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.     

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.     

Soda—Oxygen bleaching of kraft bagasse pulp

Soda—oxygen bleaching of commercially available kraft bagasse pulp has been investigated. Alkali charge, temperature and oxygen pressure are important factors in controlling brightness and physical properties of the pulps produced. Pulp yields, lignin and degree of polymerisation of the bleached pulps decreased with increasing alkali charge from 2 to 6%. Strength properties as well as brightness increased by increasing alkali charge at 368 K, whereas optimum strength properties are obtained with 4% alkali at 383 K. In the range of oxygen pressure used, 5–8 kg cm^?2, DP as well as strength properties of the bleached pulps increased with increasing oxygen pressure. Brightness up to 61% was reached by soda-oxygen alone. To obtain higher brightness an afterbleaching step is necessary. The soda—oxygen—hypochlorite and soda—oxygen—chlorite pulps prepared have strength properties comparable with those of conventionally bleached pulps.     

蔗渣化机浆制浆工艺实验

研究了以蔗渣为原料 ,用氢氧化钠、碱性亚硫酸钠 ,碱性过氧化氢预处理制化机浆的制浆工艺。并对蔗渣化机浆的物理强度和白度进行了比较     

甘蔗渣中性亚硫酸钠蒸煮最佳工艺条件的研究

本文研究了甘蔗渣中性亚硫酸钠制浆的蒸煮最佳工艺条件。研究结果表明，甘蔗渣中性亚硫酸钠蒸煮采用下列工艺条件：Na2SO3用量为18％，Na2CO3用量为3％，液比为1：5，最高温度160℃，升温2小时，保温1小时。在此蒸煮条件下，纸浆得率可达65．83％，高锰酸钾值9.14，白度50％，不透明度92．65％，以及可得到较好的纸浆强度。     

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.     

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.     

MgO替代NaOH的杨木PRC-APMP过氧化氢漂白

针对NaOH作为碱源的预处理盘磨化学处理碱性过氧化氢机械浆(PRC-APMP)漂白过程中存在的一些问题,考察了使用MgO在二段化学预浸段和高浓停留段以不同比例替代NaOH进行漂白后对浆张白度、抗张指数以及漂后废液中化学需氧量(CODCr)含量的影响。实验结果表明:在杨木PRC-APMP过氧化氢漂白过程中采用不同比例的MgO替代NaOH,漂后的浆张白度与未替代相比变化不大;抗张指数随替代比例的增加呈下降趋势;二段化学预浸段和高浓停留段废液中CODCr含量随MgO替代NaOH比例的增加呈下降趋势。     

Delignification of Bagasse with Acetic Acid and Ozone. Part 1. Acetic Acid Pulping

Two-stage delignification of sugarcane bagasse with acetic acid and ozone was investigated. The better pulp was obtained pulping bagasse in aqueous solution of acetic acid (80% volume) at 145°C during 60 min. The liquor/bagasse ratio (L/B) was 10:1 and the kappa number was 44; it fell to 10 in the ozone stage due to selectivity of acetic acid medium. Pulp reaches a brightness of almost 70% Elrepho and the strength properties are similar to those of soda pulps without refining and better than acetosolv pulps.     

草浆造纸清洁制浆工艺研究

利用碱性物质与H2O2在适当加热条件下能够发生剧烈反应并释放热能的原理,研究了NaOH和KOH两种制浆工艺对黑液性质和纸浆性能的影响。通过考察碱用量、H2O2用量、投料间隔时间及蒸煮时间对黑液的COD、色度及纸浆的高锰酸钾值、白度和得浆率等的影响,确定了草浆造纸清洁制浆最佳工艺条件。结果表明,NaOH制浆的最佳工艺条件为：NaOH用量11%（所述药品为100%含量,用量指占稻草原料质量的比例,下同）、H2O2用量18%、投料间隔1 h、蒸煮时间2.5 h;KOH制浆的最佳工艺条件为：KOH用量10%、H2O2用量18%、投料间隔30 min、蒸煮时间2 h。对比两种工艺所得纸浆及其产生黑液的性质,表明KOH清洁制浆效果明显优于NaOH。     

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     

Fibreboard from exotic raw materials. Ii. Hardboard from undebarked cotton stalks

It was possible to obtain hardboard of acceptable properties by mechanical pulping of undebarked cotton stalks previously soaked in water at room temperature. Pretreatment of the undebarked cotton stalks with 10–15% NaOH or Ca(OH)₂ at atmospheric pressure for 4 h at 100°C, before mechanical defibration, results in considerable improvement in properties of the hardboard and less added resin requirement. The improvement due to chemical pretreatment is attributed to fibre softening. The semichemical pulps prepared from undebarked cotton stalks had remarkably high freeness compared with rice straw. Bending strength and water resistance are better than those obtained from rice straw and average samples of wood wastes.     

漆酶对未漂马尾松磨木浆的酶法改性

利用NS51002和NS51003漆酶/介体分别对马尾松未漂磨石磨木浆(GP)进行生物酶处理及后续的H2O2漂白,并对酶处理浆漂白前后的白度和强度性能进行测定。研究结果表明,利用漆酶NS51003处理马尾松未漂GP,可有效提高纸浆的白度及强度性能,而且酶处理后纸浆具有更好的可漂性,并且经过H2O2漂白后的酶处理浆亦具有更高的白度和更好的强度性能;而漆酶NS51002漆酶/介体对纸浆的改性效果甚微。     

麦草亚铵法氧脱木素浆的短流程漂白

对麦草亚铵法氧脱木素浆进行了P、HP和HQP漂白对比研究,结果表明:在过氧化氢单段漂白时,Na2SiO3的适宜用量为0.4%,在所选过氧化氢用量、NaOH用量、温度和时间的四因素三水平方差分析漂白工艺中,影响纸浆白度的主要因素为NaOH用量;而采用HP和HQP漂白时,漂白浆的白度分别达到78.1%(ISO)和81.9%(ISO),可见采用螯合处理的效果明显。     

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.     

Kinetics of Neutral Sulfite Semichemical and Neutral Sulfite Semichemical-Anthraquinone Pulping

Delignification rate expressions for neutral sulfite semichemical (NSSC) and neutral sulfite semichemical anthraquinone (NSSC-AQ) pulping of black spruce have been developed. The rates take into account the effects of temperature and reaction times on the rates of delignification.

NSSC in this study is defined by an alkali ratio [sodium sulfite/(sodium sulfite + sodium carbonate)] of 0.60 (expressed as sodium oxide) giving a final pulp yield between 55 and 60%. NSSC-AQ is identical to NSSC with the addition of anthraquinone.

Reaction temperature and pulping chemical concentrations were held essentially constant in all kinetic experiments. Isothermal experiments were conducted in the temperature range between 165 and 180°C. A concentration of 150 g/L sodium sulfite with a liquor to wood ratio 62 were used.     

Lignocellulose–polymer composite. III

A linear relationship was achieved between the polymer load and the monomer concentration up to 200% when china clay or talc replaced the glass in the initiating system, sodium bisulfite–soda lime glass, for the free-radical graft polymerization reactions using semichemical pulp of bagasse as substrate. The results showed that china clay is better than talc, which may be contributed to the difference in their network structure. The properties of the composites prepared from the cografted semichemical pulp–polymethyl methacrylate revealed that the china clay leads to composites with high compression strength and hardness. Deformation percent increased with increasing polymer load. However, decreasing or increasing the polymer load affects the properties of the composites up to a limit, where there is a maximum or minimum for both compression strength and hardness at china clay ratio of 2 or 3. Composites were also prepared from poly(methyl methacrylate)-cografted-pith of bagasse using the initiating system sodium bisulfite in the absence or presence of soda lime glass. Compression strength, deformation percent, and hardness increased on decreasing the glass ratio from 1 to 0, at nearly the same polymer load. The presence of waxes and resins decreased the compression strength of the composites prepared by impregnation of the lignocellulose in polymer solution. The hardness of these composites increased on removing waxes and resins. Removal of part of hemicellulose by alkali treatment of the lignocellulose has increased the effect on hardness. Alkali treatments of the substrates lead to a high deformation percentage. The compression strength of alkali-treated lignocellulose are lower than the untreated ones. The change of compression strength to deformation percent and the compressibility due to complete removal of waxes and resins by the extraction with methanol–benzene or partial removal of the waxes, resins, and hemicellulose through alkali treatment followed the change of both the compression strength and percent of deformation. Water uptake of the composites prepared in this work was ranged between 6.8 and 7%. After 48 h the water uptake increased to the range 8.5–14.1%. Impregnation of the composites in water for 72 h increased the water uptake to the range 10.2–18.1%. © 1993 John Wiley & Sons, Inc.     

Fibreboard from exotic raw materials. I. Hardboard from rice straw pulps

The suitability of rice straw for hardboard making was studied. Both the mechanical and semichemical pulping methods were investigated. It was found that addition of a relatively high amount of resin (2–3 %) is essential if hardboard—comparable to average commercial samples made from wood—is to be made from mechanically prepared rice straw pulp. Mild chemical treatment of the mechanical straw pulp by sodium hydroxide at optimum conditions, however, enabled the amount of resin added to be reduced and improved the bending strength and water resistance of the board considerably. Treatment with calcium hydroxide or sulphuric acid was, generally, less successful. This was accounted for by changes in pulp chemical composition. On the other hand, when the straw was first subjected to mild chemical pretreatment followed by the mechanical defibration, many fines were formed and the resulting semichemical pulp was not suitable for hardboard.     

蔗渣浆制造黏液纤维的研究

<正>在黏液纤维制造中,用蔗渣浆代替木浆作原料,常被人怀疑甚至否定其可能性,其主要根据为草类纤维的形态结构不同於木材纤维,而以天然纤维的形态结构作为对原料适合与否的判断标准。我们认为:黏液丝浆的良好制备条件均应最大限度地破坏了天然纤维的形态结构,主要是细胞壁的组织。後者的存在影响丝光化与黄酸化的反应     

Effect of Totally Chlorine Free and Elemental Chlorine Free Sequences on Whole Stem Kenaf (Hibiscus cannabinus) Pulp Characteristics

Totally chlorine free (TCF) and elemental chlorine free (ECF) single and multistage sequences were used to bleach whole stem kenaf pulp. The results indicated that in contrast to unbleached kraft wood pulps, kraft kenaf pulps can be easily bleached to a brightness of 91.4% using a four-stage TCF [Q₁(PO)Q₂P] bleaching sequence. The ECF bleaching pulps had slightly higher selectivity and yield than those of the TCF bleached pulps. The strength properties of the TCF [Q₁(PO)Q₂P] and ECF (D₁ED₂EP) bleached pulps were comparable, with the exception of tear index and tensile index, which were slightly higher and lower for TCF pulps, respectively.