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Search Results: 1 - 10 of 958 matches for " alkaline pulping "
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Optimal operating points in alkaline pulping
Costanza,Vicente; Zanuttini,Miguel A.;
Latin American applied research , 2004,
Abstract: the problem of optimizing the alkaline impregnation of wood chips is posed and solved under usual restrictions. the cost to be optimized balances opposite criteria by taking economics and product quality into account, and is conditioned by the system dynamics. evolution is modeled from typical transport phenomena equations. optimization is attacked in the lines of variational calculus, although the final treatment involves numerical methods. cost function design is provided for: alkali consumption, thermal energy consumption, product quality, and total production; each one affected by a preference-weighting coefficient. a new parameter, the "deacetylation index", is introduced as an observable quantity for tracking the end of the digestion stage in pulping processes. this index turns out to be significant even at low temperatures. cost terms depend essentially on three design variables: (i) alkaline bulk concentration, (ii) digester temperature, and (iii) total duration of the process. an algorithm to ascertain the optimal values of these variables is devised. numerical results provide insight in deciding changes on design variables in case they are allowed within a certain extent to be manipulated.
Optimal operating points in alkaline pulping
Vicente Costanza,Miguel A. Zanuttini
Latin American applied research , 2004,
Abstract: The problem of optimizing the alkaline impregnation of wood chips is posed and solved under usual restrictions. The cost to be optimized balances opposite criteria by taking economics and product quality into account, and is conditioned by the system dynamics. Evolution is modeled from typical transport phenomena equations. Optimization is attacked in the lines of variational calculus, although the final treatment involves numerical methods. Cost function design is provided for: alkali consumption, thermal energy consumption, product quality, and total production; each one affected by a preference-weighting coefficient. A new parameter, the "Deacetylation Index", is introduced as an observable quantity for tracking the end of the digestion stage in pulping processes. This index turns out to be significant even at low temperatures. Cost terms depend essentially on three design variables: (i) alkaline bulk concentration, (ii) digester temperature, and (iii) total duration of the process. An algorithm to ascertain the optimal values of these variables is devised. Numerical results provide insight in deciding changes on design variables in case they are allowed within a certain extent to be manipulated.
Estimating pure diffusion contributions in alkaline pulping processes
Costanza,Vicente; Costanza,Pedro;
Latin American applied research , 2002,
Abstract: a model that predicts isothermal alkali diffusion and reaction with acetyl groups in moist wood chips was derived and approximated. system parameters were estimated from unsteady-state experimental data. simulation results reinforce the idea that the diffusion effect is not fully exploited in pulping processes. traditionally, digestion is conducted at high temperature, where delignification reaction kinetics is enhanced and the reaction effect is predominant. this approach is being reviewed by modern industry since energy and environmental savings associated with low temperature operation might compensate for high-yield productivity. the concentration of alkali at the center of the chip is a measure of the completeness of wood deacetylation, which translates into the aptitude of the final product for pulping purposes. this concentration is predicted here from the solution to a pair of coupled ode's. since alternatives combining both low and high-temperature processes are being studied, the results in this paper provide basic data for optimization analysis.
Estimating pure diffusion contributions in alkaline pulping processes
Vicente Costanza,Pedro Costanza
Latin American applied research , 2002,
Abstract: A model that predicts isothermal alkali diffusion and reaction with acetyl groups in moist wood chips was derived and approximated. System parameters were estimated from unsteady-state experimental data. Simulation results reinforce the idea that the diffusion effect is not fully exploited in pulping processes. Traditionally, digestion is conducted at high temperature, where delignification reaction kinetics is enhanced and the reaction effect is predominant. This approach is being reviewed by modern industry since energy and environmental savings associated with low temperature operation might compensate for high-yield productivity. The concentration of alkali at the center of the chip is a measure of the completeness of wood deacetylation, which translates into the aptitude of the final product for pulping purposes. This concentration is predicted here from the solution to a pair of coupled ODE's. Since alternatives combining both low and high-temperature processes are being studied, the results in this paper provide basic data for optimization analysis.
INCLUSION OF A PRESSURIZED ACIDOLYSIS STAGE IN CHEMICAL PULP BLEACHING
Samar K. Bose,Aaron Leavitt,Bertil Stromberg,Dipankar Kanungo
BioResources , 2011,
Abstract: Hardwood soda-AQ pulps are believed to be rich in benzyl sugar ethers (BSE) that can be partially cleaved by aqueous acidic treatments. The aim of this investigation was to evaluate the effect of acidolysis on final bleached brightness for kraft and soda-AQ (SAQ) hardwood pulps. The increase in final brightness due to acidolysis at 110 °C was twice as high for a eucalyptus SAQ pulp as compared to the kraft pulp. An oxygen delignified maple C-SAQ pulp (carbonate pre-treated SAQ) was acidolyzed at 120 °C and pH 2.6 for 30 min. When 1.60% ClO2 + 0.25% H2O2 on pulp was used in DEPD final bleaching of the control sample a brightness of 91.5% was achieved. When only 1.00% ClO2 + 0.25% H2O2 on pulp was used for the acidolyzed sample a brightness of 92.0% was attained. Analyses of the maple pulp after the acidolysis showed no major change in lignin content, brightness, or pulp yield. The minor changes suggest that a facile reaction such as benzyl ether cleavage was responsible for the improved bleachability. Preliminary research involving a lignin model compound and commercial birch xylan showed that lignin-carbohydrate condensation products were generated under SAQ cooking conditions. Furthermore, a fraction of these lignin-carbohydrate moieties were subsequently cleaved by acidolysis at pH 2.5 and 105 °C.
SONOCHEMICALLY MODIFIED WHEAT STRAW FOR PULP AND PAPERMAKING IN ORDER TO INCREASE ITS ECONOMICAL RATES AND REDUCE THE ENVIRONMENTAL ISSUES
Levente Csoka,Attila Lorincz,Andras Winkler
BioResources , 2008,
Abstract: Wheat straw (an agricultural by-product) was pulped by an alkaline anthraquinone (AQ) process. Then the straw pulp was treated by high-power ultrasound under different noble-gas (argon, krypton, xenon) combinations. The pulps’ degree of beating and acid-insoluble lignin content were measured. Handsheets were made from sonicated and control pulps and tested for paper tensile strength. In this study we explore which noble-gas combination with ultrasound may be more useable to reduce the lignin content and enhance fibrillation. We also describe the most effective ultrasound-assisted, modified alkaline pulping process. Overall, we found that in two steps ultrasonification decreased the residual lignin contents more then 75 %, the pulp fibrillation increased from 12 to 70 °SR within 20 min. of ultrasound irradiation, and the tensile index of the handsheets increased by 65%. For sustainable paper production, it is required to develop alternative paper resources. Paper made from alternate fiber resources with efficient technology will improve our living standards without sacrificing the environment, our habitat. High frequency ultrasound-based pulp processing offers significant improvements, and it reduces energy and chemical consump-tions for pulp and paper production.
USING A MEMBRANE FILTRATION PROCESS TO CONCENTRATE THE EFFLUENT FROM ALKALINE PEROXIDE MECHANICAL PULPING PLANTS
Yong Zhang,Chun-Yu Cao,Qing-Xi Hou,Wen-Ying Feng
BioResources , 2010,
Abstract: Using a multi-effect evaporation system to concentrate the effluent from alkaline peroxide mechanical pulping (APMP) plants is known to require a high energy consumption. In order to improve the situation, a polyethersulfone membrane was used to concentrate the effluent of APMP plants beforehand. An orthogonal experimental design was applied and a mathematical model was established to optimize the filtration parameters. An estimation of potential energy and water savings from this new concentration process was developed. The optimal filtration conditions obtained were: molecular weight cut-off at 10,000 Dalton, trans-membrane pressure at 3 bar, feed temperature at 50oC, cross-flow velocity at 420 rpm, and volume reduction factor at 0.93. The average permeate flux under these conditions was 45.31 l/m2.h. The total solids content was increased from 14.74 g/l in the feed to 95.04 g/l in the concentrate. The permeate had low total solid contents of 8.75 g/l, Chemical Oxygen Demand of 6696 mg/l, and Biochemical Oxygen Demand of 4383 mg/l. Such qualities would allow the permeate to be reused in the alkaline peroxide mechanical pulping process. With this new concentration process, about 4840.6 kwh energy can be saved and 23.3 m3 effluent discharge can be reduced for each ton of pulp produced.
PERFORMANCE OF A PILOT-SCALE MEMBRANE PROCESS FOR THE CONCENTRATION OF EFFLUENT FROM ALKALINE PEROXIDE MECHANICAL PULPING PLANTS
Yong Zhang,Chun-Yu Cao,Wen-Ying Feng,Guo-Xin Xue
BioResources , 2011,
Abstract: A pilot-scale membrane process for the concentration of effluent from an alkaline peroxide mechanical pulping (APMP) plant was investigated. Specifically, the cross-flow velocity and volume reduction were optimized again for a higher flux and a lower system energy consumption. A mathematical model was established to obtain the optimal parameters. Estimates were obtained of the expected savings in energy and water. The obtained optimal concentration conditions were: molecular weight cut-off at 10,000 Dalton, trans-membrane pressure at 3 bar, feed temperature at 50 oC, cross-flow velocity at 2 m/s, and volume reduction at 0.9. The average permeate flux under these conditions was 43.21 l/m2.h. The total solids content was increased from 25.47 g/L in the feed to 128.36 g/L in the concentrate. The permeate had low total solids content of 11.03 g/L, Chemical Oxygen Demand of 9180 mg/l, and Biochemical Oxygen Demand of 5870 mg/L. Such qualities would allow the permeate to be reused in the APMP process after a light biochemical treatment. With this new membrane concentration process, about 1402 kWh energy can be saved and 22 m3 effluent discharge can be reduced for each ton of pulp produced.
EFFECTS OF ALKALINE PRE-IMPREGNATION AND PULPING ON MALAYSIA CULTIVATED KENAF (HIBISCUS CANNABINUS
Lin Suan Ang,Cheu Peng Leh,Chong Chat Lee
BioResources , 2010,
Abstract: This study was carried out to identify an appropriate alkaline pulping condition for Malaysia cultivated kenaf (Hibiscus cannabinus L.). The chemical composition of the kenaf bast and core fibers, and also whole stalk with different growing time were examined prior to pulping attempts. The results of various soda-AQ pulping showed that the degree of carbohydrate degradation and delignification increased with the increase of active alkali and cooking temperature, but decreased with the increase of liquor to material (L:M) ratio. The most satisfactory properties of pulp and handsheets from bast could be attained by employing soda-AQ pulping with 19.4% active alkali, 0.10% AQ, and L:M ratio of 7:1 cooked for 2 hours at 160 C. Besides, it was also found that a mild alkaline pre-impregnation prior pulping improved the pulp viscosity and handsheets’ strength properties, especially the tensile index and folding endurance effectively. Moreover, among the three alkaline pulping processes—kraft, kraft-AQ, and soda-AQ—the results of pulp and handsheet properties showed that the soda-AQ pulp was comparable or even slightly of higher quality than the kraft pulps. Between the unbeaten bast and core soda-AQ handsheets, the strength properties of the core were higher than the bast, as the thin-walled core fibers exhibited much better conformability than the thick-walled bast fibers.
Tratamientos aplicables para la reducción de la DQO recalcitrantede efluentes de pulpados quimimecánicos y semiquímicos(revisión)
Area,María C; Ojeda,Sergio A; Barboza,Olga M; Bengoechea,Dora I; Felissia,Fernando E.;
Revista de ciencia y tecnolog?-a , 2010,
Abstract: semichemical and chemimechanical pulping processes, due to their high yield, do not have efficient recovery systems based on combustion of dissolved organic matter. the substances discharged with the effluent of a pulp plant vary depending on the process, but generally are colored materials, materials which could be easy and difficult to biodegrade, and toxic materials. after the biological treatment of the effluent, certain amount of organic matter which is difficult to degrade remains, known as recalcitrant, and measured as chemical oxygen demand (cod). there are different methods for the elimination or degradation of these substances, as physico-chemical treatment, conventional biological treatments also with fungi, and integrated treatment processes. this paper presents a review of these methods, related to their efficiency in removing the cod of the effluent.
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