Pulping Conditions Research Articles

Comparison of hot-water extraction and steam treatment for production of high purity-grade dissolving pulp from green bamboo

The performance of hot-water extraction (HWE) and steam treatment (ST), followed by kraft pulping were compared for production of high purity-grade dissolving pulp from green bamboo. With the same prehydrolysis intensity (represented by the P-factor), the fractionation efficiency of HWE is far lower than that of ST. Because of lower removal of non-cellulosic components, the solid residue from HWE (even at approximately double the prehydrolysis intensity, P-factor = 1,379) required more active alkali (AA) during kraft pulping to obtain a cellulose purity equivalent to that achieved by the ST (P-factor = 756)-kraft process. To reach equivalent hemicellulose removal, HWE required more severe intensity than ST. However, FTIR and SEM characterizations of solid residue confirmed that intensified HWE resulted in significant lignin condensation. Antagonistic effects of hemicellulose removal and lignin condensation extent on subsequent kraft pulping were therefore more apparent in HWE than that in ST. Under the same kraft pulping conditions, lignin condensation from a severely intensified HWE process (P-factor = 2,020) caused greater cellulose yield and viscosity loss than that found for ST. Finally, at a given residual pentosan or lignin content, the cellulose yields from all HWE-kraft pulps were about 3 % lower than those from ST-kraft pulps. Consequently, based on an optimally setup chlorine dioxide bleaching stage, a cellulosic pulp with alpha-cellulose content of 97.6 % and viscosity of 927 mL/g was successfully produced from a ST-kraft pulp (P-factor = 756, AA = 19 %).

Effect of Kraft Cooking Conditions on the Chemical Composition of the Surface and Bulk of Spruce Fibers

By varying cooking temperature, alkali charge, ionic strength, and cooking time in Kraft pulping of spruce chips, pulps ranging between kappa numbers 20–80 were obtained. The unbleached Kraft pulp fibers were subjected to mechanical peeling in order to separate the surface material from the bulk of the fibers and the carbohydrate composition and lignin content of the two fractions were analyzed. As expected, the lignin and xylan contents were higher on the fiber surface than in the fiber wall. The percentage of xylan on the fiber surface was fairly constant, independent of different pulping conditions or degree of delignification. The lignin proportion on the fiber surface gradually decreased with decreasing kappa number. At a given kappa number, pulping at a higher temperature resulted in less lignin on the fiber surface, probably because of the higher solubility of lignin at higher temperature. Cooking at lower alkali charge also resulted in lower lignin content on the fiber surface at a given kappa number. In this case, there was more time available for degradation of the surface lignin since the lower alkali charge resulted in longer cooking time needed to reach a certain kappa number.

Lignin chemistry and topochemistry during kraft delignification of Eucalyptus globulus genotypes with contrasting pulpwood characteristics

Abstract Eucalyptus globulus Labill. is a short-fibre resource for pulp and paper production. Ten different E. globulus genotypes with varied pulpwood quality and chemical composition were evaluated under kraft pulping conditions. Characterisation of the wood and pulp samples by thioacidolysis indicated that the content of syringyl units in β-O-4 linkages (S-β-O-4) was distinct for the studied genotypes. The highest S-β-O-4 levels were detected in the samples with the lowest original lignin and highest glucan levels. This group of samples provided the pulps with the lowest final lignin content at higher yields. UV microspectrophotometric (UMSP) evaluation of the wood chips revealed that the samples with the lowest lignin levels have the lowest UV absorbances at 278 nm (A278 nm) in the secondary walls (S2). During kraft pulping, lignin from the S2 was dissolved, whereas lignins from the middle lamella and cell corner lignin was not removed not even for prolonged reaction periods, independently of the evaluated genotype. The A278 nm values of the S2 were significantly lower in the pulps from the genotypes with less original lignin content.

Research on Preparation and Properities of Chemi-Mechanical Pulp from the Waste Poplar Wood

In this study, we prepared unbleached chemi-mechanical pulp from waste poplar wood using alkaline processing under normal atmospheric pressure. The influnce of alkaline dosage and time to fiber morphology and properties of the paper were discussed. The parameters of fiber including the length ,width and curl index were measured by FQA. The optimal dosage of NaOH and the optimal time of soaking period in the preparation of pulp using waste poplar wood were studied. The results showed that the optimal dosage of NaOH was 6% and the time of soaking period was one day. The performance of the handsheet made from the poplar wood under the pulping conditions are as follows: tensile strength index of 27 N·m/g, tear index of 0.51 mN·m2/g, burst index of 1.7 KPa·m2/g, folding strength of 16 times, ring crush strength index of 5.7 N.m/g, whiteness of 55.5 ISO, white opacity of 97%, paper absorption liquid rate of 0.32 mm/s.

Changes in accessibility of cellulose during kraft pulping of wood in deuterium oxide

Fresh birch chips were treated with different concentrations of sodium hydroxide and sodium sulfide in deuterium oxide in typical kraft pulping conditions and the extent of irreversible deuteration of the chips/pulps was followed by Fourier transform infrared (FT-IR) spectroscopy. Water retention values (WRV) of pulps were measured to evaluate accessibility of cellulose. The kraft pulping with deuterium oxide led to significant proton-deuterium exchange that was not reversed when the chips/pulps were washed with water. The deuteration followed a first order dynamics with a maximum obtained in the beginning of delignification stage. Higher dosages of effective alkali resulted in a higher degree of deuteration and lower WRV. An inverse relationship between the extent of deuteration and WRV suggests that both were induced by cellulose microfibril aggregation. Results also indicate that hemicellulose dissolution plays an important role in the induction of cellulose microfibril aggregation, while lignin dissolution has less influence.

Fiber Qualities of Pretreated Betung Bamboo (Dendrocalamusasper) by Mixed Culture of White-Rot Fungi with Respect to Its Use for Pulp/Paper

Previous research on anatomical structures of pretreated large ( betung ) bamboo ( Dendrocalamusasper ) using single culture of white-rot fungi has been investigated, which revealed that the pretreatment caused the decrease in the Runkel ratioas well as the coefficient rigidity and the increase in the flexibility ratio of their corresponding bamboo fibers. However, there is no study reported on the anatomical structure changes of them caused by pretreatment using mixed culture of white-rot fungi. This paper reports the results of the research on paper/pulp quality after different treatments. Pretreatment that used Trametes versicolor fungi and lasted for 45 days inflicted intensive fiber damages compared with those of untreated bamboo (control). Fresh and barkless large ( betung ) bamboo chips of 2 year's old, and 1.6 cm in length, were inoculated by 10% of mixed culture of white-rot fungi inoculums stock for 30 and 45 days in room temperature . There were four treatment groups of mixed culture, i.e T. versi color and P. ostreatus (TVPO); P. ostreatus and P. chrysosporium (POPC); P. chrysosporium and T.versi color (PCTV); and P .chrysosporium, T.versicolorand P.ostreatus (TVPCPO). After the inoculation period, the chips weremacerated into separate fibers using Scultze method to analyze the fiber dimension and its derived values. The fibers were then observed regarding their macro and microscopic structures by optical microscope . Mixed culture pretreatment of white-rot fungi accelerated improvement of fiber morphology and fiber derived value characteristics, except for Muhlsteph ratio. The fiber derived values oftreated bamboo tended to improve compared to those of untreated bamboo, there by requiring milder pulping conditions. Accordingly, the treated bamboo would indicatively produce a good quality pulp (grade I) based on FAO and LPHH (Forest Product Research Report) requirements. Co-culture treatment using P. chrysosporium and P. ostreatus for 45 days produced the best fiber dimension and its derived value properties . The fungi hypae colonized on the surface area of bamboo followed by mycelium penetration into substrate (bamboo-inner structure). The partial degradation caused by delignification indicatively attributed to the fungi activity was shown in the macroscopic images.

Study on DTPMPA as Cooking Additive in Bamboo Pulping

The application of chelating agents DTPMPA (Diethylene Triamine Penta Methylene Phosphonic Acid) as cooking aids in kraft pulping of bamboo was researched. The effect of DTPMPA dosage at different alkali charge was discussed. The results showed that the cooking aids DTPMPA added in bamboo kraft pulping was able to reduce K value of pulp, improve the screened stock yield and brightness and reduce the alkali charge. The optimized bamboo kraft pulping conditions are: DTPMPA dosage 0.4%, alkali charge 19%, when sulfidity was 20%, maximum cooking temperature was 165°C and time at maximum temperature was 90min. Under optimized conditions of cooking, the screened bamboo pulp yield is higher, the K value is lower and the bamboo pulp brightness is higher.

Comparison between Green Liquor Pretreatment-Kraft Pulping and Conventional Kraft Pulping

This paper studied the differences of pulping performances, beating characteristics and strength properties between green liquor pretreatment-Kraft pulping and conventional Kraft pulping based on previous optimized pulping conditions. The green liquor pretreatment-Kraft pulping has higher yield, lower Kappa number, reduced residual effective alkali and decreased viscosity. Green liquor pretreatment improves pulp strength properties although green liquor pretreatment-Kraft pulp has beating characteristics similar to conventional Kraft pulp.

Study on Bamboo Kraft Pulping with DTPMPA

DTPMPA (Diethylene Triamine Penta Methylene Phosphonic Acid) was used as cooking additive in Bamboo pulping. The effect of cooking parameters such as alkali charge, maximum cooking temperature, and time at maximum temperature on bamboo kraft pulping adding additive Diethylene Triamine Penta Methylene Phosphonic Acid was studied. The results show that the optimized bamboo kraft pulping conditions are: alkali charge 17%, maximum cooking temperature 162°C, and time at maximum temperature 60min when DTPMPA dosage is 0.4%. On the optimized conditions of cooking, the highest screened bamboo pulp yield 49.52%, the kappa number of bamboo pulp is 24.68, residual alkali in kraft waste liquor 3.62g/L .

Colloidal organic content and tackiness of coated broke and recycled fiber

The consistency, temperature and duration of repulping of coated broke and recycled fiber can determine the amount of colloidal organics liberated and the tackiness. In this study, old magazines, old newspapers, coated paper, envelopes, sticky notes, and office paper were repulped at differing consistency, temperature, and duration. The colloidal and dissolved organic content was measured along with the tackiness of each pulping condition to better understand the stickies and white pitch released. This understanding of released colloidal stickies and colloidal white pitch during repulping treatment by means of fixative was applied to an examination of stabilizers and detackifiers to determine best means of control. This work developed a tackiness scale for typical furnish used in recycling to help understand the tackiness associated with adhesives (envelopes and sticky notes) and paper additives (office paper, old magazines, and coated paper) compared to old newspapers and to recycled lap pulp. The study found that the adhesive-containing papers (envelopes and sticky notes) is 4–10 times tackier than old magazines and really is not comparable when considering old newspapers. Compared to recycle lap pulp, adhesive-contaminated paper is 50–150 times tackier and coated paper is 15–50 times tackier than recycle lap pulp. The evaluation shows that more tacky components are released during pulping at higher temperatures and lower consistencies.

Quantitative Difference in the Rates of the β-O-4 Bond Cleavage between Lignin Model Compounds with and without γ-Hydroxymethyl Groups during the Alkaline Pulping Process

To examine the effect of the presence of γ-hydroxymethyl groups on the rate of the β-O-4 bond cleavage during the alkaline pulping process, the rates of the β-O-4 bond cleavage of non-phenolic lignin model compounds without a γ-hydroxymethyl group, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (G’G) and 2-(2,6-dimethoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (G’S), were compared with those of analogous model compounds with a γ-hydroxymethyl group, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)propane-1,3-diol (GG) and 2-(2,6-dimethoxyphenoxy)-1-(3,4-dimethoxyphenyl)propane-1,3-diol (GS), under alkaline pulping conditions. The disappearance of G’G or G’S was accompanied by the quantitative liberation of 2-methoxyphenol or 2,6-dimethoxyphenol, respectively, indicating that the disappearance resulted from the β-O-4 bond cleavage. The disappearance rate of G’G or G’S was in between those of the erythro and threo isomers of GG or GS, respectively. This result seems to be reasonably explained when the steric repulsions of the three staggered conformations are taken into consideration. The disappearance rate of G’G or G’S increased, but the increment became moderate with increasing hydroxide concentration.

Delignification of Phragmites karka – a Wetland Grass – by Soda Pulping Process

Phragmites karka, a common wetland grass, was delignified by the soda pulping process, and all the operating parameters were optimized. The effects of both anthraquinone and surfactant on pulp yield and kappa number at optimum pulping conditions were also investigated. The pulp was beaten at different beating levels to optimize different mechanical strength properties. A detailed morphological study of soda-AQ pulp of P. karka was conducted by scanning electron microscopy.

Ink and dirt behavior in pulping after artificial aging of cold-set offset printed newspapers in different humidity conditions

Although moisture has a decisive role in the permanence of cellulose and unprinted paper, its role in ink release from the surface of printed recovered papers remains unclear. This work aimed to determine whether various relative humidity levels in the artificial aging test affect ink release from the surface of the paper and its fibers when pulping cold-set offset printed newspapers in alkaline pulping conditions. The results showed that relative humidity variations from 30% to 70% negligibly affected ink release at 60°C. However, compared with these lower humidity levels, exposure to 90% relative humidity for at least 25h resulted in a higher ink content bound to fibers, a greater formation of visible dirt specks after pulping and a smaller formation of microscopic ink particles. In practical applications, the accurate estimation of climate effects during the storage and the transportation of recycled papers requires that humidity conditions are taken into account while performing artificial aging tests with paper products.

Multivariate-parameter optimization of the alkaline peroxide mechanical pulp (APMP) process for larch (Larix gmelinii Rupr.) using Box-Behnken design

Abstract The study is aiming at the finding of optimal pulping conditions for the alkaline peroxide mechanical pulping process applied to larch in terms of brightness (% ISO) and tensile strength (TS). Based on three variables, the Box-Behnken experimental design was applied to determine the effects of the first-stage and second-stage dosages of H2O2 and the impregnation temperature on % ISO and TS. The equations based on the quadratic regression analysis were developed, which describe the response behaviors as the simultaneous functions of the selected independent variables. The best brightness achieved was 75.4% ISO under the following conditions: first-stage H2O2 3.5%, second-stage H2O2 3.54%, and impregnation temperature 81.4°C. The best TS (37.2 N·m g-1) was found under the following conditions: first-stage H2O2 2.4%, second-stage H2O2 3.9%, and impregnation temperature 90°C.

Improving pulp yield for integrated southern hardwood kraft mills—significance and impact on chemical recovery, steam and power generation, and bleaching

Researchers have been attempting to improve the yield of bleachable-grade kraft pulp for several decades. Wood is typically one of the major costs associated with kraft pulping. Therefore, it is typically assumed that improving pulp yield or conversely, reducing the amount of wood required to make a specific mass of pulp, is a cost-effective, lucrative endeavor. Although this may be true, it is important to understand the impact of increasing pulp yield on the interconnected processes within an integrated pulp and paper mill and to fully evaluate the cost implications on these processes. The current work employed several sets of laboratory pulping conditions and a WinGEMS model of a pulp mill, fully integrated with chemical recovery, power, and recausticization, and pulp drying islands to determine where the largest cost impact associated with improved pulp yield may be experienced.

Diethanolamine Pulping Process of Pinus Kesiya

In this paper, under the premise of maximum temperature not more than 200 °C, the diethanolamine pulping process of pinus kesiya was optimized. AQ was used as the additive for pulping. Under the optimum pulping condition, the pulp properties were as follows: screened pulp yield 61.9%, viscosity 1306mL•g-1 and kappa number 24.3. The handsheets physical properties were as follows: tensile index 77.6N•m•g-1, bursting index 6.40kPa•m2•g-1, tearing index 10.63mN•m2•g-1

Factors Affecting Bleachability of Eucalypt Pulp

Unbleached and oxygen-prebleached pulps were produced both in industrial and laboratory scale using Eucalyptus urograndis woods from two different sites (A and B) as a raw material. Quantitative chemical analysis of wood and pulp was performed, aiming to find a correlation with bleaching performance. Fiber dimensions measurements in wood were also performed. Carbohydrates and lignin composition in wood from A and B were found to be similar, while extractives in acetone presented variations of about 0.5% between wood from site A and B. Laboratory-made unbleached pulps from A and B had brightness varying 0.3% ISO, whereas pulps from industry presented variations over 4% ISO from each other. By virtue of its high unbleached pulp brightness, the industry-made sample A presented a higher bleachability than its sample B counterpart. The higher bleachability of the industry-made sample A was traced to its much higher content of hexenuronic acids (HexA), which was caused by differences in pulping conditions in mill sites A and B.

Bagasse hydrogels: water absorption and ions uptake

PurposeThe purpose of this paper is to prepare and optimize the preparation conditions of some new hydrogels and in addition, evaluate their water absorbance at different mediums and their ability to remove ions from aqueous solutions.Design/methodology/approachCellulose was extracted from depithed bagasse at two different pulping conditions; 3 and 6 hours cooking times, pulp (I) and (II), respectively. These pulps, in addition to cotton linter for comparison, were grafted with acrylamide followed by cross‐linking with glutaraldehyde. The networks were partially hydrolyzed and the structures of products (before and after hydrolysis) were studied using FTIR, SEM, TGA and X‐ray. The optimum preparation conditions were identified, before and after hydrolysis, to achieve maximum absorbance and the ability of prepared hydrogels to remove ions from solutions was investigated.FindingsMaximum level of absorption was recorded using hydrogels prepared with monomer concentration =0.8 mol/l, cross‐linker concentration =0.01 mol/l, reaction time =2 hours and temperature =65°C. Hydrogels prepared using pulp (I) showed the best absorbance behavior and a tendency to remove ions from water.Research limitations/implicationsThe ability of the prepared gels to remove ions from water could be further investigated to evaluate the ability of their use in a multi‐filtration system for water treatment.Practical implicationsThis piece of work has suggested a simple way to convert an agricultural waste to hydrogel able to remove metal ions from water.Social implicationsConsuming this type of waste reduces the risks resulting from its burning in some countries, such as Egypt, that produce large amounts of it.Originality/valueIn this paper, low cost hydrogels, with expected value in water treatment, were prepared using agricultural wastes. They have shown better reactivity than gels prepared using pure cellulosic materials (cotton linter).

Investigating the Possibility of Chemi-mechanical Pulping of Bagasse

Chemi-mechanical pulping was evaluated as a potential way to prepare sugarcane bagasse fibers for papermaking. Cellulose, lignin, ash, and extractives soluble in alcohol-acetone were measured as 55.75%, 20.5%, 1.85%, and 3.25%, respectively. Fiber length, diameter, lumen cavity, and cell wall thickness were measured as 1.59 mm, 20.96, 9.72, and 5.64 µm. The chemi-mechanical pulping conditions were selected as follows: three charging levels of 10, 15, and 20% sodium sulphite, and three pulping times of 20, 30, and 40 minutes after reaching the pulping temperature. Pulping temperature was held constant at 165 oC. Different pulping conditions resulted in pulp yields between 65.38 and 84.28%. The highest yield (84.28%) was obtained using a treatment combination of 20 minutes pulping time and 10% sodium sulphite. The lowest yield (65.38%) was related to 40 minutes pulping time and 20% sodium sulphite. Pulps were refined to 300 ± 25 mL CSF, 60 gm-2 handsheets were made, and then strength indices and optical properties of the handsheets were measured. The results showed that 20% sodium sulphite, 40 minutes pulping time, at 165 oC can be considered as the optimum pulping conditions for bagasse CMP pulping. Tensile, tear, and burst strength indices, as well as the opacity of this pulp were measured as 39.59 Nmg-1, 6.66 mNm2g-1, 2.1 KPa m2g-1, and 95.35%, respectively.

Study of “napier grass” delignification for production of cellulosic derivatives

Recently, much research on the evaluation of new cellulose sources has been developed. In this context, a promising source is “napier grass”, which contains 30.40% lignin, 36.34% cellulose, and 34.12% hemicellulose. In this work, conditions for the delignification of “napier grass” in the laboratory were studied by using calcium oxide (CaO) and hydrogen peroxide (H2O2). The best pulping conditions were 9.00% CaO for a period of 2.73h, which resulted in 74.99% delignification and 66.58% cellulose. The best conditions for the bleaching process were pH 12 and hydrogen peroxide at concentration of 4.2% for 6h, at a temperature of 40°C, which gave 90.98% delignification and 99.21% cellulose. The analyses were performed by using weight percent.