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  • 201.
    Gren Vikander, Lukas
    KTH, Skolan för kemivetenskap (CHE).
    Purification oflignin-based oil2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The combustion of petroleum-based fuels in the transportation sector is a major contributor to the carbon footprint humans make on the Earth. There is a big need for innovative solutions replacing today’s crude oil based fuels. RenFuel has come up with a pioneering solution to enable co-processing of lignin with crude oil fractions at refineries. This thesis is focused on proof of concept for liquid-liquid extraction purification of lignin-based oil, which will enable further processing to diesel and gasoline additives.

    Liquid-liquid extraction has been considered as the method of purification and was prove meet the separation criteria. Later laboratory trials was carried out to find design parameters for the full-scale purification procedure, which has led to a process route that has been suggested. The proposed process route meets the criteria for the separation. On a second thought, the process route will not be recommended for RenFuel´s pilot plant, the main reason for this is that it limits the plant's flexibility. Propositions for alternative purification methods and future research have been presented.

  • 202.
    Grimler, Henrik
    KTH, Skolan för kemivetenskap (CHE).
    Investigating Urea Vaporization in a Controlled Environment Using Infrared Thermography2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As the emission legislation becomes more stringent, higher demands are put on the aftertreatment system in trucks. For dealing with nitrous oxides, AdBlue® (urea–water solution) is injected into the exhausts which evaporates and reduces nitrous oxides to nitrogen. At low exhaust temperatures, it is more difficult to evaporate the injected AdBlue® as the exhausts contain less energy. The injected solution may instead form a wall film. In this wall film, side reactions can occur which leads to the formation of deposits.

    This thesis aims at understanding how and when wall films and deposits are formed. To achieve this, a test rig that allowed visual and infrared observations of the process and variation of governing properties was designed and built.

    The results show that thicker plates can sustain higher dosages than thinner plates since the temperature drop and film area are smaller for the thicker plate. It was also observed that at plate temperatures >340 °C, the water in the impacting spray evaporated, leaving a urea dust in the gas phase.

    It is also clear that deposits form faster at higher gas temperatures (> 350 °C) compared to at lower temperatures (200–250 °C). The deposits form at the edge of the wall film in a region with a temperature higher than in the middle of the wall film. At lower temperatures, a wall film that spreads out over a very large area is formed and after a longer time period, deposits form at obstacles and at the wall film edge. Experiments for 2 h at lower temperatures left approximately the same amount of deposits as experiments for 30 min at higher temperatures.

  • 203.
    Gruvnäs, Filip
    KTH, Skolan för kemivetenskap (CHE).
    Modellering av åldring av dieseloxidationskatalysatorer2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A conventional exhaust gas after treatment system (EATS) for the Euro VI legislation contains four different catalyst. The first two (particulate filter system) remove particulates and the last two (SCR system) remove nitrogen oxides (NOx). The particulate filter system also optimizes the gas composition with respect to nitrogen monoxide (NO) and nitrogen dioxide (NO2). The performance of the SCR system has a strong dependency on the NO:NO2 ratio as the so called selective catalytic reduction (SCR) reaction is kinetically favored at a NO:NO2 ratio of 1:1.

    The diesel oxidation catalyst (DOC) is placed first in the EATS. Due to this placement, the DOC is subjected to a rough environment, e.g. high temperatures and oil/fuel impurities that with time will affect its performance, i.e. the catalyst ages.

    In this master thesis, the aging of the DOC has been empirically correlated to thermal load and sulfur exposure. The study shows that it is possible to predict how the NO oxidation performance decays as a function of thermal and sulfur exposure. The empirical relation was fitted against two aging cycles and validated against an additional four. The results show that the loss of catalytic activity can to a large extent be explained by the cycle it has been used on.

  • 204.
    Grönkvist, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Bryngelsson, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Westermark, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Oxygen efficiency with regard to carbon capture2006Inngår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 31, nr 15, s. 3220-3226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon capture is often discussed in the literature with the sole focus on power processes, despite the fact that carbon dioxide emissions from other sources are just as relevant for the impact on the atmosphere. Furthermore, some carbon capture methods are relatively inefficient when applied to power production processes. Carbon capture should preferably be performed where the cost is as low as possible, i.e. not necessarily from power production processes. As an example, carbon capture using combustion with pure oxygen is far more energy efficient if it is used together with lime kilns or cement kilns than together with power production processes. A new concept termed "oxygen efficiency" is introduced in this paper. It describes the amount of carbon dioxide that can potentially be captured per unit of oxygen. As such, the oxygen efficiency quantifies the value of a certain unit of oxygen for carbon capture reasons. The base concept is that the energy penalty for the production of one part of oxygen is the same no matter where it is produced; hence, if this unit of oxygen can be used to capture more carbon dioxide, it is more efficient. Typically, the oxygen efficiency would be five times greater for carbon capture when utilising pure oxygen together with cement kilns rather than together with methane-fired power plants. Furthermore, the concept of oxygen efficiency illustrates the importance of considering how carbon capture methods can be utilised in the most efficient way, in addition to evaluating which carbon capture method is the most suitable for a particular technology.

  • 205.
    Gualtieri, Magdalena
    Luleå University of Technology.
    Synthesis and characterization of zeolite films and membranes2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this work, a seeding technique was used to synthesize films and membranes of FAU, LTA and MFI type zeolites. In the first part, hydrothermal growth was performed without organic template molecules, which resulted in template-free zeolite films and membranes. The samples were characterized by Scanning Electron Microscopy, X-ray Powder Diffraction and permeation measurements with gaseous probe molecules. Thin films of FAU-type zeolite were prepared on polished single crystals. The thickness and morphology of the films could be controlled by varying the synthesis conditions. Preparation of LTA-type membranes was also attempted. However, the membranes cracked during drying at temperatures above room temperature. Template free MFI membranes with higher quality could be prepared. These membranes had a maximum separation factor alpha of 17.8 at 220°C for a n-butane/i-butane mixture. Cracks formed at temperatures higher than 250°C. Crack formation in zeolite membranes at high temperatures has also been reported by several other groups. Since no model for the crack formation process has been established in the literature, the second part of this work was devoted to study crack formation and to develop a model. Relatively thick (ca 1800 nm) alpha-alumina supported MFI films, prepared using organic template molecules (TPA+), were selected for the study since data on crack formation in the form of SEM images and permeation measurements for these membranes had been obtained in earlier work by the group. These membranes were further studied by in-situ High Temperature X-ray Powder Diffraction experiments in the present work. In addition, MFI powder and a blank alpha-alumina support were also investigated. Data were collected with the aid of a Synchrotron radiation facility as well as with a conventional laboratory instrument for the temperature cycle 25-500-25°C. The Rietveld method was used to determine the unit cell parameters of MFI and alpha-alumina as well as the TPA+ occupancy of MFI. The out-of- plane strain (i.e. strain in the direction perpendicular to the film surface) in the film and the support was calculated. In addition, the microstructure of the support was investigated by pattern decomposition and Williamson-Hall plots. In agreement with previous reports in the literature, it was found that the TPA-MFI structure contracts as a consequence of template removal and possibly also a structure intrinsic mechanism and the alpha-alumina support expands. Hence, a large thermal expansion mismatch occurs in the membranes during heating. An overall out- of-plane compressive strain was observed for the MFI film during heating, which indicates an in-plane tensile stress (i.e. in the direction parallel to the film surface) in the film. This result was explained by the larger expansion of the support, compared to the film. The alpha-alumina support was also found to be under an overall out-of-plane compressive strain at non-ambient temperatures, presumably due to zeolite in the pores of the support. The microstrain for the MFI coated alpha-alumina support increased during heating, and remained during cooling, which indicate the formation of structural defects in the support. Based on these results and results from earlier work, a model for crack formation was proposed: In the thick films (ca 1800 nm) studied in the present work, the crystals are well intergrown. During heating, the MFI crystals contracts and the alpha- alumina support expands. Consequently, a thermal stress develops in the composite which eventually leads to formation of cracks. In addition, part of the stress is also released via formation of structural defects in the alpha-alumina support. In thinner films (ca 500 nm), the crystals are less well intergrown and the thermal expansion mismatch between the crystals in the film and the support leads to opening of grain boundaries in the film rather than cracks.

  • 206.
    Gualtieri, Magdalena Lassinantti
    et al.
    Luleå tekniska universitet.
    Andersson, Charlotte
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Gualtieri, Alessandro F.
    Dipartimento di Scienze della Terra, Universita di Modena e Reggio Emilia.
    Leoni, Matteo
    Dipartimento di Ingegneria dei Materiali, Università di Trento, I-38050 Mesiano.
    Meneghini, Carlo
    Dipartimento di Fisica ‘E. Amaldi’ Università di Roma Tre, Via della Vasca Navale 84, I-00146 Roma.
    Crack formation in α-alumina supported MFI zeolite membranes studied by in situ high temperature synchrotron powder diffraction2007Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 290, nr 1-2, s. 95-104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cracks are frequently formed in α-alumina supported MFI membranes during calcination. To better understand crack formation, in situ powder diffraction data were collected during calcination of a type of MFI membrane (ca. 1800 nm thick) which is known to crack reproducibly. In addition, data for MFI powder and a blank support were also collected. Both a synchrotron radiation facility and an in-house instrument were used. The unit cell parameters were determined with the Rietveld method, and the strain in the direction perpendicular to the film surface was calculated for the film as well as for the support. The microstrain in the support was also estimated. Based on the results obtained here, a model for crack formation in this type of MFI membrane was proposed. The lack of cracks in other types of MFI membranes (ca. 500 nm) prepared in our laboratory is also explained by the model. In thicker MFI films, the crystals are well intergrown. During heating, the MFI crystals contract and the α-alumina support expands. Consequently, a thermal stress develops in the composite which eventually leads to formation of cracks in the film and structural defects in the support. In thinner films, the crystals are less well intergrown and the thermal expansion mismatch leads to opening of grain boundaries rather than cracks.

  • 207.
    Gualtieri, Magdalena Lassinantti
    et al.
    Luleå tekniska universitet.
    Gualtieri, Alessandro
    Università di Modena e Reggio Emilia.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    The influence of heating rate on template removal in silicalite-1: an in situ HT-XRPD study2006Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 89, nr 1-3, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of heating rate on thermal behavior of TPA-silicalite-1 during calcination and the reaction kinetics for TPA decomposition were investigated. The cell parameters of the TPA-silicalite-1 during the heating cycles were determined with the aid of high temperature X-ray diffraction data and the Rietveld method. The template decomposition is accompanied by a large contraction of the unit cell. The unit cell dimensions during template removal are not affected significantly by the heating rate. Consequently, the rate of contraction is approximately proportional to the heating rate. The intensity of some diffraction peaks changes during heating, especially the 101/011 and the 200/020 peaks. The intensity change of those peaks shows the same dependence with temperature as the TPA occupancy, indicating that these parameters are related. An analysis of the kinetics for TPA decomposition based on the intensity change of the 101/011 and the 200/020 peaks was performed. The apparent activation energy (Ea) of the template decomposition in silicalite-1 determined with the Kissinger and the Flynn–Wall–Ozawa methods was 138 (±25) and 138 (±29) kJ mol−1, respectively. The reaction order, determined with the method of Kennedy and Clark, was close to 0.5 indicating that the rate-limiting step is mono-dimensional diffusion. Ea was 140 (±30) kJ mol−1, in good agreement with the results obtained with the other methods. With the results presented here, it is possible to discuss possible effects of the heating rate on the crack formation frequently observed in zeolite membranes during calcination

  • 208.
    Guan, Tingting
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Biomass-fuelled PEM FuelCell systems for small andmedium-sized enterprises2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Biomass-fuelled proton exchange membrane fuel cells (PEMFCs) offer asolution for replacing fossil fuel for hydrogen production. Through using thebiomass-derived hydrogen as fuel, PEMFCs may become an efficient andsustainable energy system for small and medium-sized enterprises. The aim ofthis thesis is to evaluate the performance and potential applications of biomassfuelledPEMFC systems which are designed to convert biomass to electricity andheat. Biomass-fuelled PEMFC systems are simulated by Aspen plus based ondata collected from experiments and literature.The impact of the quality of the hydrogen-rich gas, anode stoichiometry, CH4content in the biogas and CH4 conversion rate on the performance of the PEMFCis investigated. Also, pinch technology is used to optimize the heat exchangernetwork to improve the power generation and thermal efficiency.For liquid and solid biomass, anaerobic digestion (AD) and gasification (GF),respectively, are relatively viable and developed conversion technologies. ForAD-PEMFC, a steam reformer is also needed to convert biogas to hydrogen-richgas. For 100 kWe generation, the GF-PEMFC system yields a good technicalperformance with 20 % electrical efficiency and 57 % thermal efficiency,whereas the AD-PEMFC system only has 9 % electrical efficiency and 13 %thermal efficiency. This low efficiency is due to the low efficiency of theanaerobic digester (AD) and the high internal heat consumption of the AD andthe steam reformer (SR). For the environmental aspects, the GF-PEMFC systemhas a high CO2 emissions offset factor and the AD-PEMFC system has anefficient land-use.The applications of the biomass-fuelled PEMFC systems are investigated on adairy farm and an olive oil plant. For the dairy farm, manure is used as feedstockto generate biogas through anaerobic digestion. A PEMFC qualified for 40 %electrical efficiency may generate 360 MWh electricity and 680 MWh heat peryear to make a dairy farm with 300 milked cows self-sufficient in a sustainableway. A PEMFC-CHP system designed for an olive oil plant generating annual 50000 m3 solid olive mill waste (SOMW) and 9 000 m3 olive mill waste water(OMW) is simulated based on experimental data from the Biogas2PEM-FCproject1. After the optimization of the heat exchanger network, the PEMFC-CHP 

    system can generate 194 kW electricity which corresponds to 62 % of the totalelectricity demand of the olive oil plant.The economic performance of the PEMFC and biogas-fuelled PEMFC areassessed roughly including capital, operation & maintenance (O&M) costs of thebiogas plant and the PEMFC-CHP, the cost of heat and electricity, and the valueof the digestate as fertilizer.

  • 209.
    Guan, Tingting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    An overview of biomass-fuelled proton exchange membrane fuel cell (PEMFC) systems2015Inngår i: CLEAN, EFFICIENT AND AFFORDABLE ENERGY FOR A SUSTAINABLE FUTURE, Elsevier, 2015, s. 2003-2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    PEMFC fuelled by biomass-derived hydrogen is an efficient and sustainable energy system for small-scale residential applications. Gasification and anaerobic digestion combined with steam reforming are seen as the most suitable conversion processes for hydrogen production. Since the biomass-derived hydrogen contains many kinds of contaminants including CO, CO2, H2S, NH3 and N-2, extensive work has been done on the mechanism and mitigation methods for their poisoning the PEMFC. Although the biomass-fuelled PEMFC systems have been tested in several experiments and checked through simulation work for different perspectives, further research and demonstration work are required to improve the system efficiency and reliability. (C) 2015 The Authors. Published by Elsevier Ltd.

  • 210.
    Guan, Tingting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Cogeneration PEM fuel cell system fuelled by olive mill wastes for its application in an olive oil plantManuskript (preprint) (Annet vitenskapelig)
  • 211.
    Gunarathne, Duleeka
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Advanced Gasification of Biomass/Waste for Substitution of Fossil Fuels in Steel Industry Heat Treatment Furnaces2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    With the current trend of CO2 mitigation in process industries, the primary goal of this thesis is to promote biomass as an energy and reduction agent source to substitute fossil sources in the steel industry. The criteria for this substitution are that the steel process retains the same function and the integrated energy efficiency is as high as possible.

    This work focuses on advanced gasification of biomass and waste for substitution of fossil fuels in steel industry heat treatment furnaces. To achieve this, two approaches are included in this work. The first investigates the gasification performance of pretreated biomass and waste experimentally using thermogravimetric analysis (TGA) and a pilot plant gasifier. The second assesses the integration of the advanced gasification system with a steel heat treatment furnace.

    First, the pyrolysis and char gasification characteristics of several pretreated biomass and waste types (unpretreated biomass, steam-exploded biomass, and hydrothermal carbonized biomass) were analyzed with TGA. The important aspects of pyrolysis and char gasification of pretreated biomass were identified.

    Then, with the objective of studying the gasification performance of pretreated biomass, unpretreated biomass pellets (gray pellets), steam-exploded biomass pellets (black pellets), and two types of hydrothermal carbonized biomass pellets (spent grain biocoal and horse manure biocoal) were gasified in a fixed bed updraft gasifier with high-temperature air/steam as the gasifying agent. The gasification performance was analyzed in terms of syngas composition, lower heating value (LHV), gas yield, cold gas efficiency (CGE), tar content and composition, and particle content and size distribution. Moreover, the effects on the reactions occurring in the gasifier were identified with the aid of temperature profiles and gas ratios.

    Further, the interaction between fuel residence time in the bed (bed height), conversion, conversion rate/specific gasification rate, and superficial velocity (hearth load) was revealed. Due to the effect of bed height on the gasification performance, the bed pressure drop is an important parameter related to the operation of a fixed bed gasifier. Considering the limited studies on this relationship, an available pressure drop prediction correlation for turbulent flow in a bed with cylindrical pellets was extended to a gasifier bed with shrinking cylindrical pellets under any flow condition. Moreover, simplified graphical representations based on the developed correlation, which could be used as an effective guide for selecting a suitable pellet size and designing a grate, were introduced.

    Then, with the identified positive effects of pretreated biomass on the gasification performance, the possibility of fuel switching in a steel industry heat treatment furnace was evaluated by effective integration with a multi-stage gasification system. The performance was evaluated in terms of gasifier system efficiency, furnace efficiency, and overall system efficiency with various heat integration options. The heat integration performance was identified based on pinch analysis. Finally, the efficiency of the co-production of bio-coke and bio-H2 was analyzed to increase the added value of the whole process.

    It was found that 1) the steam gasification of pretreated biomass is more beneficial in terms of the energy value of the syngas, 2) diluting the gasifying agent and/or lowering the agent temperature compensates for the ash slagging problem in biocoal gasification, 3) the furnace efficiency can be improved by switching the fuel from natural gas (NG) to syngas, 4) the gasifier system efficiency can be improved by recovering the furnace flue gas heat for the pretreatment, and 5) the co-production of bio-coke and bio-H2 significantly improves the system efficiency.

  • 212.
    Gunnarsson, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Titanium oxide nanoparticle production using high power pulsed plasmas2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions.

    The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 – 250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.

  • 213.
    Görling, Martin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Larsson, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Bio-methane via fast pyrolysis of biomass2013Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 112, nr SI, s. 440-447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bio-methane, a renewable vehicle fuel, is today produced by anaerobic digestion and a 2nd generation production route via gasification is under development. This paper proposes a poly-generation plant that produces bio-methane, bio-char and heat via fast pyrolysis of biomass. The energy and material flows for the fuel synthesis are calculated by process simulation in Aspen Plus®. The production of bio-methane and bio-char amounts to 15.5. MW and 3.7. MW, when the total inputs are 23. MW raw biomass and 1.39. MW electricity respectively (HHV basis). The results indicate an overall efficiency of 84% including high-temperature heat and the biomass to bio-methane yield amounts to 83% after allocation of the biomass input to the final products (HHV basis). The overall energy efficiency is higher for the suggested plant than for the gasification production route and is therefore a competitive route for bio-methane production.

  • 214.
    Görling, Martin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Westermark, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Integration Feasibilities for Combined Cycles in Biofuel Production2011Inngår i: Proceedings of the 24th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2011, Nis University , 2011, s. 3498-3508Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aim of this paper is to evaluate the opportunities for gas turbine integration into biofuel production. When producing biofuels via gasification, a significant amount of the input of chemical energy is converted to reaction heat. A steam cycle is therefore used to recover the heat to useful power, but despite that, the plant often remains net users of electricity. To further enhance the production several studies suggest integration of gas turbines, often fired with offgas from the fuel synthesis. The excess of low level heat in the gas turbine exhaust is successfully integrated in the steam cycle which creates integration synergies. Gasification of biomass for fuel synthesis generally implies that oxygen is used as gasification agent. Despite the synergies in the joint steam cycle, the positive effects are outweighed by the energy penalty from oxygen production. Conclusively, serial production of biofuel and power is not beneficial. More interesting is the integrating of a parallel, air-blown gasifier to produce syngas for the gas turbine. Also the natural gas fired gas turbines have successfully been integrated.

  • 215.
    H. Moud, Pouya
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas.

    The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel.

    Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.

  • 216.
    Haghighi Moud, Pouya
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Andersson, Klas J.
    Lanza, Roberto
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Equilibrium potassium coverage and its effect on a Ni tar reforming catalyst in alkali- and sulfur-laden biomass gasification gases2016Inngår i: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 190, s. 137-146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biomass conversion to syngas via gasification produces certain levels of gaseous by-products, such as tar and inorganic impurities (sulfur, potassium, phosphorus etc.). Nickel, a commonly used catalyst for hydrocarbqn steam reforming, suffers reduced reforming activity by small amounts of sulfur (S) or potassium (K), while resistance against deleterious carbon whisker formation increases. Nevertheless, the combined effect of biomass derived gas phase alkali at varying concentrations together with sulfur on tar reforming catalyst performance under realistic steady-state conditions is largely unknown. Prior to this study, a methodology to monitor these effects by precise K dosing as well as K co-dosing with S was successfully developed. A setup consisting of a 5 kW biomass fed atmospheric bubbling fluidized bed gasifier, a high temperature hot gas ceramic filter, and a catalytic reactor operating at 800 degrees C were used in the experiments. Within the current study, two test periods were conducted, including 30 h with 1 ppmv potassium chloride (KCl) dosing followed by 6 h without KCl dosing. Besides an essentially carbon-free operation, it can be concluded that although K, above a certain threshold surface concentration, is known to block active Ni sites and decrease activity in traditional steam reforming, it appears to lower the surface S coverage (theta(s)) at active Ni sites. This reduction in theta(s) increases the conversion of methane and aromatics in tar reforming application, which is most likely related to K-induced softening of the S-Ni bond. The K-modified support surface may also contribute to the significant increase in reactivity towards tar molecules. In addition, previously unknown relevant concentrations of K during realistic operating conditions on typical Ni-based reforming catalysts are extrapolated to lie below 100 mu K/m(2), a conclusion based on the 10-40 mu K/m(2) equilibrium coverages observed for the Ni/MgAl2O4 catalyst in the present study.

  • 217.
    Haglund, Peter
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Spinnel, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A modular approach to pressurized liquid extraction with in-cell clean-up2010Inngår i: LC GC Europe, ISSN 1471-6577, Vol. 23, nr 6, s. 292-301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new concept for the extraction of solid samples has been developed. The popular pressurized liquid extraction (PLE) technique has been modified so that the extraction cell can be divided, which greatly increases the flexibility and versatility of this technique. The system uses simple adaptors to couple commercially available extraction cells, which may be loaded with either sample or adsorbent(s). These segmented extraction cells make it possible to selectively retain analytes or matrix to achieve simultaneous extraction and clean-up or fractionation. The ultimate aim is to perform simultaneous extraction and clean-up and obtain a purified extract that is ready for instrumental analysis, all in line with current trends in analytical chemistry to automate and streamline the analytical procedures to reduce the analysis costs, solvent consumption, manual labour and increase the quality of analysis. Selected modes of operations are presented and a few recent environmental applications of modular PLE are reviewed.

  • 218.
    Haglund, Peter
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Spinnel, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    A modular approach to pressurized liquid extraction with in-cell clean-up2010Inngår i: LCGC Asia Pacific, ISSN 1754-2715, Vol. 13, nr 2, s. 6-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new concept for the extraction of solid samples has been developed. The popular pressurized liquid extraction (PLE) technique has been modified so that the extraction cell can be divided, which greatly increases the flexibility and versatility of this technique. The system uses simple adaptors to couple commercially available extraction cells, which may be loaded with either sample or adsorbent(s). These segmented extraction cells make it possible to selectively retain analytes or matrix to achieve simultaneous extraction and clean-up or fractionation. The ultimate aim is to perform simultaneous extraction and clean-up and obtain a purified extract that is ready for instrumental analysis, all in line with current trends in analytical chemistry to automate and streamline the analytical procedures to reduce the analysis costs, solvent consumption, manual labour and increase the quality of analysis. Selected modes of operations are presented and a few recent environmental applications of modular PLE are reviewed.

  • 219.
    Hagman, Henrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Perstorp Specialty Chemicals AB.
    Co-firing animal waste, sludge, residue wood, peat and forest fuels in a 50MWth CFB boiler: ash transformation, availability and process improvements2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The direct variable costs for heat and electricity production based on solid biomass fuel combustion is approximately 3-5 times lower than the costs in a fossil fuel-oil based boiler in Sweden. In addition waste derived biomass fuels are typically much cheaper than biomass not classified as waste. The introduction of the waste derived fuels; wastewater treatment sludge, demolition wood, and animal waste in a 50MWth circulating fluidized bed (CFB) biomass boiler located in Perstorp, Sweden, led to rapid deposit buildup in superheaters, heavy ash accumulation in economizers and failing boiler tubes and vortex finders that forced frequent boiler shutdowns. This in turn increased the use of expensive oil (fossil fuel) in backup boilers and the CO2 footprint of the on-site energy conversion system. This work aims to increase the general mechanistic understanding of combustion systems using complex fuels, and includes: A mapping of the boiler failure and preventive maintenance statistics; elemental composition analysis of ash, deposits and fuel fractions; flue-gas composition measurements; chemical speciation analysis; an attempt to describe the overall ash transformation reactions and mass balance throughout the combustion process. Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was used to analyze the elemental composition of ash and deposits. The SEM-EDS results were used together with data from X-ray powder diffraction (XRD) analysis, thermodynamic phase data, and equilibrium calculations in an attempt to quantify the crystalline phases and the overall ash transformation of the process. Based on the findings concerning ash transformation and the failure statistics, it has been possible to identify generic key parameters regarding boiler design and process parameters, enabling major improvements of the CFB boiler availability, a lower overall energy conversion cost and a reduced CO2 footprint.

  • 220.
    Hagman, Henrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Co-firing complex biomass in a CFB boiler: ash transformation, corrosion control and materials selection2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The effects of greenhouse gas net emissions on global warming, stricter legislation on waste handling, and the pursuit of ever cheaper heat- and power production are all important factors driving the introduction of complex fuels in incineration plants. However - without fundamental knowledge regarding ash transformation, corrosion control, and materials selection – this introduction of potentially economically and environmentally beneficial fuels, might instead cause economic loss and environmentally adverse effects.

    The present work is a contribution to the transition from today's CO2 net generating energy conversion system, to a more environmentally friendly and cost-efficient one. This is done using scientific methods to generate knowledge concerning mechanisms of ash transformation, corrosion control, and materials selection, in a co-fired industrial scale circulating fluidized bed (CFB) boiler, using a novel and biomass-based fuel mix, rich in Na, K, Cl, N, S, P, Ca and Si. Fuel fractions, ashes, flue gas, deposits, and construction material samples have been collected and analyzed using various techniques, including scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray Diffraction (XRD). The experimental results have been evaluated and interpreted using chemical equilibrium calculations.

    The results of this work include:

    1) An analysis of; the failure and preventive maintenance statistics of the industrial scale CFB boiler at hand; the elemental composition of boiler ashes and deposits, the flue gas composition and elemental composition of a multitude of fuel fractions; correlations between boiler design, operational parameters, elemental composition of deposits and boiler availability; a boiler elemental mass balance revealing details regarding deposit buildup mechanisms; properties of the fly ash relevant to flue gas filter design; and findings regarding the nitrogen chemistry of the novel and nitrogen-rich fuel mix.

    2) Speciation and description of the overall ash transformation and fireside alloy interaction, enabling the implementation of on-line corrosion control which significantly inhibits superheater and dew-point corrosion in the boiler; and, an equation describing the sulfation potential of the fuel mix, as a result of the direct and indirect interactions between all major ash-forming elements.

    3) A literature review relevant for the co-fired CFB cyclone vortex finder alloy selection and corrosion at 880 °C; An alloy selection study including long term exposures of several commercially available alloys identifying materials that are more than twice as cost-efficient as the often used alloy 253MA; a suggestion of novel methods for both systematic comparison of heavily degraded alloys, and for alloy service-life estimations; a detailed analysis of heavily degraded alloys 310S, 800H/HT and 600, identifying the driving corrosion mechanisms of the VF alloy degradation, including aspects of how the alloy internal mass transport and fireside surface interaction develops over time.

    The knowledge gained during this project has been used in the improvement work of the Perstorp 50 MWth CFB boiler, improving the boiler availability with 7 %, reducing the overall energy conversion costs with around 1.7 MEUR/year.

  • 221.
    Halvarsson, Alfred
    KTH, Skolan för kemivetenskap (CHE).
    Katalytisk omvandling av pyrolysgas i WoodRoll-processen för ökad processtillförlitlighet2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This project was a cooperation between the division of Chemical Technology at KTH, Cortus Energy and Haldor Topsoe A/S. The goal was to build up a totally new setup for converting and deoxygenate pyrolysis bio-oil, in order to increase the performance of Cortus Energy’s WoodRoll process. Therefore an iron based catalyst from Haldor Topsoe was used.

    The building up of the new setup with all reactors and the control panel was a complicated and time-consuming work. This led to an only short time slot for performing experiments, which means that more work needs to be done to get more valuable results. The most important success of this project was to get all the knowledge about the system and to make everything (the whole experimental setup) running properly. However, the sampling system needs to be improved before making further experiments.

    The experiments which have been done show promising results and that the iron based catalyst was working well for converting the bio-oil. During the two hour long experiment there were not shown any indications of deactivation, when looking at the gas compositions, but the results from temperature programmed oxidation (TPO) show carbon deposition on the catalyst and the BET surface also shows a slight decrease in surface area.

  • 222.
    Halvarsson, Sören
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Manufacture of straw MDF and fibreboards2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this thesis was to develop an economical, sustainable, and environmentally friendly straw Medium Density Fibreboard (MDF) process, capable of full-scale manufacturing and to produce MDF of requested quality. The investigated straw was based on wheat (Triticum aestivum L.) and rice (Oryzae sativa L.). In this thesis three different methods were taken for manufacture of straw MDF; (A) wheat-straw fibre was blowline blended with melamine-modified urea-formaldehyde (MUF), (B) rice-straw fibre was mixed with methylene diphenyl diisocyanate (MDI) in a resin drum-blender, and (C) wheat-straw fibre was activated in the blowline by the addition of Fenton’s reagent (H2O2/Fe2+) for production of non-resin MDF panels.  The MUF/wheat straw MDF panels were approved according to the requirements of the EN standard for MDF (EN 622-5, 2006). The MDI/rice-straw MDF panels were approved according to requirements of the standard for MDF of the American National Standard Institute (ANSI A208.2-2002). The non-resin wheat-straw panels showed mediocre MDF panel properties and were not approved according to the requirements in the MDF standard. The dry process for wood-based MDF was modified for production of straw MDF. The straw MDF process was divided into seven main process steps.

    1. 1.       Size-reduction (hammer-milling) and screening of straw
    2. 2.       Wetting and heating of straw
    3. 3.       Defibration
    4. 4.       Resination of straw fibre
    5. 5.       Mat forming
    6. 6.       Pre-pressing
    7. 7.       Hot-pressing

     

     

     

    The primary results were that the straw MDF process was capable of providing satisfactory straw MDF panels based on different types of straw species and adhesives. Moreover, the straw MDF process was performed in pilot-plant scale and demonstrated as a suitable method for producing straw MDF from straw bales to finished straw MDF panels. In the environmental perspective the agricultural straw-waste is a suitable source for producing MDF to avoid open field burning and to capture carbon dioxide (CO2), the biological sink for extended time into MDF panels, instead of converting straw directly into bio energy or applying straw fibre a few times as recycled paper. Additionally, the straw MDF panels can be recycled or converted to energy after utilization.

    A relationship between water retention value (WRV) of resinated straw fibres, the thickness swelling of corresponding straw MDF panels, and the amount of applied adhesive was determined. WRV of the straw fibre increased and the TS of straw MDF declined as a function of the resin content. The empirical models developed were of acceptable significance and the R2 values were 0.69 (WRV) and 0.75 (TS), respectively. Reduced thickness swelling of MDF as the resin content is increased is well-known. The increase of WRV as a function of added polymers is not completely established within the science of fibre swelling. Fortunately, more fundamental research can be initiated and likely a simple method for prediction of thickness swelling of MDF by analysis of the dried and resinated MDF fibres is possible.

  • 223. Hansson, Anders
    et al.
    Bryngelsson, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Attitudes regarding CO2 capture and storage from a Swedish perspective2005Inngår i: Proceedings of the Fourth Annual Conference on Carbon Capture and Sequestration, 2005, s. 1-16Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study examines the attitudes of Swedish politicians, scientists, NGOs and industry regarding CO2capture and storage (CCS), i.e. actors who possess knowledge about CCS today and will influence thepublic opinion of tomorrow. The study is unique since the phenomenological approach is seldom seenin this specific context. The empirical data is gathered through interviews and is structured andanalyzed in respect to expressed basic assumptions, systems view and a theoretical frameworkstemming from history of technology. From data, different ideal types are constructed - the CCSopponent, the CCS pragmatic and the CCS supporter. Results show a lot of skepticism and evenopposition to the technology among NGOs and politicians, while industry and scientists generally areproponents. The large group of pragmatics is especially interesting since it is presumed to take a standin the foreseeable future.Over time the energy politics in Sweden has been subject to intense controversies. Betweenthe 1960s and 1980s hydropower and nuclear power were heavily debated. With arguments stemmingfrom environmental protection the public opinion, represented by a wide array of strongorganizations, restricted the expansion of those power sources far below the originally plannedcapacity. Now this new technology, CCS, is about to enter the Swedish debate. It is a controversialtechnology with similar characteristics compared to its precedents regarding e.g. large-scale, risk, andlong-term storage, i.e. characteristics that led to the referendum deciding a nuclear power phase out.Unless a careful approach to implementing the technology, could CCS also be phased outprematurely? Will history repeat itself?The results should be seen from a Swedish point of view since Sweden has vast bio-fuel andhydropower resources, which together with an extensive amount of nuclear power makes CO2emissions per capita and GDP low, and the opposition against fossil fuels high.

  • 224.
    Hassan, Mohsan
    et al.
    Department of Mathematics, CIIT, Lahore, Pakistan .
    Faisal, Abrar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemical Engineering, CIIT, Lahore, Pakistan.
    Bhatti, Muhammad Mubashir
    Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China.
    Interaction of aluminum oxide nanoparticles with flow of polyvinyl alcohol solutions base nanofluids over a wedge2018Inngår i: Applied Nanoscience, ISSN 2190-5509, E-ISSN 2190-5517, Vol. 8, nr 1-2, s. 53-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyvinyl alcohol (PVA) is an important industrial chemical, which is used in numerous chemical engineering applications. It is important to study and predict the flow behavior of PVA solutions and the role of nanoparticles in heat transfer applications to be used in chemical processes on industrial scale. Therefore, the present study deals with the PVA solution-based non-Newtonian Al2O3-nanofluid flow along with heat transfer over wedge. The power-law model is used for this non-Newtonian nanofluid which exhibited shear-thinning behavior. The influences of PVA and nanoparticles concentrations on the characteristics of velocity and temperature profiles are examined graphically. The impacts of these parameters on wall shear stress and convective heat transfer coefficient are also studied through tabular form. During the numerical computations, the impacts of these parameters on flow index and consistency index along with other physical properties of nanofluid are also considered. In this study, we found an improvement in heat transfer and temperature profile of fluid by distribution of Al2O3 nanoparticles. It is also noticed that resistance between adjacent layers of moving fluid is enhanced due to these nanoparticles which leads to decline in velocity profile and increases in shear stress at wall.

  • 225.
    He, Jie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    GASIFICATION-BASED BIOREFINERY FOR MECHANICAL PULP MILLS2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The modern concept of "biorefinery" is dominantly based on chemical pulp mills to create more value than cellulose pulp fibres, and energy from the dissolved lignins and hemicelluloses. This concept is characterized by the conversion of biomass into various biobased products. It includes thermochemical processes such as gasification and fast pyrolysis. In mechanical pulp mills, the feedstock available to the gasification-based biorefinery is significant, including logging residues, bark, fibre material rejects, biosludges and other available fuels such as peat, recycled wood, and paper products. This work is to study co-production of bio-automotive fuels, biopower, and steam via gasification in the context of the mechanical pulp industry.

     

    Biomass gasification with steam in a dual-fluidized bed gasifier (DFBG) was simulated with ASPEN Plus. From the model, the yield and composition of the syngas and the contents of tar and char can be calculated. The model has been evaluated against the experimental results measured on a 150 KWth Mid Sweden University (MIUN) DFBG. The model predicts that the content of char transferred from the gasifier to the combustor decreases from 22.5 wt.% of the dry and ash-free biomass at gasification temperature 750 ℃ to 11.5 wt.% at 950 ℃, but is insensitive to the mass ratio of steam to biomass (S/B). The H2 concentration is higher than that of CO under normal DFBG operating conditions, but they will change positions when the gasification temperature is too high above about 950 ℃, or the S/B ratio is too far below about 0.15. The biomass moisture content is a key parameter for a DFBG to be operated and maintained at a high gasification temperature. The model suggests that it is difficult to keep the gasification temperature above 850 ℃ when the biomass moisture content is higher than 15.0 wt.%. Thus, a certain amount of biomass needs to be added in the combustor to provide sufficient heat for biomass devolatilization and steam reforming. Tar content in the syngas can also be predicted from the model, which shows a decreasing trend of the tar with the gasification temperature and the S/B ratio. The tar content in the syngas decreases significantly with gasification residence time which is a key parameter.

     

    Mechanical pulping processes, as Thermomechanical pulp (TMP), Groundwood (SGW and PGW), and Chemithermomechanical pulp (CTMP) processes have very high wood-to-pulp yields. Producing pulp products by means of these processes is a prerequisite for the production of printing paper and paperboard products due especially to their important functional properties such as printability and stiffness. However, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. In mechanical pulping mills, wood (biomass) residues are commonly utilized for electricity production through an associated combined heat and power (CHP) plant. This techno-economic evaluation deals with the possibility of utilizing a biomass integrated gasification combined cycle (BIGCC) plant in place of the CHP plant. Integration of a BIGCC plant into a mechanical pulp production line might greatly improve the overall energy efficiency and cost-effectiveness, especially when the flow of biomass (such as branches and tree tops) from the forest is increased. When the fibre material that negatively affects pulp properties is utilized as a bioenergy resource, the overall efficiency of the system is further improved. A TMP+BIGCC mathematic model is developed based on ASPEN Plus. By means of this model, three cases are studied:

     

    1) adding more forest biomass logging residues in the gasifier,

    2) adding a reject fraction of low quality pulp fibers to the gasifier, and

    3) decreasing the TMP-specific electricity consumption (SEC) by up to 50%.

     

    For the TMP+BIGCC mill, the energy supply and consumption are analyzed in comparison with a TMP+CHP mill. The production profit and the internal rate of return (IRR) are calculated. The results quantify the economic benefit from the TMP+BIGCC mill.

     

    Bio-ethanol has received considerable attention as a basic chemical and fuel additive. It is currently produced from sugar/starch materials, but can also be produced from lignocellulosic biomass via a hydrolysis--fermentation or thermo-chemical route. In terms of the thermo-chemical route, a few pilot plants ranging from 0.3 to 67 MW have been built and operated for alcohols synthesis. However, commercial success has not been achieved. In order to realize cost-competitive commercial ethanol production from lignocellulosic biomass through a thermo-chemical pathway, a techno-economic analysis needs to be done.

     

    In this work, a thermo-chemical process is designed, simulated, and optimized mainly with ASPEN Plus. The techno-economic assessment is made in terms of ethanol yield, synthesis selectivity, carbon and CO conversion efficiencies, and ethanol production cost.

     

    Calculated results show that major contributions to the production cost are from biomass feedstock and syngas cleaning. A biomass-to-ethanol plant should be built at around 200 MW. Cost-competitive ethanol production can be realized with efficient equipments, optimized operation, cost-effective syngas cleaning technology, inexpensive raw material with low pretreatment cost, high-performance catalysts, off-gas and methanol recycling, optimal systematic configuration and heat integration, and a high-value byproduct.

  • 226.
    He, Jie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Engstrand, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Björkqvist, Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Techno-economic evaluation of a mechanical pulp mill with gasification2013Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, nr 3, s. 349-357Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical pulping processes, including thermomechanical pulp (TMP), groundwood (SGW andPGW), and chemithermomechanical pulp (CTMP) processes, each have a very high wood-to-pulp yield. Producing pulp by means of these processes is a prerequisite for paper (such as printing paper and paperboard) grades requiring high printability and stiffness. However, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost.

    In mechanical pulping mills, wood (biomass) residues are commonly utilized for electricity production through an associated combined heat and power (CHP) plant. This techno-economic evaluation deals with the possibility of utilizing a biomass integrated gasification combined cycle (BIGCC) plant in place of the CHP plant.

    Implementing BIGCC in a mechanical pulp production line might greatly improve the overall energy efficiency and cost-effectiveness, especially when more biomass from forest (such as branches and tree tops) is available. When the fibre material that negatively affects pulp properties is utilized as a bioenergy resource, the overall efficiency will be further improved. A TMP+BIGCC mathematical model is developed with ASPEN Plus. By means of modeling, three cases are studied:

    1) adding more forest biomass logging residues in the gasifier,2) adding the reject fibres in the gasifier, and3) decreasing the TMP-specific electricity consumption (SEC) by up to 50%.

    For a TMP+BIGCC mill, the energy supply and consumption are analyzed in comparison with a TMP+CHP mill. The production profits are evaluated.

  • 227.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Control of the preferred orientation in MFI films synthesized by seeding2000Inngår i: Journal of porous materials, ISSN 1380-2224, E-ISSN 1573-4854, Vol. 7, nr 4, s. 455-464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single crystal silicon and quartz wafers were seeded with colloidal TPA-silicate-1 crystals. Hydrothermal treatment of the seeded substrates was used to grow dense MFI films. The preferred orientation of the crystals constituting the films as a function of the amount and size of seeds, film thickness and hydrothermal treatment conditions was investigated. In thin films, most of the crystalline material was found to be oriented with the b-axes close to perpendicular to the substrate surface. In thick films, the a- or c-axes were close to perpendicular to the substrate surface depending on the conditions used for hydrothermal treatment. The seed size and amount was found to affect the rate of change in preferred orientation as a function of film thickness. A film growth mechanism which is able to explain the experimental results is proposed

  • 228.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Thin films of molecular sieves: synthesis and applications1998Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The seed film method for synthesis of ultra thin and thin molecular sieve films was developed. The versatility of the method was demonstrated by successful preparation of films of a number of molecular sieves (silicate-1, ZSM-5, NA) on various supports (silicon, alumina, gold, etc.). The preferred orientation of the crystalline material could be controlled. Silicate-1 films on silicon wafers were evaluated as optical gas sensors. Sorption isotherms of water, toluene, 1-propanol and n-hexane were recorded. ZSM-5 films with a thickness of 1.5 um were crystallized on a porous support and the membranes were evaluated in permeation experiments. The flux in single gas experiments decreased in the series H2O, H2, CO2, O2, N2 and CH4. The difference in flux between each molecule was about 1 order of magnitude which indicated the high quality of the membranes. The measured separation factors for binary mixtures of N2/SF6 and H2/i-C4 were 99 and 66.

  • 229.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Ultra thin films of molecular sieves1997Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 230.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Babouchkina, E.
    Luleå tekniska universitet.
    Sterte, Johan
    Thin zeolite NA films by the seed film method1999Inngår i: Proceedings of the 12th International Zeolite Conference / [ed] M.M.J. Treacy, Warrendale, Pa: Materials Research Society, 1999, Vol. 3, s. 1857-1862Konferansepaper (Fagfellevurdert)
  • 231.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Briddon, Patrick R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Mass transport in porous media from first principles: an experimental and theoretical study2012Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 415-416, s. 271-277Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, the mass transport of helium through zeolite is experimentally determined by measuring the flow of helium through a zeolite membrane. By using a mathematical model, the mass transport through defects was accounted for to arrive at mass transport through zeolite pores. For the first time, we could thereby experimentally show that the mass transport of helium in zeolite pores is strongly controlled by the amount and location of hydrocarbons in the zeolite pores and varies several orders of magnitude. The mass transport of helium in ZSM-5 zeolite pores is first reduced gradually more than one order of magnitude when the loading of n-hexane is increased from 0 to 47% of saturation. As the loading of n-hexane is further increased to 54% of saturation, the mass transport of helium in the zeolite pores is further reduced abruptly by more than two orders of magnitude. This gradual decrease followed by an abrupt decrease of mass transport is caused by adsorption of n-hexane in the zeolite pores. In a similar yet different fashion, the mass transport of helium in the zeolite pores is reduced abruptly by almost two orders of magnitude when the loading of benzene is increased from 0 to 19% of saturation due to adsorption of benzene in the pore intersections. Effective medium approximation percolation models with parameters estimated using density functional theory employing the local density approximation, i.e. models with no adjustable parameters and the most sophisticated theory yet applied to this system, can adequately describe the experimental observations.

  • 232.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Texture of MFI films grown from seeds2005Inngår i: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 10, nr 5-6, s. 226-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This review describes how the texture of MFI films grown from seed crystal is developed during film preparation. Reports published during the last 5 years are in focus. Relative growth rates in various crystallographic directions, competitive growth, properties of the seed layer, defects, grain boundaries and other parameters influencing the film properties are discussed. Mathematical models describing competitive growth are also discussed. Suitable characterization methods for defects are described. The last part of the review is devoted to diffusion. Diffusion models accounting for texture in MFI films and the influence of texture on diffussion are discussed.

  • 233.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Andersson, Charlotte
    Factors affecting the performance of MFI membranes2004Inngår i: Recent advances in the science and technology of zeolites and related materials. Part A: proceedings of the 14 th International Zeolite Conference, Amsterdam: Elsevier, 2004, s. 640-646Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Thin MFI membranes with varying morphology have been prepared using high flux alumina supports using all advanced synthesis procedure employing support masking and seeding. Evaluation of membrane quality by physical characterization and permeation measurements revealed a number of factors affecting the membrane performance. In the present work, the effects of film thickness, support type, preferred orientation and calcination rate are discussed. Some quality criteria for zeolite membranes are also debated and the porosimetry technique is discussed.

  • 234.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Bons, Anton-Jan
    ExxonMobil Chemical Europe Inc..
    Anthonis, Marc
    ExxonMobil Chemical Europe Inc..
    A masking technique for high quality MFI membranes2003Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 222, nr 1-2, s. 163-179Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A procedure for the preparation of high quality zeolite membranes was developed. This procedure relies on a masking approach that fills all support pores with wax while leaving the top surface free for deposition of the zeolite film, thus, protecting the support from the synthesis mixture. Zeolite films of different thickness were grown on masked and non-masked supports using a seeded growth method. The zeolite-coated supports were calcined in order to remove the wax from the support and the template molecules from the zeolite. The membranes were characterized by SEM, XRD, single gas and multi-component permeation measurements. Support masking reduces the zeolite membrane thickness and the width of the cracks in the zeolite film. Thicker films, especially those prepared without masking, are defective. Masked membranes with a film thickness of 500 nm show no cracks or pinholes. These membranes have a H2 permeance of 220×10−7 mol/(s m2 Pa), an n-butane permeance of 9.8×10−7 mol/(s m2 Pa) and an n-butane/iso-butane separation factor of 9.0 at 25 °C. The separation factor for a mixture of n-hexane/2,2-dimethyl-butane was 227 at 400 °C and the n-hexane permeance was 5.6×10−7 mol/(s m2 Pa). The p-xylene permeance was 2.7×10−7 mol/(s m2 Pa) and the para/ortho separation factor was 17 at 400 °C for a mixture of xylenes.

  • 235.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Korelskiy, Danil
    Sandström, Linda
    Lindmark, Jonas
    Permporometry analysis of zeolite membranes2009Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 345, nr 1-2, s. 276-287Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In permporometry analysis of zeolite membranes, the permeance of a non-adsorbing gas, such as helium, is measured as a function of pressure of a strongly adsorbing compound, such as n-hexane in the case of silicalite-1 membranes. The adsorbing compound effectively blocks the transport of the non-adsorbing gas already at very low activity of the adsorbing compound. The plot of the permeance of the non-adsorbing gas as a function of relative pressure of the adsorbing compound is denoted a permporometry pattern. The present work is based on experimental data for a number of thin MFI membranes with a film thickness ranging from 300 to 1800 nm. An adsorption-branch permporometry experiment is simple and straightforward and after activation of the membrane by removing adsorbed species at 300 °C in a flow of dry gas, a full permporometry pattern is recorded within about 7 h for such membranes. It is shown how the distribution of flow-through defects can be estimated from the permporometry pattern using a simple model for permeation based on Knudsen diffusion. The estimated defect distribution is supported by SEM observations. In addition, the permeance of the non-adsorbing gas through defects measured in permporometry can be used to predict the permeance of molecules diffusing through defects in the membrane in mixture separation experiments and also indicate the separation factor. For instance, the helium permeance through defects in an MFI membrane measured by helium/n-hexane permporometry at room temperature can be used to estimate the permeance of 2,2-dimethylbutane (DMB) in a mixture separation experiment at a higher temperature with a feed containing both DMB and n-hexane by assuming Knudsen diffusion for both helium and DMB in the defects. Also, the separation factor αn-hexane/DMB in a mixture separation experiment at a certain temperature with an MFI membrane with a given defect distribution can be estimated from n-hexane/helium permporometry data recorded at the same temperature through an empirical correlation. In summary, adsorption-branch permporometry is a very effective tool for analysis of thin zeolite membranes, that in short time gives data that can be used to estimate the distribution of flow-through defects in the membrane and to estimate the transport of large molecules through defects in separation experiments and also estimate separation performance.

  • 236.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kurpan, E.
    Luleå tekniska universitet.
    Synthetis of nanosized offretite crystals2001Inngår i: Zeolites and mesoporous materials at the dawn of the 21st century: proceedings of the 13th International Zeolite Conference, Amsterdam: Elsevier, 2001, s. 187-Konferansepaper (Fagfellevurdert)
  • 237.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mintova, Svetlana
    Luleå tekniska universitet.
    Sterte, Johan
    Controlling the preferred orientation in silicalite-1 films synthesized by seeding1999Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 28, nr 1, s. 185-194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single crystal silicon (100) wafers were seeded with colloidal silicalite-1 crystals and hydrothermally treated in a precursor solution to grow thin silicalite-1 films. A total of 28 experiments in eight series were investigated with SEM and XRD to evaluate the preferred orientation of the crystals constituting the films. The investigated parameters in the film formation process were seed crystal size, amount of adsorbed seed crystals and film thickness after hydrothermal treatment of the seeded substrates. In thin films, most of the crystalline material is oriented with the b-axis perpendicular to the substrate surface. In thick films, most of the crystalline material is oriented with the a-axis perpendicular to the substrate surface. The change in preferred orientation with film thickness is faster when small seeds are used. The amount of adsorbed seeds has a larger influence on the preferred orientation when large seeds are used. A mechanism explaining these trends is proposed. The choice of size and coverage of seeds can be used to control the preferred orientation of the crystals in a film of given thickness within certain limitations.

  • 238.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mintova, Svetlana
    Luleå tekniska universitet.
    Sterte, Johan
    Preferred orientation in thin silicalite films synthesized by seeding1999Inngår i: Proceedings of the 12th International Zeolite Conference / [ed] M.M.J. Treacy, Warrendale, Pa: Materials Research Society, 1999, Vol. 3, s. 1809-1816Konferansepaper (Fagfellevurdert)
  • 239.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Noack, M.
    Institute of Applied Chemistry e.V., Rudower Chaussee 5, D-12489, Berlin.
    Kölsch, P.
    Institute of Applied Chemistry e.V., Rudower Chaussee 5, D-12489, Berlin.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    Caro, J.
    Institute of Applied Chemistry e.V., Rudower Chaussee 5, D-12489, Berlin.
    ZSM-5 membranes synthesized without organic templates using a seeding technique1999Inngår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 159, nr 1-2, s. 263-273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Porous α-alumina supports were seeded with colloidal TPA-silicalite-1 crystals and calcined. The supports were treated in a synthesis solution to grow the seed crystals into ZSM-5 films. The synthesis solution was free from organic template molecules in order to avoid the calcination step which often introduces cracks in the synthesized zeolite film. An SEM investigation indicated that the zeolite films on the supports were defect free and that the film thickness was approximately 1.5 μm. XRD data showed that the film consisted of well-crystallized ZSM-5. The permeance in single gas experiments decreased in the order H2O, H2, CO2, O2, N2 and CH4. The difference in permeance between each molecular species in the series was almost one order of magnitude which indicated that the membranes were of a high quality. Molecules larger than CH4 permeated with similar and low rates, independent of their kinetic diameters, indicating a non-selective permeation path through defects in the zeolite films. However, the permeance of these larger molecules was less than 1/10 000 of that for H2O. The highest measured separation factors for binary mixtures of N2/SF6 and H2/i-C4 were 110 and 99.

  • 240.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Schoeman, B.J.
    Sterte, Johan
    Synthesis of ultra thin films of molecular sieves by the seed film method1997Inngår i: Progress in zeolite and microporous materials: Proceedings of the 11th International Zeolite Conference, Seoul, Korea, 12-17 August 1996, Amsterdam: Elsevier, 1997, s. 2203-2210Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A novel and flexible technique for synthesizing continuous ultra thin (<100 nm) molecular sieve films on substrates has been developed. The technique consists of two steps. A monolayer of discrete colloidal zeolite seed crystals is adsorbed on the substrate, whereafter the crystals are allowed to grow into a continuous film upon hydrothermal treatment in a molecular sieve precursor solution. The technique is exemplified by the formation of silicalite-1 films on silicon wafers. The final film thickness in the examples presented was in the range 80 and 800 nm. The films are continuous and crystalline as confirmed by SEM, Kr-adsorption data, ellipsometry, XRD and FTIR.

  • 241.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Schoeman, Brian
    Luleå tekniska universitet.
    Sterte, Johan
    Ultrathin oriented zeolite LTA films1997Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, nr 13, s. 1193-1194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultrathin oriented films of zeolite LTA are prepared on single-crystal alumina supports by a method including adsorption of LTA seeds on the support followed by hydrothermal film crystallization.

  • 242.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Synthesis of thin molecular sieve films1999Inngår i: Nanostructured materials, ISSN 0965-9773, E-ISSN 1872-9150, Vol. 12, nr 1-4, s. 413-416Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method to synthesize thin films of various molecular sieves on a number of substrates employing pre-seeding has been developed. The substrate is modified to enable adsorption of seed crystals. Substrates with an originally negative surface charge are charge reversed by adsorption of cationic polymer molecules. Nobel metal substrates are first silanized to obtain a negative surface charge. Nano seed crystals are adsorbed on the modified substrates from a sol and induced to grow in a synthesis solution to form a dense film with controlled thickness. The versatility of the method may be of great value in the development of novel applications. Films have been tested in membrane and sensor applications with successful results.

  • 243.
    Hedlund, Jonas
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sterte, Johan
    Anthonis, Marc
    ExxonMobil Chemical Europe Inc..
    Bons, Anton-Jan
    ExxonMobil Chemical Europe Inc..
    Carstensen, Barbara
    ExxonMobil Research & Engineering Co..
    Corcoran, Ned
    ExxonMobil Research & Engineering Co..
    Cox, Don
    ExxonMobil Research & Engineering Co..
    Deckman, Harry
    ExxonMobil Research & Engineering Co..
    Gijnst, Wim De
    ExxonMobil Chemical Europe Inc..
    Moor, Peter-Paul de
    ExxonMobil Chemical Europe Inc..
    Lai, Frank
    ExxonMobil Research & Engineering Co..
    McHenry, Jim
    ExxonMobil Research & Engineering Co..
    Mortier, Wilfried
    ExxonMobil Chemical Europe Inc..
    Reinoso, Juan
    ExxonMobil Chemical Company.
    Peters, Jack
    ECN Energy Efficiency.
    High-flux MFI membranes2002Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 52, nr 3, s. 179-189Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis and evaluation of high performance MFI-type membranes is described. These systems exhibit fluxes that are one to two orders of magnitude higher than previous literature reports, with comparable selectivities, when tested for various single component gases and for mixtures of C4, C6 and xylene isomers. These materials are the result of a rational fabrication approach targeting ultra-thin, defect-free MFI films on open supports by using a two-step support masking technique and a monolayer of colloidal nucleation seeds, followed by in situ hydrothermal growth, producing a defect-free film with a thickness of 0.5 μm. Reproducibility of the membrane preparation was excellent

  • 244.
    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.

  • 245.
    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)
  • 246. 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.

  • 247.
    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.

  • 248.
    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.

  • 249.
    Hulteberg, Christian
    et al.
    Lund University .
    Leveau, Andreas
    Biofuel-Solution AB, Tygelsjö, Sweden.
    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.

  • 250.
    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)
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