Effect of pulping variables with dimethyl formamide on the characteristics of bagasse-fiber

Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190-210 degrees C, time: 120-180 min, organic solvent ratio: 40-60% dimethyl formamide). Responses of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 14). Using values of the independent variables the variation ranges considered provided the following optimum values of the dependent variables: 82.7% (yield), 92.9 (kappa number), 1.403% (ash), 370 ml (freeness), 6290 m (breaking length), 9.4 (folding endurance), 5.955 mN m2 g(-1) (Tear index) and 2.811 kN g(-1) (Burst index) for pulps and handsheets. Results showed that acceptable physical and mechanical properties of pulps and papers similar the pulp used for bleaching could be achieved at 210 degrees C for 150 min and 50% DMF. These are the most suitable conditions for obtaining paper sheets with a high breaking length, tear and burst indices. Also bagasse could be pulped with ease to about 55.72% yield with kappa number approximately 35. The cooking temperature was a significant factor while the DMF ratio and cooking time were not as important in term of the properties of the resultant pulps and papers.     

A comparative study of the effect of refining on organosolv pulp from olive trimmings and kraft pulp from eucalyptus wood

This paper examines the influence of the degree of refining of different pulps, produced from olive trimmings and eucalyptus wood, on various physical properties. Corresponding pulps were obtained by means of different cooking processes. Pulp from olive trimmings was obtained by means of an organosolv process and pulp from eucalyptus was obtained by means of a kraft process. Pulp from olive trimmings exhibited a lower specific surface area, water retention volume, breaking length, stretch and burst index, but a higher porosity, than eucalyptus pulp. On the other hand, the same degree of refining was achieved with less energy for olive pulp than for eucalyptus pulp. Mixed pulp from olive trimmings and eucalyptus provided paper sheets with acceptable physical properties but with reduced refining energy costs relative to eucalyptus pulp alone.     

Influence of rice straw cooking conditions in the soda-ethanol-water pulping on the mechanical properties of produced paper sheets

A normalized design was used to examine the influence of independent variables (alcohol concentration, cooking time and temperature) in the catalytic soda-ethanol pulping of rice straw on various mechanical properties (breaking length, burst, tear index and folding endurance) of paper sheets obtained from each pulping process. An equation of each dependent variable as a function of cooking variables (independent variables) was obtained by multiple non-linear regression using the least square method by MATLAB software for developing of empirical models. The ranges of alcohol concentration, cooking time and temperature were 40-65% (w/w), 150-180 min and 195-210 degrees C, respectively. Three-dimensional graphs of dependent variables were also plotted versus independent variables. The optimum values of breaking length, burst and tear index and folding endurance were 4683.7 (m), 30.99 (kN/g), 376.93 (mN m2/g) and 27.31, respectively. However, short cooking time (150 min), high ethanol concentration (65%) and high temperature (210 degrees C) could be used to produce papers with suitable burst and tear index. However, for papers with best breaking length and folding endurance low temperature (195 degrees C) was desirable. Differences between optimum values of dependent variables obtained by normalized design and experimental data were less than 20%.     

Ethanol-acetone pulping of wheat straw. Influence of the cooking and the beating of the pulps on the properties of the resulting paper sheets

The influence of independent variables in the pulping of wheat straw by use of an ethanol-acetone-water mixture [processing temperature and time, ethanol/(ethanol + acetone) value and (ethanol + acetone)/(ethanol + acetone + water) value] and of the number of PFI beating revolutions to which the pulp was subjected, on the properties of the resulting pulp (yield and Shopper-Riegler index) and of the paper sheets obtained from it (breaking length, stretch, burst index and tear index) was examined. By using a central composite factor design and the BMDP software suite, equations that relate each dependent variable to the different independent variables were obtained that reproduced the experimental results for the dependent variables with errors less than 30% at temperatures, times, ethanol/(ethanol + acetone) value, (ethanol + acetone)/(ethanol + acetone + water) value and numbers of PFI beating revolutions in the ranges 140-180 degrees C, 60-120 min, 25-75%, 35-75% and 0-1750, respectively. Using values of the independent variables over the variation ranges considered provided the following optimum values of the dependent variables: 78.17% (yield), 15.21 degrees SR (Shopper-Riegler index), 5265 m (breaking length), 1.94% (stretch), 2.53 kN/g (burst index) and 4.26 mN m2/g (tear index). Obtaining reasonably good paper sheets (with properties that differed by less than 15% from their optimum values except for the burst index, which was 28% lower) entailed using a temperature of 180 degrees C, an ethanol/(ethanol + acetone) value of 50%, an (ethanol + acetone)/(ethanol + acetone + water) value of 75%, a processing time of 60 min and a number of PFI beating revolutions of 1750. The yield was 32% lower under these conditions, however. A comparison of the results provided by ethanol, acetone and ethanol-acetone pulping revealed that the second and third process-which provided an increased yield were the best choices. On the other hand, if the pulp is to be refined, ethanol pulping is the process of choice.     

Influence of dimethyl formamide pulping of wheat straw on cellulose degradation and comparison with Kraft process

The pulping of wheat straw with dimethyl formamide was studied in order to investigate the effects of the cooking variables (temperature (190 degrees C, 200 degrees C, and 210 degrees C) and time (120 min, 150 min, and 180 min) and organic solvent ratio (30%, 50%, and 70%) dimethyl formamide (DMF+water) value) on the degradation of cellulose and degree of polymerization (DP) of organosolv pulp. The SCAN viscosity was applied to estimating the extent of cellulose degradation produced by cooking condition and then, it was compared with Kraft pulp at equal Kappa number. Response of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 14). The process variables (cooking temperature and cooking time) must be set at low variables with high DMF ratio in order to ensure a high yield and high SCAN viscosity. Also, pulps with high mechanical properties can be acceptably obtained at 210 degrees C for 150 min with 50% DMF. Generally, the cooking temperature was a significant factor while the cooking time and DMF ratio had a smaller role. By the comparison of Kraft and organosolv pulp, it can be resulted that DMF basically had improvement role on reducing of cellulose degradation by reason of high SCAN viscosity of organosolv pulp than Kraft pulp under equal kappa number and, scanning electron microscopy (SEM) of obtained pulp. Consequently, the protective action of organic solvent on non-cellulosic polysaccharides of wheat straw against degradation under Kraft pulping conditions was pointed as a main reason of the fairly high yield of organosolv pulps.     

Organosolv pulping of wheat straw by use of phenol

A central composite design was used to investigate the influence of the cooking conditions (time, temperature and phenol concentration) for wheat straw with phenol-water mixtures on the properties of the pulp obtained (yield and holocellulose, -cellulose, lignin and ethanol-benzene extractable contents) and the pH of the resulting wastewater. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, -cellulose, lignin and ethanol-benzene extractable contents of the pulp, and the pH of the wastewater with multiple-R, R² and adjusted-R² high values. The process variables must be set at low variables in order to ensure a high yield and pH. Conversely, if high holocellulose and -cellulose contents, and low lignin and ethanol-benzene extractable contents are desired, then a high temperature (200°C), long cooking time (120 min), and intermediate phenol concentration (65%) must be used.     

Feasibility of utilizing Rhizoclonium in pulping and papermaking

Material of Rhizoclonium from brackish water in Taiwan was investigated for its possible use in pulping and papermaking. After beating, this filamentous alga produced a pulp with a length to width ratio of about 10, much less than that of a typical wood pulp. Handsheets made from this pulp had a moderate breaking length of 4.02 km. Cooking pre-beaten pulp with a low chemical charge (5–25%NaOH) at a low cooking temperature (100 ^°C), and for a short time (30–120 min) gave high algal pulp yields (70–80%). This cooking process was sulfur-free, but the water requirement was high. After cooking and further caustic soda and bleaching treatments, wide-angle X-ray diffraction and FTIR spectroscopy showed that the crystallinity of the algal pulp increased substantially, but type I cellulose conformation was retained. The best pulp mechanical strengths (breaking length 5.23 km,zero-span tensile strength 79.2 Nm g^-1, bursting index of 2.2 kpa m² g^-1) were obtained after cooking for 1 h with 20% NaOH. Because of the morphological characteristics of the algal strands, the pulp generally lacked bursting, tearing and folding strengths, but proper blending with softwood pulp increased the tensile breaking length to8.40 km, the tearing index to 14.5 mNm² g^-1, the bursting index to 6.42 kpam² g^-1 and the folding endurance to 4299 double folds, i.e. levels comparable to a typical kraft pulp. The algal pulp thus showed clear potential as a supplement for traditional medium strength wood pulps. This revised version was published online in August 2006 with corrections to the Cover Date.     

Wavelet neural networks applied to pulping of oil palm fronds

In the organosolv pulping of the oil palm fronds, the influence of the operational variables of the pulping reactor (viz. cooking temperature and time, ethanol and NaOH concentration) on the properties of the resulting pulp (yield and kappa number) and paper sheets (tensile index and tear index) was investigated using a wavelet neural network model. The experimental results with error less than 0.0965 (in terms of MSE) were produced, and were then compared with those obtained from the response surface methodology. Performance assessment indicated that the neural network model possessed superior predictive ability than the polynomial model, since a very close agreement between the experimental and the predicted values was obtained.     

Ethyleneglycol pulp from tagasaste

In this work, we examined the influence of operational variables [viz. Ethyleneglycol concentration (50-70%), temperature (155-185 degrees C), time (30-90 min) and number of PFI beating revolutions (500-1500)] in the ethyleneglycol pulping of tagasaste (Chamaecytisus proliferus) on pulp yield and the breaking length, stretch, burst index, tear index and brightness of paper sheets formed from it. Application of a fuzzy neural network model in combination with an experimental factorial design allowed the results for the dependent variables to be predicted as a function of the operating conditions used with errors less than 15% in all cases. The operating conditions of choice provided pulp with a high yield (56.85%) and a low brightness (22.51%) which may thus be useful to obtain non-white paper.     

Alkaline pulping of some eucalypts from Sudan

Four eucalypts (Eucalyptus camaldulensis, Eucalyptus microtheca, Eucalyptus tereticornis and Eucalyptus citriodora) grown in Sudan were examined for their suitability for pulping and papermaking with different alkaline methods. Their physical, morphological and chemical characteristics are reported. The pulping trials with E. citriodora and E. tereticornis were carried out using the kraft-AQ, soda-AQ, modified AS/AQ (ASA), ASAM and kraft methods. For the other two species, only the ASAM and the kraft process were applied. ASAM pulping gave the best results in terms of yield, degree of delignification, mechanical and optical pulp properties. The best pulps, obtained in kraft and ASAM cooking of E. citriodora, were bleached to 88% ISO brightness in a totally chlorine free bleaching sequence (OQ1O/PQ2P). The bleached pulps, especially the ASAM pulp, showed good papermaking properties and would be suitable for manufacture of writing and printing grades of paper.     

A comparison of kraft, PS, kraft-AQ and kraft-NaBH4 pulps of Brutia pine

The aim of this work was to study the effect of adding PS, AQ and NaBH(4) into kraft pulping with special attention given to NaBH(4). Kraft, kraft-AQ, PS, and kraft-NaBH(4) pulps were produced under the same cooking conditions and the pulps produced were compared in terms of pulp and paper properties. Kraft method was modified by adding 0.1% AQ, 4% PS and 2% and 4% NaBH(4) and the resultant pulps displayed an increase in pulp yield and reduction in both kappa number and screening rejects. On the other hand, there observed an increase in both pulp yield and kappa number when the kraft was modified to PS method. The benefits of NaBH(4) addition into kraft pulping was a significant reduction in kappa number and screening rejects and a significant increase in pulp yield. The most notable outcome of NaBH(4) was 66.6% increase in pulp brightness when 4% NaBH(4) was added into kraft pulping. Of unrefined pulps, unrefined kraft pulp displayed the highest strength of pulp, which is described as tear index at a constant tensile index. Of refined pulps, kraft-AQ showed the highest pulp strength when refined to 6000 and 12,000 revs in PFI mill.     

Comparative study of paper sheets from olive tree wood pulp obtained by soda,sulphite or kraft pulping

Paper sheets from olive tree wood pulp obtained by soda, sulphite or kraft pulping were studied to examine the influence of pulp beating on properties of the paper sheets.Paper sheets from kraft and sulphite pulps exhibited the highest resistance, and sulphite pulp the highest brightness. Soda pulp required more intensive beating than did kraft or sulphite pulps; in fact, the PFI beater had be operated at a 40–50% higher number of beating revolutions to obtain soda pulp with 70–80° SR.The breaking length, stretch, burst index and tear index of paper sheets obtained from kraft pulp, beaten to a Shopper–Riegler index of 70–80° SR were 20–30%, 30–50%, 50–60% and 15–35% higher, respectively, than those of sheets obtained from soda pulp.     

Comparison of polynomial and neural fuzzy models as applied to the ethanolamine pulping of vine shoots

The influence of operational variables in the pulping of vine shoots by use of ethanolamine [viz. temperature (155-185 degrees C), cooking time (30-90min) and ethanolamine concentration (50-70% v/v)] on the properties of the resulting pulp (viz. yield, kappa index, viscosity and drainability) was studied. A central composite factorial design was used in conjunction with the software BMDP and ANFIS Edit Matlab 6.5 to develop polynomial and fuzzy neural models that reproduced the experimental results of the dependent variables with errors less than 10%. Both types of models are therefore effective with a view to simulating the ethanolamine pulping process. Based on the proposed equations, the best choice is to use values of the operational valuables resulting in near-optimal pulp properties while saving energy and immobilized capital on industrial facilities by using lower temperatures and shorter processing times. One combination leading to near-optimal properties with reduced costs is using a temperature of 180 degrees C and an ethanolamine concentration of 60% for 60min, to obtain pulp with a viscosity of 6.13% lower than the maximum value (932.8ml/g) and a drainability of 5.49% lower than the maximum value (71 (o)SR).     

Influence of dimethyl formamide pulping of bagasse on pulp properties

Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190-210 degrees C, time: 120-180 min, organic solvent charge: 40-60% dimethyl formamide). Responses of pulp properties (yield and holocellulose, alpha-cellulose, kappa number, ash and ethanol-dichloromethane extractives contents) and the pH of the resulting wastewater to the process variables were analyzed using statistical software (MINITAB). Main factor analysis revealed that optimum pulp has the following characteristics: 82.7% (yield), 92.9 (kappa number), 95.84% (holocellulose), 83.53% (alpha-cellulose), 1.403% (ash), 2.562% (ethanol-dichloromethane extractives contents) and 6.39 (pH). These results showed that acceptable properties of pulps could be gained at 200-210 degrees C for 150 min and 40-60% DMF. Based on these results, this method could be used for pulping of bagasse equivalent NSSC concerning high yield at a fixed kappa number. In addition, bagasse could be pulped with ease to approximately 55% yield with a kappa number approximately 31. Numerical analyses showed that cooking temperature had the greatest influence on properties of obtained pulps within the DMF concentrations and cooking time as cooking variables.     

Influence of the holm oak soda pulping conditions on the properties of the resulting paper sheets

This paper reports on the influence of independent variables in the pulping of holm oak wood [viz. temperature (135-195 degrees C), cooking time (30-90 min) and soda concentration (10-20%)] on the properties of the resulting paper sheets. By using a central composite factorial design and a fuzzy neural model, equations relating each dependent variable to the different independent variables were derived that reproduced the experimental results for the dependent variables with errors less than 14%. Using a soda concentration of 17.5% at 195 degrees C for 30 min, it is possible to reduce the working capital (cost of chemical) and the capital investment, because it is operated with smaller values of the soda concentration and cooking time that maximum considered (20% of soda concentration and 90 min). The pulp yield thus obtained differed by less than 31.3% from the highest possible value; also, the resulting pulp and paper sheets had acceptable properties that differed by less than 21.10% from their optimum values.     

Biokraft pulping of European black pine with Ceriporiopsis subvermispora

European black pine (Pinus nigra Arn.) chips were treated with the white-rot fungus Ceriporiopsis subvermispora for periods ranging from 20 to 100 days. The effects of pretreatment on the chemical composition of wood and kraft pulping were investigated. The results showed that fungal pretreatment reduced the lignin and extractive content of wood chips. Also, weight losses occurred. Kappa number, viscosity, and reject ratio of biokraft pulps decreased. Biokraft pulps gave better response to beating, which led to significant energy saving during refining. The tear index, burst index, and tensile index of biokraft pulps were found to be lower than those of kraft pulps. However, the tensile index and burst index of 20-day biotreated and unbeaten pulp was higher than those of kraft pulp. Also, the tear index of 20-day biotreated and beaten pulp was higher than that of kraft pulp. The brightness of biokraft pulps decreased irregularly with increasing incubation time.     

Positive and negative aspects of soda/anthraquinone pulping of hardwoods

The positive aspects of the non-sulfur soda/anthraquinone (SAQ) process are mostly tied to improved energy efficiency while lower pulp brightness after bleaching is its most significant drawback. A credible method that quantifies bleachability as well as an approach that solves the problem for SAQ pulps from hardwoods will be described. A straight line correlation (R2=0.904) was obtained between O2 kappa number and final light absorption coefficient (LAC) value after standardized OD0EpD1 bleaching of nine hardwood kraft pulps from three laboratories and one pulp mill. The bleachability of pulps from four different soda processes catalyzed by anthraquinone (AQ) and 2-methylanthraquinone (MAQ) was compared to that of conventional kraft pulps by comparing O2 kappa number decrease and final LAC values. It was observed that a mild hot water pre-hydrolysis improved the bleachability of SAQ pulps to a level equal to that of kraft.     

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.     

Optimization of pulping conditions of abaca. An alternative raw material for producing cellulose pulp

The influence of temperature (150-170 degrees C), pulping time (15-45 min) and soda concentration (5-10%) in the pulping of abaca on the yield, kappa, viscosity, breaking length, stretch and tear index of pulp and paper sheets, was studied. Using a factorial design to identify the optimum operating conditions, equations relating the dependent variables to the operational variables of the pulping process were derived that reproduced the former with errors lower than 25%. Using a high temperature, and a medium time and soda concentration, led to pulp that was difficult to bleach (kappa 28.34) but provided acceptable strength-related properties (breaking length 4728 m; stretch 4.76%; tear index 18.25 mN m2/g), with good yield (77.33%) and potential savings on capital equipment costs. Obtaining pulp amenable to bleaching would entail using more drastic conditions than those employed in this work.     

Mutagenic properties of spent bleaching liquors from sulphite pulps and a comparison with kraft pulp bleaching liquors

Parameters influencing the mutagenic properties of spent bleaching liquors from sulphite pulps have been studied. In addition a comparison has been made between the properties of spent liquors from sulphite and kraft pulp bleaching. In the sulphite process the cooking base had no influence on the mutagenicity of the chlorination stage. In contrast, removing the extractives before chlorination especially for dissolving pulp resulted in an increase in mutagenic activity. The mutagenicity decreased significantly after substituting 40% of the chlorine with chlorine dioxide. Sequential addition of chlorine and chlorine dioxide resulted in higher activity than simultaneous or premixed chlorination as observed for liquors from kraft pulp. Increasing the pH of the extracts or addition of sulphur dioxide decreased the mutagenicity. Expressed as 10(7) revertants per kappa number and ton pulp the mutagenicity varied between 10 and 40 for sulphite pulp while the corresponding figures for kraft pulp were 100-225.