| 1. |
- Jönsson, Ann-Sofi, et al.
(författare)
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A concentration polarization model for the ultrafiltration of nonionic surfactants
- 2006
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 304:1, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model has been developed that describes ultrafiltration of nonionic surfactants. The model takes into account the fact that surfactants start to aggregate and form micelles at the critical micelle concentration, The model can be used to predict the performance of the membrane if the transport properties inside and at the membrane surface as well as the surfactant association behavior, are known. Three hydrophilic ultrafiltration membranes, made of regenerated cellulose, were used in the investigation. The cut-offs of the membranes were 10,000, 20,000, and 30,000 Da. The surfactant used in the investigation was the nonionic surfactant Triton X-100. The influence of the concentration of surfactant, transmembrane pressure and pure water flux were studied theoretically and experimentally. From the results presented in this work it can be concluded that the calculated values are in good agreement with experimental data. (c) 2006 Elsevier Inc. All rights reserved.
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| 2. |
- Andersson, Alexandra, et al.
(författare)
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Comparison of diafiltration and size-exclusion chromatography to recover hemicelluloses from process water from thermomechanical pulping of spruce
- 2007
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Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 1559-0291 .- 0273-2289. ; 137:1-12, s. 971-983
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Tidskriftsartikel (refereegranskat)abstract
- Hemicelluloses constitute one of the most abundant renewable resources on earth. To increase their utilization, the isolation of hemicelluloses from industrial biomass side-streams would be beneficial. A method was investigated to isolate hemicelluloses from process water from a thermomechanical pulp mill. The method consists of three steps: removal of solids by microfiltration, preconcentration of the hemicelluloses by ultrafiltration, and purification by either size-exclusion chromatography (SEC) or diafiltration. The purpose of the final purification step is to separate hemicelluloses from small oligosaccharides, monosaccharides, and salts. The ratio between galactose, glucose, and mannose in oligo- and polysaccharides after preconcentration was 0.8: 1: 2.8, which is similar to that found in galactoglucomannan. Continuous diafiltration was performed using a composite fluoro polymer membrane with cutoff of 1000 Da. After diafiltration with four diavolumes the purity of the hemicelluloses was 77% (gram oligo- and polysaccharides/gram total dissolved solids) and the recovery was 87%. Purification by SEC was performed with 5, 20, and 40% sample loadings, respectively and a flow rate of 12 or 25 mL/min (9 or 19 cm/h). The purity of hemicelluloses after SEC was approx 82%, and the recovery was above 99%. The optimal sample load and flow rate were 20% and 25 mL/min, respectively. The process water from thermomechanical pulping of spruce is inexpensive. Thus, the recovery of hemicelluloses is not of main importance. If the purity of 77%, obtained with diafiltration, is sufficient for the utilization of the hemicelluloses, diafiltration probably offers a less expensive alternative in this application.
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| 3. |
- Holmqvist, Anders, et al.
(författare)
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Ultrafiltration of kraft black liquor from two Swedish pulp mills
- 2005
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Ingår i: Chemical Engineering Research & Design. - : Elsevier BV. - 0263-8762. ; 83:A8, s. 994-999
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Tidskriftsartikel (refereegranskat)abstract
- Extraction of lignin by ultrafiltration of black liquor from two Swedish pulp mills has been studied. One of the mills employs batch digestion and the other continuous digestion. At both mills softwood was used as raw material. The black liquor was withdrawn before the evaporator unit. A ceramic membrane with a cut-off of 15 000 g mol(-1) was used in the experiments. The average flux during concentration to 90% volume reduction was 160 and 110L m(-2) h(-1) for the liquors from the batch and the continuous digestion processes, respectively, when the temperature was 90 degrees C and the transmembrane pressure 200 kPa. The retention of lignin was about the same for both liquors, 35%. A cost estimate of extraction of lignin fuel from black liquor was made, based on experimental data from ultrafiltration at various operating conditions. The cost was found to be about 20 E per MWh of calorific value of the lignin fuel.
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| 4. |
- Jönsson, Ann-Sofi, et al.
(författare)
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Concentration and purification of lignin in hardwood kraft pulping liquor by ultrafiltration and nanofiltration
- 2008
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Ingår i: Chemical Engineering Research & Design. - : Elsevier BV. - 0263-8762. ; 86:11A, s. 1271-1280
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Tidskriftsartikel (refereegranskat)abstract
- Today, there is considerable interest in integrated forest biorefineries which, besides pulp, produce high-value-added products, such as, polymers and carbon fibres. Lignin is the major non-cellulosic constituent of wood. It is a complex, amorphous highly crosslinked polyphenolic. Lignosulphonate in spent liquor in sulphite mills has long been isolated using ultra filtration. Generally, precipitation is used to extract the lignin from kraft black liquor. The liquor is commonly withdrawn from the evaporation unit in the recovery system, where the dry substance is optimal for precipitation. Lately, interest in the isolation of lignin by ultrafiltration of kraft black liquor has arisen. The concentration of the liquor is not that critical, and there is therefore considerable freedom in the choice of liquor for treatment with ultra filtration. In this work, the influence of membrane cut-off, transmembrane pressure and cross-flow velocity during ultrafiltration of cooking liquor and black liquor was studied. The extraction of lignin from hardwood black liquor withdrawn before the evaporation unit was investigated. A hybrid ultrafiltration/nanofiltration process was used. The lignin concentration was 60 g/l in the black liquor and 165 g/l in the product stream (the narrofiltration retentate). A cost estimate indicates a production cost of (sic)33 per tonne of lignin. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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| 5. |
- Jönsson, Ann-Sofi, et al.
(författare)
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Cost estimates of kraft lignin recovery by ultrafiltration
- 2009
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Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 237:1-3, s. 254-267
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Tidskriftsartikel (refereegranskat)abstract
- Climate change and endeavours towards a sustainable society have brought the interest of wood-based biorefineries to the fore. Lignin is the main energy carrier in chemical pulp mills. Today, the heat value of lignin is commonly recovered in the recovery boiler of the mill. However, interest in the extraction of lignin for use as an external biofuel and in speciality chemicals is growing. Lignosulphonates have been isolated by ultrafiltration from spent liquor in sulphite pulp mills for decades, whereas kraft lignin is mainly extracted by precipitation. The isolation of kraft lignin by ultrafiltration is currently attracting increasingly greater interest because lignin can be extracted from pulping liquors at almost all positions in a pulp mill using ceramic membranes, without altering the pH or temperature of the liquor. In this work hardwood lignin was recovered from two process streams in a kraft pulp mill by Ultrafiltration with a ceramic membrane with a cut-off of 15,000 Da. It was shown that lignin can be recovered from a cooking liquor at a cost of about 60 (sic) per tonne of lignin and from black liquor withdrawn from the evaporation unit at 33 (sic) per tonne.
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| 6. |
- Krawczyk, Holger, et al.
(författare)
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Isolation of hemicelluloses from barley husks
- 2008
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Ingår i: Food and Bioproducts Processing. - : Elsevier BV. - 1744-3571 .- 0960-3085. ; 86:1, s. 31-36
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Tidskriftsartikel (refereegranskat)abstract
- In this work, arabinoxylan, the primary hemicellulose in barley husks, was isolated from barley husks by steam explosion and ultrafiltration. Ultrafiltration and diafiltration were used to concentrate and to increase the purity of the product which was intended for use as an oxygen barrier film in food packaging. A composite fluoropolymer membrane with a nominal molecular mass cut-off of 10,000 g/mol was used during ultrafiltration and diafiltration. The average flux during ultrafiltration to a volume reduction of 0.85 was 90 L/m(2) h. The flux was approximately constant (50 L/m(2) h) during diafiltration. Polysaccharides constituted about 40% of the solids fraction before ultrafiltration and nearly 70% after diafiltration. Arabinoxylan made up 45% of the polysaccharide fraction after diafiltration.
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| 7. |
- Lindmark, Jonas
(författare)
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Modification of MFI membranes for enhanced selectivity
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Zeolite membranes can potentially be used for separation of many types of mixtures. The membranes can be tailored by a number of methods to suit a specific separation application. In this work both traditional and new innovative methods were used to tailor the properties of zeolite membranes in order to enhance the selectivity for a given separation. In this work the traditional methods for tailoring of zeolite membranes by adjusting the Si/Al-ratio of, and exchanging the counterions in the zeolite have been used. In addition, two new methods have been developed: One where the impregnation concept often used in the catalysis field is adapted to tailor the properties of zeolite membranes for the first time, and another, where methylamine is used to modify the zeolite and form more and stronger basic sites. The polarity of a zeolite can be tailored by changing the Si/Al ratio in order to facilitate the separation of polar and non polar molecules. A low Si/Al ratio gives a more polar zeolite and vice versa. In the present work, separation of mixtures of water, hydrogen and n-hexane was investigated for membranes with two different Si/Al ratios (silicalite-1 and ZSM-5). The highest separation factors α-water/hydrogen were observed at 25 °C and were 14.3 and 19.7 for silicalite-1 and ZSM-5, respectively. Mixtures of methanol/ethanol, hydrogen, carbon dioxide and water were also investigated, and the highest measured methanol/hydrogen separation factor, 32, was achieved for a ZSM-5 membrane, while a silicalite-1 membrane was found to give the highest ethanol/hydrogen separation factor of 46. The polar ZSM-5 favours the separation of the polar methanol, whereas the less polar silicalite-1 is more favourable for separation of the less polar ethanol. These results confirm that the selectivity for these separations can be controlled by tailoring the polarity the zeolite. The effect of the counter ions in ZSM-5 was studied by preparing, silicalite-1 and ZSM-5 membranes with three different counter ions (Na+, Li+ and Ba2+) and evaluating these for separation of quadrupolar carbon dioxide from binary and ternary mixtures of carbon dioxide, hydrogen and water. The aim was to develop a membrane suitable for separation of carbon dioxide from synthesis gas. A separation factor α-carbon dioxide/hydrogen of 6.2 was achieved for a BaZSM-5 membrane at room temperature. In the BaZSM-5 membranes, the permeances of both carbon dioxide and hydrogen were decreased by the presence of the Ba2+counter ion, but due to enhanced adsorption of the more quadrupolar carbon dioxide the carbon dioxide permeance was decreased much less than the hydrogen permeance. By development of a new and innovative impregnation procedure, carbon dioxide selective membranes with high flux were prepared by impregnating the pores of a silicalite-1 membrane with calcium compounds to aid the adsorption of carbon dioxide. The separation experiments with mixtures of carbon dioxide and hydrogen showed that the separation factor α-carbon dioxide/hydrogen at 25 °C was drastically changed from 0.7 (hydrogen selective) to 3.7 (carbon dioxide selective) by this modification. A second new modification procedure was also developed, where MFI membranes with high Si/Al ratio were modified with methylamine to increase the carbon dioxide affinity and thus increase the carbon dioxide selectivity. These membranes were then evaluated for separation of carbon dioxide from various mixtures of carbon dioxide, hydrogen, methane and water. The modification had significant effects on both permeances and separation factors and the selectivity towards carbon dioxide was increased considerably for all the feed mixtures tested. The results of the different modifications were evaluated by techniques such as SEM, TEM, XRD, DRIFT spectroscopy and by single component permeation and mixture separation experiments. High quality membranes with few defects are critical to study the effects of membrane modification and throughout this thesis adsorption-branch permporometry is used as a standard tool to evaluate membrane quality. The permporometry technique was also studied more in detail. It is shown how the distribution of flow-through defects can be estimated from the permporometry pattern. The estimated defect distribution is supported by SEM observations. In addition the permporometry data can be used to predict the permeance of molecules diffusing through defects in the membrane in mixture separation experiments and also indicate the separation factor.
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| 8. |
- Lipnizki, Frank, et al.
(författare)
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Hemicellulose isolation from thermomechanical pulp mill process water using UF: Optimisation and economics
- 2008
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Every year, 100,000 tons of dissolved hemicelluloses are discharge unused with wastewater from thermomechanical pulp mills around the world. Isolation of these hemicelluloses from the wastewater would not only reduce the treatment costs for the pulp mills but would also provide an excellent raw material for high value applications such as oxygen barriers in food packaging. The isolation of the hemicelluloses can be combined with polishing of the waste-water by using different filtration processes. The initial step in this combination is either a drum filter or a microfiltration treatment to remove solid residues from the wastewater followed by ultrafiltration to concentrate the hemicelluloses. The permeate from the ultra-filtration can then be further polished by reverse osmosis before recycling. The focus of this paper is on the optimisation of the ultrafiltration step concentrating on the membrane selection and its impact on the process economics. The membrane selection includes the newly developed commercial UFX5 pHt membrane (Alfa Laval, Denmark) based on hydrophilised polyethersulfone. The feed studied in this paper is process water from the thermomechanical pulp mill Stora Enso Kvarnsveden (Sweden). The temperature of this process stream is 75°C. To reduce the need for cooling and preserve the energy, temperature tolerance is an important membrane selection parameter. Further, since the process water contains resin and lignin, which tend to foul membranes, the hydrophilicity of the membrane is another important selection parameter. Based on this, five membranes with molecular weight cut-offs (MWCOs) between 1 – 10 kD were pre-selected: (1) a hydrophilised fluoro polymer membrane ETNA01PP, MWCO: 1 kD, (2) a hydrophilised fluoro polymer membrane ETNA10PP, MWCO: 10 kD, (3) a hydro¬philised polyethersulfone membrane UFX5 pHt, MWCO: 5 kD (all Alfa Laval, Denmark), (4) a regenerated cellulose membrane UC005, MWCO: 5 kD, and (5) a polyethersulfone membrane UP005, MWCO: 5 kD (all Microdyn-Nadir, Germany). The ETNA01PP, ETNA10PP, and UC005 are limited to a temperature of 60/55°C and to a pH range of 1 to 11, whereas the UP005 and UFX5 pHt can be operated up to 75°C and in a pH range from 1 to 14/13. In the initial study, a small flat test module was used to study the pure water fluxes and the fouling behaviour of the membranes related to octanoic acid, a fouling substance which represents a significant number of small hydrophobic substances. Based on this, ETNA01PP, ETNA10PP, and UFX5 pHt were selected for further experiments in 2.5” spiral wound modules using process water from Kvarnsveden pulp mill. In these experiments, among others the flux decline with increasing concentration of hemicelluloses at different transmembrane pressures and cross-flow velocities as well as the retention of hemicelluloses under these conditions were studied. The experimental results of ETNA10PP, ETNA01PP and UFX5 pHt were then used as basis for the development of a full-scale system to treat a feed stream of 100 m3/h with an initial feed temperature of 60/75ºC. Both investment and operating costs were analysed as well as the impact of retention and operating conditions on the ultrafiltration process. It was revealed that operating temperature and membrane selection/retention had an impact on both the investment and operating costs. In conclusion, the results show that ultrafiltration is an attractive process unit in the hemicelluloses isolation process.
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| 9. |
- Nordin, Anna-Karin, et al.
(författare)
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Case study of an ultrafiltration plant treating bleach plant effluent from a pulp and paper mill
- 2006
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Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 201:1-3, s. 277-289
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Tidskriftsartikel (refereegranskat)abstract
- Bleach plant effluent is treated in the ultrafiltration plant at Stora Enso Nymblla pulp and paper mill. The plant is the largest of its kind in the world, with a total membrane area of 4800 m(2) (2900 m(2) on the softwood line and 1900 m(2) on the hardwood line) and a processing capacity of 400 m(3) bleach plant effluent per hour. The ultrafiltration plant has been in operation since 1995. The operating conditions have been altered with time. In this work the present performance of the ultrafiltration plant has been evaluated and ways to improve the performance further have been investigated. The largest changes are found at the ultrafiltration plant on the hardwood line. On the hardwood line the ultrafiltration plant consists of six stages in series, with a volume reduction of about 98%. A drastic decrease of flux with axial position in the modules in the last stage was revealed. The flux was found to be zero in the last part of the modules because of the high frictional pressure drop caused by the high viscosity (7.7 cP) of the liquid in the last stage. Using a calculation tool, it is shown that the flux in the last stage can be increased and the energy requirement decreased if a higher inlet transmembrane pressure is used or if the cross-flow velocity in the last stage is decreased.
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| 10. |
- Nordin, Anna-Karin, et al.
(författare)
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Flux and energy requirement during ultrafiltration of a complex industrial process stream
- 2009
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Ingår i: Desalination and Water Treatment. - 1944-3986. ; 2:1-3, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- Membrane filtration is a separation process already used in many industrial applications. However, optimization of the design and operating conditions is necessary to lower the investment and operating costs. To achieve this for industrial (multi-component) process streams, a combination of experiments and calculations is needed. The permeate flux and energy requirement are important design parameters for ultrafiltration plants. The influence of the operating conditions on these factors should therefore be investigated. In this work, bench-scale filtration experiments were performed on kraft black liquor using a ceramic membrane. The experimental data were used to calculate the average flux and energy requirement for different transmembrane pressures and cross-flow velocities. The optimal flux at different inlet cross-flow velocities was found to vary depending on feed concentration and transmembrane pressure.
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