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     

Impact of effective alkali and sulfide profiling on Eucalyptus globulus kraft pulping. Selectivity of the impregnation phase and its effect on final pulping results

BACKGROUND: Eucalyptus globulus is an important wood source for paper production and, in the last few years, great efforts have been made to assess its chemical specificities and improve the kraft pulping efficiency. Despite the existence of several works concerning mostly the kinetics of E. globulus kraft pulping there is a lack of systematic studies on the initial phase of pulping as well as on the impact of effective alkali (EA) charge profiling on the kraft pulping performance of this species. The aim of the present work is to assess the effect of initial effective alkali and sulfide charges on the lignin and carbohydrates removal on the impregnation phase and to investigate the effect of EA splitting charge on the whole E. globulus pulping process efficiency. RESULTS: When the EA charge at impregnation phase increases, the amount of dissolved wood increases until it reaches a constant value of about 20%. Maximum polysaccharide removal at impregnation phase was about 10% of total wood weight. Glucose removal during impregnation was attributed to the degradation and/or dissolution of E. globulus glucans. For EA charges at impregnation phase higher than ～15%, xylan retention on wood was roughly constant. Despite the differences found at impregnation phase on the amount of dissolved wood and lignin removal, it was demonstrated that these differences are almost completely attenuated until the end of the kraft pulping process. CONCLUSION: In the case of E. globulus, for a constant effective alkali charge, alkali profiling does not affect the whole kraft pulping performance. Copyright © 2007 Society of Chemical Industry     

Simulating the impact of kraft pulping and bleaching parameters on Eucalyptus camaldulensis pulp properties using MATLAB

In this work, Eucalyptus camaldulensis was evaluated as the raw material for chemical pulp under different pulping and bleaching conditions. The pulping was carried out at different H‐factors, and at different effective alkalis. The resulting pulps were then oxygen delignified and bleached using various dosages of bleaching chemicals in a D₀EpD₁ sequence. The effect of independent variables (pulping or bleaching variables) on dependent variables (pulp properties) was analysed based on the multivariable least square method via MATLAB software. An agreement was found between the results predicted from the models and the experimental data. To obtain a kappa number of 15, the optimum pulping conditions were a temperature of 155°C, a time of 225 min, and an EA of 23%. Also, the hexenuronic acid (HexA) content of cooked pulp was significantly decreased in the chlorine dioxide bleaching stages, and was only marginally related to the final HexA content of bleached pulps.     

Preliminary study on products distribution in alcohol pulping of Eucalyptus globulus

The aim of the present work was to study the fractionation of Eucalyptus globulus wood into pulp and by‐products by alcohol–water pulping. Under the cooking conditions employed low lignin content pulp and a high yield of by‐products were attained. The laboratory‐scale alcohol and by‐products recovery system studied consisted of three stages: black liquor flashing, lignin precipitation from black liquor, and distillation of precipitation mother liquor. The mass balance for the process enabled the amount of pulp and by‐products produced and the consumption of chemicals to be estimated. © 1999 Society of Chemical Industry     

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     

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.     

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     

Estimating Glucan,Xylan, and Methylglucuronic Acids in Kraft Pulps of Eucalyptus globulus Using FT-NIR Spectroscopy and Multivariate Analysis

Abstract

Fourier transform near infrared (FT-NIR) associated with multivariate analysis was used to estimate glucan, xylan, 4-O-Methyl-α -D-glucuronic acid (MeGlcA) content, and pulp yield in kraft pulps of Eucalyptus globulus Labill. Several models were applied to correlate chemical composition in samples with the NIR spectral data by means of principal components regression (PCR) or partial least square (PLS) algorithms. Calibration models were built and validated by using all the spectral data and cross-validation methodology. The r_c ² values for the best calibration models for quantification of glucan, xylan, MeGlcA contents and pulp yield were between 0.71–0.92. The model was validated using a set of external samples. The amount of glucan (64–77%), xylan (12–18%), and MeGlcA (204–363 mmol kg pulp^–1) in pulps were predicted with a root mean square error of prediction (RMSEP) of 0.91%, 0.46%, and 15.21% for glucan, xylan, and MeGlcA, respectively. Pulp yield (in the range of 46–70%) was also predicted with good accuracy with a RMSEP of 1.63%. These results suggest that glucan, xylan, MeGlcA composition, and pulp yield in kraft pulps of E. globulus can be adequately estimated by NIR spectroscopy for laboratory or industrial applications. NIR predictions can also provide useful and cost-effective tools for the rapid screening of large numbers of samples.     

Detailed modeling of the kraft pulping chemistry: carbohydrate reactions

The article introduces a detailed model for carbohydrate chemistry in kraft pulping. This article is continuation to the modeling work carried out for hot water extraction and chemical pulp bleaching. The model includes galactoglucomannan, xylan, and cellulose acid–base equilibria, in addition to peeling, stopping, and alkaline hydrolysis reactions of the same carbohydrates, as well as hexenuronic acid formation and degradation reactions. The Arrhenius parameters were applied from the literature or regressed against experimental data in the present study. The model is very successful in predicting the experimental data of carbohydrate reactions during kraft pulping. Many features of the pulping-related model can be applied to specific fractionation chemistry considerations. The detailed knowledge on carbohydrates composition at any stage of pulping gives possibility for further development of biorefinery cases based on kraft pulping, such as biofuel and chemicals production.     

The kinetic modeling of carbonate formation during kraft pulping of eucalyptus wood

This article conducted an investigation on the carbonate formation during kraft pulping (KP) process of eucalyptus under different conditions, from which a kinetic model for predicting the carbonate formation was proposed. It was also found that the time‐dependent effective alkali concentration and H factor are the major parameters affecting the carbonate formation. Results showed that the proposed model could describe the carbonate formation during KP at various process conditions, and there is a good correlation (R² = 0.923) between the measured and predicted data. According to the model, about 54% of total carbonate formation was contributed from lignin in wood. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1489–1493, 2017     

Recycling kraft pulping chemicals: cyclic voltammetry of molten salt mixtures containing Na2CO3, Na2SO4, Na2S/Na2S x and Na2O/Na2O2

Cyclic voltammetry (CV) has been used to investigate molten salt mixtures in the temperature range of 820–840 °C between the initial and anticipated final compositions for the proposed electrolytic recausticizing process of inorganic pulping chemicals. A mixture simulating the initial conditions for the proposed process (sodium carbonate, sodium sulfide/polysulfide and sodium sulfate) exhibited carbonate oxidation and sulfate reduction at the limits of the potential window. Additional oxidation of sulfide to sulfur occurs at potentials inside the positive limit of the potential window with subsequent chemical reaction to form polysulfide. To simulate the final composition sodium oxide and peroxide were added to the mixtures; the resulting CVs had an additional oxidation peak attributed to oxide and peroxide oxidation. We conclude the electrolytic recycle process is feasible, producing sulfide and oxide from carbonate and sulfate of sodium in the molten state, yet separation is necessary between the anolyte and catholyte so the reduction products are not consumed by oxidation.     

预水解强度对相思木硫酸盐法制浆黑液性质的影响

经水热预水解技术处理木质纤维素,木片的主要成分发生变化,对后续的化学制浆性能及制浆黑液性质带来影响。本实验采用不同预水解强度（P因子）处理相思木片,并对其硫酸盐制浆行为和黑液性质进行分析。研究结果表明,随着P因子的增大,粗浆得率和细浆得率逐渐降低;浆料的卡伯值逐渐升高。当P因子＜200时,水解后木片的黑液固形物含量由空白组的138.48 g/L升高到162.86 g/L;木素含量由58.57 g/L升高到72.68 g/L;残碱量由4.37 g/L迅速降低到2.07 g/L。当200＜P因子＜600时,黑液固形物含量由162.86 g/L降低到142.71 g/L;黑液中木素含量由72.41 g/L降低到59.16 g/L;残碱量由2.07 g/L降低到1.26 g/L。当P因子＞600时,黑液中固形物含量由142.71 g/L升高到156.95 g/L;木素含量由59.16 g/L升高到62.16 g/L;残碱量由1.26 g/L升高到1.37 g/L。不同条件下,黑液中无机物含量变化不大;黑液固形物的热值由对照组的13.71 MJ/kg提高到14.63~15.09 MJ/kg。     

红麻硫酸盐法蒸煮中溶出木素的分子量分布及变化

采用凝胶色谱法（GPC）对红麻皮和秆芯硫酸盐法蒸煮过程中溶出木素的分子量及其分布的变化进行了研究。结果表明，随着蒸煮的进行，红麻皮和秆芯溶出木素的平均分子量逐渐增大，多分散性和特性粘数也相应增大。此外，在同一蒸煮条件下，红麻秆芯溶出木素的平均分子量高于红麻皮，这也说明了红麻秆芯比红麻皮更难脱木素。研究还发现，红麻原料木素以及溶出木素的分子量分布曲线都呈单峰现象。     

速生桉木硫酸盐法制浆过程中甲醇生成量的预测模型

以速生桉木硫酸盐法制浆为研究对象,考察了制浆过程中有效碱浓度、H因子(时间和温度)对甲醇生成量以及残余有效碱浓度变化的影响,研究发现制浆过程残余有效碱浓度与蒸煮H因子的负指数呈线性关系,结合这一关系从动力学角度建立了引入碱浓动态变化的制浆过程中预测甲醇生成量的数学模型。结果表明该模型能很好地预测速生桉木硫酸盐法蒸煮过程中各工艺条件下的甲醇生成量(R² 0.990)。模型的预测效果表明,温度对甲醇生成量影响显著,而初始有效碱浓度对甲醇生成量影响较小。实际生产中,可根据该模型对各工艺条件对甲醇生成量影响程度的预测效果适当改变工艺条件,以控制制浆过程中单位木素脱除量的甲醇生成量。     

蓝桉叶挥发油化学成分分析研究

采用乙醚为溶剂提取云南产蓝桉干叶的挥发油,经气相-质谱联用仪分析,得到57种组分,确定了其中54个化合物的结构,主要成分是1,8-桉叶素(68.61%),α-蒎烯(10.24%),别香橙烯(5.27%),乙酸松油酯(4.05%),香橙烯(1.45%),(-)-蓝桉醇(1.26%),α-松油醇(1.02%)等。采用峰面积归一法计算各组分的相对含量,所鉴定成分占总馏出峰面积的99.69%。     

Extending Near Infrared Reflectance(NIR) Pulp Yield Calibrations to NewSites and Species

Abstract

Recently, we demonstrated that the accuracy of pulp yield predictions for wood samples from a site (Gog) new to their calibration (Tasmania‐wide Eucalyptus nitens) was greatly improved by adding five Gog samples to the calibration set. In this study we investigated the addition of Gog samples to the Tasmania‐wide E. nitens set, with the aim of further improving predictive accuracy. It was demonstrated that the addition of a single Gog sample to the Tasmania‐wide calibration set was sufficient to greatly reduce predictive errors and that the inclusion of at least 3 Gog samples in the Tasmania‐wide set was sufficient to give relatively stable predictive errors. The addition of different sets of 5 Gog samples to the Tasmania‐wide calibration, however, caused predictive errors to vary between sets. The standard deviation of pulp yield for the prediction set (20 Gog samples) was important, with sets having the largest standard deviations giving the best predictive statistics. Finally, the Tasmania‐wide E. nitens calibration was enhanced using samples from a different species (Eucalyptus globulus) and applied successfully to other E. globulus samples.     

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%.     

A contribution to the modeling of kraft pulping

This paper presents a mathematical model for pulping that considers the effect of alkali diffusion and chemical reaction. An approximation for 3-dimensional diffusion in wood chips is tested against pulping data. A method for predicting pulp viscosity is also presented. The model simulates the effect of key pulping variables on pulp kappa number, viscosity, yield, residual alkalinity and pulping uniformity. Experimental data from a number of sources are successfully predicted by the model.     

蒸煮助剂对低用碱量硫酸盐法预处理毛竹竹屑的影响

毛竹竹屑经10%低用碱量 (以Na₂O计)、20%硫化度、160 ℃下保温1 h预处理,木质素脱除率达到62.35%,预处理物料酶水解48 h葡萄糖和木糖得率分别为56.04%和53.47%。研究了硼氢化钠、三聚磷酸钠、2-蒽醌磺酸钠3种蒸煮助剂对毛竹竹屑10%用碱量硫酸盐预处理的成分以及糖化效果影响,其中2-蒽醌磺酸钠影响最大。在10%用碱量和20%硫化度的预处理液中添加0.15%的2-蒽醌磺酸时,160 ℃下保温1 h的葡聚糖回收率和木质素脱除率分别为94.93%和68.55%,与空白对比分别提高5.45%和9.94%;预处理物料酶解48 h葡萄糖和木糖得率分别为62.88%和58.97%,与空白对比分别提高12.21%和10.29%。     

Manufacture of Microcrystalline Cellulose from Eucalyptus globulus Wood Using an Environmentally Friendly Biorefinery Method

In this work, hemiceluloses and lignin were solubilized by successive steps of autohydrolysis and delignification, and the resulting solids were processed to obtain microcrystalline cellulose. Eucalyptus globulus wood chips were treated with hot, compressed water under selected conditions to cause the hydrolytic breakdown of heteroxylan into substituted saccharides. The xylan-depleted solids were treated with acetic acid under optimized conditions to remove lignin, leaving a solid phase with high cellulose content. This latter was subjected to Totally Chlorine Free (TCF) bleaching to yield microcrystalline cellulose. These sequence autohydrolysis-organosolv delignification-TCF bleaching enabled the selective separation of hemicelluloses (which were mainly converted into soluble saccharides), lignin (as compounds soluble into acetic acid), and microcrystalline cellulose, according to an environmentally friendly biorefinery method.