Neutral Sulfite Semi-chemical Pulp Research Articles

The effect of operating conditions on neutral sulphite semi-chemical pulping properties: an industrial pilot plant study

The influence of pulping variables on the pulp and black liquor properties for a neutral sulphite semi-chemical pulping system was investigated in a pilot plant pulping setup situated at an industrial paper mill. Eucalyptus chips were used as raw material and the operating variables were Na2SO3 charge (8–18% w/w on oven-dry wood), Na2CO3 charge (0.5–3.0% w/w on oven-dry wood) and maximum cooking temperature (160–180 °C). Response surface methodology was used to parametrize empirical models to find the optimal conditions for maximizing the short-span compression strength index of the pulp. The derived regression models for the black liquor properties and the pulp hypo number had R2-adjusted values above 0.8 and p-values for overall significance below 0.05. The derived regression models for the handsheet strength properties had R2-adjusted values between 0.3 and 0.45 and p-values for overall significance either below 0.05 or between 0.05 and 0.1. The sulphite charge, followed by the carbonate charge, had the most notable effect on the evaluated properties with the effects of temperature being less significant. Optimization of the pilot plant system showed that the short-span compression strength index of the pulp could be maximized to 26.7 N m/g, using a sulphite charge of 9.4% (w/w on oven-dry wood) and a carbonate charge of 1.94% (w/w on oven-dry wood), similar to short-span compression strength indices typically achieved using other pulping processes.

Pulp and Paper Properties of Jenitri Wood (Elaeocarpus ganitrus)

Jenitri trees are widely distributed in community forests on Java Island and their wood is utilized for various products. The objective of the study was to assess the basic properties and quality of pulp and paper from jenitri wood. The tree was felled at the age of 5, and the base part was taken. Chips were processed using three different pulping methods in soda (17% NaOH), kraft (17% NaOH and 25% sulfidity), and neutral sulfite semi-chemical (NSSC) (12% Na2SO3 and 3% Na2CO3) processes. The fibers of jenitri had good derived values (slenderness, Runkel, and flexibility ratios) as well as chemical properties. The screened yields from the soda, kraft, and NSSC processes were 35.60 ± 4.75%, 35.05 ± 3.83%, and 46.29 ± 2.59%, respectively. The kappa numbers from the soda, kraft, and NSSC processes were 28.02 ± 7.35, 21.15 ± 1.61, and 71.28 ± 6.86, respectively. The handsheets had a burst index value of 0.65–2.94 kPa.m2/g, a tear index value of 5.23–5.47 mN.m2/g, a tensile index value of 15.13–30.49 Nm/g, a brightness value of 24.39–45.25%, and an opacity value of 98.83–99.68%. The soda pulp and the kraft pulp had slight differences in all parameters except for the Kappa number. The NSSC pulp showed slight differences in the selectivity of delignification ratio, tear index, and opacity, but produced a higher brightness level compared to chemical pulpings. The values of burst and tear indices for kraft pulp paper met the Indonesian National Standard for leaf bleached kraft pulp.

Получение лиственной целлюлозы высокого выхода бисульфитным способом

The article presents the results of the development of a technological mode for obtaining bisulfite hardwood pulp of high yield on a magnesium base for the production of various types of containerboard. The reliable and effective chemical and heat recovery technology implemented in the bisulfite method allows to use it in independent sulfite process. The effect of the duration of stay at the final temperature on the pulp yield and kappa number was studied when developing the technological mode of cooking. It was found that the increase in the duration of stay at the final temperature of 160 °C more than 40 min leads to violations of the selectivity of the cooking process. Increasing the duration of stay at the final temperature up to 70 min is accompanied by a decrease in pulp yield by 6 % at a constant value of the kappa number of the semi-finished product. Technological cooking mode: hydromodule 5, SO2 consumption 15.0 %, cooking solution pH 4.3–4.5, impregnation time at 120 °C – 35 min, cooking duration at 160 °C – 40 min. The mode allows to get a semi-finished product with a high yield of 60–65 % with a kappa number of 58–60 units without a hot grinding stage. An assessment of the mechanical strength characteristics of the laboratory samples of bisulfite pulp was carried out in accordance with the standards of the Russian Federation. The obtained values of bursting strength, resistance to flat compression, breaking strength, and breaking stress were comparable with the values of the industrial sample of hardwood neutral sulfite semi-chemical pulp with a semi-finished product yield of 75–78 %. It is shown that the presence of bark in the technological chips in the amount of 7.5 % is accompanied by a decrease in the yield of bisulfite hardwood pulp by 4.5 % and mechanical strength by 7.8 %. For citation: Koroleva T.A., Milovidova L.A., Dryakhlitsyn A.A. Production of High-Yield Hardwood Pulp by Bisulfite Cooking. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 3, pp. 161–169. DOI: 10.37482/0536-1036-2021-3-161-169

Production of fungal biomass protein by filamentous fungi cultivation on liquid waste streams from pulping process

The aim of this study was to convert the spent liquors obtained from acidic sulfite and neutral sulfite semi-chemical (NSSC) pulping processes into protein-rich fungal biomass. Three filamentous fungi, Aspergillus oryzae, Mucor indicus, and Rhizopus oryzae, were cultivated on the diluted spent liquors in an airlift bioreactor with airflow of 0.85 vvm at 35 °C and pH 5.5. Maximum values of 10.17 g, 6.14 g, and 5.47 g of biomass per liter of spent liquor were achieved in the cultivation of A. oryzae, M. indicus, and R. oryzae on the spent sulfite liquor (SSL) diluted to 60%, respectively, while A. oryzae cultivation on the spent NSSC liquor (SNL) diluted to 50% resulted in the production of 3.27 g biomass per liter SNL. The fungal biomasses contained 407 g to 477 g of protein, 31 g to 114 g of fat, 56 g to 89 g of ash, and 297 g to 384 g of alkali-insoluble material (AIM) per kg of dry biomass. The amino acids, fatty acids, and mineral elements composition of the fungal biomasses corresponded to the composition of commercial protein sources especially soybean meal. Among the fungi examined, A. oryzae showed better performance to produce protein-rich fungal biomass during cultivation in the spent liquors.

Thermal properties of lignocellulosic precipitates from neutral sulfite semichemical pulping process

In a neutral sulfite semichemical (NSSC) pulping process, wood chips are pretreated with sodium sulfite and sodium carbonate solution. This pretreatment dissolves a part of hemicellulose and lignin from wood chips. The spent liquor (SL) that is produced in the pretreatment process contains a considerable amount of lignosulfonate and hemicelluloses, but SL is generally treated in the wastewater effluent system of the mills (i.e. lignocelluloses are wasted). In this paper, these lignocelluloses were separated from SL with organic solvents, and their thermal properties were determined. The results showed that the precipitates isolated from SL/acetone, SL/ethanol or SL/isopropyl mixtures with the weight ratio of 67/33 had the highest heating values of 18.61, 17.59 and 17.05MJ/kg, respectively. The precipitates made from mixing acidified SL and solvents had lower heating values than those made from mixing untreated SL and solvents, which is likely due to the relatively high ash content of the precipitates made from mixing acidified SL and solvent. The theoretical and experimental heating values of precipitates were compared in this work. The precipitates displayed lower ignition temperatures compared with other biomass-based solid fuels, implying that the combustion of precipitates would require lower activation energies.

Acidification of prehydrolysis liquor and spent liquor of neutral sulfite semichemical pulping process

Acidification has been commercialized for producing kraft lignin from black liquor of kraft pulping process. This work intended to evaluate the effectiveness of acidification in extracting lignocelluloses from the spent liquor of neutral sulfite semichemical pulping (NSSC) process and from prehydrolysis liquor (PHL) of kraft-based dissolving pulp production process. The results showed that the NSSC and PHL spent liquors had some lignin-carbohydrate complexes (LCC), and that the square weighted counts of particles with a chord length of 50–150μm in the spent liquors were significantly increased as pH dropped to 1.5. Interestingly, the acidification reduced the lignosulfonate/lignin content of NSSC and PHL by 13% or 20%, while dropped their oligosugars content by 75% and 38%, respectively. On a dry basis, the precipitates had more carbon, hydrogen and a high heating value of 18–22MJ/kg, but less oxygen, than spent liquors. The precipitates of PHL could be used as fuel.

Anaerobic co-digestion of acetate-rich with lignin-rich wastewater and the effect of hydrotalcite addition

The methane potential and biodegradability of different ratios of acetate and lignin-rich effluents from a neutral sulfite semi-chemical (NSSC) pulp mill were investigated. Results showed ultimate methane yields up to 333±5mLCH4/gCOD when only acetate-rich substrate was added and subsequently lower methane potentials of 192±4mLCH4/gCOD when the lignin fraction was increased. The presence of lignin showed a linear decay in methane production, resulting in a 41% decrease in methane when the lignin-rich feed had a 30% increase. A negative linear correlation between lignin content and biodegradability was also observed. Furthermore, the effect of hydrotalcite (HT) addition was evaluated and showed increase in methane potential of up to 8%, a faster production rate and higher soluble lignin removal (7–12% higher). Chemical oxygen demand (COD) removal efficiencies between 64 and 83% were obtained for all samples.

NSSC pulp from planted populus and hardwood sawdust for flutting production

This research was performed with the goal of using neutral sulfite semi chemical pulp (NSSC) from populous instead of all or part of MWPI’s NSSC pulp for producing fluting paper. Firstly, NSSC pulp was prepared from populous species and hardwood sawdust under the mill’s cooking conditions. Then, the two mentioned pulp samples were replaced with the mill’s NSSC pulp in a variety of mixing ratios. Next, handsheets with 120 g/m2 were produced of mixed pulps and the properties were measured. The results showed that both raw materials could supply the pulp properties in acceptable way in comparison with control pulp (NSSC pulp of Mazandaran mill).

Sunflower stalk neutral sulfite semi-chemical pulp: an alternative fiber source for production of fluting paper

Sunflower stalk was evaluated as a potential fiber source to make fluting paper using neutral sulfite semi-chemical pulping process, in comparison with Mazandaran wood and paper industry mill made hardwood-based neutral sulfite semi-chemical (NSSC) pulp. Sunflower stalk consists of two distinct fractions including inner bulky pith and outer woody wall. The stalk has to be de-pithed for the purpose of papermaking because of lower cellulose, and higher ash content in pith-containing stalk. The results of pulping showed that the rate of delignification in NSSC cooking of de-pithed sunflower stalk with 20% lignin was surprisingly very low, despite of being a non-wood fiber source. However, sunflower stalk NSSC pulp showed very good response to refining and produced denser sheet due to lower digester yield and higher fiber flexibility coefficient, in comparison with Mazandaran wood and paper industry pulp sample. In addition, sunflower stalk pulp has been demonstrated to be an appropriate fiber source for making fluting paper at higher or comparable tensile-loaded strength properties such as tensile and burst, and higher compression-loaded strength properties including corrugated medium test and ring crush test.

Effects of Montmorillonite Clay on Mechanical and Morphological Properties of Papers Made with Cationic Starch and Neutral Sulfite Semichemical or Old Corrugated Container Pulps

The impact of montmorillonite (nanoclay) addition on the mechanical and morphological properties of paper made from neutral sulfite semichemical (NSSC) and old corrugated container (OCC) pulps was evaluated in systems utilizing cationic starch for dry-strength. The nanoclay amount was considered at five levels, and cationic starch was applied at a 1% level. In OCC pulp, by increasing the nanoclay up to 4%, the tensile index and corrugating medium test (CMT) were increased; however, there was a decrease when the nanoclay was increased to 8%. By increasing the nanoclay to 2%, the tear and burst indexes and ring crush test (RCT) increased, but there was a reduction when the nanoclay was increased to 8%. Average air resistance tended to increase as the nanoclay was increased to 8%. In the case of NSSC pulp, by increasing the nanoclay amount from 0 to 8%, the average tensile, tear, and burst indexes decreased, while the air resistance increased. The CMT amount increased with increasing nanoclay content to 2%, but a reduction was seen for other levels. The RCT exhibited an increase with increasing nanoclay up to 4%, after which it decreased. Results suggest that the proportion of nanoclay added with cationic starch needs to be optimized, depending on furnish conditions.

Study on production of fluting paper from poplar pulp mixed with hardwood NSSC pulp

This study investigated the suitability of neutral sulfite semi-chemical (NSSC) poplar pulp as an alternative for NSSC fluting pulp in Mazandaran Wood and Paper Industries (MWPI), Iran. Handsheets with a base weight of 127 g/m2 and yield of about 75 % were made by mixing the poplar and MWPI pulps at proportions of 10, 20, 30, 40 and 50 wt%. Physical, mechanical, and optical properties were evaluated using TAPPI and ISO standards. Addition of poplar NSSC pulp improved the tensile index, stiffness index, burst index, tear index, CMT index, breaking length index, and porosity index of the handsheets in comparison with the MWPI NSSC pulp. According to this study, optimum properties of fluting paper obtained by 50 % poplar NSSC pulp + 50 % MWPI NSSC pulp.

PDADMAC as a flocculant for lignosulfonate of NSSC pulping process

The spent liquor (SL) of neutral sulfite semi-chemical (NSSC) pulping process contains about 8 wt% lignocelluloses that can be extracted and used in the production of value-added materials. In this work, a flocculation process followed by centrifugation was considered for isolating lignosulfonate and hemicelluloses from SL. It was observed that, by adding 20 mg/g of polydiallyldimethylammuniom chloride (PDADMAC) with 100,000-200,000 g/mol molecular weight to SL, 45% of lignosulfonate and 39% of hemicelluloses were removed at 30°C. The lignocellulose removal was more efficient for the dual flocculation system of low and high molecular weights PDADMAC than for individual PDADMAC systems. Overall, 49% of lignosulfonate, 47% of hemicelluloses and 97% of turbidity were removed from SL from the dual system when 10 mg/g low molecular weight PDADMAC and 10 mg/g high molecular weight PDADMAC were added to the SL at 30°C, subsequently. The thermogravimetric analysis (TGA) of generated flocs showed that all samples had similar thermal behaviour and 13-16 wt% of flocs remained as ash after burning at 700°C in nitrogen. As the flocs are made of lignocellulosic materials and they are thermally stable, they could be used as fillers in paper board production. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:686-691, 2016.

Production of lignosulfonate in NSSC-based biorefinery.

The spent liquor (SL) of a neutral sulfite semichemical (NSSC) pulping process contains a considerable amount of lignocelluloses and is treated in wastewater systems. The lignocelluloses, however, can be used for producing value-added products if they are isolated from the SL. In this article, solvent treatment (mixing acetone, ethanol, or isopropyl with SL) was used as a method for isolating lignosulfonate from SL. The maximum lignosulfonate removal was obtained via mixing isopropyl alcohol with SL at the weight ratio of 20/80, room temperature, and 5.7 pH. The results also showed that the molecular weight and anionic charge density of the precipitates were in the range of 5,000-70,000 g/mol and 0.2-1.8 meq/g, respectively. Based on these results, a process was proposed for isolating lignosulfonate from SL and converting the NSSC process to an NSSC-based biorefinery.

Separation of lignosulfonate from spent liquor of neutral sulphite semichemical pulping process via surfactant treatment

The spent liquor, SL, of neutral sulphite semi chemical pulping process contains lignosulfonate and hemicelluloses, but it is currently treated in the wastewater treatment of the process. This treatment decomposes the lignosulfonate. However, lignosulfonate can be extracted for a better use, but the extraction process is not an easy task. The main objective of this work was to extract lignosulfonate from SL via treating the SL with surfactant. The results showed that the acidification of SL to pH 1.8 caused 6% lignosulfonate, 53% hemicelluloses, and 7% COD removals from SL. Acidification followed by dodecyltrimethylammonium chloride, DTAC, treatment of SL at the optimal conditions of 22°C, 1.8 pH and 10mg/g of DTAC/SL yielded 40% lignosulfonate, 78% hemicelluloses, and 25% COD removals. Model solutions were prepared via dissolving commercial lignosulfonate and xylan in solutions or purifying SL via membrane dialysis in order to investigate the impact of SL components, i.e. hemicelluloses and residual cooking chemicals, on the isolation of lignosulfonate from SL. The model analyses confirmed that the presence of impurities, i.e. residual cooking salts, significantly affected the isolation of lignosulfonate from the SL, but the presence of hemicellulose had a minor effect in extracting lignosulfonate from SL via DTAC treatment. In addition, the elemental analysis confirmed that DTAC and lignosulfonate had a ratio of 0.584mol/mol in precipitates.

Effect of Mixing Different Contents of OCC Pulp on NSSC Pulp Strength

This research was conducted to study changes in mechanical properties due to mixing of old corrugated container (OCC) pulp with virgin neutral sulfite semi-chemical (NSSC) pulp. The OCC pulp was collected after removal of printing, glued parts, and unwanted additives. To prevent cutting of fibers, dedicated containers were broken down by hand before pulping. Handsheets with a base weight of 127 g/m2 were made by mixing the NSSC and OCC pulps at proportions of 60, 70, and 80 wt% of NSSC. Mechanical properties, including tensile strength, burst strength, tearing strength, corrugated medium test, and ring crush test, were evaluated using TAPPI standards. Addition of up to 30% OCC improved the tensile strength, tear strength, and burst strength of the handsheets significantly in comparison with the control sample (21, 25, and 59%, respectively). However, the corrugated medium test and ring crush test decreased by about 13 and 9%, respectively. The results of this study revealed that mixing 30 wt% OCC with NSSC yielded a higher quality paper.

A combined adsorption and flocculation process for producing lignocellulosic complexes from spent liquors of neutral sulfite semichemical pulping process

The spent liquor (SL) of a neutral sulfite semichemical pulping process contains lignocelluloses that are currently treated in a waste water system. In this work, an adsorption process using activated carbon (AC) was considered for isolating the lignin and hemicelluloses from SL. The maximum adsorptions of 0.9 g/g lignin and 0.43 g/g of hemicelluloses on AC were achieved under the conditions of 30°C, pH 7 and 3h with SL/AC weight ratio of 90. The addition of polydiallyldimethylammonium chloride (PDADMAC) to the SL/AC system significantly improved the adsorption of lignin to 2.5 g/g on AC. The molecular weight of PDADMAC considerably affected the results in that the higher MW PDADMAC led to less lignin, but more hemicelluloses, turbidity and chemical oxygen demand removals from the SL. The thermal analysis also revealed that the higher MW PDADMAC generated precipitates with a lower incineration temperature and heating value.

Separation of lignocelluloses from spent liquor of NSSC pulping process via adsorption

Hemicelluloses and lignin present in the spent liquor (SL) of neutral sulfite semichemical (NSSC) pulping process can potentially be converted into value-added products such as furfural, hydroxymethylfurfural, levulinic acid, phenols and adhesives. However, the direct conversion of hemicelluloses and lignin of SL into value-added products is uneconomical due to the dilute nature of the SL. To have a feasible downstream process for utilizing lignocelluloses of SL, the lignocelluloses should initially be separated from the SL. In this study, an adsorption process (via applying activated carbon) was considered for isolating the dissolved lignin and hemicelluloses from the SL of an NSSC pulping process. Under the optimal conditions of pH, SL/AC weight ratio, time and temperature of 5.7, 30, 360 min and 30 °C, the maximum lignin and hemicellulose adsorptions were 0.33 and 0.25 g/g on AC. The chemical oxygen demand (COD) and turbidity of the SL were decreased by 11% and 39%, respectively, as a result of lignocellulose adsorption on AC. Also, the incineration behavior of the SL-treated AC was studied with a thermo-gravimetric analysis (TGA).

Chemical characterisation of biosludge from a wastewater treatment plant in a neutral sulphite semi-chemical pulp mill by single and sequential extraction of heavy metals and micro-/macronutrients — a case study

AbstractThe main impetus for utilising the biosludge from the neutral sulphite semi-chemical pulping process is the Finnish legislation which from 1st January 2016 prohibits the deposition of this residue in landfills in Finland. The dry matter content of the biosludge in this case study was low (12.1 mass %), meaning that incineration of this residue is uneconomical. The biosludge was rich in P (6260 mg kg−1). This, together with the high total organic carbon value of 459 g kg−1 and the metal concentrations (As, Cd, Cr, Cu, Ni, Pb, Zn and Hg) lower than the Finnish permissible limits for land application, supports wide and various end-uses for this residue. Except for S (27600 mg kg−1) and Cd (1.4 mg kg−1), the other heavy metal concentrations in the biosludge were lower than the maximum values for heavy metal concentrations in a non-contaminated soil referred to the literature. From the utilisation perspective, and in view of the high levels of S and Na, this residue could efficiently be used, for example, to landscape landfills.

Newsprint from NSSC Bagasse Pulp Mixed with Hardwood CMP Pulp and Bleached Softwood Kraft Pulp

In this work, the possibility of using neutral sulfite semi-chemical (NSSC) bagasse pulp mixed with hardwood chemimechanical pulp (CMP) and bleached softwood kraft pulp (BSKP) was investigated with the aim of reducing hardwood and BSKP consumption. The bagasse NSSC pulp had a digester yield of about 73% and was unbleached. It was refined by a PFI mill to 400 mL CSF, but in the case of the hardwood CMP and imported long fiber pulp, the final refined freeness were selected to be 350 and 500 mL CSF. Handsheets were made (60 gm-2), and their strength indices and optical properties were measured. Results of this research on a laboratory scale indicated that using bagasse NSSC pulp mixed with hardwood CMP to make newsprint with acceptable quality is possible, and this process will also noticeably reduce the consumption of imported long fiber pulp and wood for producing the grades of paper usually made from CMP.

English

This study was carried out in order to investigate the suitability of ash ( Fraxinus angustifolia Vahl.), a native tree (species) in Turkey, for pulp and paper making. Four pulping methods, which included NSSC, cold soda, kraft and kraft + anthraquinone pulping processes, were used for this study. The test materials were supplied from two different stands found in Istanbul Bahcekoy region. When ash wood samples as ash 1 and ash 2 chemical contents were analyzed, the chemical components of ash 1 were higher than that of ash 2. Pulps and handsheets were obtained from ash 1 and were suitable for use in papermaking. These pulps were obtained by NSSC (neutral sulfite semi chemical pulping), cold soda, kraft and kraft + anthraquinone processes. Handsheets made from different pulping methods were compared with each other for strength and optical properties. Strength properties were found to be higher for kraft and kraft + anthraquinone processes, while optical properties were found to be higher for cold soda and NSSC processes.