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  • 101.
    Björklund, Robert B.
    et al.
    Linköping University.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Carlsson, Bill
    Vadstena Varmförzinkning AB.
    Ellipsometric study of oxide removal from steel surfaces in hydrochloric acid solutions1999Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, nr 2, s. 494-499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Iron oxide films formed on three different steel surfaces by thermal oxidation were removed in hydrochloric acid solutions at 20 C. The oxide removal process in flowing solutions was followed in situ by ellipsometry. Two different removal mechanisms were observed in 0.5-2 M HCl, one where undermining of the film resulted in large intact pieces of the oxide leaving the substrate surface at the end of the removal period, and one where the film scaled off the surface in small pieces during the entire removal process. Oxide films which exhibited the undermining mechanism were found to contain about 10% hematite (Fe2O3) and 90% magnetite (Fe3O4). The scaling off mechanism was observed for films which were nearly pure magnetite. Optical models were constructed using data from scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements for the thicknesses and compositions of films after different immersion times in HCl solutions. Spectra calculated from the models agreed well with the experimental spectra.

  • 102.
    Björkvall, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Studie om dynamiken i en pilotrullkrets med rulltrumma2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Luossavaara-Kiirunavaara AB (LKAB) rullar järnmalmslig till råkulor, som sedan bränns till pellets. Råkulorna bildas i rullkretsar som består av rulltrummor och rullsiktar. Under 2017 färdigställdes en pilotskaleanläggning för kulrullning i LKAB:s Agglomeringslaboratorium i Malmberget. Syftet med anläggningen är att prediktera dynamiken i en storskalig rullkrets, under olika betingelser.

    Detta examensarbete är ett första försök att i forskningssyfte studera gensvaret i LKAB:s pilotrullkrets. Syftet var att undersöka om pilotrullkretsen kan prediktera dynamiken och råkulekvalitet i rullning i storskaliga rullkretsar och målet var att fastställa ett effektivt körsätt. Kulrullning är inom LKAB:s kärnkompetens och därför har reagensursprung och karaktär samt dimensionering av rullkretsen lagts med sekretess. Kodnamn används både för sliger och reagens.

    Arbetet inleddes med att skapa ett körschema med målet att så många olika blandningar som möjligt kunde köras i pilotrullkretsen under en normal arbetsdag. Fem olika blandningar kunde köras. Fyra olika tillsatser testades: bentonit, ett flotationsreagens (FLOT), ett organiskt bindemedel (OB) och en ny utvecklingsprodukt (UTV). Första körningen i pilotrullkretsen var med varierande doseringar av bentonit eftersom dess inverkan i kulrullning är välkänt hos LKAB. Försök två och tre, med FLOT respektive OB, kunde jämföras mot tidigare erfarenhet från storskaliga försök. Det fjärde och sista försöket var ett test hur pilotrullkretsen predikterade utvecklingsprodukten UTV. Varje typ av försök utfördes två gånger.

    Pilotrullkretsen predikterade väl både dynamik och råkulekvalitet i alla de tre försöken där erfarenhet från storskaliga körningar var tillgängligt. Den nya, okända, UTV-produkten visade en förbättrad råkulekvalitet, utan att dynamiken i kretsen påverkades negativt. UTV kan därför vara ett intressant alternativ för ett framtida storskaligt försök hos LKAB.

    Det framtagna körschemat fungerade mycket väl. Ett ”grundanalyspaket” har skapats för att underlätta planering och genomförande för framtida pilotrullkretsförsök hos LKAB. Antalet personer som behövs vid rullkretskörningar beror på antalet blandningar och analyser. Vid enklare körningar behövs minst fem personer, utöver försöksledaren. Mer komplexa körningar kan kräva sju personer.

    Fulltekst (pdf)
    Studie om dynamiken i en pilotrullkrets med rulltrumma
  • 103.
    Björnwall, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Impact of calcination temperature and time on quicklime slaking reactivity2021Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this master thesis work calcination parameters' impact on the resulting quicklimes slaking reactivity is investigated. This is done by calcination of three different sedimentary limestones in an N2 atmosphere according to a design of experiment matrix. The limestones are from Wolica Poland, Slite Sweden and Jutjärn Sweden. The temperatures and residence times are varied between 1000ºC, 1050ºC, and 1100ºC for 5 min, 27.5 min, and 60 min. There were seven experiments per limestone sample. The calcination experiments were conducted in an electrical muffle furnace.When the limestone samples were calcined, the resulting quicklimes slaking reactivity was tested according to standard SS-EN 459-2:2010 Building lime - Part 2: Test methods. Four different parameters were used to determine the slaking reactivity, these were the maximum temperature, how much the temperature increases under the initial 30 s, the time it takes for the temperature to reach 60ºC, and the time for the slaking to become 80% finished.From the slaking reactivity experiments, the calcination parameters to produce the most reactive quicklime for the limestone from Wolica and Jutjärn are 1000ºC for 60 min, and for the limestone from Slite 1100ºC for 5 min. For all three limestones the least reactive quicklime was received by calcining at 1100ºC for 60 min. The most and least reactive quicklimes were analyzed in SEM, where it could be seen that the least reactive quicklime samples were coarser compared to the most reactive samples. Depending on what slaking reactivity parameter is of interest, the calcination settings should be different and can be an indication for operation parameters for industrial kilns. The statistical analysis on the experimental model showed that the experiment had a poor statistical fit for most of the experiment. This could be due to that the model possibly was too simple to describe the calcination parameters complex impact on the slaking reactivity.

    Fulltekst (pdf)
    fulltext
  • 104. Blasiak, W.
    et al.
    Yang, W.
    Ekman, T.
    von Schéele, Johan
    KTH.
    Flameless oxyfuel combustion and its applications2013Inngår i: Oxygen-Enhanced Combustion, Second Edition, CRC Press , 2013, s. 495-516Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Progress in combustion technologies with fossil fuel made possible use of oxygen for combustion in industrial processes, reducing drastically CO 2 and NO x emissions as well as allowing for higher productivity at highest possible level of product quality. Since the economy of oxyfuel combustion is dependent on the cost of oxygen, the availability of lowcost oxygen is critical to the application economy as well. Development of lower-cost oxygen separation techniques allows at present use of oxidizer with almost 100% content of oxygen. 

  • 105.
    Bleken, Bjørn Tore L.
    et al.
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Wragg, David Stephen
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Arstad, Bjørnar
    SINTEF Materials and Chemistry, Blindern.
    Gunnæs, Anette Eleonora
    Department of Physics, University of Oslo FERMiO.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Helveg, Stig
    Haldor Topsøe A/S.
    Lundegaard, Lars Fahl
    Haldor Topsøe A/S.
    Beato, Pablo
    Haldor Topsøe A/S.
    Bordiga, Silvia
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Olsbye, Unni
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Svelle, Stian
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Lillerud, Karl Petter
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Unit cell thick nanosheets of zeolite H-ZSM-5: Structure and activity2013Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, nr 9-10, s. 558-566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    nosheets of zeolite H-ZSM-5 were synthesized and characterized by X-ray diffraction, transmission electron microscopy (TEM), N2- physisorption, FT-IR spectroscopy, 27Al and 29Si MAS NMR spectroscopy in addition to catalytic testing in conversion of methanol to hydrocarbons (MTH). It was found that Rietveld analysis, involving anisotropic broadening parameters, gave average crystallite dimensions in good agreement with TEM images. The selectivities in MTH is intact in the mesoporous nanosheet H-ZSM-5 with the largest difference being a higher C3/C2 ratio compared to regular H-ZSM-5.

  • 106.
    Blocksjö, Emil
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Post-Denitrification on Sand Filter at Bromma Wastewater Treatment Plant2022Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Examensarbetets syfte var att undersöka möjligheter till denitrifikation på sandfilter (SF) i industriell skala och hur det jämför sig med konventionella metoder för att uppnå denitrifikation och effekten av förändringen på processen vid Bromma reningsverk. Parametrar som undersöktes var rening av ammonium och nitrat, luftning, temperatur, pH, rening av fosfor, rening av organiskt material, rening av suspenderat material, förbigång av vatten vid SF och aktivslamanläggning (ASA), drifttider för SF:arna och total vattenbelastning på ASA och SF. Mätningarna gjordes med aCurve, ett online internt program vid Bromma reningsverk där onlineanalysatorer och driftsparametrar loggades. Nitrat- och nitritvärdena kontrollerades med standardiserade kyvettmetoder.

    Reningen av totalkväve uppnådde värden på 0,62-0,94 när denitrifikation på SF implementerades. Ökad igensättning av SF inträffade på grund av dosering av metanol på SF och tillväxt av mikroorganismer som orsakade en ökad risk för förbigång av SF, särskilt under hög vattenbelastning. Reningen av suspenderat material, organiskt material och fosfat påverkades inte av implementeringen av denitrifikation på SF.

    Resultaten av examensarbetet kan användas för att ytterligare optimera konventionella metoder för kväverening i reningsverk. För ytterligare studier kunde igensättning av SF vid användning av metanoldosering på sandfilter undersökas och metoderna kan jämföras i en kontrollerad miljö.

    Fulltekst (pdf)
    fulltext
  • 107.
    Blomberg, Jenny
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    The mechanism behind internal injector deposits2023Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Användningen av biobränslen har ökat för att minska utsläppen från fossila bränslen. Biobränslen kan dock leda till beläggningar inuti injektorn, vilka påverkar fordonets  körbarhet. Den mest trodda hypotesen bakom beläggningsbildningen är att förorening av motorolja i bränslesystemet leder till bildning av kalciumsulfatkristaller som mjuka partiklar fäster till. Dessutom påstås det att temperaturen har en signifikant påverkan på beläggningsbildningen. För att ställa om till mer förnyelsebara bränslen krävs mer förståelse bakom beläggningarnas mekanism. Därför var syftet med denna studie att undersöka mekanismen bakom interna injektorbeläggningar med en nydesignad rigg i laboratorieskala för att få en djupare förståelse av mekanismen, och i synnerhet rollen av kalciumsulfat och temperatur. Syftet uppnåddes genom att dela upp det experimentella arbetet i två delar:a) Köra riggen med testbränslen följt av analyser av de körda proverna med huvudsakligen SEM-EDX och FTIR, för att förstå rollen av temperatur och motorolja för beläggningarnas mekanism. b) Löslighetsstudier av kalciumsulfat för att förstå rollen av kalciumsulfat för beläggningarnas mekanism. Resultaten visade att den nydesignade testriggen fungerade bra med resultat som överensstämde med litteratur och erbjöd repeterbarhet. Därmed rekommenderas riggen för framtida studier av interna injektorbeläggningar. En djupare förståelse av mekanismen bakom interna injektorbeläggningar uppnåddes framgångsrikt. För första gången utfördes en FTIR och SEM-EDX studie över en temperaturgradient, vilket gjorde det möjligt att se starttemperaturen för olika reaktioner och identifiera beläggningar i olika temperaturintervall. Det visades att beläggningsbildningen var temperaturberoende med olika typer av beläggningar i olika temperaturintervall. Vid temperaturer under 100°C var zinksulfat och oreagerat metallkarboxylat de dominanta ämnena. Över 100°C ändrade metallkarboxylatet form och blev mer koncentrerat medan koncentrationen av zinksulfat minskade. Dessutom visades det att kalciumsulfat bildades i stor utsträckning när temperaturen översteg 100°C. Temperaturstudien och resultaten är unika och okända i litteraturen. Ostwald-mognad har föreslagits som en möjlig mekanism i litteraturen men visade sig vara osannolik. Upplösningen av kalciumsulfat av motoroljans additiv följt av utfällning i bränslet visade sig vara en mer sannolik mekanism. Det visades också att tvålbeläggningar främjade beläggningsbildning av kalciumsulfatkristaller, vilket överensstämmer med fältobservationer då de vanligtvis samexisterar.

    Fulltekst (pdf)
    fulltext
  • 108.
    Bolívar Caballero, José Juan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Han, Tong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Svanberg, Rikard
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Zaini, Ilman Nuran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Yang, Hanmin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Gond, Ritambhara
    Department of Chemistry, Uppsala University, Lägerhyddsvägen 1, 751 21 Uppsala, Sweden, Lägerhyddsvägen 1.
    Cao, Pengcheng
    Kanthal AB, Sörkvarnsvägen 3, 734 27 Hallstahammar, Sweden, Sörkvarnsvägen 3.
    Lewin, Thomas
    Kanthal AB, Sörkvarnsvägen 3, 734 27 Hallstahammar, Sweden, Sörkvarnsvägen 3.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Advanced application of a geometry-enhanced 3D-printed catalytic reformer for syngas production2023Inngår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 287, artikkel-id 117071Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Catalyst research on reforming processes for syngas production has mainly focused on the active metals and support materials, while the effect of the catalyst's geometry on the reforming reactions has been poorly studied. The application of 3D-printed materials with enhanced geometries has recently started to be studied in heterogeneous catalysis and is of interest to be implemented for reforming biomass and plastic waste to produce H2-rich syngas. In this study, a geometry-enhanced 3D-printed Ni/Al2O3/FeCrAl-based monolithic catalyst with a periodic open cellular structure (POCS) was designed and fabricated. The catalyst was used for batch steam reforming biomass pyrolysis volatiles for syngas production at different parameters (temperature and steam-to-carbon ratio). The results showed complete reforming of pyrolysis volatiles in all experimental cases, a high H2 yield of ≈ 7.6 wt% of biomass was obtained at the optimized steam-to-carbon ratio of 8 and a reforming temperature of 800 °C, which is a higher yield compared to other batch reforming tests reported in the literature. Moreover, CFD simulation results in COMSOL Multiphysics demonstrated that the POCS configuration improves the reforming of pyrolysis volatiles for tar/bio-oil reforming and H2 production thanks to enhanced mass and heat transfer properties compared to the regular monolithic single-channel configuration.

  • 109.
    Bolívar Caballero, José Juan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zaini, Ilman Nuran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Reforming processes for syngas production: A mini-review on the current status, challenges, and prospects for biomass conversion to fuels2022Inngår i: Applications in Energy and Combustion Science, ISSN 2666-352X, Vol. 10, s. 100064-, artikkel-id 100064Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dedicated bioenergy combined with carbon capture and storage are important elements for the mitigation scenarios to limit the global temperature rise within 1.5 °C. Thus, the productions of carbon-negative fuels and chemicals from biomass is a key for accelerating global decarbonisation. The conversion of biomass into syngas has a crucial role in the biomass-based decarbonisation routes. Syngas is an intermediate product for a variety of chemical syntheses to produce hydrogen, methanol, dimethyl ether, jet fuels, alkenes, etc. The use of biomass-derived syngas has also been seen as promising for the productions of carbon-negative metal products. This paper reviews several possible technologies for the production of syngas from biomass, especially related to the technological options and challenges of reforming processes. The scope of the review includes partial oxidation (POX), autothermal reforming (ATR), catalytic partial oxidation (CPO), catalytic steam reforming (CSR) and membrane reforming (MR). Special attention is given to the progress of CSR for biomass-derived vapours as it has gained significant interest in recent years. Heat demand and efficiency together with properties of the reformer catalyst were reviewed more deeply, in order to understand and propose solutions to the problems that arise by the reforming of biomass-derived vapours and that need to be addressed in order to implement the technology on a big scale. 

  • 110. Bonvin, D.
    et al.
    Georgakis, C.
    Pantelides, C. C.
    Barolo, M.
    Grover, M. A.
    Rodrigues, Diogo
    Schneider, R.
    Dochain, D.
    Linking Models and Experiments2016Inngår i: Industrial and Engineering Chemistry Research, ISSN 08885885, Vol. 55, nr 25, s. 6891-6903Artikkel i tidsskrift (Fagfellevurdert)
  • 111.
    Bood, Cecilia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Acid retardation: recovery and recycling of acid and metal2020Independent thesis Advanced level (professional degree), 300 hpOppgave
    Abstract [en]

    During the production of steel, an oxide scale is formed on the surface and to achieve anadequate quality of the surface the scale needs to be removed. Acid pickling is a surfacetreatment where the oxide scale is removed by acid. Over time the amount of dissolved metals in the acid solution increases leading to a decrease in the pickling efficiency, hence the acid solution needs to be renewed.

    The renewing can be performed by an operation process called acid retardation. In this process, the spent pickling solution passes through a column packed with an ion exchange material, resin. The absorption of strong acids is preferred by the resin, hence the movement of the acids in the resin bed will be retarded relative to the movement of the metal ions. Regeneration of the resin occurs when water is passing through the resin bed counter current to the flow of the spent pickling solution. This generates a by-product with low acid and high metal content, and a product containing high acid and low metal.

    The aim of this thesis was to investigate the acid retardation with regards to separation efficiency and the behaviour of acid and metal in the column. The results can further be used as the groundwork for a deeper understanding of the acid retardation and how to optimize the process. Experiments were performed in lab-scale columns with synthetic spent pickling solutions containing sulfuric, nitric and hydrofluoric acid and iron in different mixtures. During the experimental work, variation of the acid and metal concentration, the type of resin and the height of the column were performed.

    The results from the experimental work show that a concentration dependence between the concentration of acid and metal exists and the performance of different resin types varies depending on the acid and metal solution tested. The height might also affect the separation, but it is recommended that this is further investigated. Other recommendations for further work with a focus on understanding the acid retardation for optimization include variations of the volume of solution added to the column, variation in flow rate and slurry packing of the resin.

    Fulltekst (pdf)
    fulltext
  • 112.
    Brand, Manuel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Nontrivial spectral band progressions in electronic circular dichroism spectra of carbohelicenes revealed by linear response calculations2022Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, nr 32, s. 19321-19332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate that contemporary computational resources allow for accurate theoretical studies of systems matching recent advances in experimental helicene chemistry. Concerned with first-principles calculations of carbohelicenes, our work surpasses CH[12] as the largest system investigated to date and unravels trends in the electronic structure of the low-lying states of the homologous series. Utilizing a highly efficient implementation of linear response algorithms, we present electronic circular dichroism (CD) spectra of carbohelicenes ranging from CH[5] to CH[30] at the level of Kohn-Sham density-functional theory. Our results for a systematic increase in system size show the emergence of new CD bands that subsequently rise to intensities dominating the spectrum. The spectral band progressions exhibit a periodicity directly linked to the number of overlapping layers of conjugation. While our findings rectify the current understanding of the electronic structure of carbohelicenes, they also serve as a general call for caution regarding the extrapolation of trends from small system ranges.

  • 113.
    Brandin, Jan
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Bio-Propane from glycerol for biogas addition2008Rapport (Annet vitenskapelig)
    Abstract [en]

    In this report, the technical and economical feasibility to produce higher alkanes from bioglycerol has been investigated. The main purpose of producing this kind of chemicals would be to replace the fossil LPG used in upgraded biogas production. When producing biogas and exporting it to the natural gas grid, the Wobbe index and heating value does not match the existing natural gas. Therefore, the upgraded biogas that is put into the natural gas grid in Sweden today contains 8-10 vol-% of LPG. The experimental work performed in association to this report has shown that it is possible to produce propane from glycerol. However, the production of ethane from glycerol may be even more advantageous. The experimental work has included developing and testing catalysts for several intermediate reactions. The work was performed using different micro-scale reactors with a liquid feed rate of 18 g/h. The first reaction, independent on if propane or ethane is to be produced, is dehydration of glycerol to acrolein. This was showed during 60 h on an acidic catalyst with a yield of 90%. The production of propanol, the second intermediate to producing propane, was shown as well. Propanol was produced both using acrolein as the starting material as well as glycerol (combining the first and second step) with yields of 70-80% in the first case and 65-70% in the second case. The propanol produced was investigated for its dehydration to propene, witha yield of 70-75%. By using a proprietary, purposely developed catalyst the propene was hydrogenated to propane, with a yield of 85% from propanol. The formation of propane from glycerol was finally investigated, with an overall yield of 55%.

    The second part of the experimental work performed investigated the possibilities of decarbonylating acrolein to form ethane. This was made possible by the development of a proprietary catalyst which combines decarbonylation and water-gas shift functionality. By combining these two functionalities, no hydrogen have to be externally produced which is the case of the propane produced. The production of ethane from acrolein was shown with a yield of 75%, while starting from glycerol yielded 65-70% ethane using the purposely developed catalyst. However, in light of this there are still work to be performed with optimizing catalyst compositions and process conditions to further improve the process yield. The economic feasibility and the glycerol supply side of the proposed process have been investigated as well within the scope of the report. After an initial overview of the glycerol supply, it is apparent that at least the addition of alkanes to biogas can be saturated by glycerol for the Swedish market situation at the moment and for a foreseeable future. The current domestic glycerol production would sustain the upgraded biogas industry for quite some time, if necessary. However, from a cost standpoint a lower grade glycerol should perhaps be considered.

  • 114.
    Brandin, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Usage of Biofuels in Sweden2013Inngår i: CSR-2 Catalyst for renewable sources: Fuel, Energy, Chemicals Book of Abstracts / [ed] Vadim Yakovlev, Boreskov Institute of Catalysis, Novosibrisk, Russia: Boreskov Institute of Catalysis , 2013, s. 5-7Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In Sweden, biofuels have come into substantial use, in an extent that are claimed to be bigger than use of fossil oil. One driving force for this have been the CO2-tax that was introduced in 1991 (1). According to SVEBIO:s calculations (2) based on the Swedish Energy Agency´s prognosis, the total energy consumption in Sweden 2012 was 404 TWh. If the figure is broken down on the different energy sources (figure 1) one can see that the consumption roughly distribute in three different, equally sized, blocks, Biofuels, fossil fuels and water & nuclear power. The major use of the fossil fuels is for transport and the water & nuclear power is used as electric power. The main use of the biofuels is for heating in the industrial sector and as district heating. In 2009 the consumption from those two segments was 85 TWh, and 10 TWh of bio power was co-produced giving an average biomass to electricity efficiency of 12%. This indicates a substantial conversion potential from hot water production to combined heat and power (CHP) production. in Sweden 2013 broken down on the different energy sources. In 2006 the pulp, paper and sawmill industry accounted for 95% of the bio energy consumption in the industrial sector, and the major biofuel consumed was black liquor (5). However, the pulp and paper industries also produced the black liquor in their own processes. The major energy source (58%) for district heating during 2006 was woody biomass (chips, pellets etc.) followed by waste (24%), peat (6%) and others (12%) (5). The use of peat has probably decreased since 2006 since peat is no longer regarded as a renewable energy source. While the use of biofuel for heating purpose is well developed and the bio-power is expected to grow, the use in the transport sector is small, 9 TWh or 7% in 2011. The main consumption there is due to the mandatory addition (5%) of ethanol to gasoline and FAME to diesel (6). The Swedish authorities have announced plans to increase the renewable content to 7.5 % in 2015 on the way to fulfill the EU’s goal of 10 % renewable transportation fuels in 2020. However the new proposed fuel directive in EU says that a maximum of 5% renewable fuel may be produced from food sources like sugars and vegetable oils. Another bothersome fact is that, in principle, all rape seed oil produced in Sweden is consumed (95-97%) in the food sector, and consequently all FAME used (in principle) in Sweden is imported as FAME, rape seed oil or seed (6). In Sweden a new source of biodiesel have emerged, tall oil diesel. Tall oil is extracted from black liquor and refined into a diesel fraction (not FAME) and can be mixed into fossil diesel, i.e. Preem Evolution diesel. The SUNPINE plant in Piteå have a capacity of 100 000 metric tons of tall oil diesel per annum, while the total potential in all of Sweden is claimed to be 200 000 tons (7). 100 000 tons of tall oil corresponds to 1% of the total diesel consumption in Sweden. in Sweden for 2010 and a prognosis for 2014. (6). Accordingly, the profoundest task is to decrease the fossil fuel dependency in the transport sector, and clearly, the first generation biofuels can´t do this on its own. Biogas is a fuel gas with high methane content that can be used in a similar way to natural gas; for instance for cooking, heating and as transportation fuel. Today biogas is produced by fermentation of waste (municipal waste, sludge, manure), but can be produced by gasification of biomass, for instance from forest residues such as branches and rots (GROT in Swedish). To get high efficiency in the production, the lower hydrocarbons, mainly methane, in the producer gas, should not be converted into synthesis gas. Instead a synthesis gas with high methane content is sought. This limits the drainage of chemically bonded energy, due to the exothermic reaction in the synthesis step (so called methanisation). In 2011 0.7 TWh of biogas was produced in Sweden by fermentation of waste (6) and there were no production by gasification, at least not of economic importance. The potential seems to be large, though. In 2008 the total potential for biogas production, in Sweden, from waste by fermentation and gasification was estimated to 70 TWh (10 TWh fermentation and 60 TWh gasification) (8). This figure includes only different types of waste and no dedicated agricultural crops or dedicated forest harvest. Activities in the biogas sector, by gasification, in Sweden are the Göteborgs energi´s Gobigas project in Gothenburg and Eon´s Bio2G-project, now pending, in south of Sweden. If the producer gas is cleaned and upgraded into synthesis gas also other fuels could be produced. In Sweden methanol and DME productions are planned for in the Värmlands metanol-project and at Chemrecs DME production plant in Piteå.

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    extended abstract
  • 115.
    Brandin, Jan
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Hulteberg, Christian
    Biofuel-Solution AB, Limhamn .
    Multi-function catalysts for glycerol upgrading2010Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    During the last three years Biofuel-Solution, a privately held Swedish entity, has developed an IP-portfolio around gas-phase glycerol conversion into medium-value chemicals. The targeted chemicals have large to very large markets, to allow for use by more than a fraction of the glycerol available today without impacting the cost of the product. The reason behind is that glycerol is a by-product from the biofuel industry, including biodiesel and bioethanol. This indicates large production volumes, even though the glycerol is a fraction of the fuel produced. A by-product from any fuel process will be vast and therefore any chemical produced from this side-product will have to have a large market to offset it to. In order to avoid changing the fundamental market behavior, similar to what the biodiesel industry has done to the glycerol market.

    In the course of this work, several end-products have been targeted. These include plastic monomers, mono-alcohols and energy gases; using acrolein as a common starting point. To produce chemicals with high purity and efficiency, selective and active catalysts are required. For instance, a process for producing propionaldehyde and n-propanol has been developed to the point of demonstration and commercialization building on the gas-phase platform.

    By developing multi-function catalysts which perform more than one task simultaneously, synergies can be reached that cannot be achieved with traditional catalysts. For instance, by combining catalyst functionalities, reactions that are both endothermic and exothermic can be performed simultaneously.

    This mean lower inlet reactor temperatures (in this particular case) and a more even temperature distribution. By performing the dehydration of glycerol to acrolein in combination with another, exothermal reaction by-products can be suppressed and yields increased.

    It also means that new reaction pathways can be achieved, allowing for new ways to produce chemicals and fuels from glycerol. As in the case of ethane production from acrolein, where a catalyst surface has been devised where acrolein is first adsorbed. The actual mechanism is unknown but in speculation, the adsorbed acrolein is decarbonyled into ethylene and carbon monoxide on a first reaction site. The formed carbon monoxide diffuses to another active site, where it reacts with water through the so called water-gas shift reaction to carbon dioxide and hydrogen. Said carbon dioxide leaves as an end-product, and the hydrogen diffuses to another active site where it reacts with ethylene to form ethane. This gives a way of producing energy gases from glycerol in a very compact reactor set-up, effectively reducing footprint and capital cost and increasing productivity of an installation.

  • 116.
    Brandin, Jan
    et al.
    Linnaeus University.
    Hulteberg, Christian
    LTH, Lund University.
    Kusar, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    A review of thermo-chemical conversion of biomass into biofuels-focusing on gas cleaning and up-grading process steps2017Rapport (Annet vitenskapelig)
    Abstract [en]

    It is not easy to replace fossil-based fuels in the transport sector, however, an appealing solution is to use biomass and waste for the production of renewable alternatives. Thermochemical conversion of biomass for production of synthetic transport fuels by the use of gasification is a promising way to meet these goals.

    One of the key challenges in using gasification systems with biomass and waste as feedstock is the upgrading of the raw gas produced in the gasifier. These materials replacing oil and coal contain large amounts of demanding impurities, such as alkali, inorganic compounds, sulphur and chlorine compounds. Therefore, as for all multi-step processes, the heat management and hence the total efficiency depend on the different clean-up units. Unfortunately, the available conventional gas filtering units for removing particulates and impurities, and also subsequent catalytic conversion steps have lower optimum working temperatures than the operating temperature in the gasification units.

    This report focuses on on-going research and development to find new technology solutions and on the key critical technology challenges concerning the purification and upgrading of the raw gas to synthesis gas and the subsequent different fuel synthesis processes, such as hot gas filtration, clever heating solutions and a higher degree of process integration as well as catalysts more resistant towards deactivation. This means that the temperature should be as high as possible for any particular upgrading unit in the refining system. Nevertheless, the temperature and pressure of the cleaned synthesis gas must meet the requirements of the downstream application, i.e. Fischer-Tropsch diesel or methanol.

    Before using the gas produced in the gasifier a number of impurities needs to be removed. These include particles, tars, sulphur and ammonia. Particles are formed in gasification, irrespective of the type of gasifier design used. A first, coarse separation is performed in one or several cyclone filters at high temperature. Thereafter bag-house filters (e.g. ceramic or textile) maybe used to separate the finer particles. A problem is, however, tar condensation in the filters and there is much work performed on trying to achieve filtration at as high a temperature as possible.

    The far most stressed technical barriers regarding cleaning of the gases are tars. To remove the tar from the product gas there is a number of alternatives, but most important is that the gasifier is operated at optimal conditions for minimising initial tar formation. In fluid bed and entrained flow gasification a first step may be catalytic tar cracking after particle removal. In fluid bed gasification a catalyst, active in tar cracking, may be added to the fluidising bed to further remove any tar formed in the bed. In this kind of tar removal, natural minerals such as dolomite and olivine, are normally used, or catalysts normally used in hydrocarbon reforming or cracking. The tar can be reformed to CO and hydrogen by thermal reforming as well, when the temperature is increased to 1300ºC and the tar decomposes. Another method for removing tar from the gas is to scrub it by using hot oil (200-300ºC). The tar dissolves in the hot oil, which can be partly regenerated and the remaining tar-containing part is either burned or sent back to the gasifier for regasification.

    Other important aspects are that the sulphur content of the gas depends on the type of biomass used, the gasification agent used etc., but a level at or above 100 ppm is not unusual. Sulphur levels this high are not acceptable if there are catalytic processes down-stream, or if the emissions of e.g. SO2 are to be kept down. The sulphur may be separated by adsorbing it in ZnO, an irreversible process, or a commercially available reversible adsorbent can be used. There is also the possibility of scrubbing the gas with an amine solution. If a reversible alternative is chosen, elementary sulphur may be produced using the Claus process.

    Furthermore, the levels of ammonia formed in gasification (3,000 ppm is not uncommon) are normally not considered a problem. When combusting the gas, nitrogen or in the worst case NOx (so-called fuel NOx) is formed; there are, however, indications that there could be problems. Especially when the gasification is followed by down-stream catalytic processes, steam reforming in particular, where the catalyst might suffer from deactivation by long-term exposure to ammonia.

    The composition of the product gas depends very much on the gasification technology, the gasifying agent and the biomass feedstock. Of particular significance is the choice of gasifying agent, i.e. air, oxygen, water, since it has a huge impact on the composition and quality of the gas, The gasifying agent also affects the choice of cleaning and upgrading processes to syngas and its suitability for different end-use applications as fuels or green chemicals.

    The ideal upgraded syngas consists of H2 and CO at a correct ratio with very low water and CO2 content allowed. This means that the tars, particulates, alkali salts and inorganic compounds mentioned earlier have to be removed for most of the applications. By using oxygen as the gasifying agent, instead of air, the content of nitrogen may be minimised without expensive nitrogen separation.

    In summary, there are a number of uses with respect to produced synthesis gas. The major applications will be discussed, starting with the production of hydrogen and then followed by the synthesis of synthetic natural gas, methanol, dimethyl ether, Fischer-Tropsch diesel and higher alcohol synthesis, and describing alternatives combining these methods. The SNG and methanol synthesis are equilibrium constrained, while the synthesis of DME (one-step route), FT diesel and alcohols are not. All of the reactions are exothermal (with the exception of steam reforming of methane and tars) and therefore handling the temperature increase in the reactors is essential. In addition, the synthesis of methanol has to be performed at high pressure (50-100 bar) to be industrially viable.

    There will be a compromise between the capital cost of the whole cleaning unit and the system efficiency, since solid waste, e.g. ash, sorbents, bed material and waste water all involve handling costs. Consequently, installing very effective catalysts, results in unnecessary costs because of expensive gas cleaning; however the synthesis units further down-stream, especially for Fischer-Tropsch diesel, and DME/methanol will profit from an effective gas cleaning which extends the catalysts life-time. The catalyst materials in the upgrading processes essentially need to be more stable and resistant to different kinds of deactivation.

    Finally, process intensification is an important development throughout chemical industries, which includes simultaneous integration of both synthesis steps and separation, other examples are advanced heat exchangers with heat integration in order to increase the heat transfer rates. Another example is to combine exothermic and endothermic reactions to support reforming reactions by using the intrinsic energy content. For cost-effective solutions and efficient application, new solutions for cleaning and up-grading of the gases are necessary.

    Fulltekst (pdf)
    fulltext
  • 117.
    Brandin, Jan
    et al.
    Hulteberg Chemistry & Engineering AB, Sweden.
    Hulteberg, Christian
    Lund University, Sweden.
    Odenbrand, Ingemar
    Lund University, Sweden.
    High-temperature and high concentration SCR of NO with NH3: application in a CCS process for removal of carbon dioxide2012Inngår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 191, s. 218-227Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates several commercial selective catalytic reduction (SCR) catalysts (A–E) for application in a high-temperature (approximately 525 °C) and high-concentration (5000 ppm NO) system in combination with CO2 capture. The suggested process for removing high concentrations of NOx seems plausible and autothermal operation is possible for very high NO concentrations. A key property of the catalyst in this system is its thermal stability. This was tested and modelled with the general power law model using second-order decay of the BET surface area with time. Most of the materials did not have very high thermal stability. The zeolite-based materials could likely be used, but they too need improved stability. The SCR activity and the possible formation of the by-product N2O were determined by measurement in a fixed-bed reactor at 300–525 °C. All materials displayed sufficiently high activity for a designed 96% conversion in the twin-bed SCR reactor system proposed. The amount of catalyst needed varied considerably and was much higher for the zeolithic materials. The formation of N2O increased with temperature for almost all materials except the zeolithic ones. The selectivity to N2 production at 525 °C was 98.6% for the best material and 95.7% for the worst with 1000 ppm NOx in the inlet; at 5000 ppm NOx, the values were much better, i.e., 98.3 and 99.9%, respectively.

    Fulltekst (pdf)
    HighTempSCR
  • 118.
    Brandin, Jan
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Odenbrand, Ingemar
    Lund University .
    Poisoning of SCR Catalysts used in Municipal Waste Incineration Applications2017Inngår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 60, nr 17-18, s. 1306-1316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A commercial vanadia, tungsta on titania SCRcatalyst was poisoned in a side stream in a waste incinerationplant. The effect of especially alkali metal poisoning was observed resulting in a decreased activity at long times of exposure. The deactivation after 2311 h was 36% whilet he decrease in surface area was only 7.6%. Thus the major cause for deactivation was a chemical blocking of acidic sites by alkali metals. The activation–deactivation model showed excellent agreement with experimental data. The model suggests that the original adsorption sites, from the preparation of the catalyst, are rapidly deactivated but are replaced by a new population of adsorption sites due to activation of the catalyst surface by sulphur compounds (SO2, SO3) in the flue gas.

  • 119.
    Brandin, Jan
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Tunér, Martin
    Lunds Tekniska Högskola.
    Odenbrand, Ingemar
    Lunds Tekniska Högskola.
    Small Scale Gasifiction: Gas Engine CHP for Biofuels2011Rapport (Annet vitenskapelig)
    Abstract [en]

    In a joint project, Linnaeus University in Växjö (LNU) and the Faculty of Engineering at Lund University (LTH) were commissioned by the Swedish Energy Agency to make an inventory of the techniques and systems for small scale gasifier-gas engine combined heat and power (CHP) production and to evaluate the technology. Small scale is defined here as plants up to 10 MWth, and the fuel used in the gasifier is some kind of biofuel, usually woody biofuel in the form of chips, pellets, or sawdust. The study is presented in this report.

    The report has been compiled by searching the literature, participating in seminars, visiting plants, interviewing contact people, and following up contacts by e-mail and phone.

    The first, descriptive part of the report, examines the state-of-the-art technology for gasification, gas cleaning, and gas engines. The second part presents case studies of the selected plants:

    • Meva Innovation’s VIPP-VORTEX CHP plant
    • DTU’s VIKING CHP plant
    • Güssing bio-power station
    • Harboøre CHP plant
    • Skive CHP plant

    The case studies examine the features of the plants and the included unit operations, the kinds of fuels used and the net electricity and overall efficiencies obtained. The investment and operating costs are presented when available as are figures on plant availability. In addition we survey the international situation, mainly covering developing countries.

    Generally, the technology is sufficiently mature for commercialization, though some unit operations, for example catalytic tar reforming, still needs further development. Further development and optimization will probably streamline the performance of the various plants so that their biofuel-to-electricity efficiency reaches 30-40 % and overall performance efficiency in the range of 90 %.

    The Harboøre, Skive, and Güssing plant types are considered appropriate for municipal CHP systems, while the Viking and VIPP-VORTEX plants are smaller and considered appropriate for replacing hot water plants in district heating network. The Danish Technical University (DTU) Biomass Gasification Group and Meva International have identified a potentially large market in the developing countries of Asia.

    Areas for suggested further research and development include:

    • Gas      cleaning/upgrading
    • Utilization      of produced heat
    • System      integration/optimization
    • Small scale      oxygen production
    • Gas engine      developments
    Fulltekst (pdf)
    Gas Engine CHP for Biofuels.pdf
  • 120.
    Brusved Andersson, Linnea
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Future Strategy for Wastewater Treatment at Skärblacka Mill2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    To replace nonrenewable materials, glass, plastics and metals, at the market the production of the environmental friendly material paper needs to increase numerously. An increased paper production leads to an enlarged wastewater flow at the paper mill and thereby higher surface load in the biologicalwastewater plant. Higher surface load in turn, leads to lower efficiency and higher emissions. To be able to increase the capacity of the paper production, the wastewater flow to the biological wastewater treatment needs to be decreased.

    In this thesis, the wastewater at Skärblacka mill has been studied to identify how to increase the production without increasing the flow of wastewater to the biological wastewater treatment. Different wastewater has been studied to identify sufficient clean wastewater flows that today are directed to the biological wastewater treatment.

    The outcome of this thesis is that up to 600 m3/h wastewater could be removed from the biological wastewater treatment due to sufficiently high purity. This outcome is primarily based on measurements of the emission parameters, Total Organic Carbon, Suspended Solids, Total Phosphorus and Total Nitrogen and the calculation of PEC/PNEC, environmental assessment, for the chemicals in the wastewater.

    The unload of up to 600 m3/h will contribute to an increased efficiency in the biological wastewater treatment and thereby lower emissions. Increased efficiency and lower levels of emissions will in turn contribute to a possibility to increase the paper production at Skärblacka mill without interfering withenvironmental demands.

    Fulltekst (pdf)
    fulltext
  • 121.
    Bryngelsson, Mårten
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Hansson, Anders
    Energy policy on shaky ground?: A study of CCS-scenarios2009Inngår i: Energy Procedia, ISSN 1876-6102, nr 1, s. 4673-4680Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scenarios play an important role for the societal acceptance of CCS. This paper looks into influential reports containing CCS scenarios and analyses results, key assumptions and drivers for CCS' deployment. Significant uncertainties regarding CCS' development were in several cases excluded or marginalized. Despite these shortcomings, scenarios support a massive deployment of CCS and reflect an undivided optimism. If CCS would fail to meet the high expectations a backlash could follow. Indications were found that new scenarios including uncertainties are needed to balance this over-optimism. So-called unpleasant scenarios are often valuable in helping decision makers develop flexible strategies and policies.

  • 122.
    Bryngelsson, Mårten
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Lindfeldt, Erik G.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Heller, Jan
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture2009Inngår i: International journal of greenhouse gas control, ISSN 1750-5836, Vol. 3, nr 3, s. 255-262Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.

  • 123.
    Bryngelsson, Mårten
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Westermark, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    CO2 capture pilot test at a pressurized coal fired CHP plant2009Inngår i: Energy Procedia, ISSN 1876-6102, Vol. 1, nr 1, s. 1403-1410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CO2 capture from pressurized flue gas using a variation of the hot potassium carbonate process has been demonstrated at a pilot plant with authentic flue gas from the Vartan combined heat and power plant in Stockholm. The plant has served as a proof of concept installation, and has confirmed that: i) the pre-treatment of the flue gas is adequate for protecting the absorbent from degradation, ii) the CO2 capture efficiency is high (> 98 %), iii) no harmful components are fed to the gas turbine, and iv) absorbent degradation is low (0.85 mole percent/month).

  • 124.
    Bryngelsson, Mårten
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Westermark, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Feasibility study of CO2 removal from pressurized flue gas in a fully fired combined cycle: the Sargas project2005Inngår i: Proceedings of the 18th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS, 2005, s. 703-710Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this article a novel concept for CO2 removal from power plants is discussed from a systems perspective. The main advantage of the process is that the investment cost and the power penalty for CO2 removal can be substantially reduced compared to conventional combined cycles. The proposed technical solution comprises fully fired combined cycle, which minimizes the amount of flue gas. Furthermore, the CO2 absorption is performed at pressurized conditions prior to the expansion, which further enhances the CO2 removal. The modification of the power cycle and integration of absorption stages makes CO2 removal equipment much more compact and allows the use Of CO2 absorbents with lower heat demand for the regeneration. The partial pressure of CO2 is above atmospheric pressure and removal efficiencies above 95% can be obtained with potassium carbonate absorption (the Benfield process). The treated flue gas is then reheated and re-humidified before the expansion in the gas turbine.

    A Norwegian consortium has developed the concept and feasibility studies have been performed for 100 MW and 400 MW power plants based on natural gas in Norway. The produced carbon dioxide is intended for storage in the Norwegian oil and gas fields in order to enhance the oil recovery. The suggested localizations of the power plants have been chosen accordingly. The design study is based on the same gas turbine and steam cycle as used in the commercial Pressurized Fluidized Bed Combustion (PFBC) cycle. PFBC plants are presently fired with coal but the fluid bed combustor for coal will be replaced by a gas combustor if natural gas is used. A key advantage is that the process can be built solely from commercially available components.

    This report is an assessment of the features, capabilities, advantages and future possibilities of the suggested power cycle with integrated CO2 removal. A power plant for 100 MW power output and based on natural gas is considered suitable as a first demonstration plant to be built in Hammerfest, Norway. A permit application has been turned in. For such a demonstration plant the process simulations have indicated that an efficiency of about 40% can be obtained, including the penalties from CO2 capture and compression. Further improvements, e.g. supercritical steam cycle or more advanced gas turbine increases the efficiency and for a 400 MW power cycle a net efficiency of about 44-48% has been simulated (including CO2 capture and compression). The cycle may also be suitable for CO2 removal from coal-fired plants.

  • 125.
    Brännvall, Elisabet
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Jansson, Zheng
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Characterisation of dissolved spruce xylan in kraft cooking2011Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, nr 4, s. 380-385Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been demonstrated to affect paper strength properties. Earlier studies have demonstrated that it is the xylan characteristics, rather than simply the amount of xylan, that influence the strength-enhancing effect of xylan. To use xylan optimally, it is useful to understand xylan’s beneficial characteristics and how cooking conditions affect them.

    In this study, spruce chips were kraft cooked under various cooking conditions and the xylan in the black liquor was characterized. We found that dissolved spruce xylan had a much higher amount of bound lignin than found in previous studies of xylan dissolved from hardwoods. The ionic strength of the cooking liquor affected the amount of dissolved xylan as well as the uronic acid content of the xylan.

  • 126.
    Bui, Thai Q.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Konwar, Lakhya Jyoti
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Nikjoo, Dariush
    Division of Materials Science, Luleå University of Technology, Luleå, Sweden.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Mesoporous Melamine-Formaldehyde Resins as Efficient Heterogeneous Catalyst for Continuous Synthesis of Cyclic Carbonates from Epoxides and gaseous CO22020Inngår i: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 8, nr 34, s. 12852-12869Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein we report the application of inexpensive mesoporous melamine-formaldehyde resins (MMFR and MMFR250) obtained by a novel template-free and organosolvent-free hydrothermal method as efficient heterogeneous catalysts for direct synthesis of cyclic carbonates from CO2 and epoxides (epichlorohydrin, butylene oxide and styrene oxide). The catalytic activity of the melamine resins was attributed to the abundant Lewis basic N-sites capable of activating CO2 molecules. Based on CO2-Temperature programmed desorption, the concentration of surface basic sites for MMFR and MMFR250 were estimated to be 172 and 56 µmol/g, while the activation energy of CO2 desorption (strength of basic sites) were calculated to be 92.1 and 64.5 kJ/mol. We also observed considerable differences in the catalytic activity and stability of polymeric catalysts in batch and in continuous-flow mode; due to the existence of a synergism between adsorption of CO2 and cyclic carbonates (poison). Our experiments also revealed important role of catalyst surface chemistry and CO2 partial pressure upon catalyst poisoning. Nevertheless, owing to their unique properties (large specific surface area, large mesoporous and CO2 basicity) melamine resins presented excellent activity (turnover frequency 207-2147 h-1), selectivity (>99%) for carbonation of epoxides with CO2 (20 bar initial CO2 or CO2:epoxide mole ratio ~1.5) under solvent-free and co-catalyst-free conditions at 100-120 oC. Most importantly, these low-cost polymeric catalysts were reusable and demonstrated exceptional stability in a flow reactor (tested upto 13 days time on stream, weight hourly space velocity 0.26-1.91 h-1) for continuous cyclic carbonate production from gaseous CO2 with different epoxides (conversion 76-100% and selectivity >99%) under industrially relevant conditions (120 oC, 13 bar, solvent-free/co-catalyst-free) confirming their superiority over the previously reported catalytic materials.

  • 127.
    Bäbler, Matthäus
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    A collision efficiency model for flow-induced coagulation of fractal aggregates2008Inngår i: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 54, nr 7, s. 1748-1760Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model for flow-induced collisions of fractal aggregates is developed. The model is based on the analysis of the relative trajectories between a pair of aggregates that takes into account their hydrodynamic and their colloidal interactions. Regarding the former, the aggregates are modeled as permeable spheres where the Brinkman equation is used to describe the flow inside the aggregates. Interparticle forces are incorporated by considering the forces between the primary particles in the two aggregates that are the nearest. The model results in a collision efficiency that depends on the masses of the colliding aggregates, the fractal dimension, and a nondimensional Hamaker constant characterizing the interparticle forces. The collision efficiency model is used to investigate the dynamics of a suspension undergoing coagulation. Significant deviations with respect to existing collision efficiency models are evidenced. 

  • 128.
    Bäbler, Matthäus
    ETH Zurich.
    Modelling of aggregation and breakage of colloidal aggregates in turbulent flows: Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 17139, 20072007Doktoravhandling, monografi (Annet vitenskapelig)
  • 129.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Mazzotti, Marco
    Soos, Miroslav
    Morbidelli, Massimo
    Breakup and aggregation in turbulently stirred vessels2009Inngår i: 13th European Conference on Mixing, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The breakup and aggregation of small solid particle aggregates in hetero-geneous °ows is modeled through a multizonal population balance model. Breakupand aggregation are described through comprehensive rate expressions that takeinto account the local properties of the turbulent °ow. Two approaches are pursuedto de¯ne the zones: in the ¯rst approach the zones are prede¯ned and computational°uid dynamics is used to compute the zone properties. In the second approach thezone properties are directly ¯tted to experimental data. Model results compare wellwith experiments for the aggregation of a polystyrene latex in a stirred tank evenwhen only two zones are used.

  • 130.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Analysis of the aggregation-fragmentation population balance equation with application to coagulation2007Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 316, nr 2, s. 428-441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Coagulation of small particles in agitated suspensions is governed by aggregation and breakage. These two processes control the time evolution of the cluster mass distribution (CMD) which is described through a population balance equation (PBE). In this work, a PBE model that includes an aggregation rate function, which is a superposition of Brownian and flow induced aggregation, and a power law breakage rate function is investigated. Both rate functions are formulated assuming the clusters are fractals. Further, two modes of breakage are considered: in the fragmentation mode a particles splits into w ≥ 2 fragments of equal size, and in the erosion mode a particle splits into two fragments of different size. The scaling theory of the aggregation-breakage PBE is revised which leads to the result that under the negligence of Brownian aggregation the steady state CMD is self-similar with respect to a non-dimensional breakage coefficient θ. The self-similarity is confirmed by solving the PBE numerically. The self-similar CMD is found to deviate significantly from a log-normal distribution, and in the case of erosion it exhibits traces of multimodality. The model is compared to experimental data for the coagulationof a polystyrene latex. It is revealed that the model is not flexible enough to describecoagulation over an extended range of operation conditions with a unique set of parameters. In particular, it cannot predict the correct behavior for both a variation in the solid volume fraction of the suspension and in the agitation rate (shear rate).

  • 131.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Morbidelli, M.
    Baldyga, Jerzy
    Modelling the breakup of solid aggregates in turbulent flows2008Inngår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 612, s. 261-289Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The breakup of solid aggregates suspended in a turbulent flow is considered. The aggregates are assumed to be small with respect to the Kolmogorov length scale and the flow is assumed to be homogeneous. Further, it is assumed that breakup is caused by hydrodynamic stresses acting on the aggregates, and breakup is therefore assumed to follow a first-order kinetic where K-B(x) is the breakup rate function and x is the aggregate mass. To model K-B(x), it is assumed that an aggregate breaks instantaneously when the surrounding flow is violent enough to create a hydrodynamic stress that exceeds a critical value required to break the aggregate. For aggregates smaller than the Kolmogorov length scale the hydrodynamic stress is determined by the viscosity and local energy dissipation rate whose fluctuations are highly intermittent. Hence, the first-order breakup kinetics are governed by the frequency with which the local energy dissipation rate exceeds a critical value (that corresponds to the critical stress). A multifractal model is adopted to describe the statistical properties of the local energy dissipation rate, and a power-law relation is used to relate the critical energy dissipation rate above which breakup occurs to the aggregate mass. The model leads to an expression for K-B(x) that is zero below a limiting aggregate mass, and diverges for x -> infinity. When simulating the breakup process, the former leads to an asymptotic mean aggregate size whose scaling with the mean energy dissipation rate differs by one third from the scaling expected in a non-fluctuating flow.

  • 132.
    Bäbler, Matthäus
    et al.
    Swiss Fed Inst Technol, Inst Proc Engn.
    Moussa, Amgad S.
    Soos, Miroslav
    Morbidelli, Massimo
    Structure and Kinetics of Shear Aggregation in Turbulent Flows: I. Early Stage of Aggregation2010Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 16, s. 13142-13152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aggregation of rigid colloidal particles leads to fractal-like structures that are characterized by a fractal dimension d(f) which is a key parameter for describing aggregation processes. This is particularly true in shear aggregation where d(f) strongly influences aggregation kinetics. Direct measurement of d(f) in the early stages of shear aggregation is however difficult, as the aggregates are small and few in number. An alternative method for determining d(f) is to use an aggregation model that when fitted to the time evolution of the cluster mass distribution allows for estimating d(f). Here, we explore three such models, two of which are based on an effective collision sphere and one which directly incorporates the permeable structure of the aggregates, and we apply them for interpreting the initial aggregate growth measured experimentally in a turbulent stirred tank reactor. For the latter, three polystyrene latexes were used that differed only in the size of the primary particles (d(p) = 420, 600, and 810 nm). It was found that all three models describe initial aggregation kinetics reasonably well using, however, substantially different values for 4 To discriminate among the models, we therefore also studied the regrowth of preformed aggregates where d(f) was experimentally accessible. It was found that only the model that directly incorporates the permeable structure of the aggregates is able to predict correctly this second type of experiments. Applying this model to the initial aggregation kinetics, we conclude that the actual initial fractal dimension is d(f) = 2.07 +/- 0.04 as found from this model.

  • 133.
    Bäbler, Matthäus
    et al.
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Sefcik, J
    Morbidelli, M
    Baldyga, J
    Hydrodynamic interactions and orthokinetic collisions of porous aggregates in the Stokes regime2006Inngår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 18, nr 1, s. 013302-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hydrodynamic interaction of two neutrally buoyant porous aggregates is investigated under creeping flow conditions for the case where the undisturbed velocity of the surrounding flow field is a linear function of position. In this framework, the relative velocity between two aggregates is given by the deformation of the undisturbed flow expressed through the rate of strain and the angular velocity of the flow field, and by two flow-independent hydrodynamic functions, typically referred to as A and B, which account for the disturbance of the flow field due to the presence of the particles [G. K. Batchelor and J. T. Green, J. Fluid Mech. 56, 375 (1972)]. In the present paper, the analysis of thehydrodynamic interaction that is known for the case of two impermeable, solid particles is extended to the case of porous aggregates by applying Brinkman's equation to describe the flow within the aggregates. A reflection scheme is applied to calculate A and B and the obtained expressions are applied to interpret the orthokinetic aggregation ofaggregates in diluted suspensions, where the collision frequency is computed using the method of relative trajectories of a pair of aggregates.

  • 134.
    Bäckström Nilsson, Wilma
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Carbon Filters for Drinking Water Treatment – How Flow Rate and Empty Bed Contact Time Influence the Performance2021Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Dricksvatten är en essentiell del av ett hållbart samhälle. Därför är det viktigt att säkerställa säkert dricksvatten genom fungerande vattenreningsverk. En viktig förorening att behandla är NOM, som i sig är ofarligt men som kan producera farliga föroreningar. En teknik som används för behandling av NOM är kolfiltrering.

    Hur ökad flödeshastighet och ökad kontakttid påverkade kolfiltrens effektivitet undersöktes vid dricksvattenreningsverket Norrvatten. De undersökta parametrarna var partiklar, ultraviolett absorbans vid 254 nm, turbiditet, konduktivitet, fluorescent löst organiskt material, totalt organiskt kol, kemisk syreförbrukning, odlingsbara mikroorganismer och lukt. Tre kolfilter studerades vid olika flödeshastigheter; 190, 220, 250 och 280 L/s under ett dygn var. Samtidigt hade två filter ökad kontakttid på 60 och 76 % under sex veckor, medan ett filter fortsatte med den vanliga flödeshastigheten på 190 L/s. Utgående vatten från filtren analyserades för att se om dessa ändringar hade någon effekt på vattenreningen.

    Denna preliminära studie fann ingen signifikant effekt på kolfiltreringens rening på grund av ökad flödeshastighet eller uppehållstid. Detta kan vara en indikation på att kolfiltreringen kan hantera en framtida flödesökning och därmed vara en väsentlig del av en framtida expansionen av vattenreningsverket. De tecken som visade på att kolfiltren påverkades av ökningen av flödeshastigheter kunde förklaras av fluktuationer i inkommande vatten och skillnader mellan de olika filtren.

    I framtiden bör effekten av inkommande vatten studeras i detalj. En mer ingående analys av både inkommande och utgående vatten till kolfiltren bör utföras, där provtagning sker oftare för att bättre förstå fluktuationerna i inkommande föroreningskoncentrationer. Dessutom bör testerna upprepas för att se hur reningen skiljer sig från dag till dag. Hur kolfiltren hanterar ökade flödeshastigheter över längre tidsperioder bör också undersökas vidare.

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  • 135.
    Börjesson, Anders
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Computational Studies of Metal Clusters and Carbon Nanotubes2008Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Carbon nanotubes constitute a promising candidate material in the realisation of nanoscaled electronics. This requires the ability for systematic production of carbon nanotubes with certain properties. This is called selective carbon nanotube growth. Two important aspects related to carbon nanotube growth are investigated in order to shed some light on this issue. First the melting behaviour of nanometer sized iron particles is investigated using molec- ular dynamics simulations. The iron nanoparticles studied are mounted on a porous Al2 O3 substrate in order to mimic the experimental situation during nanotube growth with the chemical vapour deposition method. This showed that the melting temperature of a cluster on a porous substrate may be lower than the melting temperature of a cluster on a flat sub- strate. This means that the catalyst particles used for nanotube growth may be liquid. In association with these studies the role of surface curvature to melting behaviour is explored further. The second presented study concerns the docking of nickel clusters to open single wall carbon nanotube ends. The motivation for this study was the possibility to continue growth of a carbon nanotube by docking of catalyst particles to its end. This work may also be of importance for the creation of electric junctions between carbon nanotubes and metal elec- trodes. This study showed that independent of whether the metal was gently put on the nanotube end or brutally forced to the end, it is the metal that adapts to the nanotube and not vice versa. For forced docking it was seen that carbon might dissolve in to the metal. This was not seen for the gently docked clusters. Carbon dissolution might affect the electronic properties of the metal (carbide) and nanotube-metal junction.

  • 136.
    Börjesson, Anders
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Bolton, Kim
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    First Principles Studies of the Effect of Nickel Carbide Catalyst Composition on Carbon Nanotube Growth2010Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 42, s. 18045-18050Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Density functional theory calculations were used to investigate the stability of single-walled carbon nanotubes (CNTs) attached to nanoparticles. The total energies and the adhesion energies between the CNTs and the nanoparticles were calculated for systems where the nanoparticles were either pure Ni or Ni carbide. It was found that the adhesion between the CNT and a pure Ni cluster is stronger than between the same CNT and a Ni carbide cluster although the energy difference was small compared to the total adhesion energies. This adhesion strength implies that CNTs are likely to remain attached to both pure Ni and Ni carbide clusters and that either pure Ni or Ni carbide clusters may be docked onto the open CNT ends to achieve continued growth or electronic contacts between CNTs and electrode materials. The system with a CNT attached to a pure Ni cluster was found to be energetically favored compared to a system containing the same CNT attached to a Ni carbide. The difference in total energy implies that a CNT should act as a sink for C atoms dissolved in the Ni carbide cluster, which means that the dissolved C atoms will be drained from the cluster, yielding a pure metal in the zero Kelvin thermodynamic limit. It is argued that this draining procedure is likely to occur even if carbon is added to the cluster at a proper rate, for example, during CNT growth.

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  • 137.
    Cai, Juanjaun
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Jiang, Leilei
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Wei, Huaming
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Wang, Chongqing
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Yu, Liang
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Zhang, Lixiong
    State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Preparation of carbon/cobalt composite from phenolic resin and ZIF-67 for efficient tannic acid adsorption2019Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 287, s. 9-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, a carbon/cobalt composite was prepared and evaluated for adsorption of ecologically harmful tannic acid (TA). The composite was prepared by simply mixing phenolic resin with ZIF-67 and following by carbonization. TEM and SEM images showed that ZIF-67 was etched by phenolic resin and cobalt nanoparticles were formed and evenly distributed in carbon. Macroporous structure was generated between the carbonized phenolic resin and ZIF-67. N2 adsorption-desorption isotherms results exhibited that the composite also had both micro- and meso-pores (average pore size of 5 nm) with a high surface area of 393 m2 g−1. Porous structure and evenly distributed cobalt nanoparticles facilitated the diffusion and adsorption of TA due to the formation of the complex between TA macromolecules and cobalt. The highest observed adsorption amount was as high as 2778 mg g−1, significantly higher than that of the carbon prepared from carbonization of phenolic resin (205 mg g−1) and ZIF-67 (1375 mg g−1). The carbon composite material is easy to recover and reuse due to the magnetic property. The reuse experiment also showed high stability of the composite. All of the results indicated a great potential of the developed carbon composite material in wastewater treatment in the industry.

  • 138.
    Calmanovici Pacoste, Laura
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Boman, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Ardakani, Rebecka
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Degerman, Martina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Kammarbo, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Näslund, Emil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Processdesign av emulsionsberedningssystem2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    At the request of Fresenius Kabi an emulsion preparation system was designed with a maximum production capacity of  15 L and minimum of 3 L emulsion. The system was required to consist of one oil-tank, one pre-emulsion tank, two storage tanks and one homogenizer. The storage tanks were positioned on a movable carriage on the left side of the homogenizer and the pre-emulsion tank and oil tank was placed on a separate frame on the right side of the homogenizer. All tanks were equipped with individual temperature control and a stand-alone parallel cleaning system was designed.

    The system also had to be optimized for the specific process and extensive calculations were done.  The emulsion system was designed using CAD-software and produced a detailed 3D-model. The tanks were designed from scratch and all other parts of the system consist of standardized components readily available. A list of the components in the system with manufacturer article number of all components was also produced. Actual drawings for the tanks were also made. The 3D-model and the list of components provide a good base for future construction of the system.

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  • 139.
    Cameli, Fabio
    KTH, Skolan för kemivetenskap (CHE).
    Microbial Fuel Cell for Waste Water Treatment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Microbial Fuel Cell is a novel technology that can be used for a waste water treatment in order to simultaneously remove carbonaceous matter and nitrogen while producing electrical power.

    Even if it is not an established technology so far, MFC could be a cost effective option for waste water treatment and the major challenge of this process will be the device scale-up. Exoelectrogenic bacteria are capable of converting the chemical energy of organic matter into electrical energy by transferring the electrons produced in the oxidation to the anode electrode.

    This project focused on developing a single device for nitrification, denitrification and carbon removal. Two double air-cathode single chamber MFCs are used to test the feasibility of this process that could replace the biological unit in a waste water treatment train.

    The cells tested in this study were manufactured with the purpose of achieving a high surface area on both the anode electrode (vitreous carbon foam) and the air-cathode electrodes (metallic mesh with diffusion layer and active layer) with different catalysts for the reduction reaction (cobalt and platinum). The bacterial biofilm growth is a fundamental step and the cells Open Circuit Potential was monitored during all the start-up period to determine the microorganism acclimation: a three days lag period was observed in both cells before the potential rise. The second cell was forced to reach higher voltage through an anode polarization and that seems to positively affect the biofilm stability at lower voltages transferring a greater amount of electrons and hence obtaining a higher current and power generation. For this reason after three weeks of inoculation the second cell reached an open circuit potential of 0.76 V which is a promising value for such a system.

    Electrochemical and biological tests were conduced in order to test the power production of the cell and the substrate removal from the waste water. Polarization curves were used to evaluate power generation (and the maximum production under a specific external load) and the cell voltage trend which is characterized by activation and ohmic losses: 32 mW/ and 41 mW/  are the power density normalized by cathode surface (72 ) reached by respectively first and second cell. The experimental conditions were varied from low to high temperature and from low to high inlet flow rate but the most affecting phenomenon seems to be the biofilm formation since significant voltage drops were noticed after long closed circuit operation. Higher cell voltage characterized the second cell thanks to more active cathode (platinum catalyst used) and more negative bacterial biofilm but a bigger drop in current generation over time affects the system performance and the most reliable reason is the shorter acclimation time compared to the first cell.

    Cyclic voltammetry tests were carried out on both electrodes to study the potential range of activity and determine an optimal operational voltage despite of mass transport or kinetic limitations.

    Substrate removal tests at different retention times in power generation conditions (external load 100 Ω) showed a relatively high total nitrogen consumption (maximum 72.2 %) for the first cell while lower values were achieved by the second system meaning that a longer acclimation period is beneficial for nitrifying and denitrifying bacteria to thrive on the cathode biofilm.

    Effluent pH level are almost similar to the initial values probably because of nitrification and denitrification protons offset.

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  • 140.
    Cao, Wenhan
    et al.
    University of Strathclyde, UK.
    Li, Jun
    University of Strathclyde, UK.
    Lin, Leteng
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Zhang, Xiaolei
    University of Strathclyde, UK.
    Release of potassium in association with structural evolution during biomass combustion2021Inngår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 287, s. 1-9, artikkel-id 119524Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mechanistic understanding of potassium release is essential to mitigate the potassium-induced ash problems during biomass combustion. This work studies the effects of operational condition on the potassium release and transition during the combustion of wheat straw, and elucidate the release potential of potassium associated with the structural change of biomass particles. The combustion tests were carried out in a laboratory-scale reactor, working in a wide range of temperatures and heating rates. It was found that the combustion of biomass sample at a temperature up to 1000 °C results in a release of over 60% of its initial potassium content. Raising the heating rate from 8 °C/min to 25 °C/min could lead to an additional release of up to 20% of the initial amount of potassium. A three-stage potassium release mechanism has been concluded from this work: the initial-step release stage (below 400 °C), the holding stage (400–700 °C) and the second-step release stage (above 700 °C). Comprehensive morphology analysis with elemental (i.e. K, S, O, Si) distribution was carried out; the results further confirmed that potassium is likely to exist inside the stem-like tunnel of biomass particles, mainly in forms of inorganic salts. During the heating-up process, the breakdown and collapse of biomass particle structure could expose the internally located potassium and thus accelerate the release of potassium and the transform of its existing forms. Lastly, a detailed temperature-dependent release mechanism of potassium was proposed, which could be used as the guidance to mitigate the release of detrimental potassium compounds by optimising the combustion process.

  • 141.
    Carabante, Ivan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Arsenic (V) adsorption on iron oxide: implications for soil remedeation and water purification2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Addition of iron oxide based adsorbents to arsenic contaminated soils has been proposed as a mean to reduce the mobility of arsenic in the soil. However, the conditions in the soil such as pH value, the presence of phosphate after addition of fertilizer to the soil or the presence of Zn (II) as a co-contaminant may affect the adsorption of arsenate on the iron oxide and may therefore have implications for the mobility of arsenic in the remediated soil.In the present work, a new flow method was developed to study the adsorption of arsenate on synthetic iron oxide with high surface area (ferrihydrite) in situ by means of Attenuated Total Reflection – Fourier Transform Infrared (ATR – FTIR) spectroscopy and the method was used for studying how the adsorption of arsenate was affected by the pH/pD value, the presence of phosphate and Zn (II) in the system. The highest adsorption of arsenate was found at pD 4 and decreased as the pD value increased. The arsenate complexes formed on ferrihydrite appeared to be very stable at pD 4, while the stability decreased as the pD value increased. Arsenate showed a higher adsorption affinity than phosphate on ferrihydrite under the conditions studied. However, phosphate was able to replace about 10 % of pre-adsorbed arsenate on ferrihydrite at pD 4 and about 20 % of the pre-adsorbed arsenate at pD 8.5 in equimolar concentrations of phosphate and arsenate. Phosphate replaced 30 % of pre-adsorbed arsenate at pD 4 and up to 50 % of pre-adsorbed arsenate at pD 8.5 when the concentration of phosphate in the system was 5 times higher than that of arsenate. Batch adsorption experiments indicated an enhancement in the arsenate removal from a ferrihydrite suspension in the presence of Zn (II) at pH 8 in accordance with previous reports. However, no adsorption of arsenate on ferrihydrite in the presence of high concentrations of Zn (II) in the system was observed by infrared spectroscopy. Instead, precipitation of zinc hydroxide carbonate followed by arsenate adsorption on the zinc precipitate was found to be the most likely explanation of these results.Although iron oxides are selective towards arsenate, high specific surface areas are required to achieve sufficiently high adsorption capacity. A method of increasing the specific surface area of coarse hematite particles to obtain a good adsorbent was also developed in the present work. The method comprises an acid treatment to produce iron ions followed by hydrolysis to precipitate an iron oxy-hydroxide coating on the hematite particles. While the arsenate adsorption capacity of the original coarse hematite particles was found to be negligible, the sintered coarse hematite particles showed good potential as an adsorbent for arsenate with an adsorption capacity of about 0.65 mg[As]/g.The method developed for studying adsorption on iron oxides by in situ ATR - FTIR spectroscopy was further developed for studying the adsorption of flotation collectors on iron oxides. Iron ore is often separated from gangue minerals by means of reverse flotation in which a surfactant should selectively adsorb on the gangue mineral rendering it hydrophobic. However, unwanted adsorption of the surfactants on the iron oxide has been reported to affect the production of iron ore pellets. A method was developed to study the adsorption of the surfactant Atrac 1563 on synthetic hematite in situ by means of ATR - FTIR spectroscopy. The adsorption of Atrac 1563 on hematite at pH 8.5 was found to mostly occur via interactions between the polar ester and ethoxy groups of the surfactant and the hematite surface.

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  • 142.
    Carabante, Ivan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Study of arsenate adsorption on iron oxide by in situ ATR-FTIR spectroscopy2009Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. However, fundamental studies are needed to establish under which conditions the complexes formed are stable. A new method based on ATR-FTIR spectroscopy was adapted to study the adsorption of arsenate species on iron oxides. The measurements required the use of D2O as solvent. The amount of arsenate complexes adsorbed on the iron oxide increased with decreasing pD in the range studied, viz. pD 4-12. Arsenate complexes adsorbed at pD 4 desorbed from the film to some extent as the pD was increased to 8.5 or 12. The stability of arsenate complexes adsorbed on the iron oxide evidently changed with the change in pD, most likely due to the electrostatic repulsion between the negatively charged oxoanion and the more negatively charged iron oxide as the pD increased. From competitive adsorption experiments it was found that arsenate species were more strongly bonded to the iron oxide than phosphate species. Furthermore, it was found that two different phosphate complexes formed on the iron surface at pD 4, one deuterated and the other one de-deuterated. The complexes showed very different stability. The deuterated phosphate complex was desorbed easily from the iron oxide film as arsenate was added to the system whereas the de-deuterated phosphate complex only desorbed slightly from the film upon adding arsenate.This work has increased the fundamental knowledge of the iron oxide/arsenate/phosphate system, which will be of importance for the development of more effective soil remediation techniques.

    Fulltekst (pdf)
    FULLTEXT01
  • 143. Carabante, Ivan
    et al.
    Grahn, Mattias
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    In situ ATR-FTIR studies on the competitive adsorption of arsenate and phosphate on ferrihydrite2010Inngår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 351, nr 2, s. 523-531Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present study, in-situ ATR-FTIR spectroscopy was used for the first time to study the competitive adsorption of phosphate and arsenate on ferrihydrite. Deuterium oxide was used as solvent to facilitate the interpretations of recorded infrared spectra.It was found that arsenate and phosphate adsorbed more strongly at lower pD values, showing similarities in the adsorption behavior as a function of pD. However, arsenate complexes were found to be more strongly adsorbed than phosphate complexes in the pD range studied. About five times higher concentration of phosphate in solution was needed to reduce the absorbance due to pre-adsorbed arsenate to the same relative level as for pre-adsorbed phosphate, which was desorbed using a solution containing equal (molar) concentrations in arsenate and phosphate. At pD 4, two phosphate complexes were adsorbed on the iron oxide, one deuterated and one de-deuterated. When phosphate was pre-adsorbed and arsenate subsequently added to the system, the deuterated phosphate complex desorbed rapidly while the de-deuterated phosphate complex was quite stable. At pD 8.5, only the de-deuterated phosphate complex was adsorbed on the iron oxide. Moreover, the arsenate adsorbed was also predominantly de-deuterated as opposite to the arsenate adsorbed at pD 4. During the substitution experiments the configuration of these complexes on the iron oxide surface did not change. To the best of our knowledge, this is the first time this difference in stability of the different phosphate complexes is reported and shows the power of employing in-situ spectroscopy for this kind of studies.

  • 144. Carabante, Ivan
    et al.
    Grahn, Mattias
    Holmgren, Allan
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    The influence of Zn2+ ions on the adsorption of arsenate onto ferrihydrite studied by in situ ATR-FTIR spectroscopy2010Konferansepaper (Annet vitenskapelig)
  • 145.
    Carabante, Ivan
    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.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Adsorption of As (V) on iron oxide nanoparticle films studied by in situ ATR-FTIR spectroscopy2009Inngår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 346, nr 1-3, s. 106-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. Fundamental studies are needed to establish under which conditions the complexes formed are stable. In the present work, a powerful technique, viz. ATR-FTIR spectroscopy, is adapted to studies of adsorption of arsenate species on iron oxides. This technique facilitates acquisition of both quantitative and qualitative in situ adsorption data.In the present work, about 800 nm thick films of 6-lineferrihydrite were deposited on ZnSe ATR crystals. Arsenate adsorption on the ferrihydrite film was studied at pD values ranging from 4 to 12 and at an arsenate concentration of 0.03 mM in D2O solution. The amount of adsorbed arsenate decreased with increasing pD as a result of the more negatively charged iron oxide surface at higher pD values. The adsorption and desorption kinetics were also studied. Arsenate showed a higher adsorption rate within the first 70 minutes and a much lower adsorption rate from 70 up to 300 minutes. The low adsorption rate at longer reaction times was partly due to a low desorption rate of already adsorbed carbonate species adsorbed at the surface. The desorption of carbonate species was evidenced by the appearance of negative absorption bands. The desorption of adsorbed arsenate complexes was examined by flushing with D2O at pD 4 and 8.5 and it was found that the complexes were very stable at pD 4 suggesting formation of mostly inner-sphere complexes whereas a fraction of the complexes at pD 8.5 were less stable than at pD 4, possibly due to the formation of outer-sphere complexes.In summary, the ATR technique was shown to provide in situ information about the adsorption rate, desorption rate and the speciation of the complexes formed within a single experiment, which is very difficult to obtain using other techniques.

  • 146.
    Carabante, Ivan
    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.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Influence of Zn(II) on the adsorption of arsenate onto ferrihydrite2012Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 46, nr 24, s. 13152-13159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Addition of iron oxide to arsenic-contaminated soil has been proposed as a means of reducing the mobility of arsenic in the soil. Arsenic and zinc are common coexisting contaminants in soils. The presence of zinc therefore may affect the adsorption properties of arsenic on iron oxide, and may thus affect its mobility in the soil. The influence of Zn(II) on the adsorption of arsenate ions on iron oxide was studied. Batch adsorption experiments indicated that Zn(II) increased the arsenate removal from a solution by ferrihydrite at pH 8. However, ATR-FTIR spectroscopy showed that no adsorption of arsenate on a ferrihydrite film occurred at pD 8 in the presence of Zn(II). Precipitation of zinc hydroxide carbonate followed by arsenate adorption onto the precipitate was found to be a plausible mechanism explaining the arsenate removal from a solution in the presence of Zn(II) at pH/pD 8. The previously suggested mechanisms attributing the enhanced removal of arsenate from solution in the presence of Zn(II) to additional adsorption on iron oxides could not be verified under the experimental conditions studied. It was also shown that at pH/pD 4, the presence of Zn(II) in the system did not significantly affect the adsorption of arsenate on ferrihydrite.

  • 147.
    Carabante, Ivan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    A powerful method for studying the adsorption of As(V) on iron oxides in situ2008Inngår i: Arsenic in the environment - Arsenic from nature to humans: Book of Abstracts, 2008Konferansepaper (Annet vitenskapelig)
  • 148.
    Carabante, Ivan
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Kumpiene, Jurate
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Grahn, Mattias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Fredriksson, Andreas
    Mining Technology R and D, LKAB Kiruna Mine.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Reutilization of porous sintered hematite bodies as effective adsorbents for arsenic(V) removal from water2014Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 53, nr 32, s. 12689-12696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method was developed to enhance the arsenic adsorption capacity of porous bodies of sintered hematite. The method comprised the formation of a coating of 1 wt % iron oxide nanoparticles on the raw material. The nanoparticles showed two distinct habits: spherical habit, likely ferrihydrite, and acicular habit, likely goethite and/or akaganéite. The specific surface area of the hematite raw material increased from 0.5 to 3.75 m2/g, and the adsorption capacity increased from negligible to 0.65 mg of [As]/g as calculated from equilibrium and breakthrough adsorption data. Equilibrium adsorption data of arsenate on the adsorbent from a solution at pH 5 followed the Langmuir model, while breakthrough adsorption data for a 500 μg/L arsenate solution at pH 5 followed the Thomas model. The adsorbed arsenic could be desorbed using distilled water at pH 12. These results show the potential for the reutilization of waste products comprising coarse hematite bodies as adsorbents.

  • 149.
    Cardenas, Edgar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Synthesis of zeolites from economic raw materials2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Synthesis methods using economic raw materials, such as kaolin and diatomite have been developed for the production of zeolites in the present work. Zeolite Y and ZSM-5 have been synthetized successfully from diatomite and kaolin, respectively. 

    The synthesis of zeolite Y was extensively studied (Paper I) in order to obtain final products with high crystallinity and an appropriate SiO2/Al2O3 ratio to be suitable for application as catalyst. Then, the influence of the alkalinity (in terms of SiO2/Na2O ratio) on the outcome of the synthesis was studied. Thus, an optimum range of alkalinity that satisfies the requirements stated before was found. Additionally, the results also showed that diatomite produce similar products as colloidal silica, which may be expected since both silica sources are highly polymerized forms of silica.

    The synthesized zeolite Y crystals were also ion-exchanged with Lanthanum to obtain a Rare Earth zeolite Y (REY) catalyst (Paper V).  The REY catalyst was shown to be thermally stable up to 800°C as expected for this catalyst. The REY catalyst was also evaluated in the reaction of Catalytic Cracking of cumene. The results of catalytic tests shown that the REY catalyst synthetized from diatomite holds activity towards the catalytic cracking of cumene.

    In addition, studies of synthesis of ZSM-5 zeolite from kaolin have been performed to understand the crystal growth and morphology, crystal size, and aluminum distribution. In particular, the influence of the gel on the morphology of the crystals (Paper II) has been studied. It was observed that when the crystal surface is in contact with the gel phase, dendritic features appear at the crystal surface, that become smoother as the reaction proceeds. On the contrary, when only liquid phase is in contact with crystal surface there is no presence of dendritic features and the growth rate is higher.

    Further studies demonstrated that the ZSM-5 crystals possess a non-homogeneous aluminum distribution, a phenomenon known as Al-zoning.  A thorough characterization at distinct stages of the reaction has been performed (Paper III), on the different reaction mixture phases such as solid part, gel phase and liquid phase. The main finding was that the gel phase consists of a nanoparticle skeleton rich in alumina, filled by a silica rich matrix. In the beginning of crystallization, the silica rich matrix is preferentially consumed to form the crystals, leaving behind the alumina rich nanoparticle skeleton that is consumed later, resulting in the non-homogeneous distribution of aluminum in the crystals.

    Finally, studies of the microstructure of a TPA-ZSM-5 system using fumed silica as silicon source have been performed (paper IV). In this system, three stages of crystallization were observed. Stage I, formation of amorphous gel phase. Stage II formation of XRD amorphous spherical entities denoted as Condensed Agregates (CAs). Stage III, Crystallization of CAs into ZSM-5. This study was focused only in the stage III. Findings showed that ZSM-5 nanocrystals are formed in the core of the CA (beginning of stage III), surrounded by an amorphous shell composed of alumino-silica. As the crystallization proceeds, the amorphous shell crystallizes into ZSM-5 by competitive growth, but the nanocrystals of the core remain intact. Moreover, compositional analysis results showed that the silicon from the liquid phase provided most of the nutrients for growth of the ZSM-5 crystals resulting in polycrystalline ZSM-5 aggregates with an Al rich core - Si rich shell morphology.

    Fulltekst (pdf)
    fulltext
  • 150.
    Cardenas, Edgar
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Aguilar, Wilson
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Zhou, Ming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Influence of the internal structure of the gel on Al-zoning in NBA-ZSM-5 crystalsInngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The crystallization of ZSM-5 from a gel comprising n-butylamine as structure directing agent was investigated. The samples were characterized by X-ray diffraction, nitrogen gas adsorption, extreme high-resolution transmission and scanning electron microscopy, and energy dispersive spectroscopy. The gel was found to be composed by a silica-rich matrix embedded in a skeleton of alumina-rich nanoparticles. During growth of the crystals, the silica-rich matrix is consumed first, and an increasing fraction of the alumina-rich nanoparticles are utilized later in the growth process. This leads to a non-uniform consumption of the gel walls during crystal growth. Consequently, the Si/Al ratio of the gel is steadily decreasing, which is accompanied by a corresponding decrease in the Si/Al ratio from the center to the outer surface of the crystals, i.e. Al-zoning of the ZSM-5 crystals.

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