Eucalyptus globulus kraft process modifications: Effect on pulping and bleaching performance and papermaking properties of bleached pulps

BACKGROUND: Increasing the yield of the wood pulping process allows the reduction of specific wood costs. Process modifications with a great impact on pulp yield are the profiling of chemical charges and addition of anthraquinone (AQ). The aim of the present work is to investigate the influence of effective alkali (EA) profiling and addition of anthraquinone on E. globulus kraft pulping performance. The impact of such process modifications on the ECF bleaching process and on the papermaking properties of the resulting bleached pulps is also evaluated. RESULTS: An EA profiling cook may lead to a pulp yield gain, which is more significant as the total EA charge used in the kraft cook increases. AQ addition to kraft pulping leads to a significant yield increase. The ClO₂ charge required to fully bleach the pulps is lower for EA profiling and higher for kraft + AQ unbleached pulps. Bleached AQ pulp presents a high beatability due to high pulp xylan retention. CONCLUSION: A low total EA charge is the key parameter for high polysaccharide retention on pulp. AQ addition constitutes a feasible strategy to increase pulp yield. Bleaching performance and papermaking properties of pulps produced with the three different methods may be affected by the kraft pulping modifications. Copyright © 2008 Society of Chemical Industry     

Extractive Profiles in the Production of Sulfite Dissolving Pulp from Eucalyptus Globulus WOOD

The profile of major families of extractives soluble in acetone and dichloromethane during the production of acid sulfite dissolving pulp from Eucalyptus globulus wood was assessed. Nearly 85% of total extractives were removed from wood during pulping and nearly 11% in the course of E-O-P pulp bleaching and secondary pulp screening. Unlike extractives of polyphenolic origin that were almost completely removed after the alkaline extraction stage (E), fatty acids were the main retained component in fully bleached pulp followed by sterols and fatty alcohols. Throughout the bleaching steps, the profiles of extractives were not necessarily decreasing and depended on their reactions with bleaching reagents and the presence of auxiliary chemicals (e.g. antifoams). In this context, the content of fatty acids and fatty alcohols was mostly vulnerable. It has been suggested that Fock reactivity of dissolving pulps is unaffected by extractives at concentrations up to 0.3%.     

TCF BLEACHED PULPS FROM MISCANTHUS SINENSIS BY THE IMPREGNATION RAPID STEAM PULPING (IRSP) PROCESS

ABSTRACT

The production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated in this work. The impregnation rapid steam pulping process (IRSP) involves impregnating of the lignocellulosic material with the pulping liquor, withdrawing the excess liquor and rapidly steaming the impregnated material at 180–200°C for a short time. In this paper the process variables and their effect on the kappa number, yield and viscosity of the unbleached pulps are discussed. Bleaching by an ozone-based TCF sequence was tested, and the papermaking properties of the bleached pulp were determined. A kappa number of 19 was obtained by impregnating at an alkali charge of 30 + 0.1% anthraquinone carboxylic acid (AQCA) and pulping at 180°C for only 15 min. Kappa was reduced to 16 by extending pulping time to 26 min. The alkali consumption during impregnation and pulping was 10.2 g NaOH/100 g of dry Miscanthus. Screened pulp yield, viscosity and brightness for this pulp were 54.6%, 913 mL/g and 37.3%, respectively. After bleaching, the pulp had an ISO brightness of 87.4% and a viscosity of 700 mL/g. Refining in a PFI mill provided optimal strength properties of the bleached pulp at 4500 revolutions (71°SR): breaking length 7.2 km, tensile index 72 N m/g, and burst index 4.3 kN/g. Tear index was 7.9 mN m²/g at this degree of refining.     

Totally chlorine‐free bleaching of Acetosolv pulps: a clean approach to dissolving pulp manufacture

Eucalyptus globulus wood samples were delignified in media containing concentrated acetic acid, water and hydrochloric acid (Acetosolv process) under optimized conditions, and the pulps were subjected to totally chlorine‐free (TCF) bleaching. Alkaline extractions, oxygen delignification, ozone treatment, enzymatic xylan removal and hydrogen peroxide oxidation in alkaline media were investigated as individual steps in selected bleaching sequences. Under the best conditions, fully bleached pulps with favourable characteristics for dissolving pulp manufacture were obtained. © 2001 Society of Chemical Industry     

Behavior of Eucalyptus Kraft Pulp Extractives Components across ECF Bleaching and Their Impact on Brightness Reversion

Abstract

This study investigated the chemical composition of the dichloromethane and acetone extracts of eucalypt pulp across D(EP)DP and AZDP bleaching sequences by gas chromatography-mass spectrometry (GC-MS). The bleaching stages led to the partial removal and to several oxidative transformations of fatty acids and sterols, the main lipophilic extractives found in the unbleached pulp. The pulp samples were bleached to 90–91% ISO by D(EP)DP and AZDP sequences and their brightness stability and chemical characteristics determined. The effect of aging on brightness was investigated. The AZDP bleaching sequence resulted in pulps of higher brightness stability. Furoic structures representing the main acid degradation products of HexA are suggested as the actual intermediates that cause yellowing by forming colored compounds. The AZDP process removed larger amounts of HexA across bleaching.     

Infrared Absorption Spectra of Cellulose Pulps of Palm Tree

Palm leaves are used for the production of different cellulose pulps; their properties are investigated, the resulting pulps were bleached by a multistage process, the effects of the addition of solvent during the pulping process on the chemical structure of the pulps are discussed. The strength properties of the paper which is produced from unbleached and bleached pulps increased with increasing cellulose percentage and decreasing lignin content in the pulp. Infrared absorption spectra were recorded for different unbleached and bleached pulp in the frequency range 200–4000 cm^-1 by using the alkali halide disk technique; the factors which affect the experimental technique were calibrated through these studies. The structural units within pulping yield (holocellulose, hemicellulose, cellulose, lignin, and ash) were interpreted within the pulp network structure by the infrared absorption spectra, where different samples of unbleached, bleached soda, and kraft pulps were also elucidated by IR spectra, after preheating at different temperatures and with using different ratios of organic solvents. The addition of organic solvents decreased or increased the crystallinity indices, depending on the type of solvent and the pulping temperature. It was also found that, at the same pulping temperature (155°C) and with the same percent of organic solvents in the pulping liquor, the asymmetry indices also the mean hydrogen bonding strength (A _OH/A_CH) of the unbleached soda pulps (organosolv or nonorganosolv pulping) were less than that of unbleached kraft pulps, except for the pulps obtained by pulping with dioxan at 155°C. The mean hydrogen bond strength of the bleached pulps decreased or increased, depending on the type solvent used and the pulping temperature.     

Mechanistic Differences Between Kraft and Soda/AQ Pulping. Part 1: Results from Wood Chips and Pulps

Abstract

Soda pulping catalyzed by anthraquinone (AQ) or 2-methylanthraquinone (MAQ) can produce hardwood chemical pulps similar to kraft pulps in all respect but for bleachability. Results accumulated in our laboratory suggest that the residual lignin in pulps from anthraquinone catalyzed processes is less reactive toward bleaching chemicals than that in kraft pulps. Analyses of pulps by periodate and permanganate oxidations suggest that the residual lignin from the non-sulfur processes contained more condensed structures than kraft residual lignin. The low reactivity of these structures is believed to be responsible for the lower brightness of bleached soda-AQ (SAQ) pulps. Pulping and bleaching trials with hardwood chips demonstrated that shortening of the cooking time and/or increasing the alkalinity is one strategy for improving bleachability of SAQ pulps. When sugar maple (Acer saccharum) chips were SAQ cooked for 1.0 and 2.0 h at 165°C, the higher kappa number pulp produced after 1.0 h of cooking bleached to a significantly higher brightness with a small increase in the chlorine dioxide application.     

Methanol-based pulping of eucalyptus globulus

The autocatalyzed pulping of Eucalyptus globulus wood with methanol-water mixtures was studied. A surface response design was employed to develop mathematical models describing the pulp properties as a function of cooking time, cooking temperature and methanol concentration. The ranges studied for these variables were 40–120 min, 170-200°C and 30-70% (w/w), respectively. The pulp properties modeled were kappa number, total yield, screenings content, screened yield and viscosity. Under the optimum cooking conditions pulps with low kappa number and acceptable viscosity can be obtained with a high yield.     

Modification of Loblolly Pine Chips with Ceriporiopsis subvermispora Part 2: Kraft Pulping of Treated Chips

Abstract

Loblolly pine (Pinus taeda) chips treated with Ceriporiopsis subvermispora for two or four weeks were pulped with different combinations of kraft pulping conditions to obtain a better understanding of the interaction between the fungal action and the pulping variables. Two different levels of effective alkali (18 or 22%), two times at maximum T_max (60 or 90 min), 22% sulfidity, and a T_max of 170°C, were used. The best delignification without adversely affecting pulp viscosity was found in pulps made from chips treated with the fungus for 2 weeks and at the mildest pulping conditions. At all pulping conditions there was a substantial decrease in the amount of rejects with 2 weeks of fungal treatment. Pulps from fungally‐treated chips refined more easily than the control pulp and strength properties of pulps of fungally‐treated chips were superior to those of the control pulp.     

Kraft pulping of Eucalyptus nitens wood chips biotreated by Ceriporiopsis subvermispora

Eucalyptus nitens and E. globulus are wood species used in kraft pulping in Chile and Australia. Although E. nitens adapts very well to cold regions it requires more severe cooking conditions to produce bleachable kraft pulps. An attempt was made to find out whether a pre‐treatment with Ceriporiopsis subvermispora would improve its performance during kraft pulping and the pulp properties. The biotreatment of the chips carried out for a period of 15 days resulted in 13.3% lignin loss and a limited glucan degradation (2%). The pulping of biotreated samples required lower active alkali charge to reach the target kappa number compared to the control untreated sample and exhibited better pulping selectivity. The pulp yield increased by 3% and 1.5% for the pulps of 22 and 16 kappa numbers, respectively. The biotreated pulp's strength properties were improved and were similar to those of E. globulus reference pulp. Copyright © 2006 Society of Chemical Industry     

IR and X-ray of Non Conventional Pulping Methods for Production of High Efficiency Pulp

Abstract

In X-ray diffraction analysis studies for different pulping methods in this study, it was found that the half height width (H.H.W.) do not vary much from one method of pulping to the other, but they are all lower than that of the starting bagasse. Moreover, the crystallinity indices for different bagasse pulps are in good agreement with the results of IR-spectra for these pulps where, it was found that, the higher crystallinity index is for (AO) and PA-EDTA bagasse pulps while, the lower crystallinity index is for curde bagasse. Moreover, it was found that the interplanar spacing (d) values of different bagasse pulps are slightly affected by the pulping methods.

In case of bleached bagasse pulps, it has been found that, the (H.H.W.) of bleached different bagasse pulps is lower than that of unbleached pulps. However, it has been also found that the crystallinity indices of bleached different bagasse pulps were higher than that of unbleached bagasse pulps. Moreover, the interplanar spacing (d) values for bleached different pulps are also slightly affected during bleaching process.     

Elemental chlorine-free bleaching halfa pulp

Halfa, also known as Stipa tenacissima, is grown in North Africa and south Spain. Due to its short fiber length, paper of halfa remains bulk and takes the block letters well. In this study halfa was evaluated for bleached pulp production. Two cellulose pulps with different chemical compositions were pulped by conventional Kraft process: one from the original halfa material and the other from halfa pretreated by diluted acid. The pulp produced from halfa pretreated by diluted acid was bleached by elemental chlorine-free sequences, DEPD and DEDP. Yield, Kappa number, brightness and α-cellulose contents of bleached and unbleached pulps were evaluated. The results show that during the chemical pulping process, treated halfa was easily cooked than that original halfa. Treated halfa pulp also showed very good bleaching, showing brightness level of 94.8% ISO, yield 93.6% and α-cellulose content 96.8% with DEDP bleaching sequence compared to 83.2% ISO brightness level, 92.8% yield and 95.1% α-cellulose content for bleached pulp with DEPD bleaching sequence. On the other hand, the physicomechanical properties of pulp were not notably reduced by the bleaching process. Breaking length, tear and burst index of paper sheets were acceptable. Therefore, this halfa material could be a worthwhile choice for cellulosic fiber supply.     

Effect of Eucalypt Pulp Pretreatment with Hot Acid Hydrolysis on (aZe)DP and (aZe)(EP)P Bleaching Performance

The effect of pulp pretreatment with hot acid hydrolysis on high consistency ozone bleaching was evaluated. An experimental plan was set up involving the full optimization of the A-stage and its application in Elemental Chlorine Free–ECF–[A/(aZe)DP and A(aZe)DP] and Total Chlorine Free–TCF–[A/(aZe)(EP)P and A(aZe)(EP)P] sequences for eucalypt kraft pulp bleaching. The A-stage removed a significant amount of lignin and HexA from the pulp, and the subsequent Z-stage remained efficient after completion of the A-stage. The chemical savings caused by the A-stage were significant (～7 kg ClO₂/adt). The optimum conditions for the A-stage were pH 3.0, 90°C for 120 min, and 10% consistency. The strength properties of pulps bleached with the (aZe)DP (reference) and A/(aZe)DP ECF sequences were similar, but the TCF sequence A/(aZe)(EP)P delivered slightly lower strength properties than the ECF sequences. Fiber peeling studies indicated that the HexA present in the kraft pulp is not concentrated on the fiber surface, as previously thought.     

Optimization of beech wood pulping in catalyzed acetic acid media

Fagus sylvatica wood samples were treated in HCl‐catalyzed, acetic acid solutions. The effects of selected operational variables (catalyst concentration, reaction time and liquor to wood ratio) on pulp yield, composition of pulps and composition of pulping liquors were assessed using incomplete, second‐order, centred, factorial designs. Pulp composition was measured by the contents in cellulose, xylan and lignin. The concentrations of glucose, xylose and furfural in pulping liquors were also considered as experimental variables. Under selected conditions, pulps with 5.8% to 7.5% Klason lignin (kappa numbers in the range 25 to 33), 77.2% to 85.3% cellulose and 3.3% to 6.1% xylan were obtained at 45.8% to 50.0% pulp yield. The selected pulps showed good SCAN viscosity (723 to 814 mL/g) and alkaline resistances which were affected by the acetyl group content of samples (6.6 to 7.6 weight percent).     

Ethanol‐based pulping from Cynara cardunculus L

A non‐conventional pulping process based on the delignification of cardoon (Cynara cardunculus L) in ethanol–water mixtures has been studied to evaluate its pulping potential and to establish the optimum pulping conditions for this lignocellulosic material. The variables analyzed were the concentration of ethanol in the cooking liquor, the pulping time and temperature. Variable optimization was performed by a central composite design. High viscosity, low kappa number and acceptable screened yield were used as pulp quality criteria to optimize cooking conditions. Pulps having low kappa numbers and viscosities greater than 900 cm³/g^?1 were obtained. The total pulp yield was low compared with wood pulping due to the high contents of extractives and ash in cardoon. The amount of rejects in the pulp is of importance, especially for pulps with a high kappa number. The most suitable pulping conditions were 188 °C, 135 min and 50% (w/w) ethanol concentration. In these conditions the kappa number of the pulp was around 26, the pulp viscosity greater than 1100 cm³ g^?1 and a screened pulp yield of about 31% was obtained. Copyright © 2005 Society of Chemical Industry     

Dissolving pulp from TCF bleached Acetosolv beech pulp

Beech wood samples subjected to pulping in HCl‐catalysed acetic acid media (Acetosolv process) under selected conditions were bleached using several Totally Chlorine Free (TCF) sequences including peracetic acid (Paa), alkaline (E), oxygen (O), chelating (Q) and peroxide (P) treatments. PaaEQPP sequences starting from acetic acid media led to pulps with poor brightness, which was improved when the same sequence was carried out starting from aqueous media. An EOQPP sequence led to a pulp with acceptable properties, which were improved by a optimised EOQPaaP sequence, in which a fully bleached pulp was obtained at a SCAN viscosity of 604 cm³ g^?1. EOQPaaP‐bleached pulp was explored for carboxymethyl cellulose (CMC) manufacture employing heterogeneous conditions in isopropanol media, and a CMC with a degree of substitution of 1.16 was obtained. Copyright © 2004 Society of Chemical Industry     

A modified method of nitric acid pulping of bagasse

Pulping of bagasse by a rapid and mild nitric acid process was successfully carried out to produce different grades of pulp. Nitric chemimechanical bagasse pulp was produced in a high yield of 91 % on pulping depithed bagasse with 4% HNO₃ for a period of 30 min at 80°C, followed by alkali pulping with 2% NaOH at 95°C for 30 min. The pulp had a satisfactory strength and high opacity. On increasing the strengths of nitric acid to 7% and alkali to 7% a nitric semichemical pulp of 65% yield was obtained. The pulp had a superior strength and high opacity. The pulp was easily bleached to 71% general electric brightness (GE) with the chlorination-alkali-extraction-hypochlorite (CEH) sequence. With 15% HNO₃ and 8% NaOH, nitric chemical bagasse pulp was produced. The pulp was easily bleached to a high brightness of 82% GE with one stage hypochlorite. The pulp had a higher strength than kraft bagasse pulp. A satisfactory newsprint paper was produced on an experimental paper machine with a furnish composed of 80% bleached nitric semichemical bagasse pulp, 10% bleached softwood pulp and 10% clay.     

Strategies to reduce the brightness reversion of industrial ECF bleached Eucalyptus globulus kraft pulp

BACKGROUND: Brightness stability is a key property of bleached chemical pulps and is primarily determined by wood species and bleaching process conditions. Eucalyptus globulus is becoming a very important raw material for hardwood pulp production. In spite of this importance, there is a relative lack of systematic studies in the literature dealing with the subject. This research aims to study the effect of some of the foremost bleaching parameters of a DEDD bleaching sequence as well as the effect of a final P stage (DEDP instead of DEDD) in the brightness stability of bleached E. globulus kraft pulps. RESULTS: The increase of the D₀ stage temperature from 55 °C to 90 °C caused an increase in brightness stability. Increasing the ClO₂ charges from 2.8% to 3.2% also improved significantly the brightness stability. A high H₂SO₄ charge in the D₀ stage (10 kg tonne^?1 pulp) diminished the brightness stability. The combination of H₂O₂ addition to the E stage and ClO₂ reduction in the two final D stages does not affect brightness reversion. Raising the D₂ stage temperature from 65 °C to 82 °C decreased the brightness reversion, while an increase was obtained when the temperature rose above 82 °C. Substitution of the last ClO₂ stage in the DEDD sequence by a H₂O₂ stage (DEDP) significantly reduced the brightness reversion. CONCLUSION: For an existing pulp mill in which the implementation of new technologies to improve brightness reversion is considered, the results obtained showed that brightness stability can be improved without any significant capital investment. Copyright © 2007 Society of Chemical Industry     

Rapid nitric acid cooking of rice straw

A rapid and mild nitric acid pulping of rice straw was developed and different grades of pulp were produced. A satisfactory nitric chemimechanical rice straw pulp was obtained in a yield of 80% by two stage pulping. In the first stage 5% HNO₃ was used at 80°C and a 6:1 liquor ratio for 30 min, followed by a second alkali stage, 3% NaOH at 95°C for 30 min. The pulp had a satisfactory strength and high opacity and it was bleached by an HP sequence to a 67% general electric brightness (GE). Semichemical pulp of 65% yield was produced by cooking with 10% HNO₃ and 10% NaOH at 20:1 liquor ratio. The pulp had superior strength and it was bleached to a 61% GE by a chlorination-alkali extraction hypochlorite (CEH) sequence. Nitric bleached chemical pulp of 48% and 82% GE was produced by cooking with 6% HNO₃ and 7% NaOH at 10:1 liquor ratio and bleached by a CEH sequence. The chemical pulp is of higher yield and strength than soda pulp. Newsprint that fulfils all the requirements was produced on an experimental paper machine from a furnish composed of 80% bleached nitric chemimechanical rice straw pulp, 10% bleached softwood pulp and 10% clay.     

Assessment of potential approaches to improve Eucalyptus globulus kraft pulping yield

The main goal of this work is to study the potential approaches to improve polysaccharides retention during Eucalyptus globulus kraft pulping. The addition of anthraquinone to kraft pulping leads to the highest pulp yield while the addition of urea promotes lower depolymerization of polysaccharides (higher pulp viscosity), but does not have a significant effect on yield. The early interruption of kraft cooking followed by oxygen delignification is a reliable approach to increase pulp yield, particularly when pulping is interrupted at the end of the faster and more selective kinetic regime (bulk phase). Yield loss during oxygen delignification is considerably lower than that incurred in the last phase of kraft pulping. Pulping with OH^?/HS^? charge profiling, carried out with liquor injection in three different phases leads to a yield increase. However, this increase results from a lower total alkali charge applied when profiling pulping is compared to standard pulping conditions, rather than to alkali profiling. Standard kraft pulping with different active alkali (AA) charges demonstrated that this operational variable is determinant for pulp yield and viscosity. Pulping experiences with lower AA (14%) resulted in a higher and almost constant pulp viscosity and in a higher pulp yield, assigned to improved retention of both cellulose and xylan. During the last stage of pulping, cellulose content decreases, this being mainly responsible for the decrease of pulp yield, while xylan content is almost constant, a feature attributed to the peculiar structure of this E. globulus's hemicellulose. Copyright © 2007 Society of Chemical Industry