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  • 251.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Öhrman, Olov
    Msimang, Velaphi
    University of Cape Town.
    Steen, Eric van
    University of Cape Town.
    Böhringer, Walter
    University of Cape Town.
    Sibya, Sifiso
    University of Cape Town.
    Möller, Klaus
    University of Cape Town.
    The synthesis and testing of thin film ZSM-5 catalysts2004Inngår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 59, nr 13, s. 2647-2657Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis and catalytic testing of thin ZSM-5 films on glass and alumina beads is described. The thickness of the ZSM-5 films was controlled to 150, 350, 800 and 2300 nm. The samples were characterised by SEM, gas adsorption and p-xylene isomerisation and 1,3,5-tri-isopropyl benzene cracking test reactions. A reaction–diffusion model adequately described the p-xylene isomerisation data. Estimates of model parameters were obtained by fitting the model to the experimental data. In both cases, the reaction rate constant increased with increasing film thickness. The xylene reaction data showed that secondary reaction products increased as expected with increasing diffusion limitations, but the increase was less than that predicted by the variation of thickness only. The trends in the reaction data could be explained by more defects in the thicker films and/or partial poisoning of the zeolite by mobile support cations in thinner films and/or orientation effects.

  • 252.
    Holmgren, Per
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Strandberg, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Wagner, David R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Molinder, Roger
    Energitekniskt Centrum, Piteå.
    Wiinikka, Henrik
    Energitekniskt Centrum, Piteå.
    Umeki, Kentaro
    Luleå Technical University.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Size, Shape and Density Changes of Biomass Particles during Devolatilization in a Drop Tube Furnace2014Inngår i: Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Konferansepaper (Annet vitenskapelig)
  • 253. Horacek, J.
    et al.
    St'avova, Gabriela
    Hora, Lukas
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akad Univ, Proc Chem Ctr, Ind Chem & React Engn, FIN-20500 Turku, Finland.
    Kubicka, David
    Lignin transformations to chemicals2013Inngår i: Proceedings of the 1st INTERNATIONAL CONFERENCE ON CHEMICAL TECHNOLOGY / [ed] Kalenda, P., Lubojacky, J., Czech Chemical Society , 2013, s. 382-388Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sodium lignosulfonate was decomposed at 320 degrees C and 130 bar over various catalysts. Zeolites Beta modified with 0.5 % of Pt showed important effect of Al content in the support on product yields. Alumina-supported NiO was also found as active in lignosulfonate decomposition to guaiacol: Moreover, the contact time of substrate with the active centers was identified as the key reaction factor in lignosulfonate decomposition. Model compounds of lignin decomposition were hydrodeoxygenated at 180 degrees C and 5 MPa over Pt modified zeolites Beta. Dealuminated zeolite was found as more active in phenol conversion than zeolite with similar Si/Al ratio obtained by direct synthesis. Reactivity of cresols increased in order m>o>p for catalyst with higher Si/Al ratio, decrease of Al content resulted in lower reactivity of cresols and change of reactivity order of isomers to o>m>p.

  • 254.
    Hu, Lan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rexed, Ivan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical performance of reversible molten carbonate fuel cells2014Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, nr 23, s. 12323-12329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrochemical performance of a state-of-the-art molten carbonate cell was investigated in both fuel cell (MCFC) and electrolysis cell (MCEC) modes by using polarization curves and electrochemical impedance spectroscopy (EIS). The results show that it is feasible to run a reversible molten carbonate fuel cell and that the cell actually exhibits lower polarization in the MCEC mode, at least for the short-term tests undertaken in this study. The Ni hydrogen electrode and the NiO oxygen electrode were also studied in fuel cell and electrolysis cell modes under different operating conditions, including temperatures and gas compositions. The polarization of the Ni hydrogen electrode turned out to be slightly higher in the electrolysis cell mode than in the fuel cell mode at all operating temperatures and water contents. This was probably due to the slightly larger mass-transfer polarization rather than to charge-transfer polarization according to the impedance results. The CO2 content has an important effect on the Ni electrode in electrolysis cell mode. Increasing the CO2 content the Ni electrode exhibits slightly lower polarization in the electrolysis cell mode. The NiO oxygen electrode shows lower polarization loss in the electrolysis cell mode than in the fuel cell mode in the temperature range of 600-675 degrees C. The impedance showed that both charge-transfer and mass-transfer polarization of the NiO electrode are lower in the electrolysis cell than in the fuel cell mode.

  • 255.
    Hulteberg, Christian
    et al.
    Lund University.
    Leveau, Andreas
    Biofuel-Solution AB, Limhamn.
    Brandin, Jan
    Biofuel-Solution AB, Limhamn.
    Pore Condensation i Glycerol Dehydration2013Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, nr 9-10, s. 813-821Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pore condensation followed by polymerizationis proposed as an explanatory model of several observationsreported in the literature regarding the dehydration ofglycerol to acrolein. The major conclusion is that glycerolpore condensation in the micro- and mesopores, followedby polymerization in the pores, play a role in catalystdeactivation.

  • 256.
    Hulteberg, Christian
    et al.
    Lund University .
    Leveau, Andreas
    Biofuel-Solution AB.
    Brandin, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Pore Condensation in Glycerol Dehydration: Modification of a Mixed Oxide Catalyst2017Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 60, nr 17-18, s. 1462-1472Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pore condensation has been suggested as an initiator of deactivation in the dehydration of glycerol to acrolein. To avoid potential pore condensation of the glycerol, a series of WO3supported on ZrO2 catalysts have been prepared through thermal sintering, with modified pore systems. It was shown that catalysts heat treated at temperatures above 800 °C yielded suitable pore system and the catalyst also showed a substantial increase in acrolein yield. The longevity of the heat-treated catalysts was also improved, indeed a catalyst heat treated at 850 °C displayed significantly higher yields and lower pressure-drop build up over the 600 h of testing. Further, the catalyst characterisation work gave evidence for a transition from monoclinic to triclinic tungsten oxide between 850 and 900 °C. There is also an increase in acid-site concentration of the heat-treated catalysts. Given the improved catalyst performance after heat-treatment, it is not unlikely that pore condensation is a significant contributing factor in catalyst deactivation for WO3 supported on ZrO2 catalysts in the glycerol dehydration reaction.

  • 257.
    Hulteberg, Christian
    et al.
    Lund University.
    Odenbrand, Ingemar
    Lund University.
    Gustafson, Johan
    Lund University.
    Brandin, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Lundgren, Edvin
    Lund University.
    Preface: Special issue of Topics in Catalysis constitutes the Proceedings of the 17th Nordic Symposium of Catalysis2017Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 60, nr 17-18, s. 1275-1275Artikkel i tidsskrift (Annet vitenskapelig)
  • 258.
    Häggström, Caroline
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Synthesis gas from black liquor: trace components and methanol synthesis2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The common European Energy and Climate policy states that in 2020 the share of biofuels for inland transports should be 10 %. Such a stipulation calls for a commercially sustainable biofuel production. A promising route for Sweden is biofuel production via gasification of black liquor, which could replace about 25 % of the current Swedish consumption of transportation fuel. The main components in the gas produced by black liquor gasification are H2, CO, CO2, N2, CH4 and H2S, which has been reported in previous work. In the present work, trace components in synthesis gas produced via black liquor gasification have been characterized, since trace components could influence the subsequent fuel synthesis. Of the trace components, the most abundant ones were benzene at an average concentration of about 60 ppm, followed by COS, with an average concentration of about 50 ppm. In addition, low amounts (i.e. a few ppm), of C2-hydrocarbons were observed in the gas. No tars were observed in the gas, but tars were observed in some deposits at pipe walls. The concentration of particles in the synthesis gas was very low; < 0.1 mg/Nm3. Submicron particles were comprised of elements such as C, O, Na, Si, S, Cl, K, and Ca, and these particles probably originated from black liquor. Larger particles were comprised mainly of Fe, S and Ni and were probably the result of corrosion of steel in the plant pipe-work. Synthesis gas was also purified by passing beds of active carbon and zinc oxide, mixed with hydrogen gas from cylinders and in the present work, for the first time, catalytically converted to methanol using bench scale equipment during 45 hours in total. The space time yield of methanol produced at a pressure of 25 bar was 0.16-0.19 g methanol/ (g catalyst h) and comparable results were obtained using synthesis gas from gas cylinders with pure gas. The spent catalyst, exposed to gas from the gasifier, was slightly enriched in Ca and Na at the inlet of the reactor and in B and Ni at the outlet of the reactor. Ca, Na and B probably stem from black liquor whereas Ni probably originates from the stainless steel in the equipment. A slight deactivation of the catalyst exposed to gas from the gasifier was identified but it was not possible to reveal the origin of the deactivation. However, the surface area and mesoporosity of the catalyst was reduced. As expected, the produced methanol also contained water and traces of hydrocarbons up to C4, ethanol and dimethyl ether. In summary, this work has shown that the synthesis gas produced by gasification of black liquor is pure and that methanol synthesis from the gas is quite feasible.

  • 259.
    Häggström, Caroline
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Öhrman, Olov
    Rownaghi, Ali
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gebart, Rikard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Catalytic methanol synthesis via black liquor gasification2012Inngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 94, nr 1, s. 10-15Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biofuel production from gasified black liquor is an interesting route to decrease green house gas emissions. The only pressurised black liquor gasifier currently in pilot operation is located in Sweden. In this work, synthesis gas was taken online directly from this gasifier, purified from hydrocarbons and sulphur compounds and for the first time catalytically converted to methanol in a bench scale equipment. Methanol was successfully synthesised during 45 h in total and the space time yield of methanol produced at 25 bar pressure was 0.16–0.19 g methanol/(g catalyst h). The spent catalyst exposed to gas from the gasifier was slightly enriched in calcium and sodium at the inlet of the reactor and in boron and nickel at the outlet of the reactor. Calcium, sodium and boron likely stem from black liquor whereas nickel probably originates from the stainless steel in the equipment. A slight deactivation, reduced surface area and mesoporosity of the catalyst exposed to gas from the gasifier were observed but it was not possible to reveal the origin of the deactivation. In addition to water, the produced methanol contained traces of hydrocarbons up to C4, ethanol and dimethyl ether.

  • 260.
    Håkansson, Katarina
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Nordwaeger, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Ingemar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Svanberg, Martin
    Logistics and Transportation, Chalmers University of Technology.
    Process and system integration aspects of biomass torrefaction2010Inngår i: 18th European Biomass Conference and Exhibition: Proceedings, 2010Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The pre-treatment method torrefaction has been shown to significantly improve biomass fuel characteristics such as energy density, moisture content, milling energy, feeding and hydrophobic properties. These improvements establish torrefaction as a key process in facilitating an expanding market for biomass raw materials. Most of the previous work has focused on evaluating and optimizing the torrefaction process alone. However, to fully explore the maximum energy/exergy and cost efficiency of biomass torrefaction, the entire fuel supply chain and site specific systems must be considered; including logistics, scale and integration with other processes. The present work in progress aims to develop a model that incorporates optimization of the biomass supply chain and process integration systems together with the torrefaction process in order to avoid sub-optimization.

  • 261.
    Håkansson, Katarina
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Olofsson, Ingemar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Persson, Kristoffer
    Nordin, Anders
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Torrefaction and Gasification of Hydrolysis Residue2008Inngår i: 16th European Biomass Conference and Exhibition: Proceedings, 2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    When producing ethanol from lignocellulosic material using hydrolysis combined with fermentation, a large amount of residue consisting of mainly lignin is generated. A significant amount of energy is retained in this residue which may be utilised as a measure for the process to become economically viable. One possibility is as fuel in a gasification process for synthesis gas production, improving the fuel yield and the overall plant efficiency. Furthermore, the pre-treatment method torrefaction has been shown to significantly improve biomass fuel characteristics such as energy density, moisture content, feeding and hydrophobic properties, as well as significantly facilitate particle size reduction. Therefore, the process chain from hydrolysis residue to synthesis gas was investigated and demonstrated in the present work through bench-scale experiments in a batch torrefaction reactor and a bubbling fluidised bed gasifier. The results from the torrefaction work confirmed the improved fuel characteristics and the effects of process variables were evaluated by factorial designed experiments. The torrefaction residence time was identified as the most influential variable. The results from reactivity tests and gasification experiments indicate that hydrolysis residue and corresponding torrefied residue are suitable for synthesis gas production, with some improved feedstock handling characteristics for the latter.

  • 262.
    Hökfors, Bodil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Phase chemistry in process models for cement clinker and lime production2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The goal of the thesis is to evaluate if developed phase chemical process models for cement clinker and lime production processes are reliable to use as predictive tools in understanding the changes when introducing sustainability measures.

    The thesis describes the development of process simulation models in the application of sustainability measures as well as the evaluation of these models. The motivation for developing these types of models arises from the need to predict the chemical and the process changes in the production process, the impact on the product quality and the emissions from the flue gas.

    The main chemical reactions involving the major elements (calcium, silicon, aluminium and iron) are relatively well known. As for the minor elements, such as sodium and potassium metals, sulphur, chlorine, phosphorus and other trace elements, their influence on the main reactions and the formation of clinker minerals is not entirely known. When the concentrations of minor and trace elements increase due to the use of alternative materials and fuels, a model that can accurately predict their chemistry is invaluable. For example, the shift towards using less carbon intensive fuels and more biomass fuels often leads to an increased phosphorus concentration in the products.

    One way to commit to sustainable development methods in cement clinker and lime production is to use new combustion technologies, which increase the ability to capture carbon dioxide. Introducing oxy-fuel combustion achieves this, but at the same time, the overall process changes in many other ways. Some of these changes are evaluated by the models in this work.

    In this thesis, a combination of the software programs Aspen Plus™ and ChemApp™ constitutes the simulation model. Thermodynamic data from FACT are evaluated and adjusted to suit the chemistry of cement clinker and lime.

    The resulting model has been verified for one lime and two cement industrial processes.

    Simulated scenarios of co-combustion involving different fuels and different oxy-fuel combustion cases in both cement clinker and lime rotary kiln production are described as well as the influence of greater amounts of phosphorus on the cement clinker quality.

  • 263.
    Hökfors, Bodil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boström, Dan
    Viggh, Erik
    Backman, Rainer
    On the phase chemistry of Portland cement clinker2015Inngår i: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 27, nr 1, s. 50-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the formation of a phosphorous belite solid solution and its impact on alite formation. A sub-solidus phase relation for the ternary system silicon dioxide–calcium oxide–phosphorus pentoxide (SiO2–CaO–P2O5) is reported. The ternary system is based on Rietveld refinements of X-ray diffraction patterns from experimental tests. The overall picture is based on known phase diagrams, relevant Rietveld refinements models, stoichiometric relationships as a function of increasing phosphorus pentoxide concentration and vacancy theories for solid solutions of phosphate belites. A tool is developed for predicting the chemistry of the product as well as the chemistry during heating when producing Portland cement clinker. A thermodynamic database for phase chemistry calculations of clinkering reactions has been created and evaluated. Suitable compounds and solution species have been selected from the thermochemical database included in FactSage software. Some solution compositions have been uniquely designed to allow for the proper prediction of the cement clinker chemistry. The calculated results from the developed database for heating raw materials in cement clinker production and cooling of the product are presented in this paper. The calculated results provide a good prediction of the phases and quantities formed during heating and non-equilibrium cooling. The prediction of the amounts of alite, belite and aluminoferrite phases in the product according to the Scheil method is good. The temperature interval for the existence of all of the major phases is relevant. The thermodynamic data for a solution phase of alite with substituting ions of primarily magnesium oxide and phosphorus pentoxide would improve the predictability of the developed database.

  • 264.
    Hökfors, Bodil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Cementa AB, Res & Dev, Heidelberg Cement Grp, Heidelberg, Germany.
    Eriksson, Matias
    Nordkalk Oy Ab, FIN-21600 Pargas, Finland.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Åbo Akad Univ, Proc Chem Res Grp, Turku, Finland.
    Improved Process Modeling for a Lime Rotary Kiln Using Equilibrium Chemistry2012Inngår i: Journal of engineering technology, ISSN 0747-9964, Vol. 29, nr 1, s. 8-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article describes an improved process model for simulation of the manufacturing process of lime in a rotary kiln. The model simulates ideal behavior of complex chemical systems with an assumed homogenous mixing without time-dependent factors. It is a totally predictive model that excludes the empirical parameters. The model is a chemical phase equilibrium model that calculates the final product in a non-equilibrium mode, according to established methods. The phase chemistry is among the most complex found in the literature for lime manufacturing. The thermodynamic data used in the model is based on 11 components (Ca, Si, Al, Fe, K, S, Cl, C, H, O and N). The fuel has an important role in the lime manufacturing process. Special attention is required since it is fed directly into the process via the burner and can influence the process and final product. In the model, the fuel is defined in order to have it behave in a realistic way, and operational data from a full scale lime plant verify the simulation results. The simulated amounts of gas and solids correlate well with operational data. The predicting chemical composition of the product needs improvement by adding more system components and their related compounds to the thermodynamic database. Simulation results from co-combustion of coal and processed waste based fuel oil that it is a versatile tool for predicting product quality and amount, temperature profiles of the rotary kiln, and exhaust gas composition and amount.

  • 265.
    Hökfors, Bodil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Cementa AB, Stockholm, Sweden.
    Eriksson, Matias
    NorFraKalk, Verdal, Norway.
    Viggh, Erik
    Cementa AB, Malmö, Sweden.
    Modelling the cement process and cement clinker quality2014Inngår i: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 26, nr 6, s. 311-318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a recently developed simulation model that can be used as a tool for evaluating sustainable development measures for cement and lime production processes. Examples of such measures are introducing new combustion technologies such as oxy-fuel combustion, using biomass fuel and using alternative materials in the raw material feed. One major issue when introducing process changes is the need to maintain product quality. In some ways, oxygen-enriched air combustion resembles oxy-fuel combustion. The model results were validated and found to be consistent with full-scale operational data for normal running conditions and for a full-scale test with oxygenenriched air. The model shows, for example, that with an additional 1500 m3/h of oxygen, fuel addition at the calciners can increase up to 108% and the raw material feed rate can increase up to 116% for a process with a raw meal feed of 335.5 t/h.

  • 266.
    Hökfors, Bodil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Thermal Energy Conversion Laboratory, Umeå University.
    Viggh, Erik
    Cementa AB, Malmö.
    Eriksson, Matias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. NorFraKalk, Verdal, Norway and Thermal Energy Conversion Laboratory, Umeå University.
    Simulation of oxy-fuel combustion in cement clinker manufacturing2015Inngår i: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 27, nr 1, s. 42-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A thermodynamic process model is used as an evaluation tool. Full oxy-fuel combustion is evaluated for circulation of 20–80% of flue gases to the burn zone of a rotary kiln. The full oxy-fuel combustion simulations exhibit altered temperature profiles for the process. With 60% recirculation of flue gases, the temperature in the burn zone is comparable to the reference temperature, and carbon dioxide concentration in the flue gases increases from 33 to 76%. If water is excluded, carbon dioxide concentration is 90%. The partial oxy-fuel combustion method is evaluated for 20 and 40% recirculation of flue gases from one cyclone string to both calciners. Fuel and oxygen feed to the burning zone and calciners are optimised for the partial oxy-fuel scenario. The lowest specific energy consumption is desired while maximising the amount of carbon dioxide theoretically possible to capture. By introducing partial oxy-fuel combustion with 20% recirculation of flue gases in the carbon dioxide string, total carbon dioxide emissions increases by 4%, with 84% possible to capture. Within the limits of the model, the introduction of full oxy-fuel and partial oxyfuel combustion is possible while maintaining product quality. When simulating partial oxy-fuel combustion, the energy consumption will increase even when no power consumption for the production of oxygen is included.

  • 267.
    Hökfors Wilhelmsson, Bodil
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Viggh, Erik O.
    Cementa AB, Limhamn, Sweden.
    Backman, Rainer
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    A predictive chemistry model for the cement process2008Inngår i: Zement, Kalk, Gips International: ZKG international, ISSN 0949-0205, Vol. 61, nr 7, s. 60-70Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    A tool has been developed that enables prediction of the chemistry in cement production with thermodynamic phase equilibrium calculations. Reactions in gas, solid and liquid phases are calculated in the process from preheating tower, including exhaust gas cleaning, through rotary kiln, clinker cooler and ends at the output of clinker. The simulated values are compared to measured or calculated data from a full scale plant. This is a cement plant producing 2000 t clinker per day using both traditional and alternative fuels. The chemistry model shows good agreement especially on material chemistry at various places in the process and on composition of the clinker. A new way to define fuels is used and is straightforward and reliable. In the future work the model has to be improved and more elements are to be added to the thermodynamic database.

  • 268.
    Ishola, Mofoluwake M.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Novel application of membrane bioreactors in lignocellulosic ethanol production: simultaneous saccharification, filtration and fermentation (SSFF)2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Biofuels production and utilisation can reduce the emission of greenhouse gases, dependence on fossil fuels and also improve energy security. Ethanol is the most important biofuel in the transportation sector; however, its production from lignocelluloses faces some challenges. Conventionally, lignocellulosic hydrolysis and fermentation has mostly been performed by separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). SHF results in product inhibition during enzymatic hydrolysis and increased contamination risk. During SSF, suboptimal conditions are used and the fermenting organism cannot be reused. Bacterial contamination is another major concern in ethanol production, which usually results in low ethanol yield. In these studies, the above-mentioned challenges have been addressed. A novel method for lignocellulosic ethanol production ‘Simultaneous saccharification filtration and fermentation (SSFF)’ was developed. It circumvents the disadvantages of SSF and SHF; specifically, it uses a membrane for filtration and allows both the hydrolysis and fermentation to be carried out at different optimum conditions. SSFF also offers the possibility of cell reuse for several cultivations. The method was initially applied to pretreated spruce, with a flocculating strain of yeast Saccharomyces cerevisiae. SSFF was further developed and applied to pretreated wheat straw, a xylose rich lignocellulosic material, using encapsulated xylose fermenting strain of S. cerevisiae. High solids loading of 12% suspended solids (SS) was used to combat bacterial contamination and improve ethanol yield. Oil palm empty fruit bunch (OPEFB) was pretreated with fungal and phosphoric acid in order to improve its ethanol yield. An evaluation of biofuel production in Nigeria was also carried out. SSFF resulted in ethanol yield of 85% of the theoretical yield from pretreated spruce with the flocculating strain. Combination of SSFF with encapsulated xylose fermenting strain facilitated simultaneous glucose and xylose utilisation when applied to pretreated wheat straw; this resulted in complete glucose consumption and 80% xylose utilisation and consequently, 90% ethanol yield of the theoretical level. High solids loading of 12% SS of pretreated birch resulted in 47.2 g/L ethanol concentration and kept bacterial infection under control; only 2.9 g/L of lactic acid was produced at the end of fermentation, which lasted for 160 h while high lactic acid concentrations of 42.6 g/L and 35.5 g/L were produced from 10% SS and 8% SS, respectively. Phosphoric acid pretreatment as well as combination of fungal and phosphoric pretreatment improved the ethanol yield of raw OPEFB from 15% to 89% and 63% of the theoretical value, respectively. In conclusion, these studies show that SSFF can potentially replace the conventional methods of lignocellulosic ethanol production and that high solids loading can be used to suppress bacterial infections during ethanol productions, as well as that phosphoric acid pretreatment can improve ethanol yield from lignocellulosic biomass.

  • 269.
    Ishola, Mofoluwake M.
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Brandberg, Tomas
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Taherzadeh, Mohammad J
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Minimization of Bacterial Contamination with High Solid Loading during Ethanol Production from Lignocellulosic Materials2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ethanol is the most important renewable fuel in the transportation sector. Its production from lignocellulosic materials, commonly referred to as second generation ethanol, is considered more attractive than production from starch and sugar crops. Bacterial contamination by lactic acid-producing bacteria is still a major problem during ethanol production processes. Bacteria compete with the yeast by consuming the sugars and the nutrients required by the yeast for efficient ethanol production. This often causes substantial economic losses at industrial fermentations. In this study, without any sterilization of the substrate, simultaneous saccharification and fermentation (SSF) was performed using cellulase Cellic® Ctec2 enzyme for hydrolysis and Baker’s yeast, Saccharomyces cerevisiae, was used as the fermenting organism with different loads of suspended solids - 8%, 10% and 12%. With8%and 10% SS, there was a significant contamination, which caused consumption of both hexoses pentose sugars in the fermentation medium, this resulted in lactic acid concentrations of 43 g/L and 36 g/L from 10% SS and 8% SS respectively. In contrast, only 2.9 g/L lactic acid was observed with 12% SS. An ethanol concentration of 47 g/L was produced from high solid loading of 12% SS while just 26 g/L and 23 g/L were produced from 10% and 8% SS respectively. Our results show that SSF with 12% SS has an increased concentration of inhibitors, particularly acetic acid which selectively inhibited the bacterial growth without affecting the metabolic activities of the yeast during the fermentation.

  • 270.
    Jacobson, Karin
    et al.
    Swerea KIMAB AB, Kista Sweden.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Lindblad, Philip
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Non-Destructive Testing of Plastics and Composites in the Chemical Processing Industry2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Equipment and components made of plastics and composites are widely used in highly corrosive environments in the processing industry. Examples are the storage tanks, pumps and pipes for chemical transport and stacks in combustion plants. The demand for reliable nondestructive testing of plastic process equipment has increased significantly in recent years. Glass fiber reinforced plastics (GRP) is a common construction material for process equipment in the chemical industry. It can be used both as structural bearing in a dual laminate with a thermoplastic material as a corrosion barrier or as a solid GRP. In the latter case, the laminate is generally built up with a resin rich corrosion barrier (about 2.5 to 5 mm thick) with a low content of glass closest to the chemical. The glass fiber in this layer is usually a surface veil and chopped strand mats (CSM), i.e. it has no general fiber orientation. Outside this is the structural bearing layer with much higher glass content, usually wound fiber and / or woven fiber mats with a preferential fiber direction. The corrosion barrier is not load bearing and corrosion of this layer can be allowed. However, no corrosion can be permitted in the structural support layer. Because of this it is important to measure the thickness of the corrosion barrier for quality control but also to determine how far an attack has reached in the corrosion barrier. Today there is no non-destructive testing method that can answer this. Instead destructive sampling (often a drill core) must be made. This is difficult, expensive and sometimes impossible. There is thus a great interest in a method that, preferably at any time during operation, can provide answers to these questions. Due to the heterogeneity of the GRP material in terms of amount, type and direction of the fibers, conventional algorithm for ultrasound imaging will not work. One aim of our work is thus to develop new signal processing methods to handle this heterogeneity. In addition we are also looking at the possibility to use optical fibers and Fiber Bragg Grating (FBG) sensors for corrosion monitoring of GRP structures

  • 271.
    Jakobsson, Elsa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Particle Removal from Chlorate Electrolyte2016Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis project was carried out as a part of the chlorate research conducted at the Process RD&I department for bleaching chemicals at AkzoNobel Pulp and Performance Chemicals AB in Bohus. During the project already implemented filter cloths as well as new types of filters were studied and compared by experimental trials. The results were then examined in an attempt to evaluate existing filtration systems as well as investigate if there are other, better alternatives. The impurities found in a chlorate plant account for an efficiency loss in the process and a reduction of impurities would hence result in an energy reduction and a cleaner product.

    The trials were conducted at one of AkzoNobel’s chlorate plants. Six filters were studied and evaluated by measuring turbidity of the electrolyte and pressure over the filter during the experiments. Samples of the electrolyte were analyzed to obtain the metal content, and thereby the impurity content, of the electrolyte. The structures of the filters were studied by optical microscopy. The results from the trials show that all filter types except one, a needle felt filter, seem to be suitable for chlorate electrolyte filtration (including the filter types already used in the plants). The other filters all reach turbidity values below 0.1 FNU immediately or within 90 minutes of filtration, which is considered good enough. The results from the metal content analysis show a similar trend where the metal concentrations decrease to levels below the detection limits immediately or within 90 minutes of filtration. Apart from the lab trials performed some measurements were made on the existing filtration equipment in the chlorate plant. The measurements show varying results, partly similar to those achieved during the lab filter trials but also results showing a higher turbidity value and metal content, indicating that full scale operation are more complicated than lab scale operation. The lab trial results obtained with the filter types already used in the plants show that lower impurity content is possible to achieve. However, this would require closer monitoring of the filtration systems in the plants.

    Apart from the filtration trials, an attempt to determine the sizes of the particles present in the electrolyte using laser diffraction was performed. However, too little was known of the chlorate electrolyte’s optical data for the measurements to be reliable. Further work is needed before a method for size determination of the particles in a chlorate electrolyte can be achieved. Also, an Optical Filtration Test was tried on the electrolyte but was not sensitive enough for utilization on electrolyte with low (below 1 FNU) turbidity values. 

    The project concluded that a switch to another filtration system is unmotivated, unless a change in the product requirements would occur. Since the impurities have proven to affect the efficiency of the process, it is recommended to make an effort into utilizing the filtration system to its full extent.

  • 272.
    Jansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Bentonite Erosion, Laboratory Studies2009Rapport (Annet vitenskapelig)
    Abstract [en]

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project “Bentonite Erosion”. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple.

    One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM.

    An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to the bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used.

    Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain mostly feldspar developed at the border between the two phases.

    After 45 weeks the clay had expanded some 20 cm into the fracture. The colloid content in the outlet solution was however stable and less than 200 mg/l. The size of the colloids was however much smaller than that obtained when MX-80 is dispersed in water. The development of the clay profile into the fracture and the colloid content in the outlet solutions were the same in both experiments.

    In one of the fracture experiments the fracture was tilted, inclining some 2–3 degrees with the higher end at the water outlet. A relatively thick gel accumulated at the inlet side of the fracture, i.e. the clay sedimented towards the water flow, clearly showing that gravity plays a big role in this system.

  • 273.
    Jansson, Zheng
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Characterization of Spruce Xylan and Its Potential for Strength Improvement2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been shown to give higher pulp yield and better strength properties. This is economically interesting from an industrial point of view. Many studies have been done to investigate xylan behaviour during kraft cooking, to discover the xylan-cellulose attachment mechanism, to find the optimal xylan retention or adsorption process, and to discover relations between xylan structure and strength enhancement. Most of them have concentrated on hardwood xylan. However, softwoods are the major raw materials for the pulp industries in the northern hemisphere. Earlier studies have shown that the xylan characteristics, rather than simply the amount of xylan, influence the strength-enhancing effect of xylan. To obtain optimal utilization of spruce xylan as a strength enhancer, it is essential to know what the beneficial xylan characteristics are and how cooking conditions affect the characteristics.

    In this study, kraft cooking of spruce chips was performed under varied cooking conditions and the xylan in the black liquor was precipitated and characterized. It was found that dissolved spruce xylan had a much higher amount of bound lignin compared to previous studies on xylan dissolved from hardwoods. Increased cooking temperature increased the dissolution rate of xylan. The lower alkali charge and higher ionic strength of the cooking liquor resulted in a lower amount of dissolved xylan. Apart from the effect of the amount, cooking conditions also affected substitution of dissolved xylan. Higher temperature and higher ionic strength led to a lower amount of MeGlcA, while the MeGlcA amount of dissolved xylan was preserved during lower alkali cooking.

    By distinguishing how different cooking conditions affect the characteristics of the xylan dissolved in the black liquor, xylans with different structures were designed to study their effects on pulp strength, that is, the addition of black liquors with certain known xylan characteristics in the kraft cooking process. It was found that the best effect of xylan on tensile strength occurred when the xylan penetrated some distance into the subsurface of the fibre wall. Both low molecular weight and high degree of substitution lowered the tendency of xylan to aggregate, which enabled the dissolved xylan to penetrate some distance into the exposed fibre surface. Upon beating, this xylan was exposed, thus facilitating improvement of fibre-fibre joint formation, which led to increased tensile strength.

  • 274.
    Jareman, Fredrik
    Luleå tekniska universitet.
    MFI-molecular sieve membranes: synthesis, characterization and modelling2002Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This work concerns evaluation by permeation measurements and modeling of thin (<2µm) MFI molecular sieve membranes and, to a smaller extent, synthesis of such materials. The membranes have been synthesized on graded a-alumina microfiltration filters using The seed film method. Scanning electron microscopy and x-ray diffraction were used for characterization in addition to permeation measurements. Mathematical models describing membrane flux for real membranes and defect distributions were developed. Defect distributions were calculated from porosimetry data and were further used for prediction of single gas permeation characteristics for real membranes. The models confirm the experimental findings, with respect to ideal selectivities as a measurement of membrane quality. Membrane permeation simulations indicate increasing ideal selectivities, with increasing film thickness, for quotients containing SF6. Thereby a high quality membrane could possess low ideal selectivities. This finding was confirmed by comparing experimental data of several membranes with varying thickness. The correlation between multi component separation data and commonly used quality criteria was investigated. It was found that commonly used single gas permeation quotients (ideal selectivity) between light inorganic gases, especially those containing sulphurhexaflouride (SF6), is less appropriate for membrane quality measurement. The porosimetry experiment showed on the other hand a good agreement between experimental data and separation performance of the membranes, as expected. ZSM-5 membranes with low aluminum content and silicalite-1 membranes with similar material properties, such as defect distribution and thickness were evaluated with multi component hydrocarbon isomers permeation. The ZSM-5 membrane had lower permeances and a slightly better butane isomer separation performance than the silicalite-1 membrane. The latter membrane showed a minimum in separation selectivity between two C6 isomers whereas the ZSM-5 membrane showed an almost constant selectivity, independent of temperature, but with lower permeances. ZSM-5 membranes with a high aluminum content catalyzed the formation of diethylether and ethylen at temperatures exceeding 150°C from a water/ethanol mixture. The membrane separated a mixture of C4 isomers with good performance at elevated temperatures. However these membranes suffered from temperature instability problems.

  • 275.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Properties and modeling of MFI membranes2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The permeation properties of thin (<2µm) film MFI molecular sieve membranes have been studied in the present work and a model has been developed. The synthesis of such materials has been studied to a smaller extent. The films have been grown on graded a-alumina microfiltration filters using a seeding method. Scanning electron microscopy and x-ray diffraction were used in addition to permeation measurements for characterization of the materials. In particular, a simple and unique model describing single component permeation was developed. The model is a combination of simple and basic equations for permeation and adsorption. The important defect distribution of the membrane and the properties of the support are measured in separate experiments. The model is unique since it is accounting for the effect of defects and support on the permeation properties. The model can adequately describe the performance of various MFI membranes. The model indicates mass transfer limitations of the supports that strongly affect, for instance, permeance ratios. It was also found that these ratios are dependent on crystallographic orientation, film thickness and experimental conditions in addition to the amount of defects. Permeance ratios can thus only be used to compare membranes with similar morphology and tested under similar conditions. It was found that defects formed in thicker films. Membranes prepared on masked substrates were of higher quality than membranes prepared on unmasked substrates. MFI membranes with low and varying aluminum content with similar material properties, such as defect distribution and thickness, were evaluated with multi-component hydrocarbon isomers permeation. The silicalite-1 membrane showed a minimum in separation selectivity between two C6 isomers whereas the ZSM5 membrane showed an almost constant selectivity, independent of temperature, but with lower permeances. The effect of the calcination rate on the membrane quality was investigated for silicalite-1 membranes. Based on a number of permeation characterization techniques, the membrane quality was independent of the calcination rate. It was found that the permeation properties of membranes comprised of small crystals in several layers were different from membranes comprised of one layer of larger crystals, although the quality of the membranes was similar. ZSM-5 membranes with high aluminum content showed catalytic conversion of ethanol into diethylether and ethylene under simultaneous separation of the ethanol / water azeotrope

  • 276.
    Jareman, Fredrik
    et al.
    Luleå tekniska universitet.
    Andersson, Charlotte
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    The influence of the calcination rate on silicalite-1 membranes2005Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 79, nr 1-3, s. 1-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicalite-1 films with a thickness of 500 nm on asymmetric α-alumina micro filtration filters were calcined at 500 °C with heating and cooling rates varying between 0.2 °C/min and 5.0 °C/min. The membranes were characterized with single gas permeation, porosimetry, and xylene isomer separation experiments. It was found that the quality of the prepared membranes was independent of the heating/cooling rate according to the single gas permeation and porosimetry characterization. Xylene isomer separation data was found to vary between the samples, but none of the variations could be attributed to the heating/cooling rate during calcination since the variations did not follow a trend but occurred randomly. It is thus concluded that the calcination rate does not influence the quality of these membranes.

  • 277.
    Jareman, Fredrik
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Permeation of H2, N2, He and SF6 in real MFI membranes2005Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 83, nr 1-3, s. 326-332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work shows that a previously developed model for single gas permeation in real MFI membranes is applicable to an arbitrary MFI membrane with a different film thickness and defect distribution. The model can predict the flow of H2, N2 and He resonably. Deviations in SF6 flux for thick and oriented films were observed and attributed to a lower diffusion coefficient for the narrower pores in the a-direction of the MFI crystals. By guidance from the model, variations in previously reported single gas permeance ratios for selected membranes can now be attributed to variations in feed pressure, film thickness preferred orientation and defect distribution. It was found that high feed pressures and thick oriented films resulted in large single gas permeance ratios with SF6 in the denominator, even though these membranes were more defective than thinner membranes with more randomly oriented crystals. In general, single gas permeance ratios are strongly dependent on material properties and experimental conditions. These ratios can only be used for comparison of membranes with similar morphology and the ratios must be measured under identical conditions.

  • 278.
    Jareman, Fredrik
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Single gas permeance ratios in MFI membranes: effects of material properties and experimental conditions2005Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 82, nr 1-2, s. 201-207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A previously developed mathematical model with parameters fitted to experimental data was used to study effects of material properties and experimental conditions on single gas permeance ratios of MFI membranes. The model showed that single gas permeance ratios are highly dependent on substrate morphology, feed pressure, crystallographic orientation and defects in the film. It was found that the pore size and the thickness of the substrate affected permeance ratios, due to mass transfer resistance in the substrate. The applied feed pressure also had a significant effect on the permeance ratios. This is due to differences in mass transfer resistance of the substrate and adsorption characteristics with varying feed pressures. The crystallographic orientation of the zeolite film also affected permeance ratios due to changes in diffusivity with varying orientation of the crystals in the film. Finally, the effect of defects was investigated. As expected, it was found that the permeance ratios decreased when more defects were added in the model. However, if the membrane is not very defective, the permeance ratio is much more affected by the substrate and by variation in pressure drop than by defects. The results in the present work show that single gas permeance ratios cannot be used directly as a benchmark of membrane quality unless all other parameters are kept constant.

  • 279.
    Jareman, Fredrik
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Creaser, Derek
    Chalmers University of Technology.
    Sterte, Johan
    Modelling of single gas permeation in real MFI membranes2004Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 236, nr 1-2, s. 81-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel permeation model for flow through defects and zeolite pores in real MFI membranes, also accounting for substrate effects has been developed. Defect distributions for two types of MFI membranes were determined from porosimetry data using the model, which incorporated the Horvath Kawazoe (micropores) or the Kelvin equation (mesopores). The narrowest (1.08 nm) and also most common defects were found to be separated with a distance of 10–40 μm according to the model. Diffusion coefficients for hydrogen, helium, nitrogen and SF6 in the zeolite were further determined from single gas permeation data using the model using the independently determined defect distribution. The coefficients are consistent with values previously reported in the literature.

  • 280.
    Jareman, Fredrik
    et al.
    Luleå University of Technology.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Effects of aluminum content on the separation properties of MFI membranes2003Inngår i: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 32, nr 1-3, s. 159-163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    MFI membranes with almost identical film thickness and defect distribution but different Si/Al ratio were evaluated by separation of butane and hexane isomers. Film thickness was evaluated by SEM and defect distribution by porosimetry. When the temperature was varied, the membranes showed similar separation trends for butanes, but clear differences were observed for hexane separation. The hexane separation factor varied with temperature for the silicalite-1 membrane but was constant for the ZSM-5 membrane. It is believed that this difference may be a result of differences in adsorption properties.

  • 281.
    Jiang, Junfei
    et al.
    Chinese Academy of Sciences (CAS), China.
    Lang, Lin
    Chinese Academy of Sciences (CAS), China.
    Lin, Leteng
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Liu, Huacai
    Chinese Academy of Sciences (CAS), China.
    Yin, Xiuli
    Chinese Academy of Sciences (CAS), China.
    Wu, Chuang-zhi
    Chinese Academy of Sciences (CAS), China.
    Partial oxidation of filter cake particles from biomass gasification process in the simulated product gas environment2018Inngår i: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 32, nr 2, s. 1703-1710Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Filtration failure occurs when filter media is blocked by accumulated solid particles. Suitable operating conditions were investigated for cake cleaning by partial oxidation of filter-cake particles (FCP) during biomass gasification. The mechanism of the FCP partial oxidation was investigated in a ceramic filter and by using thermo-gravimetric analysis through a temperature-programmed route in a 2 vol.% O2–N2 environment. Partial oxidation of the FCP in the simulated product gas environment was examined at 300–600°C in a ceramic filter that was set and heated in a laboratory-scale fixed reactor. Four reaction stages, namely drying, pre-oxidation, complex oxidation and non-oxidation, occurred in the FCP partial oxidation when the temperature increased from 30°C to 800°C in a 2 vol.% O2–N2 environment. Partial oxidation was more effective for FCP mass loss from 275 to 725°C. Experimental results obtained in a ceramic filter indicated that the best operating temperature and FCP loading occurred at 400°C and 1.59 g/cm2, respectively. The FCP were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy and Brunaeur–Emmett–Teller before and after partial oxidation. Fourier-transform infrared spectroscopy analysis revealed that partial oxidation of the FCP can result in a significant decrease in C–Hn (alkyl and aromatic) groups and an increase in C=O (carboxylic acids) groups. The scanning electron microscopy and Brunaeur–Emmett–Teller analysis suggests that during partial oxidation, the FCP underwent pore or pit formation, expansion, amalgamation and destruction.

  • 282. Jiang, Xi
    et al.
    Kraft, Markus
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Selected papers from the Twelfth International Conference on Combustion and Energy Utilisation (12th ICCEU) Preface2015Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 156, s. 747-748Artikkel i tidsskrift (Annet vitenskapelig)
  • 283.
    Joakim, Gustavsson
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Industriell ekologi.
    Niclas, Lager
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Industriell ekologi.
    Absorption av CO2 i ammoniaklösning2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I detta arbete studeras absorption av växthusgasen koldioxid (CO2) i ammoniaklösning. Målet med arbetet är att undersöka hur väl teknik med vegetabilisk olja kan förhindra avdunstning av ammoniaklösning vid absorptionen och på så vis främja grön kemi. En jämförelse görs sedan med en mer beprövad teknik med nedkylning. Därefter undersöks vilka salter som fälls ut vid absorptionen vid de båda teknikerna samt olika koncentration ammoniak (NH3).

    Genom att blanda ammoniak, etanol (C2H5OH) och vatten (H2O) i olika förhållanden i ett absorptionstorn erhölls den absorberande lösningen. CO2 i gasform fördes sedan in i reaktorn. I genomförda experiment gav teknik med vegetabiliskt oljemembran samma eller lägre materialförlust av ammoniaklösning som teknik med nedkylning.

    Högre halt av etanol innebar sänkt löslighet av ammoniumsalter vilket gav större utfällning av salter i utförda experiment. Detta kan observeras genom att jämföra kristallvikten i utförda experiment.

    Kristallerna analyserades med röntgendiffraktion (XRD). Salterna kunde identifieras genomatt jämföra erhållet resultat med standardprov från litteratur. Dock fanns avvikelser mellanresultatet och standardprov, vilket gjorde analysen svårtolkad.

  • 284.
    Johansson, Maria
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Kemiteknik.
    Jansson, Linda
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Kemiteknik.
    Elektrolytisk reduktion av zink vid reningsprocess2007Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    When cylinders for motor saws are manufactured there are high demands on the cylinders strength and wearing qualities. Aluminum is a material with low density and is used by Husqvarna AB for their motor saw cylinders. The aluminum is strengthening with nickel that is attached to the cylinders through electrolysis. When aluminum is in contact with oxygen a film of oxide is formed. To eliminate the oxide and to prevent formation of new oxide zinc is used. The cylinders are dipped into a bath of zinc before they pass on to a pre-nickel process, which purpose is to remove the excess of zinc so the “real” nickel process won’t be contaminated. In the process there is a selective bath where zinc is precipitated on sheet-metals through electrolysis. The problem is that while zinc is precipitated so is nickel and in a much greater extend, about 1 % zinc and 99 % nickel.

    Husqvarna AB needs a technique to increase precipitation of zinc and reduce the precipitation of nickel. A small copy of the selective bath was constructed where adjustments of different parameters were possible. In the bath there was an anode of nickel, a cathode, process liquid, a pump for stirring and a plant installation from an aquarium for the temperature. In the bath different voltages, distance between anode – cathode and different sheets of metal were tested. Every test were in progress for about three days and then pieces of sheet-metals were cut and sent for analysis of zinc/nickel percentage.

    A couple of the tested sheet-metals didn’t work and the ones that did work showed no special difference in zinc/nickel percentage. An increase in distance between the anode and cathode showed a small difference but not much. The alteration that showed to be most effective was to decrease the voltage. The normal voltage is 2, 8 V but when it was decreased to 2, 0 V it gave a much better result. The layer on the sheet-metal showed to contain 12 % zinc and 88 % nickel. A couple of other tests were performed with decreased voltage but no one gave as good result as 2, 0 V. If Husqvarna AB shall be able to use a lower voltage they need a greater cathode surface then they have today. That is because of the lower reaction rate. The lower reaction rate conducts an increasing amount of zinc in the bath and an electrolysis that doesn’t work completely.

    Other methods for precipitation could have been tested e.g. change of anode, precipitation of zinc as a salt or a powder that could have been filtrated or a process that reduces the excess of zinc. To test any of these methods big changes in the process structure would be needed which costs both time and money. The authors therefore concluded that the best thing for Husqvarna AB to do is to increase the cathode surface by connecting another bath next to the existent.

  • 285.
    JOOS LINDBERG, JOHAN
    KTH, Skolan för kemivetenskap (CHE).
    Design of an Advanced Oxidation Process for the Decomposition of PFAA2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The process of designing, constructing, and evaluating a novel catalyzed AOP (Advanced oxidation process) for decomposition of PFAAs (Perfluorinated alkyl acids) is covered in this master thesis study. A complete water treatment system with the capacity of treating polluted water was designed and constructed. Various parameters were investigated regarding the potential of the process to degrade PFAAs. A significant reduction of PFOS (perfluorooctanesulfonic acid) level (80 %) was achieved during the trial. Further studies are required to examine the main degradation mechanisms to improve the process.

  • 286.
    Ju, Minhua
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University.
    Li, Yupeng
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University.
    Yu, Liang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, Nanjing.
    Preparation of size-controllable monodispersed carbon@silica core-shell microspheres and hollow silica microspheres2017Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 247, s. 75-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Size-controllable monodispersed carbon@silica core-shell microspheres and hollow silica microspheres were prepared in a simple homemade T-type mixer by polymerization of furfuryl alcohol (FA) and hydrolysis of TEOS in H2SO4 water phase microdroplets to obtain polyfurfuryl alcohol (PFA)@silica microspheres, followed by carbonization and calcination. The FA and TEOS diffuse into the water phase from an oil phase. The flow rates of oil and water phase were 4 and 2 ml h−1, respectively. It was found that the concentration of FA has a more significant effect on the diameter of carbon@silica core-shell microspheres than TEOS due to the template effect of the PFA core. However, the diameter of the hollow silica microspheres was influenced by the concentration of TEOS more significantly. The obtained core-shell microspheres and hollow silica microspheres have large surface area of 555 and 769 m2 g−1, respectively. The hollow silica microspheres have both microporous and mesoporous structure, and the percentage of mesoporous volume was as high as 89%. In addition, based on the study results, a rational formation process of the carbon@silica core-shell microsphere and hollow silica microspheres was assumed.

  • 287.
    Ju, Minhua
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Li, Yupeng
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Yu, Liang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University , P. R. China.
    Two-Phase Diffusion Technique for the Preparation of Ultramacroporous/Mesoporous Silica Microspheres via Interface Hydrolysis, Diffusion, and Gelation of TEOS2018Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 5, s. 2046-2056Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Honeycombed hierarchical ultramacroporous/mesoporous silica microspheres were prepared via the hydrolysis of TEOS in the oil-water interface, with subsequent diffusion and gelation in the acidic water-phase microdroplets with the assistance of a simple homemade microdevice. The diffusion of furfuryl alcohol (FA) also happened at a relatively high rate during the hydrolysis and diffusion of TEOS. Therefore, plenty of FA will be inside of the water microdroplets and form a decent number of polyfurfuryl alcohol (PFA) microparticles, thereby obtaining honeycombed hierarchical porosity silica microspheres with abundant ultramacroporous cavities and mesopores after calcination. It was found that the concentration of FA, residence time, and reaction temperature have significant effects on the porosity and pore size due to the influence on the diffusion rate and amount of FA in water-phase microdroplets. The honeycombed silica microspheres have obvious microscopic visible ultramacroporous cavities with the submicrometer cavity diameter as high as 85% porosity based on the rough overall volume of microsphere. N2 adsorption-desorption isotherms show that the honeycombed hierarchical porosity silica microspheres have a high surface area of 602 m2 g-1, a mesopore volume of 0.77 cm3/g, and a mesopore porosity of 99.6% based on the total pore volume of N2 adsorption-desorption. On the basis of the experiment results, a rational formation process of the honeycombed hierarchical porosity silica microspheres was deduced.

  • 288.
    Kangas, Jani
    et al.
    University of Oulu.
    Sandström, Linda
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Malinen, Ilkka
    University of Oulu.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Tanskanen, Juha
    University of Oulu.
    Maxwell-Stefan modeling of the separation of H2 and CO2 at high pressure in an MFI membrane2013Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 435, s. 186-206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, a Maxwell-Stefan based model was developed for the separation of CO2 from H2 at high pressure in an MFI membrane. The usage of the Vignes interpolation formula for mixture surface diffusivities together with the IAST (ideal adsorbed solution theory) using bulk gas phase fugacities for mixture adsorption proved to be a feasible combination for this case. Both the effects of defects in the zeolite film and the mass transfer resistance caused by the support layers were studied and included in the model. Only pure component experimental data was used in the model building to predict the gas mixture permeation. The fitted diffusion parameters were in line with the literature values. The occupancy fraction dependence of CO2 surface diffusivity was utilized for the first time in the prediction of binary separation of H2/CO2 at high pressure on a real MFI membrane. Usage of an occupancy fraction dependence for CO2 surface diffusivity improved the model predictions. The adsorption parameter fitting for hydrogen based on the permeation measurements resulted in a feasible adsorption model, but should be used with caution. The model predicts binary separation measurement results relatively well. Both defects and support have a noticeable impact on the overall performance of the membrane.

  • 289.
    Kantarelis, Efthymios
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Catalytic Steam Pyrolysis of Biomass for Production of Liquid Feedstock2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The current societal needs for fuels and chemical commodities strongly depend on fossil resources. This dependence can lead to economic instabilities, political problems and insecurity of supplies. Moreover, global warming, which is associated with the massive use of fossil resources, is a dramatic “collateral damage” that endangers the future of the planet.

    Biomass is the main renewable source available today that can, produce various liquid, gaseous and solid products. Due to their lignocellulosic origin are considered CO2 neutral and thus can generate CO2 credits. Biomass processing can meet to the challenge of reducing of fossil resources by producing a liquid feedstock that can lessen the “fossil dependence” and /or meet the increased demand via a rapidly emerging thermochemical technology: pyrolysis.

    The ultimate goal of this process is to produce liquid with improved properties that could directly be used as liquid fuel, fuel additive and/or feedstock in modern oil refineries and petrochemical complexes.

    However, the liquids derived from biomass thermal processing are problematic with respect to their handling and end use applications. Thus, alternative routes of advanced liquid feedstock production are needed. Heterogeneous catalysis has long served the oil refining and petrochemical industries to produce a wide range of fuels and products. The combination of biomass pyrolysis and heterogeneous catalysis (by bringing in contact the produced vapours/liquids with suitable catalysts) is a very promising route.

    In this dissertation, the exploitation of biomass to produce of liquid feedstock via pyrolysis over a multifunctional catalyst and in a steam atmosphere is investigated. 

    Steam pyrolysis in a fixed bed reactor demonstrated that steam can be considered a reactive agent even at lower temperatures affecting the yields and the composition of all the products. The devolatilisation accelerates and the amount of final volatile matter in the char.

    Fast pyrolysis in the presence of steam results in improved and controlled thermal decomposition of the biomass; higher liquid yields and slightly deoxygenated liquid products are also obtained.

    Steam pyrolysis over a bi-metallic Ni-V catalyst can produce liquids of improved quality (lower O content) and also provide routes for selective deoxygenation. However, a decrease in liquid yield was observed.

    The combination of metal and acid catalysts (Ni-V/HZSM5) shows enhanced deoxygenation activity and increased H preservation in the produced liquid. The final O content in the liquid was 12.83wt% at a zeolite (HZSM5) loading of~75wt%; however, the yield of the obtained liquid was substantially decreased. Moreover, increased coke formation on the catalyst was observed at highest zeolite rate.

    The increased catalyst space time (τ) results in a lower liquid yield with reduced oxygen (7.79 wt% at τ =2h) and increased aromatic content. The coke deposited per unit mass of catalyst is lower for longer catalyst space times, while the char yield seems to be unaffected.

    The evaluation of the stability of the hybrid catalyst showed no significant structural defects and activity loss when the catalyst was regenerated at a low temperature (550οC).

  • 290.
    Kantarelis, Efthymios
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Javed, Rashed
    Stefanidis, Stylianos
    Psarras, Antonios
    Iliopoulou, Eleni
    Lappas, Angelos
    Upgrading biomass pyrolysis vapors over hierarchical Co/HZSM5: Activity and coking characteristics2018Inngår i: 18th Nordic Symposium on Catalysis Book of Abstracts, Copenhagen, 2018, s. 29-29, artikkel-id O3.2Konferansepaper (Fagfellevurdert)
  • 291.
    Kantarelis, Efthymios
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Biomass pyrolysis  for energy and fuels production2013Inngår i: Technologies for Converting Biomass to Useful Energy: Combustion, Gasification, Pyrolysis, Torrefaction and Fermentation / [ed] Erik Dahlquist, CRC Press, 2013, s. 245-277Kapittel i bok, del av antologi (Fagfellevurdert)
  • 292.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Claudpierre, Simon
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nanocellulose based functional membranes for water cleaning: Tailoring of mechanical properties, porosity and metal ion capture2016Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 514, s. 418-428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers (CNF) suspensions followed by dip coating with cellulose nanocrystals having sulphate (CNCSL) or carboxyl surface groups (CNCBE). It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes based on drying conditions and acetone treatment. CNF coated with CNCBE showed the highest a tensile strength (95 MPa), which decreased in wet conditions (≈3.7 MPa) and with acetone (2.7 MPa) treatment. The water dried membranes showed pore sizes in nanofiltration range (74 Å) from liquid nitrogen adsorption/desorption data and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194Å) with a concomitant increase (7000%) of the BET surface area. The water flux, also increased from zero to 25 Lm-2h-1 at a pressure differential of 0.45 MPa, for acetone treated ones. The membranes irrespective of the surface functionality showed exceptional capability (≈100%) to remove Ag+, Cu2+ and Fe3+ ions from mirror industry effluents. Surface adsorption followed by microprecipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultrafiltration membranes with high selectivity towards ions and low-pressure demands.

  • 293.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Chitosan based nanocomposite membranes with cellulose nanowhisker as nanoadditive2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biobased nanocomposite membranes were prepared using chitosan as te matrix and cellulose nano whisker as the reinforcing phase. Cellulosee production. Atomic force microscopy of the nanowhiskers showed diameters of 10 -20nm and lengths of 250 - 350nm. Nanocomposites were prepared in 1:1, 1:2 and 1:3 ratios to investigate the effect of nanoadditive concentration on the membrane properties. The nanocomposites were prepared by solution mixing followed by freeze-drying, to obtain porous structures with high degree of internal surface area. These nanocomposites were further treated with ammonia vapours to prepare the crosslinked nanocomposites and thereby stabilize it towards moisture and pH variations. The morphology, surface area, crystallinity, porosity, and mechanical properties of prepared membranes were studied. The effect of the nanocomposite composition, crosslinking and the pore size distribution on the water transport through the membranes was also evaluated.

  • 294.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nanoporous membranes with cellulose nanocrystals as functional entity in chitosan: removal of dyes from water2014Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 112, s. 668-676Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fully biobased composite membranes for water purification were fabricated with cellulose nanocrystals (CNCs) as functional entities in chitosan matrix via freeze-drying process followed by compacting. The chitosan (10 wt%) bound the CNCs in a stable and nanoporous membrane structure with thickness of 250-270 μm, which was further stabilized by cross-linking with gluteraldehyde vapors. Scanning electron microscopy (SEM) studies revealed well-individualized CNCs embedded in a matrix of chitosan. Brunauer, Emmett and Teller (BET) measurements showed that the membranes were nanoporous with pores in the range of 13-10 nm. In spite of the low water flux (64 L m-2 h-1), the membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, after a contact time of 24 h. The removal of dyes was expected to be driven by the electrostatic attraction between negatively charged CNCs and the positively charged dyes.

  • 295.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kokol, Vanja
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Wei, Jiang
    Alfa Laval Nakskov A/S, Business Center Membranes, Stavangervej 10, DK-4900, Nakskov, Denmark.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    High-flux affinity membranes based on cellulose nanocomposites for removal of heavy metal ions from industrial effluents2016Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 25, s. 20644-20653Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fully biobased affinity membrane processing and its application in the removal of heavy metal ions from mirror industry effluents were successfully demonstrated; indicating the potential use of these membranes in point-of-use or point-of-entry water cleaning products that are cheap, environmentally friendly and efficient. Layered cellulose nanocomposite membranes were fabricated using cellulose microfiber sludge as a support layer and cellulose nanocrystals (CNCSL, CNCBE or PCNCSL) in a gelatin matrix as the functional layer. Scanning electron microscopy (SEM) studies revealed the bi-layered morphology of the membrane and well-individualized nanocelluloses in the functional layer. Bubble point measurements confirmed the membrane pore structure in the microfiltration range (5.0-6.1 μm), which provided very high water permeability (900-4000 L h-1 m-2) at <1.5 bars. A tensile strength of 16 MPa in dry conditions and a wet strength of 0.2 MPa, was considered sufficient for use of these membranes in spiral wound modules. Mirror industry effluent laden with metal ions (Ag+ and Cu2+/Fe3+/Fe2+) when treated with cellulose nanocomposite membranes, showed high ion removal capacity, being 100% for PCNCSL followed by CNCBE than CNCSL. The removal of metal ions was expected to be driven by interactions between negatively charged nanocellulose and the positively charged metal ions.

  • 296.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Cellulose nanocrystals based nanocompositemembranes for water purification: Process-Property correlation2015Konferansepaper (Annet vitenskapelig)
  • 297.
    Karim, Zoheb
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mathew, Aji P.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oksman, Kristiina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fully biobased nanocomposite membranes: removal of heavy metals from polluted water2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biobased nanoparticles viz cellulose nanocrystals (CNCs) and cellulose nanofiber (CNFs) isolated by mechanical process (grinding) were used to fabricate of fully biobased nanocomposite membranes. Biobased nanofibers were used as support layer via a very simple process of vacuum filtration was used for the fabrication of CNF support layer. In order to coat CNCs or CNCbio on the two sides to CNF layer, the membrane was dipped in a solution of cellulose nanocrystals. Scanning electron microscopy (SEM) confirmed the infusion of functional layer within supportive layer. Tensile strength was measured in dry as well as in wet conditions, illustrated mechanical performances compareble to commercially available membranes. To increase the flux, membranes were treated with acetone for 24 and 72 h. The drastic increase in the flux for acetone treated membranes confirmed the discontinuities of hydrogen . The membranes succefully removed two metal ions Ag+ and As3- from real wastewater, from mirror making and mining industries respectively, within Europe. Complete removal of Ag+ was reported after 24 h of incubation. The study concludes that, the developed membranes having good mechanical stability in wet conditions, high water flux and adsorption efficiency are potential candidates for heavy metal ion remediation of industrial effluents.

  • 298.
    Karimi, Somayeh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Sardari, Kaymar
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Esmaeili, Mohammad
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Antzutkin, Oleg
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Shah, Faiz Ullah
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    High flux acetate functionalized silica membranes based on in-situ co-condensation for CO2/N2 separation2016Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 520, s. 574-582Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acetate-functionalized silica membranes were prepared via co-condensation. The molar ratio of functional groups in the silica matrix was varied in the range of 0–0.6, denoted by x. The presence of functional groups bonded to the silica network was revealed by FTIR and 29Si and 13C solid-state NMR analysis. The stability of the groups was studied by TG analysis. The membranes were evaluated for CO2/N2 mixture separation in a temperature range of 253–373 K using a feed pressure of 9 bar and a sweep gas kept at atmospheric pressure on the permeate side. The membranes were found to be CO2-selective at all the conditions studied. The highest observed selectivity was 16 for x=0.4, with a CO2 permeance of 5.12×10−7 mol s−1 m−2 Pa−1. For x=0.2, a permeance of as high as 20.74×10−7 mol s−1 m−2 Pa−1 with a CO2/N2 selectivity of 7.5 was obtained. This permeance is the highest reported for CO2/N2 separation using functionalized silica membranes. It is proposed that the separation mechanism between CO2 and N2 was the preferential adsorption of CO2, which inhibited adsorption and permeation of N2 through the silica pore network. Permporometry results revealed that as the loading of functional groups increased, the He permeance decreased. It was also indicated that the quantity of micropores in the functionalized membrane was higher than that in the parent silica membrane.

  • 299.
    Karimi, Somayeh
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Yu, Liang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Esmaeili, Mohammad
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    A simple method for blocking defects in zeolite membranes2015Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 489, s. 270-274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The abatement of defects in zeolite membranes is essential for achieving high selectivity. In the present work, a simple and effective method for blocking defects in ultra-thin (ca. 0.5 μm) MFI zeolite membranes has been developed. The method is based on deposition of an ultra-thin (∼15 nm) layer of amorphous silica on the top surface of the membrane. Permporometry data indicated that the amount of defects, especially defects larger than 4 nm, in the membranes was significantly reduced after the modification. In mixture separation experiments, the CO2/H2 separation factor increased dramatically after blocking the defects in a defective membrane that was selected for the experiments. For instance, at 263 K and 9 bar feed pressure, the CO2/H2 separation factor increased from 8.5 to 36 after modification of the membrane, whereas the CO2 flux only decreased by ca. 40%.

  • 300.
    Karimineghlani, Parvin
    et al.
    Texas A&M University, Department of Material Science and Engineering, College Station, TX 77843, USA.
    Karimi Neghlani, Paria
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Azadmehr, Amirreza
    Amirkabir University of Technology, Department of Mining and Metallurgical Engineering,Tehran, Iran, 15875-4413.
    Optimization of lead ions adsorption on hydrolyzed polyacrylonitrile fibers using central composite design2017Inngår i: Desalination and Water Treatment, ISSN 1944-3994, E-ISSN 1944-3986, Vol. 83, s. 133-143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optimization of lead ions (Pb++) adsorption on the hydrolyzed polyacrylonitrile (PAN) fibers was reported by using statistical approach. Electrospinning of PAN solutions in dimethylformamide (DMF) was performed with different concentrations. The electrospun fibres, with various diame-ters, were then hydrolyzed in a sodium hydroxide solution (NaOH) for different reaction times and temperatures. Response surface methodology (RSM) helped optimizing the hydrolysis reaction con-ditions to maximize the adsorption capacity of the PAN fibers. The maximum value of adsorption capacity was experimentally determined to be 141 mg/g with the optimized values of hydrolysis reaction time, temperature and fiber diameter being 61.6°C, 82.1 min and 280 nm, respectively. The as-prepared electrospun fibers, hydrolyzed fibers and fibers after adsorption process were charac-terized by scanning electron microscope (SEM). Experimental adsorption data fit very well with the Langmuir isotherm model. It was found that Pb++ ions adsorption on the nanofibers was 20 times higher than that on microfibers under the same conditions. Adsorption kinetics followed the second order kinetics model. © 2017 Desalination Publications. All rights reserved.

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