Design, optimization and modelling of a chemical recovery system for wet spinning of cellulose in sodium carbonate solutions

Abstract The aim of this study is to present the design, optimization and modelling of a chemical recovery system for a novel CS2-free viscose-type process that entails dissolution of pre-treated dissolving pulp in a continuous-flow reactor in cold alkali and wet spinning of cellulose in sodium carbonate solutions. Technologies already known to other industries for the recovery and reuse of chemicals, such as causticizing, recalcination, recarbonization and freeze-separation, were used. Chemical equilibria simulations were performed with OLI Studio 9.5, with the purpose to select experimental conditions which avoid undesired precipitations in each unit operation. Synthetic solutions mimicking the spent coagulation liquor were used in the laboratorial experiments. The proposed chemical recovery system was shown to be technically feasible and reduce chemical make-ups to a minimum of 45 kg/ton of NaOH and 4 kg/ton of H2SO4. Small amounts of Zn are expected to precipitate during recarbonization of the coagulation liquor at 30 °C and causticizing at 98 °C. Thus, a filter for ZnO particles should be included in the design of the recarbonization unit and a continuous purge of lime mud and input of fresh lime make-up should be needed to keep burnt lime availability at an acceptable level. Overall, the results presented in this study portray a solution to reduce operating costs and the environmental impact of novel viscose-type processes with alkaline spin dopes and wet spinning of cellulose in sodium carbonate solutions.

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Thermal Decomposition of Sodium Carbonate Solutions.

Journal of Chemical & Engineering Data ◽

10.1021/je60016a014 ◽

1963 ◽

Vol 8 (1) ◽

pp. 51-54 ◽

Cited By ~ 7

Author(s):

Authur M. Thomas

Keyword(s):

Thermal Decomposition ◽

Sodium Carbonate ◽

Carbonate Solutions

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MEA/water/AQ-pulping of wheat straw

Holzforschung ◽

10.1515/hf.2009.110 ◽

2009 ◽

Vol 63 (5) ◽

Cited By ~ 4

Author(s):

Sahab Hedjazi ◽

Othar Kordsachia ◽

Rudolf Patt ◽

Andreas Kreipl

Keyword(s):

Wheat Straw ◽

Total Yield ◽

Strength Properties ◽

Kappa Number ◽

Chemical Recovery ◽

Oxygen Delignification ◽

Cooking Temperature ◽

Recovery System ◽

Environmentally Sound ◽

High Yields

Abstract Annual plant pulping is faced with serious challenges. Traditional pulping processes with bleaching in chlorine based sequences and without appropriate chemical recovery system cannot be tolerated anymore. Alternative pulping processes with non-conventional chemicals, such as organic solvents, e.g., monoethanolamine (MEA), might be suited for an environmentally sound process with a closed mill system. Thus, pulping of wheat straw with MEA as the main delignifying agent was investigated in comparison to soda and soda/AQ pulps as references. The main focus was placed on reduction of the cooking temperature in order to avoid heat-induced MEA degradation. The temperature was reduced stepwise from 165°C to 130°C. At 150°C, a sufficient delignification was achieved. MEA was partly substituted by water and the resulting decrease of the delignification rate could be compensated by addition of anthraquinone (AQ). After optimization of the process, a pulp with a kappa number of 17 was obtained at a total yield of 56% based on o.d. straw. This pulp was selected for bleaching. Both, O/Q/OP/DQ/P (“ECF light”) and O/Q/OP/ZQ/P (TCFZ) bleaching were applied. NaOH was substituted by MEA as alkali source in the oxygen delignification stage. Up to 50% delignification rate was achieved under these moderate conditions. In the ECF light bleaching sequence, a brightness of 80% ISO was reached at a kappa number level below 3. In TCFZ bleaching, an even somewhat higher brightness was achieved at a kappa number level below 1. A yield of fully bleached screened pulp of around 50% (based on o.d. straw) was obtained. The strength properties of the MEA pulp were improved after bleaching. ECF bleaching resulted in slightly better pulp strengths than the TCFZ alternative. MEA forms in combination with water and AQ a very selective pulping system providing effective delignification and maintaining extremely high yields. MEA/water/AQ pulping should be regarded as a serious, environmentally friendly alternative to soda or soda/AQ pulping to produce high-quality pulp from wheat straw.

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Assessment of non-standard reaction conditions for asymmetric 1,3-dipolar organocatalytic cycloaddition of nitrone with α,β-unsaturated aldehydes

Chemical Papers ◽

10.1515/chempap-2015-0020 ◽

2015 ◽

Vol 69 (5) ◽

Cited By ~ 3

Author(s):

Melinda Mojzesová ◽

Mária Mečiarová ◽

Ambroz Almássy ◽

Roger Marti ◽

Radovan Šebesta

Keyword(s):

Ionic Liquids ◽

Flow Reactor ◽

Dipolar Cycloaddition ◽

Reaction Conditions ◽

Experimental Conditions ◽

Flow Process ◽

Unsaturated Aldehydes ◽

Solvent Free Conditions ◽

Standard Reaction ◽

Organocatalytic Reactions

AbstractNon-standard experimental conditions can often enhance organocatalytic reactions considerably. The current study explores the effectiveness of a range of non-standard reaction conditions for the asymmetric organocatalytic 1,3-dipolar cycloaddition of a nitrone with α,β-unsaturated aldehydes. The influence of ionic liquids, high-pressure conditions, ultrasound, microwave irradiation and ballmilling was tested as well as the flow process. Because of the low reactivity of the nitrone and unsaturated aldehydes in the 1,3-dipolar cycloaddition, cycloadducts were isolated in only moderate yields from the majority of experiments. However, high diastereo- and enantioselectivities were observed in ionic liquids under solvent-free conditions and in the flow reactor.

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THE EVOLUTION OF CARBON DIOXIDE IN THE A.-C. ELECTROLYSIS OF SODIUM CARBONATE AND BICARBONATE SOLUTIONS, AND THE DISCHARGE POTENTIALS OF CARBONATE AND BICARBONATE IONS

Canadian Journal of Research ◽

10.1139/cjr34-111 ◽

1934 ◽

Vol 11 (4) ◽

pp. 539-546

Author(s):

J. W. Shipley

Keyword(s):

Carbon Dioxide ◽

Sodium Bicarbonate ◽

Sodium Carbonate ◽

Current Flow ◽

Platinum Electrodes ◽

Sodium Salts ◽

Bicarbonate Ions ◽

Carbonate Solutions ◽

Bicarbonate Solutions ◽

Discharge Potential

The a.-c. electrolysis of sodium carbonate solutions at voltages as high as 110, even when arcing occurs on the electrodes, does not cause the evolution of carbon dioxide. In the a.-c. electrolysis of aqueous bicarbonate solutions with platinum electrodes, hydrogen, oxygen and carbon dioxide are evolved freely until all the bicarbonate has been transformed to carbonate, after which the evolution of carbon dioxide ceases and only hydrogen and oxygen are given off. In a.-c. electrolysis of sodium bicarbonate solutions and solutions of the sodium salts of aliphatic acids, a deposit of finely divided platinum is formed on the electrodes. This deposit inhibits the evolution of carbon dioxide, hydrogen and oxygen, but does not affect the current flow. The decomposition potential of bicarbonate solutions in respect to the evolution of carbon dioxide on smooth platinum and with d.c. was found to be 2.2 volts, and of carbonate solutions, 3.5 volts. The anodic discharge potential of HCO3− is − 1.45 to − 1.50 volts, and of CO3−−, − 1.90 to − 1.95 volts. The evolution of carbon dioxide does not appear to cause any polarizing effect on the anode.

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pH and conductivity of concentrated aqueous sodium sulfide/sodium carbonate solutions undergoing carbonation

The Canadian Journal of Chemical Engineering ◽

10.1002/cjce.5450680224 ◽

1990 ◽

Vol 68 (2) ◽

pp. 346-348 ◽

Cited By ~ 1

Author(s):

Jack C. Norman ◽

Nancy J. Sell ◽

John A. Ciriacks

Keyword(s):

Sodium Carbonate ◽

Sodium Sulfide ◽

Aqueous Sodium ◽

Carbonate Solutions

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The application of resonance enhanced multiphoton ionization to the detection of hydrogen atoms during the oscillatory combustion of hydrogen

Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences ◽

10.1098/rspa.1991.0099 ◽

1991 ◽

Vol 434 (1891) ◽

pp. 399-412 ◽

Cited By ~ 5

Keyword(s):

Numerical Analysis ◽

Flow Reactor ◽

Multiphoton Ionization ◽

Laser Wavelength ◽

Time Profile ◽

Experimental Result ◽

Oh Radicals ◽

Hydrogen Atoms ◽

Experimental Conditions ◽

Concentration Time

The relative concentrations of hydrogen atoms were measured during the oscillatory ignition of hydrogen in a well stirred flow reactor. Comparisons were made with the experimental concentration—time profiles of the hydroxyl radical obtained previously under similar experimental conditions. The predicted concentration profiles obtained from numerical analysis of a thermokinetic model were also compared with the experimental results. Experiments were performed in a 600 cm 3 Pyrex glass, jet-stirred reactor with the reactants, 2H 2 + O 2 , at a total pressure of 16 Torr ( ca . 2132.8 Pa) and at a vessel temperature of 753 K. The mean residence time was 1.2 s. Oscillatory ignition was established at a period of 3 s in which high radical concentrations were attained and in which the temperature rise was almost adiabatic. The concentration-time profile of hydrogen atoms was obtained by a resonance enhanced multiphoton ionization (rempi) which was induced by a laser pulse at energies in the vicinity of 364 nm, with ion collection at a stainless steel probe inserted into the reactor. Supplementary studies were made to characterize the signals and to identify effects of the probe within the reaction volume. A measurement of the relative concentrations of hydrogen atoms was obtained from an integration of the area of the rempi spectrum determined over the laser wavelength range 363.8-364.6 nm. The spectrum was measured at successive times in the oscillatory cycle by imposing a variable delay on the laser firing signal. The results show that, during oscillatory ignition, the maximum concentration of hydrogen atoms was reached and a sharp decay was already well advanced before that of the hydroxyl radicals was attained. The numerical analysis was in very good quantitative accord with this experimental result. The phase difference of the cyclic variation in the H atoms relative to that of OH radicals is a key feature of the kinetic mechanisms which control the oscillatory oxidation of hydrogen.

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