Pulp Viscosity Research Articles

Acetosolv treatment of fibers from waste agave leaves: Influence of process variables and microstructural study

The Acetosolv process is an organosolv treatment that has been used to separate cellulose, hemicellulose and lignin from lignocellulosic material by taking advantage of the higher affinity for the lignin oligomers to dissolve in organic solvents. However, the process conditions depend on the material used, thus the influence of process variables (time process, acetic acid concentration and hydrochloric acid concentration) on the Acetosolv delignification of agave leaves to obtain cellulose was evaluated. Using a face-centered factorial design, it was possible to obtain high quality pulp by the Acetosolv pulping process with the following results: pulp yield 24.5%; 8.2kappa number and a pulp viscosity of 571mL/g. The low kappa number values obtained indicate a high degree of whiteness and a low content of lignin cellulose; this has been confirmed by confocal and scanning electron microscopy while Raman spectroscopy and X-ray diffraction analyses indicate that the type of cellulose remaining in pulp is cellulose I. Paper with a similar or higher quality than commercial Bond paper in terms of whiteness could was obtained from Acetosolv pulp. A comprehensive and quantitative view of the phenomena occurring in the delignification of agave fibers using different characterization techniques is demonstrated.

Pretreatment with xylanase and its significance in hemicellulose removal from mixed hardwood kraft pulp as a process step for viscose

The upturn of viscose fiber market has triggered an augmented dissolving pulp usage over the last decade. Dissolving pulp is feasible to obtain from kraft pulp after two essential steps including hemicellulose removal and subsequent pulp activation. Prerequisite of conversion being hemicellulose reduction can be gently done by using xylanase treatment prior to alkali extraction. Herein, the significance of xylanase treatment and the optimum xylanase dose required in conjunction with subsequent alkali extraction was investigated. An increase in xylanase dose prior to alkali extraction had no significant effect on pentosans while the Fock reactivity and viscosity both improved at the dose of 50AXU/g. Also, alkali extraction without xylanase pretreatment resulted in decreased Fock reactivity, alpha cellulose, brightness and viscosity of paper grade pulp. A moderate dose of xylanase prior to alkali extraction can thus be used to facilitate the hemicellulose removal while simultaneously protecting the native structure of cellulose.

Sodium sulphite pulping of Scots pine under neutral and mildly alkaline conditions (NS pulping)

Abstract Sodium sulphite pulping of Scots pine chips in the initial pH range of 7.5–9 was investigated at 180°C and 165°C (for 120–240 min), using chemical charges between 25 and 50% and anthraquinone (AQ) charges 0–0.2%. As a result, pulps with yields of 52–73% and kappa numbers of 35–106 were produced. Delignification was accelerated by higher Na2SO3 charges and temperatures, and by AQ addition, whereas the effect of initial pH was negligible. The high pulp yields at a given kappa number were attributable to high retention of hemicelluloses, especially that of galactoglucomannan. The relatively low viscosities of pulps were apparently caused by depolymerisation of cellulose by sulphite. The sulphonic acid groups in the pulps correlated well with the residual lignin content, although some sulphonation of polysaccharides may also be possible. The results indicate that pulping of softwood in buffer-free (without Na2CO3 and/or NaOH) sodium sulphite liquor may result in pulps with tailored characteristics.

Control of clay minerals effect in flotation. A review

The increased exposure to low grade ores highlights the importance of understanding phyllosilicate gangue mineralogy which consists of common gangue minerals. To improve the flotation performance and ore quality the negative effect of the clay minerals on flotation should be identified. The presence of clay minerals leads to problems, such as changing the froth stability, which are related to swelling behaviour, increase in pulp viscosity, overconsumption of reagents, slime coating and mechanical entrainment. The clay content in the ore is changing from time to time and it is necessary to provide quick solutions to the issues caused by the new ore composition. The objective of this paper is to give an overview how to control the colloidal properties of clay minerals on flotation.

Effect of shortening kraft pulping integrated with extended oxygen delignification on biorefinery process performance of eucalyptus

The aim of this work was to study the impact of shortening kraft pulping (KP) process integrated with extended oxygen delignification (OD) on the biorefinery process performance of eucalyptus. Data showed that using kraft pulps with high kappa number could improve the delignification efficiency of OD, reduce hexenuronic acid formation in kraft pulps. Pulp viscosity for a target kappa number of ∼10 was comparable to that obtained from conventional KP and OD process. The energy and alkali consumption in the integrated biorefinery process could be optimized when using a KP pulp with kappa number of ∼27. The process could minimize the overall methanol formation, but greater amounts of carbonate and oxalate were formed. The information from this study will be helpful to the future implementation of short-time KP integrated with extended OD process in actual pulp mill applications for biorefinery, aiming at further improvement in the biorefinery effectiveness of hardwood.

VISCOSIDADE APARENTE DA POLPA DE MURTA INTEGRAL EM DIFERENTES TEMPERATURAS

RESUMO: a industrialização de polpa de frutas frequentemente são utilizados processos térmicos (aquecimento e/ou resfriamento) que podem acarretar modificação na sua viscosidade, o que faz com que o estudo da influência da temperatura sobre o comportamento reológico desse tipo de produto seja de grande importância. Dados da viscosidade aparente de polpas de frutas são utilizados no projeto de equipamentos e na otimização de processos. Diante disso, objetivou-se avaliar a influência da temperatura na viscosidade aparente da polpa da murta. As análises reológicas foram conduzidas em um viscosímetro Brookfield modelo DV-II + Pro. As curvas de viscosidade aparente em função da taxa de deformação foram descritas pelos modelos reológicos de Sisko, Lei da Potência e de Falguera-Ibarz. A polpa da murta integral foi classificada como fluido não-newtoniano e pseudoplástico. O comportamento deste fluído pode ser bem descrito pelos modelos de Sisko, Lei da Potência e Falguera-Ibarz, com destaque para o modelo de Sisko. O efeito da temperatura sobre a viscosidade aparente foi descrita por uma equação tipo Arrhenius, com a energia de ativação apresentando altos valores à baixas taxas de deformação.

Application of pure, thermostable, alkali-tolerant xylanase in bleaching of oxygen-delignified pine kraft pulp

The effect of oxygen (O2)-delignified pine kraft pulp pretreatment by high-purity, thermostable, and alkaline-tolerant xylanases on elemental chlorine free (ECF) bleaching of O2-delignification kraft pulp was studied. The study found that xylanase pretreatment preserved the intrinsic viscosity and yield of O2-delignified pulp while causing about 7% of delignification with high delignification selectivity. The xylanases with high purity, higher thermostability (75°C~80°C) in highly alkaline media (pH 8.0~9.5) could be applied on an industrial scale. Pulp pretreatment by the high-purity, thermostable, and alkaline tolerant xylanases could improve pulp brightness or reduce the chlorine dioxide (ClO2) consumption. In a D0ED1D2 bleaching sequence using the same amount of ClO2, the xylanase-pretreated pulp obtained a higher brightness (88.2% vs. 89.7% ISO) at the enzyme dose of 2 U/g pulp; or for the same brightness as control (88.2% ISO), the ClO2 dosage in the D0 stage was reduced by 27%, which represents a 16% savings in total ClO2 used for bleaching.

Numerical simulation of turbulent pulp flow of concentrated suspensions: Influence of the non-Newtonian properties of the pulp

ABSTRACTComputational tools such as Computational Fluid Dynamics can be useful to predict the flow of pulp suspensions. The present study aims to simulate numerically the flow of concentrated pulp suspensions using CFD tools. A commercial CFD software was used, Ansys Fluent, to simulate the turbulent flow of Eucalyptus and Pine suspensions. A pseudo-homogenous approach was followed by considering the pulp viscosity as a function of shear rate and pulp consistency. The model takes into account the existence of a very thin layer surrounding the core region, near the pipe wall. It is studied the influence of the presence of fibers in the lubrication layer, by considering that the pulp consistency depends on the distance to the pipe wall. Two low-Reynolds number (LRN) k-ϵ turbulence models, Abe-Kondoh-Nagano and Chang-Hsieh-Chen, implemented in Ansys Fluent by using User-Defined-Functions, were studied. The drag reduction effect observed experimentally could be reproduced by both models. The LRN models were modified taking into account the modifications proposed in literature for the turbulent flow of polymers and solid particles when a drag reduction effect is present. The models were validated by comparing the calculated pressure drop with the experimental values.

Comparison of sensory and compositions of five selected persimmon cultivars (Diospyros kaki L.) and correlations between chemical components and processing characteristics.

Persimmon is one of the most popular and valuable fruits in markets because of its distinguished flavor as well as its significant benefits to health. The present study systematically compared the sensory characteristics and chemical compositions of five commercial persimmon fruits, and the correlations between chemical components and processing characteristics were also included. Our results showed that obvious differences in aroma and taste were found among the cultivars. Likewise, the contents of chemical components including sugar, total phenol, β-carotene and ascorbic acid, varied significantly (p<0.05) across different persimmon cultivars. The processing characteristics of persimmon fruit closely correlated with the chemical compositions. Pectin (r=0.76, p<0.01) and total phenol (r=0.576, p<0.05) were found to enhance the viscosity of persimmon pulp, and the colour of persimmon powder was greatly influenced by β-carotene, ascorbic acid and sugar contents (r=0.823, -0.729 and -0.685, p<0.01, respectively). Powder recovery of persimmon was positively correlated with pectin content (r=0.503, p<0.05) and negatively related to total sugar content (r=-0.668, p<0.01). Pectin content exerted positive effect (r=0.719, p<0.01) on hygroscopicity of persimmon powder, and the powder solubility showed a positive correlation to sugar and a negative relationship to pectin contents (r=0.662 and -0.716, p<0.01, respectively). In addition, a positive correlation (r=0.642, p<0.01) of the content of ascorbic acid to phenolic retention was also observed.

Effect of Tree Age and Active Alkali on Kraft Pulping of White Jabon

White Jabon (Anthocephalus cadamba Miq.) is one of the fast growing species in Indonesia and has the potential as the raw material for pulp and paper. In this research, 3, 5, and 7 years old White Jabon woods were pulped under different active alkali charge of 15%, 18%, 21%, 24%, and 27%, and its effect on delignification degree, kappa number, pulp yield, pulp viscosity, brightness, unbeaten freeness, and delignification selectivity was investigated. The results showed that tree age and active alkali concentration influenced the quality of pulp and pulping properties, except for that of unbeaten freeness. Delignification degree increased with increasing active alkali charge, and this brought about the decrease of pulp kappa number. The pulping yield tended to decrease below the Klason lignin of approximately 4%. Even though the 3 years old wood resulted in the highest brightness and highest delignification selectivity, the highest pulp viscosity was obtained with the 5 years old wood. The dominant fiber length of all wood ages was in the range of 1.2 - 2.0 mm. The 3 years old wood was considered to be the most promising raw material for kraft pulping in the view point of pulping properties, pulp quality and harvesting rotation.

The effect of the outermost fibre layers on solubility of dissolving grade pulp

Dissolving pulps are used to manufacture various cellulose derived products through cellulose dissolution. Solubility of cellulose pulp has been claimed to be strongly dependent on the porosity development, the degree of polymerisation and the pulp viscosity. The removal of external cell walls has been proposed to have a key role in the pulp solubility. In this paper, the effect of the outermost surface layers on the solubility of a dissolving grade pulp was studied. Furthermore the effect of mechanical peeling and combined mechanical and enzymatic treatment on pulp solubility was compared. Based on the results combined mechanical and enzymatic treatment efficiently opens up the fibre structure and has a clear positive effect on the solubility of dissolving pulp. It seems that long fibre fraction is less accessible to solvent chemicals than the other pulp fractions. Mechanical peeling of outer fibre layers does not improve fibre dissolution to NaOH/ZnO. Thus, it seems that peeling alone is not a sufficient pre-treatment prior to dissolution. The results also revealed that the peeling treatment does not enhance the effects of enzymes as the studied mechanical treatment does.

Kraft Pulping of Reduced Metal Content Eucalyptus Wood: Process Impacts

The effect of using acid pretreated eucalyptus wood chips in the Lo-Solids® pulping process was evaluated in the laboratory. Lo-Solids® cooking technology was chosen to evaluate the impact of acid pretreatments on the cooking performance, brown stock chemical composition, and black liquor heating value. The acid leaching stage reduced the contents of transition metals and other non-process elements in the wood chips and in the pulps produced. Benefits were detected in terms of the reduction in white liquor charge, increase in pulp yield, as well as pulp viscosity and black liquor heating value. Carbohydrate content and other wood/pulp constituents were not affected by the acid leaching pretreatments.

Comparison of pulp species in IONCELL-P: selective hemicellulose extraction method with ionic liquids

Abstract In our recent studies, it was demonstrated that the IONCELL-P process selectively dissolves hemicelluloses from bleached birch kraft pulp in a mixture of 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) and water as a solvent system. The IONCELL-P method refines paper-grade pulp to dissolving pulp with &lt;5% hemicelluloses and allows isolation of polymeric xylan without yield losses or polymer degradation. This paper is a comparative study where paper-grade pine, birch, and eucalyptus pulps are subjected to the IONCELL-P process with two [emim]-based ionic liquids (ILs), i.e. [emim]acetate and [emim]dimethylphosphate. Also, the effect of an endoglucanase pretreatment was investigated to check whether 1) the pulp viscosity could be adjusted for the following process steps before the hemicellulose extraction and 2) the decreasing pulp viscosity would open the fiber structure and thus enhance the extraction. Under optimum conditions, the birch xylan content could be reduced from 25.4% down to 1.3% and for eucalyptus from 16.6% to 2.4%. Pine pulp xylan and glucomannan were decreased from 8.1% and 7.1% to 0.9% and 2.2%, respectively. The residual hemicellulose contents of the pine pulp could be further decreased with a hemicellulase pretreatment. The selectivity of the dissolution towards hemicelluloses was better for hardwoods. Adjusting the pulp viscosity by endoglucanase prior to the IONCELL-P process reduced the selectivity as short-chain cellulose molecules were extracted along with the hemicelluloses.

Application of response surface method of optimization in flocculant assisted filtration of uranium bearing alkaline leach slurry of limestone origin

Leach slurries of alkaline nature often show very low rate of filtration due to high pulp viscosity contributed by dissolved solutes in solution and very fine grained nature of the unleached solids. Maximisation of filtration performance generally needs exhaustive experimentation involving various parameters which influence the solid–liquid separation process. The study reported in this paper pertains to optimisation of parameters in vacuum filtration of uranium bearing alkaline leach slurry generated from a brecciated limestone ore using response surface methodology. The d80 size of solids in the leach slurry is 60 μm and the pH of the pulp is 9·5–10. Initial screening of various commercial flocculants of anionic, cationic and non-ionic nature was carried out using the capillary suction time (CST) as basis. Minimum CST was achieved using a combination of anionic and non-ionic flocculant namely the Indfloc (IF) 477 and Guargum. The dosages of the flocculant combination and the slurry temperature were optimised to achieve maximum rate of filtration with optimal cake moisture under vacuum filtration conditions.

Estimating process design gold extraction, leach residence time and cyanide consumption for high cyanide-consuming gold ore

Plant design parameters for gold extraction, leach residence time and cyanide consumption are generally determined from standard bench-scale bottle roll or agitation leach tests. The application of laboratory data to process design has essentially evolved from the testing of oxide or low cyanide-consuming ores. Such scale-up factors may not be appropriate for ores that deplete cyanide and oxygen since this interferes with gold extraction kinetics. High cyanide-consuming ores also exacerbate the differences between the conditions applicable to small batch tests and large continuous operations. Testing a reactive high-sulfide South American ore deposit necessitated the re-evaluation of conventional bench-scale cyanidation procedures. Pulp density can be a major factor affecting the results for plant design purposes and should be treated as a test work variable. As with high clay-bearing ore, where pulp viscosity can hinder mass transfer, minimizing the influence of test equipment on gold extraction kinetics may require low pulp densities. This introduces interpretative complexity since cyanide consumption changes as a function of pulp density. Activated carbon also consumes cyanide, so its effect has to be accounted for in the case of carbon-in-leach (CIL) or carbon-in-pulp (CIP) plant flowsheets. Since cyanide is an expensive reagent, often a major component of plant operating costs, it is important that the scale-up of cyanide consumption from laboratory to plant be representative. The traditional method of reporting cyanide consumption in bench-scale testing is questioned since it takes credit for residual free cyanide in leach tails. The projected plant consumption may be better estimated by using the total cyanide addition in a laboratory test. We propose a test work protocol that categorizes the cyanide consumption into its components but requires more extensive testing to generate design data. The ultimate validation of scale-up factors used by project engineers requires rigorous bench-scale versus commercial plant comparative data. Such data are not readily available.

Achnatherum inebrians straw as a potential raw material for pulp and paper production

Cellulosic pulps were prepared from Achnatherum inebrians straw using soda, soda anthraquinone (soda-AQ), and Kraft pulping processes. The main chemical compositions in A. inebrians straw are 70.5% holocellulose, 41.6% alpha-cellulose, and 18.2% lignin, similar to those in other non-wood materials. The conditions of a liquid/solid ratio of 4.5:1, a time-to-maximum temperature of 100 min, a maximum temperature of 165 °C and a time-at-maximum temperature of 40 min were used in all pulping processes. The results showed that the pulp yield was 35.12–37.01%, the kappa number was 13.23–17.67, drainage index was 19–21 °SR and the viscosity of pulps was 846–898 mL/g. Tear index, tensile index, burst index and brightness of the paper were 5.27–5.83 mN m2/g, 16.58–18.11 mN/g, 1.76–2.37 kPa m2/g and 40.7–43.1% ISO respectively. It is indicated that A. inebrians straw can be used as an alternative raw material for pulping.

Acid leaching and rheological behaviour of a siliceous goethitic nickel laterite ore: Influence of particle size and temperature

This study investigates the isothermal, batch, H2SO4 acid leaching behaviour of siliceous goethitic (SG) nickel (Ni) laterite ore and its links to pulp rheology. Specifically, the effect of feed ore particle size (−0.2 vs −2.0mm), leaching temperature (70 vs 95°C) and pulp rheology on Ni and pay metal, cobalt (Co) extraction kinetics and yield was studied for 4h on 40wt.% solid dispersions at pH 1. The leaching behaviour was distinctly incongruent, reflecting the disproportionate proliferation of major gangue mineral’s constituent elements (e.g., Fe, Al, Mg, Na, Si) alongside Ni and Co in the pregnant leach solution. At 70°C, Ni/Co extraction rates were notably lower (<20%) in contrast with 95°C where a significant increase in Ni/Co extraction to 78/77% and 74/77%, respectively, for the −0.2 and −2.0mm feeds occurred. The slurries displayed a non-Newtonian, shear thinning Bingham plastic rheological behaviour of which the viscosity and shear yield stress increased markedly in the course of 4h leaching. The pulp viscosity and shear yield stress were greater at lower temperature than at higher temperature and they were also greater in slurries with finer than coarser feed particles. The dynamic pulp rheology, however, had no marked effect on the overall Ni/Co extraction rates. Whilst the feed ore particle size had no remarkable impact on overall Ni/Co extraction, it led to noticeably higher acid consumption and enhanced slurry rheology in the finer sized ore. The mechanism of leaching the SG ore followed a two-stage, first order chemical reaction-controlled shrinking core model, the kinetics of which gave higher rate constants and lower activation energies for the release of Ni, Co, Fe and Mg in the first stage. A faster leaching process involving more reactive minerals during the first 30min is envisaged to be followed by leaching of the more refractory minerals.

Kinetics of Viscosity Decrease by Cellulase Treatment of Bleached Hardwood Kraft-Based Dissolving Pulp

A dissolving pulp of low cellulose viscosity represents a pulp of high quality; hence, it is often necessary to decrease the initial dissolving pulp viscosity. One so-called environmentally friendly approach to further reducing the dissolving pulp viscosity is to treat the dissolving pulp with cellulase enzymes. In this study, the kinetics of the decrease in cellulose viscosity during a cellulase treatment was investigated. The study showed that the kinetics of the cellulose degradation during a cellulase treatment can be divided into at least two phases, where the initial phase is very fast and the final phase is very slow. The kinetic two-phase model for the viscosity degradation that has been developed in this project can be used to predict and control the final pulp viscosity of dissolving pulps.

Bio-bleaching of Anthocephalus cadamba Kraft Pulp through Direct Fungal Treatment by FEQP Sequence

Aims: The study aims at mitigating pulp kappa number before bleaching to minimize pollution load. Study Design: An experimental study. Methodology: The various parameters of direct fungal (Coprinellus disseminatus MLK01) treatment (F-stage) of unbleached kraft pulp of Anthocephalus cadamba were optimized and compared with the results of enzymatically pre-bleaching. Finally, the pulp was bleached by EQP three-stage and XECEHH six stages bleaching sequences. Results: Direct fungal treatment (F-stage) delignified the Anthocephalus cadamba kraft pulp more selectively with Coprinellus disseminatus MLK01 compared to xylanase prebleached pulp from the same fungus and oxygen delignification. F-stage mitigated the unbleached pulp kappa number by 55.0% and improved brightness and viscosity by 17.3 and 7.63% respectively. Kappa number reduction and brightness improvement were 22.1 and 6.3% more in F-stage compared to XE-stage. The kappa number and pulp brightness of oxygen delignified were 0.9 and 5.2% less compared to F-stage. The viscosity of oxygen delignified pulp reduced drastically due to alkaline peeling reactions compared to XE-stage (‒26.86%) and F-stage (‒27.09%). The brightness and viscosity of XECEHH bleached pulp were 80.1% and 7.4 cps at a chlorine demand of 4.3% while FEQP bleached pulp produced brightness of 79.7% and viscosity 8.2 cps. COD and colour values in Original Research Article Lal et al.; BBJ, 8(4): 1-13, 2015; Article no.BBJ.18845 2 effluent generated during FEQP bleaching were 53.29% and 54.36% less compared to CEHH bleaching.

BIOMIMETIC TCF BLEACHING OF PULP BY SIMPLE INORGANIC COMPLEXES OF CUPRIC/COBALT ACETATE

Oxygen delignified kraft pulp from eucalyptus (E. urophylla × E. grandis) was catalytically pretreated in aerobic condition using ammonium persulfate in present of catalists like cupric acetate and/or cobalt acetate in acetic acid-water solution, i. e. S2O8 2- -Cu 2+ , S2O8 2- -Co 2+ and S2O8 2- -(Cu 2+ +Co 2+ ). Final bleached pulp after pretreatment with the three catalytic systems showed higher delignification (23.45%, 21.85% and 19.63% respectively), better optical properties (82.93, 82.18 and 81.92% ISO brightness respectively) and pulp viscosity (787, 791 and 762 mL/g respectively; mL/g: intrinsic viscosity unit of pulp) than the control pulp (14.12% delignification, 77.33% ISO brightness and 746 mL/g viscosity). S2O8 2- -Cu 2+ and S2O8 2- -Co 2+ showed similar reduction in hydrogen peroxide consumption (61.91%, 62.48%), and S2O8 2- -(Cu 2+ +Co 2+ ) showed a greater reduction in hydrogen peroxide consumption than the two treatments (83.05%). Some improvements in tensile and tear strength of the resulting pulp were observed. The new sequence also yields composite effluents with larger percentage of lignin aromatic compounds compared to the control.