NaOH Charge Research Articles

Production of Long-Fiber Pulp from Enset Plant Residues by Soda Pulping.

This paper evaluates the modification of fiber morphology and the strength property development of paper from Enset fiber as a function of soda pulping conditions and refining energy. Soda pulping was conducted at pulping temperatures between 160 and 180 °C. The NaOH charge was 16, 20, and 24% based on the initial raw material. The beating of pulp was conducted using a Jokro mill. The refining of pulp was conducted in a laboratory refiner at different refining intensities. The mild Jokro mill beating was not effective on Enset fiber pulp. On the other hand, the laboratory refiner effectively refined the pulp. The fiber morphology was altered in the way of improving the paper formation and strength. The beating degree of the pulp was increased to about 49 °SR. The tensile index was enhanced to around 80 Nm/g using a refining energy input of 250 kwh/t. From the results, it can be concluded that Enset fiber pulp is suitable for packaging papers due to its high strength level. On the other hand, Enset fiber can be a potential raw material for specialty papers like filter paper and tea bags because of its high porosity.

Optimization of alkali concentration in the pretreatment of sugarcane bagasse for ethanol production

This study was aimed for the investigation of the effect of pretreatment procedure of alkaline, based on the chemical arrangement, surface morphology, structural composition and enzymatic assimilation of sugarcane bagasse for sugars and ethanol production. Alkali pretreatment (0 to 8% w/v of NaOH) assists to reduce the lignin portion (from 19.57±0.03% to 9.91±0.02%) and increase the cellulose content of the treated SB (from 34.66±0.05% to 63.58±0.05%) simultaneously. The optimal conditions for alkali pretreatment were 8% NaOH charge at 100oC for 90 min. Enzymatic digestibility of alkali treated SB was significantly improved and hydrolysis yield reached to 89.59% glucose and 61.23% xylose at an prime level using Trichoderma viridae. Further hydrolysate of 8% (w/v) alkali treated SB sample was fermented by Saccharomyces cerevisiae to convert sugar into ethanol and yield was 16.81±0.32% in 24 h. Alkali pretreatment was found to be a treatment of choice for cellulose hydrolysis in SB and subsequent sugar acquired for the production of ethanol during fermentation. Bangladesh J. Sci. Ind. Res. 58(2), 89-98, 2023

Improvement of Reaction Selectivity Performance with Alkali Charge and Reaction Time on Oxygen Delignification Process

The chemicals of NaOH is highly related to the quality of the pulp in the medium consistency oxygen process. This research used Acacia mangium and Eucalyptus pulp with KaNo 18. The condition of the medium consistency oxygen process, the temperature of 80 o C, oxygen pressure of 1 bar. Reaction time was 20 to 100 minutes at intervals of 20 minutes. NaOH charges 5 to 25 kg /t at intervals of 5 kg/t. The analysis parameters used are KaNo and viscosity. The higher value of NaOH charge and reaction time, the higher value of the delignification degree. The higher value of NaOH charge and the reaction time, the higher the value of chain scission number. The variation of NaOH charge in the same reaction time indicated that the higher NaOH charge value, the lower value of the polymerization degree. The variation in reaction time indicated the longer the reaction time, the lower the polymerization degree. The reaction selectivity value was not affected by the high value of NaOH charge. The longer the reaction time used, the lower the reaction selectivity.

Characterization of alkali-extracted wood by FTIR-ATR spectroscopy

Attenuated total reflectance (ATR) infrared (IR) spectroscopy analyses were performed with silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips pretreated under alkaline (from 1 to 8% NaOH charge on wood dry solids) conditions to determine the suitability of this method in quickly determining chemical changes caused by varying treatment conditions on wood chemical structure. In addition to the alkali charge, pretreatment conditions varied with respect to temperature (130 and 150 °C) and treatment time (from 30 to 120 min). The spectral data of pretreated wood samples were compared to those of untreated reference samples, and the effects of the pretreatments conducted were determined based on these data. Results indicated that the most essential phenomena taking place during alkaline pretreatments could be detected by applying this simple and rapid spectral method requiring only a small sample amount. Such information included, for example, the cleavage of common lignin and carbohydrate bonds together with the significant removal of organics, especially hemicelluloses during pretreatments.

Antagonistic, synergistic and interaction effects of process parameters during oxygen delignification of Melia dubia kraft pulp

Melia dubia is a recently identified hardwood for papermaking. This study reports oxygen delignification of its kraft pulp. Modeling of O2 delignification was done implementing central composite design taking temperature, time and NaOH charge as process parameters while pulp yield, kappa number, intrinsic viscosity and brightness were the process outputs. The high precision quadratic models developed for O2 delignification revealed antagonistic, synergistic and significant interaction effects between temperature, time and NaOH charge. The optimum values of process parameters estimated were 90 °C, 90 min and 1.39% respectively which gave pulp yield 96.64%, total kappa number 10.52, intrinsic viscosity 628.54 cm3/g and brightness 42.52% which were very much comparable to other papermaking raw materials. On the whole, the optimization desirability obtained for O2 delignification was 0.621. The overall O2 delignification efficiency based on the total kappa number and the true lignin kappa number was found to be 30.33% and 38.23% respectively. The O2 delignification practiced in this investigation led to 10.42% increase in brightness and 19.93% reduction in viscosity which would prove advantageous for subsequent elemental and total chlorine free bleaching.

A comparable study on the hot-water treatment of wheat straw and okra stalk prior to delignification

Wheat straw and okra stalk were studied to evaluate their potential use for integrated lignocellulosic biorefining. Besides chemical pulp, a wide spectrum of value-added by-products were prepared by hot-water extraction of the feedstocks under varying conditions (140 °C for 60 and 240 min and 150 °C for 25 and 100 min) prior to sulfur-free soda-anthraquinone (AQ) pulping (NaOH charge 15 and 20% by weight on o.d. feedstock for wheat straw and okra stalk, respectively, with an AQ charge of 0.05% by weight on o.d. for both feedstocks). During the hot-water pre-treatment, the most significant mass removal, respectively, 12% (w/w) and 23% (w/w) of the initial wheat straw and okra stalk was obtained at 150 °C with a treatment time of 100 min. The hydrolysates were characterized in terms of pH and the content of carbohydrates (6–20% (w/w) of the initial amount), volatile acids (acetic and formic acids), and furans. The pre-treatment stage also facilitated the delignification stage, and, for example, the pulp yields (w/w), 57% (145 °C, 15 min, and kappa number 18) and 41% (165 °C, 180 min, and kappa number 32) were obtained for the pre-treated (150 °C, P200) wheat straw and okra stalk, respectively. Results clearly indicated that both non-wood materials were suitable for this kind of biorefining approach.

Characterization of pre-treatments on wood chips prior to delignification by near infrared spectroscopy

A near infrared (NIR) spectroscopy-based method for predicting yields and lignin contents of differently pre-treated silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips was developed. The approach was to create multivariate calibration models from the NIR data by the partial least squares (PLS) method. Both parameters are important factors when adjusting adequate conditions for pre-treatments either with hot-water (HW) as such and slightly acidified HW (collectively referred to as autohydrolysis) or dilute alkaline aqueous solutions prior to alkaline pulping. Pre-treatment conditions were varied with respect to temperature (130 °C and 150 °C) and treatment time (from 30 min to 120 min). In the case of alkaline pre-treatments, the NaOH charge was 1% to 8% NaOH on wood dry solids (DS). The yields varied in the range 81.2% to 99.3% (in autohydrolyses) and 83.5% to 97.9% (in alkaline pre-treatments). High correlation coefficients and low prediction errors in relation to conventional yield and lignin content data clearly indicated the suitability of NIR spectroscopy combined with the multivariate modeling as an effective and fast tool for this purpose. This technique also showed promising possibilities for developing practical process control methods to follow such pre-treatments.

A biorefinery scheme to fractionate bamboo into high-grade dissolving pulp and ethanol

BackgroundBamboo is a highly abundant source of biomass which is underutilized despite having a chemical composition and fiber structure similar as wood. The main challenge for the industrial processing of bamboo is the high level of silica, which forms water-insoluble precipitates negetively affecting the process systems. A cost-competitive and eco-friendly scheme for the production of high-purity dissolving grade pulp from bamboo not only requires a process for silica removal, but also needs to fully utilize all of the materials dissolved in the process which includes lignin, and cellulosic and hemicellulosic sugars as well as the silica. Many investigations have been carried out to resolve the silica issue, but none of them has led to a commercial process. In this work, alkaline pretreatment of bamboo was conducted to extract silica prior to pulping process. The silica-free substrate was used to produce high-grade dissolving pulp. The dissolved silica, lignin, hemicellulosic sugars, and degraded cellulose in the spent liquors obtained from alkaline pretreatment and pulping process were recovered for providing high-value bio-based chemicals and fuel.ResultsAn integrated process which combines dissolving pulp production with the recovery of excellent sustainable biofuel and biochemical feedstocks is presented in this work. Pretreatment at 95 °C with 12% NaOH charge for 150 min extracted all the silica and about 30% of the hemicellulose from bamboo. After kraft pulping, xylanase treatment and cold caustic extraction, pulp with hemicellulose content of about 3.5% was obtained. This pulp, after bleaching, provided a cellulose acetate grade dissolving pulp with α-cellulose content higher than 97% and hemicellulose content less than 2%. The amount of silica and lignin that could be recovered from the process corresponded to 95 and 77.86% of the two components in the original chips, respectively. Enzymatic hydrolysis and fermentation of the concentrated and detoxified sugar mixture liquor showed that an ethanol recovery of 0.46 g/g sugar was achieved with 93.2% of hydrolyzed sugars being consumed. A mass balance of the overall process showed that 76.59 g of solids was recovered from 100 g (o.d.) of green bamboo.ConclusionsThe present work proposes an integrated biorefinery process that contains alkaline pre-extraction, kraft pulping, enzyme treatment and cold caustic extraction for the production of high-grade dissolving pulp and recovery of silica, lignin, and hemicellulose from bamboo. This process could alleviate the silica-associated challenges and provide feedstocks for bio-based products, thereby allowing the improvement and expansion of bamboo utilization in industrial processes.

Impact of dissolved matter in the oxygen delignification stage

The presence of dissolved matter in the pulp suspension in an oxygen (O2) delignification stage, consisting mainly of dissolved lignin, is normally considered to negatively affect the delignification rate due to the competing reactions between the fiber bound lignin and the lignin dissolved in the filtrate. Recirculated oxidized filtrate from the post-O2 washing is usually considered to be less harmful to the delignification efficiency than unoxidized dissolved matter originating from the cooking stage. To develop a better understanding of the mechanisms of the dissolved matter’s reactions and impact on the O2 stage performance, laboratory oxygen delignification experiments with varying levels of unoxidized and oxidized dissolved matter were conducted. The results showed that unoxidized dissolved matter had a negative impact on the delignification in the O2 stage, whereas oxidized dissolved matter actually had a positive effect. The delignification efficiency of the laboratory experiments thus depends on both the amount of dissolved matter and its origin. The pulp viscosity decreased with increasing dissolved matter content irrespective of its origin but at higher COD levels; however, the viscosity drop was larger for the unoxidized dissolved matter. In terms of selectivity, the oxidized filtrate had a similar impact as additional NaOH charge. Both types of filtrates consumed hydroxide and the final pH decreased with increasing dissolved matter content. The final pH was significantly lower in the unoxidized filtrate experiments at higher COD levels, indicating a high reactivity between the unoxidized dissolved matter and the oxygen in the reactor. Based on the results, further understanding is achieved about the relation between pre-O2 washing performance and process configuration in an actual mill case, as well as the impact of dissolved matter on delignification. The importance of efficient removal of harmful unoxidized dissolved matter is verified, but the results also suggest that the oxidized dissolved matter that is recirculated from post-O2 washing actually has a significant positive impact on the delignification and is not just a potential problem in case of carryover to the bleach plant. Subsequently, pulp washing efficiency is critical both pre- and post-O2.

Organic Material Dissolved During Oxygen-Alkali Pulping of Hot-Water-Extracted Spruce Sawdust

Untreated and hot-water-extracted (HWE) Norway spruce (Picea abies) sawdust was cooked using the sulfur-free oxygen-alkali (OA) method under the following conditions: temperature, 170 °C; liquor-to-wood ratio, 5:1 L/kg; and NaOH charge, 19% on the oven-dry sawdust. In comparison with earlier studies conducted with birch sawdust, the spruce cooking yield data, together with the amount of the pulp rejects (78% to 86% for reference pulps from the initial feedstock and 73% to 83% for pulps from the HWE feedstock), revealed that the pretreatment stage prior to spruce OA pulping caused different effects on pulping performance. The analyses of the three main compound groups (i.e., lignin, volatile acids, and hydroxy acids) in black liquor indicated that slightly higher contents (25.5 to 45.9 g/L) of dissolved lignin were detected in black liquors originating from the HWE sawdust than in the black liquors from the reference material (27.2 to 39.6 g/L). In contrast, considerably lower (~20% decrease) volatile acid contents and similar or slightly decreased hydroxy acids contents were detected in the black liquors from the HWE sawdust.

Manufacture of Specialty Paper with Hemp Bast Fiber Cultivated in Korea (Part 1)- Characteristics of Hemp-Wood Paper by Soda Pulping -

To conserve wood resources for papermaking, chemical compositions of the hemp (Cannabis sativa L.) bast fiber cultivated in Korea such as holocellulose, <TEX>${\alpha}$</TEX>-cellulose, lignin, alcohol-benzene extractives, hot and cold water extractives, and ash contents were investigated to manufacture the specialty packaging paper effectively. Significantly very low klason lignin content of 3.3% was accomplished by removing of the outer shell of bark. Laboratory soda pulping method which is very useful for the nonwood fiber was adapted, and it was found that there was no significant difference in both kappa number and H-factor between 25% and 30% NaOH charge. Hemp pulp cooked with the laboratory digester in 25% NaOH at <TEX>$170^{\circ}C$</TEX> were mixed together with the wood pulp(NBKP:LBKP=1:1) in order to find the optimum mixture ratio which exhibited acceptable paper strength properties such as tensile index, burst index, and tear strength. When 10% of hemp soda pulps was mixed with 90% of wood pulps comprised of SwBKP and HwBKP (1:1), all physical strength increased significantly. The physical strength decreased as the amount of hemp pulp increased because the cell wall of bast fiber is very thick which causes low conformability and low fiber-fiber bonding. These results showed that paper made of hemp-wood pulp can be used for the specialty packaging paper which requires both the characteristic surface properties and the high physical strength of hemp fiber.

Reed Soda Pulping Modified by Green Liquor Pretreatment

The soda pulping modified by green liquor pretreatment was adopted to explore optimal green liquor pretreatment conditions. Results shows that optimum pretreatment conditions are as follows: max temperature, 130°C; holding time, 90min; wood to liquor ratio, 1:4; and green liquor charge, 0.9L/kg. Pretreated reed was pulped under following conditions: heating-up time, 60min; maximum temperature, 160°C; holding time, 60min; NaOH charge, 20% (pretreatment alkali included). Results shows that this process produces pulp with screened yield of 49.05%, Kappa number of 14.6, and viscosity of 1274mL/g. Compared with the results of industrial simulation pulping (21% NaOH), screened yield increases by 2.14%, Kappa number decreases by 5.6 and viscosity rises by 556 mL/g. Therefore, green liquor pretreatment before soda pulping improves pulp performance and yield. Meanwhile the pretreatment utilizes material effectively, thus has practical significance to decrease alkaline consumption and pulping cost.

Optimization of isolation of cellulose from orange peel using sodium hydroxide and chelating agents

Response surface methodology was used to optimize cellulose recovery from orange peel using sodium hydroxide (NaOH) as isolation reagent, and to minimize its ash content using ethylenediaminetetraacetic acid (EDTA) as chelating agent. The independent variables were NaOH charge, EDTA charge and cooking time. Other two constant parameters were cooking temperature (98°C) and liquid-to-solid ratio (7.5). The dependent variables were cellulose yield and ash content. A second-order polynomial model was used for plotting response surfaces and for determining optimum cooking conditions. The analysis of coefficient values for independent variables in the regression equation showed that NaOH and EDTA charges were major factors influencing the cellulose yield and ash content, respectively. Optimum conditions were defined by: NaOH charge 38.2%, EDTA charge 9.56%, and cooking time 317min. The predicted cellulose yield was 24.06% and ash content 0.69%. A good agreement between the experimental values and the predicted was observed.

Study on Comprehensive Utilization of Wheat Straw---XOS, Pulp and Energy

Pre-extraction of hemicellulose from wheat straw using alkaline cooking process was performed while the extract was enzymatic hydrolyzed and decolorized, and then the residual material after pre-extraction was cooked subsequently by soda pulping process. After that, the yield and characteristics of xylo-oligosaccharides (XOS) were analyzed, and the properties of the pulp and black liquor were also determined. The results indicate that the optimal dosage of alkali in the pre-extraction stage is 6%, the yield of XOS reaches to 40.45kg/t, and the degree of polymerization (DP) of XOS is 2.32. The yield of the subsequent soda pulp with lower NaOH charge is 378.1kg/t, its Kappa number and viscosity are similar to the control pulp, brightness, breaking length, tear index and folding endurance are higher than those of control. The viscosity of the black liquor is lower, and its gross calorific value is higher than that of control, over 15MJ/kg.

Removal of hemicelluloses by NaOH pre-extraction from aspen chips prior to mechanical pulping

chips prior to mechanical pulping, which would offer new feedstocks for the production of chemicals and fuels. The aim of this study was to evaluate pre-extraction to maximize pre-extraction yield, while minimizing negative impacts on wood chips. The effects of three independent process variables (NaOH charge, pre-extraction temperature, and time) on three dependent variables (pre-extraction yield, xylan extraction yield, and cellulose content based on original wood) were studied using a Box-Behnken experimental design. The mathematical models were obtained and validated well. It was found that NaOH charge, time, interaction between NaOH charge and time, and interaction between temperature and time have significant effects on xylan extraction yield. The xylan extraction yield was 22.55%; i.e., about 37.3 kg of xylan could be extracted from one ton of oven-dried aspen chips under the conditions of 5.68% NaOH charge, 100 °C, and 35 min.

Characterization of the Potential of Soda Cooking to Extract Fibrous Residues from Rice Hulls

In this paper, the potential of soda cooking to extract fibrous residues from rice hulls was investigated. Soda cooking was carried out at 170°C for 60 minutes using 5 to 13% NaOH. The goal was to selectively degrade silica and lignin from the structure of the rice hulls and produce fibrous carbohydrates that could be used as fillers in polymer biocomposites. This was studied by characterizing the physical and chemical properties of the fibrous residues and the spent liquor products. Results of scanning electron microscopy have revealed a substantial fragmentation of rice hulls above 7.5% NaOH charge. The fragmentation was accompanied with a significant removal of silica and lignin and the reduction of fibrous residues yield to 57% at 13%NaOH. Wet chemical composition analyses, infrared spectroscopy and x-ray spectroscopy have also revealed that lignin and silica were partly retained in the fibrous residue while the carbohydrates content were not affected. It is therefore concluded that soda cooking could be among the best processes for dissolving lignin and silica from rice hulls if the cooking conditions are optimized.

Process optimization of tetra acetyl ethylene diamine activated hydrogen peroxide bleaching of populus nigra CTMP

To enhance the bleaching efficiency, the activator of tetra acetyl ethylene diamine (TAED) was used in conventional H2O2 bleaching. The H2O2/TAED bleaching system can accelerate the reaction rate and shorten bleaching time at relative low temperature, which can reduce the production cost. In this research, the process with hydrogen peroxide activated by TAED bleaching of Populus nigra chemi-thermo mechanical pulp was optimized. Suitable bleaching conditions were confirmed as follows: pulp consistency 10%, bleaching temperature 70oC, bleaching time 60 min when the charge of H2O2 was 4%, NaOH charge 2%, and molar ratio of TAED to H2O2 0.3. The pulp brightness gain reached 23.6% ISO with the optimized bleaching conditions. FTIR analysis indicated that the H2O2/TAED bleaching system can decrease carbonyl group further than that of conventional H2O2 bleaching, which contributed to the higher bleaching efficiency and final brightness. The H2O2/TAED bleaching had stronger oxidation ability on lignin than that of H2O2 bleaching.

Effects of xylanase treatment on fibre morphology in totally chlorine free bleaching (TCF) of Eucalyptus pulp

The effects of xylanase on pulp properties and fibre morphology in a TCF (totally chlorine free) bleaching sequence has been studied. Enzymatic treatment is usually applied after oxygen delignification, but in this paper the effect of xylanase treatment before the oxygen delignification bleaching stage was studied. The application of xylanases in TCF bleaching of Eucalyptus kraft pulps enables the production of fully bleached pulps with high brightness (90% ISO) and viscosity (above 800 mL/g). The optimal NaOH charge in the oxygen delignification stage was studied. Xylanase treatment improves the accessibility of the bleaching chemicals to the fibres. The improvement of ‘bleachability’ produced by the enzyme reduces the quantity of ozone needed in subsequent bleaching stages. SEM (scanning electron microscopy) performed after oxygen delignification showed notable changes on fibre surfaces.

Researches on the Bleaching of NSSC Pulps With OP Sequences

In this study, to determine optimum bleaching conditions of NSSC pulps with OP sequences 15 oxygen prebleaching trials and 8 hydrogen peroxide bleaching trials were realized. As a result of statistical analysis of the data obtained, optimum oxygen and peroxide bleaching conditions of NSSC pulps were found as indicated below: Oxygen prebleaching; Reaction temperature: 110¼C Reaction time:20 min. NaOH charge:5% Consistency:12 % Magnesium sulfate:0.5 % Oxygen pressure:12 % Hydrogen prebleaching; Reaction temperature: 80¼C Reaction time:90 min. NaOH charge:4% Consistency:1.5 % Magnesium sulfate:10 % Oxygen pressure:1 % Brightness, breaking length, burst and tear index of NSSC pulps bleached with OP sequences were found 83.60%, 4.63%, 48,87% and 20.70% respectively higher than those of unbleached NSSC pulps. It is also possible bleaching NSSC pulps with OP sequences as high as 72 brighthess level. The content of colored and toxic organic material of OP bleaching sequences effluents is lower than those of chlorine based bleachings. The pulps bleached with OP sequences can be used in the production of printing and tissue papers in combination with sulphate and sulphite pulps. Additionally, these pulps may also be used in the production of newspaper.

Integrated cereal straw valorization by an alkaline pre-extraction of hemicellulose prior to soda-anthraquinone pulping. Case study of barley straw

Hemicellulose alkaline extraction was integrated prior to the well-known soda-anthraquinone (soda-AQ) pulping process. The resulting integrated process is called the integrated soda pulping (ISP) process. By the means of central compositely designed experiments, the ISP process was optimized in order to produce a good quality pulp from barley straw along with a significant amount of xylan-containing hemicellulose. The identified pre-extraction parameters to be optimized were the NaOH charge (dry straw basis), operating temperature, and extraction time. For comparison purposes, a reference soda-AQ pulp was also produced under the same cooking conditions. The optimized hemicellulose pre-extraction conditions were found with a 13% NaOH charge, at 60°C and for 2 h. By operating the pre-extraction stage under these conditions, 57% of the barley straw hemicellulose was recovered and was usable as a substrate for further chemical transformations. The strength properties of the ISP pulp at 40°SR (Shopper-Riegler beating degree) remain at a very good level for a cereal straw pulp; they were: breaking length = 9800 m, tear index = 5.40, burst index = 5.70. Only a very slight difference was detected between the ISP pulp and the reference soda-AQ pulp. A possible improvement regarding cereal straw black liquor processing and papermaking was suggested after analysis of the silica in the ISP black liquor and analysis of pentosans in the ISP pulp.