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This article focuses on a multiscale modelling approach to describe the delignification of softwood during the kraft pulping process. A framework for modelling the lignocellulosic feedstock on a fibre scale which considered the fundamental chemical components of wood as a distributed variable is re-assessed and extended to include chip-level phenomena such as diffusion limitations and initial component distributions within a softwood chip mixture. A new description of the wood chip is presented using a finite volume discretisation along one spatial dimension by simultaneously considering the anisotropic structural differences of the wood. Additionally, based on literature data, a distinction between the softwood chips' early- and latewood regions with their differences in densities and chemical composition is suggested. The presented model framework uses published sub-models for kinetics, diffusion etc. The validation and estimation of the remaining parameters are conducted from experimental data that quantifies the kappa number distribution of individual softwood fibres after kraft pulping. The investigation hypothesises a Gaussian distribution for the initial chemical component distribution within wood chips from a well-defined region. In contrast, a Log-normal distribution is used to describe the initial chemical distribution within a softwood chip mixture. The established sub-models for the kraft pulping process's kinetics and mass transfer phenomena could not predict the experimental data satisfactorily. However, modifying the sub-models by including a change in lignin reactivity and a temperature dependency of the lignin reactivity decline during the delignification progress could predict the essence of the observed experimental kappa number distribution.

Munksunds pappersbruk är ett integrerat massa- och pappersbruk som består av två fiberlinjer, en barr- och en lövlinje där båda kokarna är kontinuerliga med efterföljande tvättsteg. En kartering av COD (eng. Chemical Oxygen Demand) och natrium utfördes för båda linjerna för att utvärdera tvätteffektiviteten. COD anger hur mycket syre som krävs för att bryta ned det kvarvarande organiska materialet och natrium används som en indikator på tvättförlusten av kokkemikalierna. Karteringen utfördes genom att analysera in- och utgående flöden vid varje tvättsteg, exklusive kokarna. En förenklad metod användes, där tre flöden analyserades och den fjärde beräknades genom flödes- och massbalanser. Modellen som användes för att beskriva tvätteffektiviteten för respektive utrustning var tvättutbytet Y, som erhölls genom en massbalans. Studien visade att halten COD och Natrium minskar mest från början för respektive linje och når ett gränsvärde runt 8,2 kg COD/adt och 6,6 kg Na/adt för barrlinjen, respektive 8,5 kg COD/adt och 4,8 kg Na/adt för lövlinjen, där ytterligare substans inte kan tvättas bort. Båda linjerna tvättar likvärt med avseende på COD, men lövlinjen tvättar bättre med avseende på natrium. I det sista tvättsteget hade båda fiberlinjerna eliminerat 98% av den inkommande COD-mängden med massan från kokarna. Vidare hade barrlinjen eliminerat 86% och lövlinjen 93% med avseende på natrium i det sista tvättsteget. Utvärderingen av de olika tvättutrustningarna visade att DD-filtret i lövlinjen var effektivast både med avseende på COD och natrium, följt av PO-pressen. På barrlinjen var filter 1 mest effektivt med avseende på COD och natrium., A mapping of COD (Chemical oxygen demand) and sodium will be done to evaluate the different washing steps. COD describe the amount of oxygen needed to dissolve the organic matter left in the pulp and sodium is used as an indicator of the washing loss of the cooking chemicals. The in- and outgoing streams of the washing steps was analyzed to examine the efficiency. A simplified method was applied where three streams were analyzed and the fourth was calculated through flow-and mass balances. The model used to describe the wash efficiency in this study was the wash yield, which can be obtained by mass balances. The study showed that the content of COD and sodium decreased most in the beginning and reaches a limit value of 8,2 kg COD/adt and 6,6 kg Na/adt in the softwood pulp line and 8,5 kg COD/adt and 4,8 kg Na/adt in the soft wood pulp line, where no more content could be removed. Both pulp lines washed efficient with aspect of COD, but the hardwood pulp line washed more efficient in the aspect of natrium compared to the softwood pulp line. In the last washing step, both pulp lines had removed 98% of the ingoing COD from the digester. With aspect to natrium the softwood pulp line had removed 86% and the hardwood pulp line 93% in the last washing step. The evaluation of the different washing equipment showed that the DD-filter in the hardwood pulp line was the most efficient with aspect of both COD and Sodium, followed by the PO-press. In the softwood pulp line, filter 2 was the most efficient regarding both COD and Sodium. The flow- and mass balances turned out to be complicated at some of the washing steps, especially around the Q1-press in the hardwood pulp line and press 1-3 and filter 2 in the softwood pulp line. The reason for this could be that different functional chemicals are added before the Q1-press, which was not considered in this study, additional causes could be unidentified flows that affect the balances. The study was limited to only analyze three st

Understanding cellulose hornification provides crucial information regarding drying of pulp, paper, and other cellulosic materials as well as recycling them. By measuring drainage, fiber width, and water retention value of hardwood and softwood pulps before and after sheet forming and after different drying procedures at different achieved levels of solids, the hornification was evaluated. The water retention value was also measured for the pulps when dried from acetone to observe what happens when hydrogen bonds are not available in the liquid phase. The drainage and fiber width decreased with increasing solids content; the fibers became increasingly stiff with increased water removal. Water retention measurements indicated that hornification is a stepwise process with large drops in fiber flexibility as soon as the fibers are being processed and later after a certain amount of water has been removed. In sum, the fibers must achieve a certain solids content to show hornification, and hydrogen bonds in water draw the cellulose surfaces together to create hornification. The mechanism of hornification is believed to be driven by hydrogen bonds and related to the distance between cellulose chains inside the fiber wall. Other types of bonds are probably also present and help with the irreversibility of hornification.

Munksunds pappersbruk är ett integrerat massa- och pappersbruk som består av två fiberlinjer, en barr- och en lövlinje där båda kokarna är kontinuerliga med efterföljande tvättsteg. En kartering av COD (eng. Chemical Oxygen Demand) och natrium utfördes för båda linjerna för att utvärdera tvätteffektiviteten. COD anger hur mycket syre som krävs för att bryta ned det kvarvarande organiska materialet och natrium används som en indikator på tvättförlusten av kokkemikalierna. Karteringen utfördes genom att analysera in- och utgående flöden vid varje tvättsteg, exklusive kokarna. En förenklad metod användes, där tre flöden analyserades och den fjärde beräknades genom flödes- och massbalanser. Modellen som användes för att beskriva tvätteffektiviteten för respektive utrustning var tvättutbytet Y, som erhölls genom en massbalans. Studien visade att halten COD och Natrium minskar mest från början för respektive linje och når ett gränsvärde runt 8,2 kg COD/adt och 6,6 kg Na/adt för barrlinjen, respektive 8,5 kg COD/adt och 4,8 kg Na/adt för lövlinjen, där ytterligare substans inte kan tvättas bort. Båda linjerna tvättar likvärt med avseende på COD, men lövlinjen tvättar bättre med avseende på natrium. I det sista tvättsteget hade båda fiberlinjerna eliminerat 98% av den inkommande COD-mängden med massan från kokarna. Vidare hade barrlinjen eliminerat 86% och lövlinjen 93% med avseende på natrium i det sista tvättsteget. Utvärderingen av de olika tvättutrustningarna visade att DD-filtret i lövlinjen var effektivast både med avseende på COD och natrium, följt av PO-pressen. På barrlinjen var filter 1 mest effektivt med avseende på COD och natrium., A mapping of COD (Chemical oxygen demand) and sodium will be done to evaluate the different washing steps. COD describe the amount of oxygen needed to dissolve the organic matter left in the pulp and sodium is used as an indicator of the washing loss of the cooking chemicals. The in- and outgoing streams of the washing steps was analyzed to examine the efficiency. A simplified method was applied where three streams were analyzed and the fourth was calculated through flow-and mass balances. The model used to describe the wash efficiency in this study was the wash yield, which can be obtained by mass balances. The study showed that the content of COD and sodium decreased most in the beginning and reaches a limit value of 8,2 kg COD/adt and 6,6 kg Na/adt in the softwood pulp line and 8,5 kg COD/adt and 4,8 kg Na/adt in the soft wood pulp line, where no more content could be removed. Both pulp lines washed efficient with aspect of COD, but the hardwood pulp line washed more efficient in the aspect of natrium compared to the softwood pulp line. In the last washing step, both pulp lines had removed 98% of the ingoing COD from the digester. With aspect to natrium the softwood pulp line had removed 86% and the hardwood pulp line 93% in the last washing step. The evaluation of the different washing equipment showed that the DD-filter in the hardwood pulp line was the most efficient with aspect of both COD and Sodium, followed by the PO-press. In the softwood pulp line, filter 2 was the most efficient regarding both COD and Sodium. The flow- and mass balances turned out to be complicated at some of the washing steps, especially around the Q1-press in the hardwood pulp line and press 1-3 and filter 2 in the softwood pulp line. The reason for this could be that different functional chemicals are added before the Q1-press, which was not considered in this study, additional causes could be unidentified flows that affect the balances. The study was limited to only analyze three st

Enzymes are biological catalysts and are very specific, catalyzing either a single chemical reaction or a limited number of closely related reactions. For example, xylanases are enzymes that catalyze the cleavage of polymeric xylan and thereby break down this hemicellulose. The first xylanase enzyme preparations used in the bleaching process of chemical pulp also contained cellulase, which catalyzes the hydrolysis of cellulose. This obviously had an adverse effect on pulp yield and quality. Unfortunately, this setback gave enzyme-assisted pulp bleaching a negative reputation. At a later stage, enzyme producers managed to engineer enzyme production strains that generated cellulase-free xylanase preparations. However, due to the initial negative experiences with the earlier enzyme mixtures, only a limited number of companies in the pulp industry have seriously considered using these so-called second-generation enzymes in their bleach plants. It is apparent that these improved enzyme preparations would bring about significant benefits in terms of chemical cost savings and effluent quality. In addition to xylanase-aided bleaching, it is possible to improve the effectivity further by adding other enzymes, such as lipase and esterase, to create an enzyme cocktail. This may be particularly beneficial in the bleaching of hardwood pulp, such as white birch, which often encounters complex and troublesome problems with wood extractives. By adding different types of enzymes at more than one position in the fiberline, even further improvements are possible. The main objective of this review is to discuss the advantages of incorporating modern enzyme preparations in the bleaching of chemical pulp.

Renewable raw materials such as lignocellulose are inherently complex and demanding in chemical processing compared to petroleum-based feedstocks. This article addresses the challenge of developing a general model framework for modelling lignocellulosic feedstock on a fibre scale, considering its inherent heterogeneous nature in terms of the fundamental chemical component distribution in addition to its anisotropic structural properties. The presented model is tested and validated for the well-established kraft pulping process. Simulations and parameter estimation are carried out to investigate the kappa number distribution of softwood fibres during kraft pulping by using experimental data from the literature showing non-uniform delignification. A moving grid discretisation method for the distributed concentration variables is used to predict the reaction of the wood solids. The results suggest that an inherent fundamental chemical component distribution can be hypothesised as one source of the non-uniform delignification. The model indicates that a Gaussian distribution can be assumed for the initial lignin concentration within softwood. In addition, an investigation of the lignin kinetics suggests that the reactivity of lignin during kraft pulping decreases as the delignification progresses.

Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries.

Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries.

The objective in this work was to obtain a fine fraction of kraft pulp, with as high concentration as possible, in a pilot-scale fractionation with micro-perforated screen baskets. The influence of screen basket surface, hole size, feed concentration, pulp type and refining segment design was investigated. The results showed that a smooth screen basket surface improved the fractionation efficiency of the unrefined pulp compared to a profiled screen basket, despite a larger hole size. A significantly higher fine fraction concentration was obtained when using refined hardwood pulp compared to when using softwood pulp, which was explained with its lower average fibre length and narrower and thus more flexible fibre fragments. The pilot trials also showed that the screening process could be operated at feed concentrations similar to those directly after a refiner, 30-40 g/l. This was demonstrated in a process layout with partial recirculation where a refiner and a micro-perforated screen basket were operated in series in pilot scale.

Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries.

In our previous work, we demonstrated how lignin condensation and precipitation taking place in kraft pulping can be detected and even quantified by Fourier Transform Infrared (FTIR) spectroscopy. Because lignin reactions in acid sulfite pulping are very different from those occurring during kraft cooking, a new analysis method is proposed to rapidly analyze the condensed lignin in acid sulfite pulp. This kind of analysis is useful for sulfite pulp mills to detect the elevated risk of black cook. This paper presents and discusses the novel method using FTIR spectroscopy to rapidly analyze lignin condensation in softwood pulp samples from acid sulfite processes. Several softwood pulp samples from acid sulfite pulping at varying levels of condensation were included in this research. According to the results, FTIR spectroscopy allows indirect quantification of lignin condensation in a difficult matrix of wood constituents, such as in incompletely delignified acid sulfite pulp.

Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries.

Conversion of biomass into saleable biochemicals and fuels requires the use of a pretreatment to enable subsequent processing. Acid sulfite pulping is one of the most cost-effective strategies, because the chemicals are inexpensive and the technology is available on an industrial scale. It also allows the simultaneous production of cellulosic fibers and lignosulfonate. However, too little is known about the feasibility of acid sulfite pulping of tropical hardwoods. The objective of this research was to gain a better understanding of the response of Acacia mangium and Eucalyptus pellita in acid sulfite pulping. The plantation-grown hardwood chip samples were obtained from Sabah, Malaysia. The sulfite cooking experiments were carried out in autoclaves with temperatures of 130°C and 140°C and varied chemical charges. The results revealed that a cooking temperature of 140°C was needed to reach kappa numbers below 30, but this also resulted in much reduced fiber length and higher fines content than 130°C, probably due to the intensified acid hydrolysis. To reach kappa numbers below 20, more severe cooking conditions are needed. These results demonstrate that using A. mangium and E. pellita as feedstocks allows feasible production of chemical pulp and sulfonated lignin, which are intermediate products for biorefineries.