soda-AQ Process Research Articles

Effect of Valley Beater Refining on Tensile Properties of Molded Pulps from Rice Straws

Rice straw, an abundant agricultural waste, is shown to be a promising resource for pulp and paper packaging manufacturing. In this study, rice straw pulps or cellulose fibers were extracted using a soda-AQ process and then the rice straw pulp slurries were refined by a Valley beater. The effect of refining time (15-60 min) on the pulp fiber characteristics was studied. It was found that both initial fiber length and width were decreased with refining time. The refined fibers became fibrillated, finer, and also more uniform in size confirmed by SEM. The pulp freeness (CSF) was reduced with increasing refining time as expected due to higher water-holding capacity of more fibrillated pulps. Then, the molded sheets were formed from the prepared rice straw pulps and examined. From tensile testing, the results indicated that the tensile properties of the molded sheets from the refined pulps were significantly enhanced (p < 0.05), thanks to an increase in fibrillated fiber surface area and inter-fiber bonding degree. The Valley beater refined rice straw pulp provided the molded sheet with the highest tensile index of 51.96 ± 4.08 Nm/g which are comparable to that of the sheets prepared from PFI mill refining process. The tensile properties of the current refined sheets were also in the acceptable range for typical commercial molded pulp packaging. In addition, the freeness values of the optimal Valley beater refined pulps are relatively high (348-423 ml), implying a benefit in forming process and manufacturing of pulp products.

Pulping and bleaching potential of banana pseudo stem, banana leaf and banana peduncle

The chemical, morphological and anatomical characteristics of banana pseudo stem, banana leaf (midrib) and banana peduncle were determined. Banana wastes were characterized with good amount of α-cellulose (40–45%), moderate amount of lignin (20–24%) and medium to long fiber length (1.22–1.92 mm). Alkaline nitrobenzene oxidation (ANO) showed that the main lignin unit of banana stem and leaf was p-hydroxybenzaldehyde and that of banana peduncle was syringaldehyde. The yield of ANO was very low (17–24%). Soda-anthraquinone (AQ) and formic acid/peroxyformic (FA/PFA) acid pulping processes of these banana wastes were evaluated. In soda-AQ process, pulping at 20% alkali charge, pulp yields were 30.0%, 34.55% and 39.12%, for banana stem, leaf and peduncle, respectively, with kappa number below 20. Higher pulp yield was found in FA/PFA process than soda-AQ process due to very high ash content in the samples. The banana waste pulps showed excellent papermaking properties.

Characterization of chia plant (Salvia hispanica) for pulping

In this paper, chia plant was characterized in terms of chemical, morphological, and anatomical properties. Chia plant was characterized with low α-cellulose (30.5%); moderate lignin (23.2%) with syringyl to guaiacyl ratio of 1.41; and shorter fiber length (0.67 mm) with thinner cell wall (1.91 μm) and good flexibility coefficient (71.44). Anatomical features showed that chia plant consists of vessels, fibers, parenchyma cells, and collenchyma cells. Chia plant pulping was evaluated in soda-anthraquinone (soda-AQ) and formic acid/peroxyformic acid (FA/PFA) processes. Chia plant was difficult to delignify in the alkaline process. The FA/PFA process produced higher pulp yield at the same kappa number than the soda-AQ process. Unbleached soda-AQ chia pulp exhibited good proper-ties in terms of tensile, bursting, and tearing strengths, even at the unrefined stage, due to high drainability of the pulps. Alkaline peroxide bleached FA/PFA pulp exhibited better papermaking properties and 2% higher brightness than the D0(EP)D1 bleached soda-AQ pulp.

Pulping of bagasse (Saccrarum officinarum), kash (Saccharum spontaneum) and corn stalks (Zea mays)

Bangladesh being a small and populated country faces shortage of fibrous raw materials. The only bagasse-based pulp mill was forced to close down due to inadequate supply of bagasse. In this context, similar alternative raw materials need to be evaluated to support small scale pulp mills in this country. Whole bagasse, kash and corn stalks were assessed in terms of their chemical and morphological characteristics. These fibres showed a moderate level of α-cellulose (43.3, 39.3 and 35.1% respectively) and low level of lignin content (~20%). Alkaline oxidation showed that the lignin of these non-woods was composed of high proportion of p-hydroxyphenyl propane unit. The fiber length of whole bagasse, kash and corn stalks was 1.36 ​mm, 0.86 and 0.90 ​mm, respectively. Soda-anthraquinone (AQ) and formic acid/peroxyformic acid (FA/PFA) pulping processes of these three non-woods were evaluated. FA/PFA process showed higher pulp yield than soda-AQ process. Corn stalk was easier to delignify in soda-AQ process, and showed the lowest pulp yield and kappa number. The papermaking properties of these pulps showed good tensile index (75–85 ​N ​m/g) and moderate tear index (4.5–6 ​mN/m2/g). Brightness of these pulps reached to 84–90% in D(EP)D bleaching and 73–85% in alkaline peroxide bleaching.

Optimization of Alkaline Pulp Extraction from Napier Grass Using Response Surface Methodology

Napier grass which has several types of them has been studied by researchers for few applications such as biofuel, sugar and pulp production. This research focused on specific type of Napier grass which is the Dwarf Napier due to high cellulose content to produce pulp. Delignification of Dwarf Napier grass was carried out by soda anthraquinone pulping under varying conditions selected according to experimental design software with three factors. The influence of these three factors including concentration of sodium hydroxide (15%, 17.5% and 20%), concentration of anthraquinone (0.05% and 0.1%) and duration of cooking time (30, 60 and 90 min) on pulp yield was studied. 18 runs of experiment were conducted and the result obtained was used to analyse the optimized condition for pulp extraction by using RSM. Results indicated that the optimized response obtained while Napier grass stem is treated with 17.5% sodium hydroxide and 0.05% AQ with 66 mins of cooking time meanwhile the predicted yield is 34.87 %. However, the actual pulp yield obtained (36.38%) is higher than the predicted yield. The pulp which extracted with optimized condition is then bleached with hydroxide peroxide. Fourier transform infrared spectroscopy (FTIR) was used to characterize the raw grass fiber and pulp obtained. Napier grass is successfully demonstrated to be an effective alternative source for producing paper pulp. In the this study Dwarf Napier grass fibres were successfully pulped applying soda AQ process although the obtained pulp is not as high as the studied done before due to the limitations. FTIR analysis also confirmed the removal of lignin as well as most of the hemicellulose during the pulping process. Therefore, the abundance and fast growth of Napier grass are an added advantage as an alternative non-wood source for papermaking

Deposition of xylan isolated from Pennisetum purpureum on fibres of Eucalyptus globulus and characterisation of the composition of the surface xylans by immunolabelling and enzymatic peeling

Abstract Adsorption of xylan on pulp is a potential method to improve its properties, especially refinability for high quality printing and writing (P&W) paper grades. In this study, elephant grass [Pennisetum purpureum (Schumach.)] xylan was used for this purpose. The xylan was extracted using cold caustic extraction (CCE) from P. purpureum brown pulp, produced by the Soda-AQ process (kappa 20). Xylan resorption was accomplished during the oxygen delignification phase of eucalypt [Eucalyptus globulus (Labill.)] pulp to avoid problems induced by the colour of the lignin-contaminated deposited xylan. Immunolabelling and enzymatic peeling methodologies were compared for the analysis of the spatial distribution of xylan in the fibre wall. The labelling appeared unevenly as faint and brighter patches on fibre surfaces. Increased labelling of xylan was detected on the samples with precipitated P. purpureum xylan. The enzymatic peeling method using a total hydrolysis enzyme mixture yielded a composition gradient as a function of time, showing clear xylose (Xyl) enrichment in the very beginning of the reaction, reflecting hydrolysis of fibre surfaces. Pure xylanase and endoglucanase hydrolyses yielded different product patterns and kinetics compared to total hydrolysis, but interpretation of those results in terms of xylan localisation was not straightforward.

Environmental Aspect of Using Chlorine Dioxide to Improve Effluent and Pulp Quality During Wheat Straw Bleaching

This paper illustrates the need of using the agro waste (wheat straw) as a substitute for forest products in paper industry. It aims on using the soda-AQ pulping process for converting waste to fibrous pulp. Further, it emphasizes on use of chlorine dioxide in place of elemental chlorine and hypochlorite during bleaching with aim of reducing the wastewater load and improving the pulp quality. Complete chemical characterization of wheat straw was performed. The soda-AQ (anthraquinone) method was opted for cooking and to make a pulp of kappa number 13. The pulp was bleached with elemental chlorine and calcium hypochlorite based sequences. To study the impact of adding chlorine dioxide on paper properties and effluent quality, elemental chlorine and hypochlorite were replaced with dioxide. The total elemental chlorine free bleaching sequence was also studied. The hand sheets were prepared to analyze the bleached and unbleached pulp properties using standard methodology. The effluent quality was studied by measuring the properties COD, BOD, TDS, TSS, TS, colour, lignin and adsorbable organic halides. Proximate chemical analysis of wheat straw showed that it contains holocellulose 67.3 ± 0.16%, hemicelluloses 39.2 ± 0.7%, cellulose 34.2 ± 0.9%, lignin content 14.9 ± 0.09% and ash 9.2% that mainly composed of silica (7.7%). With soda-AQ process a pulp with 53% yield and good strength properties was obtained. The bleached pulp of chlorine dioxide based sequences was having better strength properties in comparison to chlorine based sequences. Total replacement of elemental chlorine with chlorine dioxide reduced the BOD (52%), COD (49%), colour (43%), lignin (57%) and AOX (63%). Research concluded that wheat straw can be utilized by paper mills to combat the problem of waste management, air pollution due to its burning and issues of raw material for papermaking. Soda-AQ pulping method was found to be effective for preparing the wheat straw pulp. Use of elemental chlorine free bleaching may prove to be a reliable approach for better environmental management with high pulp characteristics.

Sodium carbonate pre-extraction of bamboo prior to soda-anthraquinone pulping

A part of hemicelluloses is dissolved in black liquor during pulping process, which can be extracted prior to pulping, that would be used for producing biofuels, biopolymers, paper additives, and other chemicals in addition to pulp. However, the amount of hemicellulose extraction must be limited to maintain pulp yield and pulp quality. In this investigation, hemicelluloses were pre-extracted from bamboo with weak alkali (Na2CO3) and compared with hot water and dilute H2SO4 extraction prior to kraft, soda, and soda-anthraquinone (AQ) pulping. Bamboo chips were also pulped by the kraft process without pre-extraction. The biomass dissolution in weak alkaline pre-extraction was 11.1 %, which was 1.2 and 7.9 % lower than the hot water and dilute H2SO4 pre-extraction, respectively. In the alkaline pre-extraction process, 1.3 % lignin, 1.7 % acetic acid, and about 6.4 % sugars (on oven-dried mass of bamboo) were extracted. The soda-AQ process responded well in terms of pulp yield and pulp quality. Pulp yield after alkaline pre-extraction was higher and kappa number was lower than the hot water and dilute H2SO4 pre-extraction. Alkaline pre-extraction followed by kraft and soda-AQ pulping produced pulp with lower kappa number than non-extracted kraft pulp at almost similar pulp yield. This pulp showed better results in pre-bleaching with peroxyformic acid. Alkaline pre-extracted kraft and soda-AQ pulps had better tear index and slightly inferior tensile index than the non-extracted kraft pulp after D0EpD1 bleaching. Final brightness for soda-AQ and kraft pulp was 1.1 and 2.8 %, respectively, higher than the control pulp. Alkaline pre-extraction is a better option to integrate pulp mill with hemicellulose extraction and pulp production biorefinery.

Evaluation of alkaline deconstruction processes for Brazilian new generation of eucalypt clones

Wood utilization for pulp and paper and biorefinery applications requires some kind of mechanical and/or physical–chemical pretreatment. Among the chemical treatments the alkaline ones are the most used worldwide, although acid and solvent treatments have also being used. This paper deals with eucalypt wood deconstruction with alkaline processes including soda-AQ, soda-AQ-O2, soda-O2, and kraft. The kraft process is largely used by the pulp industry and is evaluated here only to serve as a reference. The behavior of the four eucalypt clones selected in chapter 2 were investigated when submitted to the aforementioned processes regarding their screened yield, chemical demands and pulp quality at different kappa number levels (15, 35, 50, and 70). The two most promising processes (kraft and soda-AQ) were chosen for producing pulps (kappa 15 and 20) which were studied in depth (content of carbohydrates, uronic acid, hexenuronic acid, polysaccharide molecular weight, residual lignin structure, etc.), as well as their respective black liquors (heating value, solid content, elemental analysis, and lignin structure). The main findings of this work were: (1) the wood of the four different hybrid eucalypt clones behave similarly in the various alkaline deconstruction treatments; (2) the soda-AQ and Kraft were considered the most suitable processes for producing pulp on the basis of yield, chemical demands and pulp fiber integrity; (3) the soda-AQ process can potentially replace the kraft for a high degree of wood delignification (kappa number 15); (4) the alkaline processes using oxygen (soda-AQ-O2 and soda-O2) are more suitable for wood deconstruction aimed at biofuels; and (5) the soda-AQ process resulted black liquor of more suitable burning characteristics than the kraft.

Structural Changes of Lignin in the Soda-AQ Pulping Process Studied Using the Carbon-13 Tracer Method

To reveal the structural changes of lignin during the soda–AQ cooking process and chemical bonds between lignin and xylan of wheat straw, 13C isotope-labeled technology was used in this study. First, 13C isotope-labeled xylose was injected into the living wheat straw. The success of 13C isotope-labeling was confirmed by the results of 13C abundance determination. Then, milled wood lignin-13C was extracted from wheat straw. The wheat straw, which had already been labeled by xylose-13C, was cooked by the soda-AQ process. Soda-AQ Lignin-13C and Residual Lignin-13C were extracted from black liquor and residual pulp. FT-IR, 13C-NMR, and 2D HSQC NMR analyses indicated that all lignin preparations were HGS-type lignin. The main lignin linkages were β-O-4’ units, β-β’ units, β-5’ units, and β-1 units, with the highest content of β-O-4’. Furthermore, 82.8% of β-O-4’ units, 77.2% of β-β’ units, 75.4% of β-5’ units, and 75.4% of β-1 units were degraded during the cooking process. LC bonds between lignin and xylan were at C2 and C5 positions of xylan. It was found that the C-2 position of xylan in wheat straw could be mainly connected to lignin by γ-ester bonds, and C-5 position of xylan in wheat straw was possibly linked with lignin by benzyl ether bonds.

Potential of Elephant Grass for Pulp Production

Elephant grass (Pennisetum purpureum) (EG) is a fast-growing plant with high biomass productivity in the range of 30-45 bone dry t/ha/yr. This high productivity qualifies EG as a potential raw material for bleached pulp production. This study evaluated elephant grass as a raw material for paper pulp production. This was accomplished through determining its full chemical and morphological characterization, pulpability at kappa numbers 15 and 20 via the kraft and soda-AQ processes, and its pulp bleachability to 90% ISO brightness. The results were compared with those of a commercial hybrid eucalyptus wood clone (Eucalyptus urophylla x Eucalyptus grandis) (EUCA) that is widely planted in Brazil. Concerning its chemical composition, the elephant grass presented a high ash (60,100 mg/kg) and total extractives content (14.8%). However, the elephant grass showed good potential for pulp production. The kraft process was the ideal cooking process at kappa number 20, producing the highest screened yield (47.9%), bleachability (0.163 Δkappa/TAC), and good viscosity (812 dm3/kg). For EUCA, the ideal cooking process was the kraft process at kappa number 20, resulting in a screened yield of 52%, bleachability of 0.217 Δkappa/TAC, and final viscosity of 886 dm3/kg. This high productivity qualifies EG as a potential raw material for bleached pulp production.

Process of Soda-AQ Pulping of Fast-Growing Poplar and Defibration Point

Fast-growing Poplar cooked by Soda-AQ process was studied, by determining the lignin contents including Klason lignin and acid soluble lignin, the yield of pulping, the rate of carbohydtare degradation and the rate of delignification.Results indicated that the delignificaton of Fast-growing Poplar in Soda-AQ pulping can be divided into three distinguishable stages. (a)The initial delignification stage before 140°C,the rate of delignification reaches to 30.87%;(b)The bulk delignification stage, the rate of delignification reaches to 86.97%，in the period from 140°C to 170°C and for 30 min;(c)The residual delignification stage,the rate of delignification exceeds 91.60%. The defibration point was reached when cooking temperature raised to 170°C and for 30 min with 57.50% pulping yield ,24.94 kappa nomber.

Optimization the soda-AQ process for cellulose pulp production and energy content of black liquor from L. leucocephala K360

A commercial variety of Leucaena leucocephala K360 was used for pulp production and papermaking employing the soda-anthraquinone process. Also, the chemical and energy contents of the resultant black liquors were determined to simultaneously optimize: pulp and paper production and energy generation. A process temperature of (185°C), an operating time of (120min) and an active alkali concentration of (21%) provided sheets of paper with good strength (tensile index of 12.12Nm/g, burst index of 0.38kPam2/g, tear index of 1.29mNm2/g and a Kappa number of 20.5) and black liquor with a greater calorific value (14.1MJ/kg) than that obtained with higher active alkali concentrations.However, reducing the active alkali concentration to a level in the low operation range led to less marked degradation of cellulose and allowed paper sheets with good properties to be obtained and energy to be optimally produced from the black liquor.

Soda/AQ Pulping of a Hardwood with Trapping of the Generated Coniferyl Alcohol

Coniferyl alcohol is generated from the cleavage of β-O-4 bonds during alkaline pulping of hardwoods and softwoods. Once formed, some of the coniferyl alcohol (CA) is transformed into vinylguaiacol (VG) and isoeugenol (IE). All three of these compounds (CA, VG, and IE) can rearrange to quinone methides (QMs) under alkaline conditions and become involved in condensation reactions with lignin and carbohydrate moieties. The aim of this investigation was to see if ethylguaiacol (EG) addition to soda-AQ (SAQ) pulping systems would lead to its reaction with the QMs from CA, VG, and IE to form dimers that are unreactive towards further condensation. Sugar maple wood meal was delignified by the SAQ process with EG added at 5.0 wt% on wood meal. Three dimers were detected in the pulping effluent and identified as a combination of EG with CA, VG, and IE. The total yield of the three dimers corresponded to ∼80% of the estimated CA that would have been generated. Conventional kraft, SAQ, and SAQ+EG pulping of the maple chips were then performed. The bleachability of the SAQ+EG pulp was significantly improved as compared to the SAQ pulp and it was estimated to be superior to the kraft pulp as well.

The effects of processing variables on the soda and soda-AQ pulping of kenaf bast fiber

Iran is facing a severe lack of fibrous raw materials for paper production. Kenaf (Hibiscus cannubinus L.) is a superior complement to wood as a source of fiber. Kenaf bast fibers are excellent for making pulp and paper of various grades due to the presence of high alpha cellulose (56.43), holocellulose (77.71), and ultimate fiber length (2.77 mm). Fiber length is an important factor in the development of tear and tensile properties. The aim of this work is to study the effect of charge alkali (20 and 25% oven dried, as NaOH) and cooking time (30, 60, 90, 120, 150, and 180 min) of kenaf bast fiber on soda and soda-anthraquinone (AQ) pulp yield, kappa number, rejects, and strength properties of their handsheets. Results indicated that alkali charge and cooking time had significant influence on kappa number, yield, and rejects of pulps, whereas PFI revolution had only a minimal effect, especially at higher cooking times. The soda method was modified by adding 0.2% anthraquinone, and the resultant pulps displayed an increase in pulp yield and reduction in both kappa number (by 6 to 9 units) and screening rejects. The strength properties obtained with the two cooking processes used were compared, and those provided by soda-AQ process were found to be best. Regarding handsheet properties, a significant improvement in tensile index could be obtained by the soda-AQ process, compared to the soda process.

Effect of hot-water extraction on alkaline pulping of bagasse

The effect of hot-water extraction on alkaline pulping was investigated. The properties of black liquor and pulp strength of bagasse were analyzed. The extraction was conducted at 160 °C for 30 min where 13.2% of the mass was dissolved in the extraction liquor. Untreated bagasse and extracted bagasse were digested by soda and soda-AQ processes at 17% and 15.5% (with 0.1% AQ) alkali charge (NaOH). Cooking temperatures were 160 °C and 155 °C respectively. The pulp from extracted bagasse had a lower Kappa number and a higher viscosity compared to the pulp from the untreated bagasse. The black liquor from pulping extracted bagasse had a lower solid content, a lower viscosity and a lower silica content, but a higher heating value than that from pulping of untreated bagasse. Hot-water extraction resulted in a significant decrease in bleaching chemical consumption and the formation of chlorinated organics. Pulp strength properties such as the tensile index and the burst index were found to be lower, but the tear index, bulk, opacity and pulp freeness were found to be higher when hot-water extraction was applied.

English

  In this study, cotton stalks (Gossypium hirsutum L.) were cooked using soda and soda-anthraquinone (AQ) process. Nine soda cooks were conducted by changing cooking conditions including active alkali charge and pulping time. Soda-AQ cooks were obtained by adding 0.075, 0.10, 0.15, 0.2% AQ (based on o.d stalks) to optimum soda pulping. Adding AQ to soda pulps led to the increase in regarding to pulp yield and kappa numbers. On the other hand, soda-AQ pulps made from cotton stalks showed higher mechanical properties than soda pulps. The results indicated a major increase in pulp brightness when soda pulping was modified with %0.15 AQ. Also, the results showed that better pulp and paper can be produced from cotton stalks by soda-AQ process compared to the soda process.   Key words: Alkaline pulping, anthraquinone, cotton stalks, delignification, mechanical properties, yield.

Reinforcing potential of jute pulp with Trema orientalis (nalita) pulp

Two morphologically different pulps, a long-fiber jute pulp from a soda-AQ process and a short-fiber Trema orientalis pulp from a kraft process, were evaluated and compared for their reinforcing potential. T. orientalis pulp needed less beating energy than jute pulp at the same drainage resistance. Addition of jute fiber pulp to the T. orientalis pulp increased tear strength. Sheet density of pulp blends was increased with the increase of beating degree of both pulps and the proportion of T. orientalis pulp. Tensile index and burst index of blended pulp were increased when the beating degree and proportion of T. orientalis pulp increased.

Effect of anthraquinone on brightness value and crystalline structure of pulp during soda processes

AbstractThe dependence of crystalline structure and optical properties of pulp on anthraquinone (AQ) added to the soda process at different cooking times was determined in this study. Wheat (Triticum aestevum L.) straw was used as the raw material for pulp. Soda and soda-AQ processes were selected for pulping at 80 min and 120 min. The soda-AQ process improved the yield and viscosity of pulp delignification ratio for pulping in comparison with the soda process. Crystallinity of pulp samples decreased by adding anthraquinone to the soda process because of stabilized less ordered cellulose and amorphous hemicelluloses in pulp. It was determined that crystallinity of pulp samples decreased with longer cooking time, from 80 min to 120 min, in both soda and soda-AQ processes. Monoclinic structure was dominant in pulp samples; however, the triclinic structure ratio increased in both soda and soda-AQ processes compared to raw material. It was found that brightness and lightness values in pulp samples decreased when using anthraquinone depending on the changes of the crystalline structure.

Cynara cardunculus L. alkaline pulps: Alternatives fibres for paper and paperboard production

The pulping of Cynara cardunculus L. (cardoon) was performed under conditions for kraft, kraft-AQ and soda-AQ processes. The best results in terms of delignification degree, expressed as kappa number, pulp viscosity and screened yield, were obtained for the kraft-AQ process with 0.20% of anthraquinone (AQ). The papermaking potential of the selected pulp was studied attending to biometric fibre characterisation, refining aptitude, optical and strength properties. All properties were compared against a Eucalyptus globulus pulp at different refining degrees. The cardoon pulp was also evaluated concerning its potential to board manufacture, alone and in mixtures with pine pulp, giving rise to promising results for liner manufacture.