneity on paper properties was investigated by mixing less refined or unrefined pulps and highly refined pulps in different proportions giving a wide distribution on energy input to individual fibres, as well giving swelling distribution curves. The mechanical properties of the produced paper were surprisingly alike, and the influence of the extreme inhomogeneity was rather small. In a pilot paper machine trial, clear effects due to heterogeneous refining was only observed when 50% of the stock fed to the paper machine was unrefined. This implies that the mills can have large freedom in refining strategies without any significant negative impact on the tensile strength properties at a given density. Industriell tillverkning av massa och papper har skett under en lång tid. Trots detta så finns det fort-farande behov av att bättre förstå enhetsoperationerna vid tillverkningen. Detta är viktigt för att kunna utnyttja hela potentialen av såväl startmaterialet som för de enskilda enhetsprocesserna. För att göra detta är förståelsen för egenskaperna hos de producerade massafibrerna, hur de är uppbyggda och hur de svarar på olika förhållanden vid malningen viktiga. Målet med detta arbete har varit att klargöra hur malningseffektiviteten, dvs energibehov och utveckling av papperets mekaniska egenskaper påverkas av den omgivande miljön vid malningen av kemisk massa. Huvudhypotesen har varit att fibrerna ur svällningssynpunkt kan betraktas som polyelektrolytiska geler och att detta kommer att påverka fibern och även ha betydelse för styrkan hos fiberflockarna som utsätts för den mekaniska bearbetningen mellan bommarna i kvarnen och på så sätt påverka malningseffektiviteten. Huvudfokus har varit att studera hur den kemiska miljön, i synnerhet hur den initiala fibersvällningen, påverkar malningseffektiviteten. Därför har…
Nordic Pulp and Paper Research Journal
Appita Journal
The influence of modifications to the kraft process on the cooking selectivity and strength prope... more The influence of modifications to the kraft process on the cooking selectivity and strength properties of the pulp has been studied in the high Kappa number region. Three different process modifications were investigated: Modified Continuous Cooking (MCC), Isothermal Cooking (ITC) and Modified Batch Cooking. The results show that no improvements were obtained by these modifications. It is however important to note that the cooking conditions for modified kraft pulping to low Kappa numbers were applied to the higher Kappa number region without optimisation of the cooking conditions. The results also demonstrate that it is always an advantage to decrease the cooking temperature. A lower cooking temperature is beneficial for pulp yield, amount of rejects and pulp viscosity. If the cooking temperature is too high, the pulp quality may be affected negatively.
The refining of unbleached kraft pulps in their Na+-form has shown energy saving potential. In th... more The refining of unbleached kraft pulps in their Na+-form has shown energy saving potential. In this study, the fibre network strength of unrefined and laboratory refined samples of an unbleached neverdried kraft pulp in different ionic forms was studied. The external fibrillation and the fibre flexibility were also studied. The objective was to investigate whether the improved refinability of fibres in the Na+-form could be related to the floc network strength or to fibrillation characteristics. The results showed that the rheological properties may not explain the improved refinability of fibres in the Na+-form, since fibres showed similar rheological properties regardless of their ionic form. Measurements using the MMS (Pulp Measuring System) showed that fibres refined in the Na+-form have a larger amount of external fibrillation, and microscopic investigation confirmed that the characteristics of the fibrils are different for fibres refined in the Na+-form from those of fibres re...
Bioresources
Refining of bleached hardwood pulps and bleached softwood pulps having different counter-ions to ... more Refining of bleached hardwood pulps and bleached softwood pulps having different counter-ions to the charged groups within the fibres was studied. The results show that an energy reduction of 50% for the hardwood pulps and 20% for the softwood pulp can be achieved if the fibres are converted into the Na +-form prior to refining. The results also show that the amount of charged groups in the fibres is important for the refinability, which explains why the refining efficiency is much lower for bleached softwood fibres, which have a much smaller amount of charged groups than the bleached hardwood pulp.
Nordic Pulp and Paper Research Journal, 1999
Nordic Pulp and Paper Research Journal, 1999
ABSTRACT When pulp is separated into fibre fractions on the basis of size, the smallest fraction ... more ABSTRACT When pulp is separated into fibre fractions on the basis of size, the smallest fraction obtained is called fines. Primary fines are found in cooked pulp not subjected to beating and secondary fines are created in the cause of beating. Fines have higher lignin and metal ion contents than the fibre fractions of the pulp. In this study, the effect of the primary fines on cooking and bleaching has been investigated. The results showed that removal of the primary fines during cooking had no positive effect on the delignification. The pulp viscosity at a certain kappa number and the H-factor to reach this kappa number were the same, regardless of whether or not the primary fines were present. However, the primary fines had a profound effect on bleaching when a QP sequence was used. An increase of approximately 2 ISO-brightness units was obtained by removing the primary fines prior to bleaching. Pulps with and without primary fines showed no significant difference in metal ion content or light scattering coefficient. The light absorption coefficient was, however, higher in the pulp with fines. The improved bleachability of the pulps without fines was therefore probably caused by differences in lignin content and in the lignin structure rather than by differences in metal ion content.
Nordic Pulp and Paper Research Journal, 2000
Nordic Pulp and Paper Research Journal, 1999
ABSTRACT : The objective of this investigation was to study the influence of the kappa number and... more ABSTRACT : The objective of this investigation was to study the influence of the kappa number and extractives content on paper-to-paper friction and to explore whether the friction could be related to the surface free energy, measured by contact angle measurements. The experiments were performed on handsheets made from a number of commercial pulps with different kappa numbers. Both hardwood and softwood pulps were tested since they are known to have different amounts and different compositions of extractives. The chemical composition of the investigated handsheets made of softwood pulps had no influence on the friction. In contrast to the softwood papers, the friction of the hardwood paper increased when the extractives were removed. No general relation existed between friction and surface energy , determined by contact angle measurements. It still remains to be shown which is the key factor that describes the mechanism of paper-to-paper friction. The results also indicate the importance of knowing the prehistory of paper samples used for research within the field of friction.
Nordic Pulp and Paper Research Journal, 2009
The objective of the present investigation was to study the influence of flocculants and defloccu... more The objective of the present investigation was to study the influence of flocculants and deflocculants on refining efficiency. The refining was performed with the aid of a conical refiner at EuroFEX, and the refining response was evaluated as the change in fibre properties and in the mechanical properties of handsheets. Using the same furnish, an unbleached neverdried softwood pulp, the effect of fibre dimensions on floc strength was excluded as much as possible. The degree of flocculation was changed by addition of APAM, CPAM, guar gum and CMC. The floc strength was characterized using a parallel plate rheometer. The added chemicals, except for APAM, affected the relation between power input and gap clearance. To reach a certain power the fibres treated with guar gum, CMC or CPAM required a narrower gap clearance than the reference pulp or when APAM was added to the fibres. Refining at a narrower gap clearance increased the refining efficiency in terms of WRV and paper property development, as long as fibre length reduction could be avoided.
Nordic Pulp and Paper Research Journal, 2009
It has earlier been shown that the counter-ion to the charged groups in the fibre has a significa... more It has earlier been shown that the counter-ion to the charged groups in the fibre has a significant effect on the beatability of fibres, but large-scale investigations of this effect are scarce in the literature. The objectives of the present study were therefore to develop a technique to ion-exchange large quantities of industrial pulp into the Na +-form using complexing agents and to study the effect of industrial-scale refining on pulp fibres in the Na +-form and how the fibres respond to industrial-like papermaking. The results show that ion-exchange can indeed be conducted on a pilot-scale using complexing agents such as DTPA. The study further indicates that an energy reduction of 50% at a given WRV or tensile index may be achieved if the fibres are converted to Na +-form prior to pilot-scale refining. By applying these techniques in full-scale production, it should thus be possible to save significant amount of energy, especially in the case of papers made from unbleached pulp that usually demands a higher degree of beating to achieve sufficient strength.
Nordic Pulp and Paper Research Journal, 2000
Nordic Pulp & Paper Research Journal, 1998
The purpose of this investigation was to study the effect of moisture content, paper structure an... more The purpose of this investigation was to study the effect of moisture content, paper structure and surface energy on paper-to-paper friction. The friction measurements were performed using a newly developed apparatus, designed and constructed at STFI in cooperation with the US Forest Products Laboratory, FPL. This device allows for the measurement of the first static, S l , the third static, S3 and the kinetic, K, coefficients of friction. Experiments were conducted on different types of commercial papers and handsheets covering a wide range of surface energies, roughnesses and sheet structures. Different structures in the handsheets were created by beating, wet pressing and calendering. Friction increased with increasing moisture ratio. Friction could not however be significantly changed by the surface roughness or structure of the handsheets. Friction values for the smooth side were always found to be higher or equal to those for the rough side. It is suggested that these results and previous results in the literature can be explained by assuming that the contact area is higher for the smooth side and that it is the "micro-roughness" of these contact areas together with the intermolecular interactions that take place across the interfaces that determines the paper-to-paper friction.
hfsg, 2008
Fines are an essential component in the papermaking process because they have a profound influenc... more Fines are an essential component in the papermaking process because they have a profound influence on the behaviour of the wet web and on the mechanical properties of the final sheet. Primary fines are present in the pulp prior to refining, and secondary fines are produced during refining. In the present investigation, two commercially manufactured unbleached pulps with kappa numbers of 45 and 90 were studied in terms of how they responded to refining with respect to the quality of fibre and fines. Primary and secondary fines were collected and characterised and their impact on sheet strength was evaluated by addition of known amounts to a refined and decrilled pulp. All the measured paper strength properties improved when primary and secondary fines were added. The strength improvement was generally somewhat higher in the second case. The effect was more pronounced at a higher level of addition. We attribute the main strength improvements associated with fines to improved consolida...
Impulse technology is a high-intensity web consolidation technique in which water is removed from... more Impulse technology is a high-intensity web consolidation technique in which water is removed from a wet paper web by the combined action of mechanical pressure and intense heat. Pilot trials show t ...
Holzforschung, 2016
A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effec... more A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali (EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.
Holzforschung, 2016
Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregna... more Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.
Journal of Pulp and Paper Science
Nous avons etudie la sorption du sulfure durant le traitement du bois dans differentes conditions... more Nous avons etudie la sorption du sulfure durant le traitement du bois dans differentes conditions du procede et a l'aide de differentes compositions de liqueur de traitement. Nous avons aussi etudie des traitements avec differentes sortes de liqueur noire et constituants de liqueur noire. Nous avons observe que la sorption du sulfure par les copeaux de bois augmentait avec l'accroissement de la concentration des ions d'hydrosulfure, l'augmentation du temps de traitement, l'augmentation de la temperature de traitement et l'augmentation de la concentration des ions positifs. Par ailleurs, nous avons note que cette meme sorption diminuait avec l'augmentation de la concentration des ions d'hydroxyde. Le rapport entre les ions d'hydrosulfure et les ions d'hydroxyde doit etre d'au moins 6 si l'on veut obtenir une sorption elevee du sulfure. L'augmentation de la sorption du sulfure durant ce traitement a ameliore la viscosite de la pâte apres la cuisson subsequente de la pâte kraft. Des traitements realises avec differents types de liqueur noire ou avec une liqueur blanche (ne contenant pas de substances organiques) avant la cuisson de la pâte kraft ont montre que les subtances inorganiques dans la liqueur noire n'ont aucun effet sur la selectivite de la cuisson de la pâte kraft et sur les proprietes physiques de la pâte ecrue.
BioResources
This paper studies the impact of refining heterogeneity on paper property development and pressab... more This paper studies the impact of refining heterogeneity on paper property development and pressability. Three trials were performed in different refining equipment. The results showed that the strength development was due mostly to the water retention value (WRV) and the fiber straightness. Curly fibers require more energy to reach a given strength property. A heterogeneous refining, which in this case was performed by mixing less refined and highly refined pulps in different proportions, increased the energy requirement to reach a given tensile index or tensile stiffness index. The pressability of the pulps was not affected by the refining heterogeneity. At a given WRV, the pulp had the same solids content after dynamic pressing independent of the degree of heterogeneity.
KTH Royal Institute of Technology, 2020
Although the pulp and paper mill processes have been operational for long time there is still a n... more Although the pulp and paper mill processes have been operational for long time there is still a need to understand the unit operations in paper making and how they interact with the ingoing pulp material. This is crucial in order to fully utilize the potential of the wood as well as of the unit operations. In order to do that it is vital to have an understanding about the produced pulp fibres, how they are constructed and how they respond to different conditions of their environment. The aim of this work has been to clarify how the environment influences the refining efficiency of kraft pulps in terms of energy requirement and paper property development. The main hypothesis has been that the swelling of the fibres, due to their inherited polyelectrolytic gel nature, will not only affect the fibre as such but also the strength and properties of the fibre flocs that are mechanically treated between bars in the refiner and in this way affect the refining efficiency. The main focus has been to study how the chemical environment, in particular the initial fibre swelling, affects the refining efficiency. Therefore, the influence of counter-ions to the charged groups, the number of charged groups, electrolyte concentration, pH and rheological behaviour was studied. Additionally, the importance of fibre flocculation for the refining efficiency was investigated by chemical means, i.e. to chemically flocculate and deflocculate a fibre suspension just before entering the refiner and evaluate the refining efficiency. An investigation to clarify the importance of refining homogeneity was also performed. The work was performed both on a laboratory scale and in pilot scale using industrial refiners to ensure the validity of the results. The importance of the counter-ions to the charged groups on refining was demonstrated. When the counter-ions was sodium the refinability, defined as the required energy input to reach a certain WRV or tensile index, was reduced by up to 50%. The more energy-efficient refining of pulps in the Na+-form may be explained as a co-operation between a higher osmotic pressure in the fibre wall and the mechanical stress applied during refining, so called “electrostatic repulsion-assisted refining”. When mechanical forces are applied on the fibre and the fibre wall, the electrostatic repulsion forces due to the ionization act as an additional aid to increase the swelling, and this in turn helps to delaminate the fibre wall. This “electrostatic repulsion-assisted refining” also resulted in another type of external fibrillation of the fibres than that produced for the reference pulp in calcium form. The fibrils were very short and tiny. The improved refining efficiency could not be attributed to any rheological effect such as floc strength or floc size. The number of charges correlated to refinabiliy of the pulp material, but there has to be a balance between the number of charges and ultrastructure of the pulp fibre. If too many charges were introduced, the internal ultrastructure was eventually damaged, and no property development was obtained in the refining. The importance of refining heterogeneity on paper properties was investigated by mixing less refined or unrefined pulps and highly refined pulps in different proportions giving a wide distribution on energy input to individual fibres, as well giving swelling distribution curves. The mechanical properties of the produced paper were surprisingly alike, and the influence of the extreme inhomogeneity was rather small. In a pilot paper machine trial, clear effects due to heterogeneous refining was only observed when 50% of the stock fed to the paper machine was unrefined. This implies that the mills can have large freedom in refining strategies without any significant negative impact on the tensile strength properties at a given density. Industriell tillverkning av massa och papper har skett under en lång tid. Trots detta så finns det fort-farande behov av att bättre förstå enhetsoperationerna vid tillverkningen. Detta är viktigt för att kunna utnyttja hela potentialen av såväl startmaterialet som för de enskilda enhetsprocesserna. För att göra detta är förståelsen för egenskaperna hos de producerade massafibrerna, hur de är uppbyggda och hur de svarar på olika förhållanden vid malningen viktiga. Målet med detta arbete har varit att klargöra hur malningseffektiviteten, dvs energibehov och utveckling av papperets mekaniska egenskaper påverkas av den omgivande miljön vid malningen av kemisk massa. Huvudhypotesen har varit att fibrerna ur svällningssynpunkt kan betraktas som polyelektrolytiska geler och att detta kommer att påverka fibern och även ha betydelse för styrkan hos fiberflockarna som utsätts för den mekaniska bearbetningen mellan bommarna i kvarnen och på så sätt påverka malningseffektiviteten. Huvudfokus har varit att studera hur den kemiska miljön, i synnerhet hur den initiala fibersvällningen, påverkar malningseffektiviteten. Därför har…
Nordic Pulp and Paper Research Journal
Appita Journal
The influence of modifications to the kraft process on the cooking selectivity and strength prope... more The influence of modifications to the kraft process on the cooking selectivity and strength properties of the pulp has been studied in the high Kappa number region. Three different process modifications were investigated: Modified Continuous Cooking (MCC), Isothermal Cooking (ITC) and Modified Batch Cooking. The results show that no improvements were obtained by these modifications. It is however important to note that the cooking conditions for modified kraft pulping to low Kappa numbers were applied to the higher Kappa number region without optimisation of the cooking conditions. The results also demonstrate that it is always an advantage to decrease the cooking temperature. A lower cooking temperature is beneficial for pulp yield, amount of rejects and pulp viscosity. If the cooking temperature is too high, the pulp quality may be affected negatively.
The refining of unbleached kraft pulps in their Na+-form has shown energy saving potential. In th... more The refining of unbleached kraft pulps in their Na+-form has shown energy saving potential. In this study, the fibre network strength of unrefined and laboratory refined samples of an unbleached neverdried kraft pulp in different ionic forms was studied. The external fibrillation and the fibre flexibility were also studied. The objective was to investigate whether the improved refinability of fibres in the Na+-form could be related to the floc network strength or to fibrillation characteristics. The results showed that the rheological properties may not explain the improved refinability of fibres in the Na+-form, since fibres showed similar rheological properties regardless of their ionic form. Measurements using the MMS (Pulp Measuring System) showed that fibres refined in the Na+-form have a larger amount of external fibrillation, and microscopic investigation confirmed that the characteristics of the fibrils are different for fibres refined in the Na+-form from those of fibres re...
Bioresources
Refining of bleached hardwood pulps and bleached softwood pulps having different counter-ions to ... more Refining of bleached hardwood pulps and bleached softwood pulps having different counter-ions to the charged groups within the fibres was studied. The results show that an energy reduction of 50% for the hardwood pulps and 20% for the softwood pulp can be achieved if the fibres are converted into the Na +-form prior to refining. The results also show that the amount of charged groups in the fibres is important for the refinability, which explains why the refining efficiency is much lower for bleached softwood fibres, which have a much smaller amount of charged groups than the bleached hardwood pulp.
Nordic Pulp and Paper Research Journal, 1999
Nordic Pulp and Paper Research Journal, 1999
ABSTRACT When pulp is separated into fibre fractions on the basis of size, the smallest fraction ... more ABSTRACT When pulp is separated into fibre fractions on the basis of size, the smallest fraction obtained is called fines. Primary fines are found in cooked pulp not subjected to beating and secondary fines are created in the cause of beating. Fines have higher lignin and metal ion contents than the fibre fractions of the pulp. In this study, the effect of the primary fines on cooking and bleaching has been investigated. The results showed that removal of the primary fines during cooking had no positive effect on the delignification. The pulp viscosity at a certain kappa number and the H-factor to reach this kappa number were the same, regardless of whether or not the primary fines were present. However, the primary fines had a profound effect on bleaching when a QP sequence was used. An increase of approximately 2 ISO-brightness units was obtained by removing the primary fines prior to bleaching. Pulps with and without primary fines showed no significant difference in metal ion content or light scattering coefficient. The light absorption coefficient was, however, higher in the pulp with fines. The improved bleachability of the pulps without fines was therefore probably caused by differences in lignin content and in the lignin structure rather than by differences in metal ion content.
Nordic Pulp and Paper Research Journal, 2000
Nordic Pulp and Paper Research Journal, 1999
ABSTRACT : The objective of this investigation was to study the influence of the kappa number and... more ABSTRACT : The objective of this investigation was to study the influence of the kappa number and extractives content on paper-to-paper friction and to explore whether the friction could be related to the surface free energy, measured by contact angle measurements. The experiments were performed on handsheets made from a number of commercial pulps with different kappa numbers. Both hardwood and softwood pulps were tested since they are known to have different amounts and different compositions of extractives. The chemical composition of the investigated handsheets made of softwood pulps had no influence on the friction. In contrast to the softwood papers, the friction of the hardwood paper increased when the extractives were removed. No general relation existed between friction and surface energy , determined by contact angle measurements. It still remains to be shown which is the key factor that describes the mechanism of paper-to-paper friction. The results also indicate the importance of knowing the prehistory of paper samples used for research within the field of friction.
Nordic Pulp and Paper Research Journal, 2009
The objective of the present investigation was to study the influence of flocculants and defloccu... more The objective of the present investigation was to study the influence of flocculants and deflocculants on refining efficiency. The refining was performed with the aid of a conical refiner at EuroFEX, and the refining response was evaluated as the change in fibre properties and in the mechanical properties of handsheets. Using the same furnish, an unbleached neverdried softwood pulp, the effect of fibre dimensions on floc strength was excluded as much as possible. The degree of flocculation was changed by addition of APAM, CPAM, guar gum and CMC. The floc strength was characterized using a parallel plate rheometer. The added chemicals, except for APAM, affected the relation between power input and gap clearance. To reach a certain power the fibres treated with guar gum, CMC or CPAM required a narrower gap clearance than the reference pulp or when APAM was added to the fibres. Refining at a narrower gap clearance increased the refining efficiency in terms of WRV and paper property development, as long as fibre length reduction could be avoided.
Nordic Pulp and Paper Research Journal, 2009
It has earlier been shown that the counter-ion to the charged groups in the fibre has a significa... more It has earlier been shown that the counter-ion to the charged groups in the fibre has a significant effect on the beatability of fibres, but large-scale investigations of this effect are scarce in the literature. The objectives of the present study were therefore to develop a technique to ion-exchange large quantities of industrial pulp into the Na +-form using complexing agents and to study the effect of industrial-scale refining on pulp fibres in the Na +-form and how the fibres respond to industrial-like papermaking. The results show that ion-exchange can indeed be conducted on a pilot-scale using complexing agents such as DTPA. The study further indicates that an energy reduction of 50% at a given WRV or tensile index may be achieved if the fibres are converted to Na +-form prior to pilot-scale refining. By applying these techniques in full-scale production, it should thus be possible to save significant amount of energy, especially in the case of papers made from unbleached pulp that usually demands a higher degree of beating to achieve sufficient strength.
Nordic Pulp and Paper Research Journal, 2000
Nordic Pulp & Paper Research Journal, 1998
The purpose of this investigation was to study the effect of moisture content, paper structure an... more The purpose of this investigation was to study the effect of moisture content, paper structure and surface energy on paper-to-paper friction. The friction measurements were performed using a newly developed apparatus, designed and constructed at STFI in cooperation with the US Forest Products Laboratory, FPL. This device allows for the measurement of the first static, S l , the third static, S3 and the kinetic, K, coefficients of friction. Experiments were conducted on different types of commercial papers and handsheets covering a wide range of surface energies, roughnesses and sheet structures. Different structures in the handsheets were created by beating, wet pressing and calendering. Friction increased with increasing moisture ratio. Friction could not however be significantly changed by the surface roughness or structure of the handsheets. Friction values for the smooth side were always found to be higher or equal to those for the rough side. It is suggested that these results and previous results in the literature can be explained by assuming that the contact area is higher for the smooth side and that it is the "micro-roughness" of these contact areas together with the intermolecular interactions that take place across the interfaces that determines the paper-to-paper friction.
hfsg, 2008
Fines are an essential component in the papermaking process because they have a profound influenc... more Fines are an essential component in the papermaking process because they have a profound influence on the behaviour of the wet web and on the mechanical properties of the final sheet. Primary fines are present in the pulp prior to refining, and secondary fines are produced during refining. In the present investigation, two commercially manufactured unbleached pulps with kappa numbers of 45 and 90 were studied in terms of how they responded to refining with respect to the quality of fibre and fines. Primary and secondary fines were collected and characterised and their impact on sheet strength was evaluated by addition of known amounts to a refined and decrilled pulp. All the measured paper strength properties improved when primary and secondary fines were added. The strength improvement was generally somewhat higher in the second case. The effect was more pronounced at a higher level of addition. We attribute the main strength improvements associated with fines to improved consolida...
Impulse technology is a high-intensity web consolidation technique in which water is removed from... more Impulse technology is a high-intensity web consolidation technique in which water is removed from a wet paper web by the combined action of mechanical pressure and intense heat. Pilot trials show t ...
Holzforschung, 2016
A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effec... more A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali (EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.
Holzforschung, 2016
Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregna... more Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.
Journal of Pulp and Paper Science
Nous avons etudie la sorption du sulfure durant le traitement du bois dans differentes conditions... more Nous avons etudie la sorption du sulfure durant le traitement du bois dans differentes conditions du procede et a l'aide de differentes compositions de liqueur de traitement. Nous avons aussi etudie des traitements avec differentes sortes de liqueur noire et constituants de liqueur noire. Nous avons observe que la sorption du sulfure par les copeaux de bois augmentait avec l'accroissement de la concentration des ions d'hydrosulfure, l'augmentation du temps de traitement, l'augmentation de la temperature de traitement et l'augmentation de la concentration des ions positifs. Par ailleurs, nous avons note que cette meme sorption diminuait avec l'augmentation de la concentration des ions d'hydroxyde. Le rapport entre les ions d'hydrosulfure et les ions d'hydroxyde doit etre d'au moins 6 si l'on veut obtenir une sorption elevee du sulfure. L'augmentation de la sorption du sulfure durant ce traitement a ameliore la viscosite de la pâte apres la cuisson subsequente de la pâte kraft. Des traitements realises avec differents types de liqueur noire ou avec une liqueur blanche (ne contenant pas de substances organiques) avant la cuisson de la pâte kraft ont montre que les subtances inorganiques dans la liqueur noire n'ont aucun effet sur la selectivite de la cuisson de la pâte kraft et sur les proprietes physiques de la pâte ecrue.