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  • 51.
    Strandberg, Martin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    From torrefaction to gasification: Pilot scale studies for upgrading of biomass2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increasing the share of biomass, preferably by replacing fossil fuels, is one way to mitigate the present climate change. Fossil coal can be directly replaced by co-combustion of coal and biomass and fossil engine fuels (gasoline and diesel) could potentially partly be replaced by synthetic renewable fuels produced via entrained flow gasification of biomass. The use of biomass in these processes is so far limited, partly because of the fibrous and hygroscopic nature of biomass which leads to problem in storing, transportation, handling and feeding.

    This thesis demonstrates how the challenging characteristics of raw biomass are mitigated by the pretreatment method torrefaction. Torrefaction is a process where biomass is heated in an oxygen deficient atmosphere to typically between 240 and 350°C for a time period of 2 minutes to 1 hour. Most of the torrefaction R&D in the literature have so far been performed with bench-scale batch reactors. For the purpose of carefully studying continuous torrefaction, a 20 kg/h torrefaction pilot plant was therefore designed, constructed and evaluated.

    The overall conclusion from this thesis is that the many benefits of torrefied biomass are valid also when produced with a continuous pilot plant and for typically Swedish forest biomasses. Some of the documented improved biomass properties are increased heating value, increased energy density, higher friability (lower milling energy) and less hydrophilic biomass (less moisture uptake). Most of the improvements can be attributed to the decomposition of hemicellulose and cellulose during torrefaction.

    The most common variables for describing the torrefaction degree are mass yield or anhydrous weight loss but both are challenging to determine for continuous processes. We therefore evaluated three different methods (one existing and two new suggestions) to determine degree of torrefaction that not require measurement of mass loss. The degree of torrefaction based on analyzed higher heating value of the raw and torrefied biomass (DTFHHV) predicted mass yield most accurate and had lowest combined uncertainty.

    Pelletizing biomass enhance transportation and handling but results from pelletization of torrefied biomass is still very limited in the literature and mainly reported from single pellet presses. A pelletization study of torrefied spruce with a ring die in pilot scale was therefore performed. The bulk energy density was found to be 14.6 GJ/m3 for pelletized torrefied spruce (mass yield 75%), a 40% increase compared to regular white pellets and therefore are torrefied pellets more favorable for long distance transports. More optimization of the torrefied biomass and the pelletization process is though needed for acquiring industrial quality pellets with lower amount of fines and higher pellet durability than attained in the present study.

    Powders from milled raw biomass are generally problematic for feeding and handling and torrefied biomass has been proposed to mitigate these issues. The influence of torrefaction and pelletization on powder and particle properties after milling was therefore studied. The results show that powder from torrefied biomass were enhanced with higher bulk densities, lower angle of repose as well as smaller less elongated particles with less surface roughness. Even higher powder qualities were achieved by pelletizing the torrefied biomass before milling, i.e. another reason for commercial torrefied biomass to be pelletized.

    Entrained flow gasification (EFG) is a promising option for conversion of biomass to other more convenient renewable energy carriers such as electricity, liquid biofuels and green petrochemicals. Also for EFGs are torrefied fuels very limited studied. Raw and torrefied logging residues were successfully gasified in a pilot scale pressurized entrained flow biomass gasifier at 2 bar(a) with a fuel feed corresponding to 270 kWth. Significantly lower methane content (50% decrease) in the syngas was also demonstrated for the torrefied fuel with mass yield 49%. The low milling energy consumption for the torrefied fuels compared to the raw fuel was beneficial for the gasification plant efficiency.

  • 52.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kollberg, Kristoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Powder characteristics of torrefied and pelletized biomass2014Conference paper (Other academic)
    Abstract [en]

    Co-firing biomass with coal is an efficient way of mitigating severe climate change by reducing the total atmospheric greenhouse gas burden. Although biomass is considered close to CO2-neutral, present biomass based energy carriers all however suffer from several logistical challenges. The high moisture content, hydrophobic and fibrous nature, low energy density and bulky characteristics are all challenges impeding large-scale industrial use. The thermal pre-treatment method torrefaction enhances the above biomass fuel qualities and significantly facilitate large scale industrial use of biomass raw materials with respect to, handling, storage, feeding as well as for final conversion. In the present work we evaluate the influence of torrefaction on some fuel powder quality aspects. Five different types of torrefied pellets was compared to a reference (regular white wood pellets) with respect to milling energy and different powder characteristics such as aerated and tapped bulk density, particle size distribution, angle of repose and image analysis. Milling energy decreased by between 77 and 93 % for torrefied pellets compared to wood pellets, and the resulting black powders consisted of considerably smaller particle sizes. Particles from torrefied fuels were also less elongated and more circular/less rough, properties which positively influence flowability. Powder bulk density increased by 90 % at most. Angle of repose, previously documented to be negatively correlated to flowability, decreased from 66° for the reference powder to 57° for the torrefied sample with the lowest angle. Torrefaction temperature affected the results considerably more than moisture content prior to pelletization. The total evidences found therefore suggest a positive effect of torrefaction on both powder production and characteristics.

  • 53.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Evaluation of existing and new approaches to determine degree of torrefactionManuscript (preprint) (Other academic)
    Abstract [en]

    Torrefaction is a promising thermal pretreatment method for biomass in which many material properties are enhanced. The biomass components (hemicellulose, cellulose and lignin) degrade in this thermal process to different extents depending on type of process, treatment temperature, residence time and biomass type. Torrefaction severity is usually defined by biomass weight loss or mass yield, but other approaches to determine degree of torrefaction have also been suggested. For continuous and large scale facilities, mass yield can be challenging to determine and another approach to determine torrefaction severity is therefore desired. In this study, one existing and two new approaches for determining degree of torrefaction are presented, compared and evaluated including uncertainty analysis. The three approaches were based on analysis of; volatile matter, thermochemical properties (enthalpy of formation), and higher heating value. 

    All three methods were highly correlated to mass yield and independent of torrefaction process. The degree of torrefaction based on higher heating value predicted mass yield most accurate, had lowest measurement uncertainty and the results were independent of biomass type. In the evaluation of the method based on formation enthalpy it was revealed that the increase in heating values for torrefied biomasses could be explained by the combination of increase in enthalpy of formation and decrease in oxygen content.

  • 54.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiklund-Lindström, Susanne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Åberg, Katarina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effects of temperature and residence time on continuous torrefaction of spruce wood2015In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 134, p. 387-398Article in journal (Refereed)
    Abstract [en]

    As a solid energy carrier, biomass generally has a few disadvantages, which limits its use for coal replacement and as a feedstock for entrained flow gasification. The hydrophilic and fibrous nature, the low calorific value and low bulk energy content imply high accumulated costs in the whole supply chain and severe challenges in more advanced conversion systems. By thermally pretreating the biomass by torrefaction, these properties may be significantly improved. A continuous torrefaction rotary drum reactor was designed, constructed and evaluated to enable an accurate process control and allow a homogeneous well-defined high quality product to be produced. The combined effects of torrefaction temperature (260–310 °C) and residence time (8–25 min) on a large number of product properties (> 25) were determined for Norway spruce. The resulting mass and energy yields were 46–97% and 62–99%, respectively. Exothermic reactions were evident both at low (260 °C) and high temperatures (310 °C) but with no thermal runaway observed. Increased torrefaction severity resulted in decreased milling energy consumption, angle of repose, mass and energy yield, content of volatile matter, hydrogen, cellulose and hemicellulose. Hydrophobicity, heating value, carbon and fixed carbon contents increased. For all responses, the effect of torrefaction temperature was larger than the effect of residence time. Substantial interaction effects were present for mass and energy yields, volatile matter and hydrogen content. Another correlation found was the relationship of hemicellulose degradation and the brittleness of the torrefied product. Data also suggest secondary char forming reactions during the torrefaction process, resulting in higher fixed carbon content in the torrefied material than expected. The results also suggest torrefaction temperature and residence time not to be totally interchangeable.

  • 55.
    Strandberg, Martin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Ingemar
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiklund-Lindström, Susanne
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Swedish Defence Research Agency, FOI.
    Åberg, Katarina
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effects of temperature and residence time on torrefaction of spruce woodManuscript (preprint) (Other academic)
  • 56.
    Trubetskaya, Anna
    et al.
    Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Bygning 229, Kgs. Lyngby 2800, Denmark.
    Arendt Jensen, Peter
    Degn Jensen, Anker
    Glarborg, Peter
    Hofmann Larsen, Flemming
    Larsen Andersen, Mogens
    Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 94, p. 117-129Article in journal (Refereed)
    Abstract [en]

    The concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000 degrees C) in biomass char have been studied. A room temperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7.10(16) and 1.5.10(18) spins g(-1). The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 10(3)-10(4) K s(-1). The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g = 2.0026-2.0028) and PAH radicals (g = 2.0027-2.0031) were formed.

  • 57.
    Trubetskaya, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kling, Jens
    Brown, Avery
    Tompsett, Geoffrey
    Umeki, Kentaro
    Effects of Lignocellulosic Compounds on the Yield, Nanostructure and Reactivity of Soot from Fast Pyrolysis at High Temperatures2017Conference paper (Other academic)
  • 58.
    Trubetskaya, Anna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hofmann Larsen, Flemming
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ståhl, Kenny
    Umeki, Kentaro
    Potassium and soot interaction in fast biomass pyrolysis at high temperatures2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 225, p. 89-94Article in journal (Refereed)
    Abstract [en]

    This study aims to investigate the interaction between potassium and carbonaceous matrix of soot produced from wood and herbaceous biomass pyrolysis at high heating rates at 1250°C in a drop tube reactor. The influence of soot carbon chemistry and potassium content in the original biomass on the CO2 reactivity was studied by thermogravimetric analysis. The XPS results showed that potassium incorporation with oxygen-containing surface groups in the soot matrix did not occur during high temperature pyrolysis. The potassium was mostly found as water-soluble salts such as KCl, KOH, KHCO3 and K2CO3 in herbaceous biomass soot. The low ash-containing pinewood soot was less reactive than the potassium rich herbaceous biomass soot, indicating a dominating role of potassium on the soot reactivity. However, the catalytic effect of potassium on the reactivity remained the same after a certain potassium amount was incorporated in the soot matrix during pyrolysis. Raman spectroscopy results showed that the carbon chemistry of biomass soot also affected the CO2 reactivity. The less reactive pinewood soot was more graphitic than herbaceous biomass soot samples with the disordered carbon structure.

  • 59.
    Ur Rehman, Bilal
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Modelling a Mineral Froth Flotation Process: Case Study: Minerals process at Boliden AB2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We present an approach to model the dynamic of a copper flotation process. The conventional approach of system identification is applied to model the dynamics. In this research, experiments are performed to collect process data of determined input and output variables. It is followed by data pre-processing to handle outliers and to remove high frequency disturbances. Simulation and validation responses of linear estimated models, which captured the dynamic of the process, are presented. The long term goal is to use estimated models to design a models-based control system.

  • 60. Virtanen, Pasi
    et al.
    Mikkola, Jyri-Pekka
    Åbo Akademi.
    Salmi, Tapio
    Miljövänliga katalysatorer av joniska vätskor2010In: Kemia, ISSN 0355-1628, no 6, p. 32-34Article in journal (Other academic)
  • 61. Virtanen, Pasi
    et al.
    Salminen, Eero
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University.
    Modeling of Supported Ionic Liquid Catalysts Systems: From Idea to Applications2017In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 56, no 45, p. 12852-12862Article in journal (Refereed)
    Abstract [en]

    The modeling of chemical reactions studied in small scale, often carried out in Academia, is very important since it gives more information about the system and better possibilities to scale-up the processes in the future. Supported ionic liquid catalysts (SILCAs) have been studied in a number of different processes. However, the modeling of these processes have been studied only in a few cases. In this paper the sample cases are reviewed. These processes include hydrogenation of unsaturated aldehydes as well as isomerization of terpenes, α- and β-pinene oxides.

  • 62.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    The effect of particle size, temperature, and residence time on biomass devolatilization behavior in a wire-mesh reactor2014In: Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 63.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Time-dependent variations of activation energy during rapid devolatilization of biomass2016In: Journal of Analytical and Applied Pyrolysis, ISSN 0165-2370, E-ISSN 1873-250X, Vol. 118, p. 98-104Article in journal (Refereed)
    Abstract [en]

    Industrial gasifiers and combustors are assumed to reach particle heating rates of 10(5)-10(6) degrees C/s and understanding how particles behave in these extreme conditions can improve the utilization of solid fuels in these reactors and in downstream applications. By studying intermediate devolatilization processes during solid fuel pyrolysis, detailed models for solid fuel conversion can be formulated. Key objectives of this study included (1) investigate possible mechanisms that promote the formation of synthesis gas components and char, (2) compare the devolatilization behavior of pyrolysis by varying particle size, hold time, and temperature and (3) correlate char deactivation with hold time. The objectives of the study were accomplished using a wire-mesh reactor with a uniform heating rate of 500 degrees C/s in nitrogen under atmospheric pressure. A design of experiments approach was used to quantify the effects that hold time, temperature, and particle size had on char yield, evolved gas composition, and apparent activation energy of pine stem wood and wheat straw. Key results indicate that with increased temperature and hold time more volatiles evolve from the fuels and favor carbon monoxide and methane production at higher temperatures. Apparent activation energy of the volatile matter decreases with hold time. An abbreviated model for apparent activation energy correlates well with experimental data and assumes that along a devolatilization pathway, that not all volatiles are driven from the fuel.

  • 64.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Strandberg, Anna
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiinikka, Henrik
    Energitekniskt Centrum, Piteå.
    Molinder, Roger
    Energitekniskt Centrum, Piteå.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fate of Inorganic Species during Biomass Devolatilization in a Drop Tube Furnace2014In: Impacts of Fuel Quality on Power Production October 26–31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 65.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Zhechao, Qu
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Florian, Schmidt
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Validation of reacting flow models via tunable diode laser absorption spectroscopy2014In: Impacts of Fuel Quality on Power Production October 26 –31, 2014, Snowbird, Utah, USA, 2014Conference paper (Other academic)
  • 66. Wagner, Katharina
    et al.
    Haggstrom, Gustav
    Mauerhofer, Anna Magdalena
    Kuba, Matthias
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ohman, Marcus
    Hofbauer, Hermann
    Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure2019In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 127, article id UNSP 105251Article in journal (Refereed)
    Abstract [en]

    Understanding layer formation on bed materials used in fluidized beds is a key step for advances in the application of alternative fuels. Layers can be responsible for agglomeration-caused shut-downs but they can also improve the gas composition in fluidized bed gasification. Layers were observed on K-feldspar (KAlSi3O8) impurities originating from the combined heat and power plant Senden which applies the dual fluidized bed (DFB) steam gasification technology. Pure K-feldspar was therefore considered as alternative bed material in DFB steam gasification. Focusing on the interactions between fuel ash and bed material, K-feldspar was tested in combustion and DFB steam gasification atmospheres using different fuels, namely Ca-rich bark, Ca -and P-rich chicken manure, and an admixture of chicken manure to bark. The bed particle layers formed on the bed material surface were characterized using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans were carried out for all samples. The obtained data show no essential influence of operational mode on the layer-formation process. During the combustion and DFB steam gasification of Ca-rich bark, a layer rich in Ca formed while K was diffusing out of the layer. The use of Ca -and P-rich chicken manure inhibited the diffusion of K, and a layer rich in Ca and P formed. The addition of P to bark via chicken manure also changed the underlying layer-formation processes to reflect the same processes as observed for pure chicken manure.

  • 67.
    Waltersson, Evelina
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Optimization of Expancel Product and Process: Through the use of Multivariate Planning, Data Analysis and Evaluation.2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The company Expancel produces expandable microspheres. The microspheres are microscopic spherical particles that consist of a polymer shell encapsulating a gas (the blowing agent). Heat causes the particles to expand. The microspheres have many application areas; they are used as additives in for example thermoplastics, coatings, civil explosives, paper and board. The microspheres are produced through a method called suspension polymerization. In suspension polymerization the starting material for the spheres (monomers, initiator and blowing agent) is through vigorous stirring split into small droplets in a surrounding water phase. Polymerization (initiated by heating the emulsion) occurs inside the microscopic droplets, the monomers react to form the polymer shell with the blowing agent captured inside. After the polymerization the product can be filtered and dried.

    This degree project consisted of two parts. In the first (and major) part the consequences of replacing a chemical used in the production of the microspheres with a more environmentally friendly alternative was examined. The goal was to produce microspheres with an alternative chemical without changing the properties of the microspheres. First five different alternative chemicals were examined in a selected production recipe in 50 ml scale. The software MODDE was used for design of these experiments and analysis of results. Then the best alternative of the five was examined in three other recipes in 50 ml scale. One of the recipes was also examined in 1 liter scale. Several of the alternative chemicals showed good results in the first recipe, but one of them showed more stable results than the others and was selected to proceed with in the other recipes. The conclusion from the experiments with this chemical was that the amount added affected the particle size, and that best results were achieved when adding the chemical before the flocculation step in the process.

    The objective of the second part was to study and evaluate a production process in order to find optimization possibilities. The chosen process was the filtering of the produced microsphere slurry for a specific recipe. Data were collected from the polymerization process, the dewatering process and the characterization analyses performed on the produced microsphere slurry. Production rate was used as response variable. The multivariate analysis software package SIMCA-P+12.0.1 was then used to analyze the data. The conclusion of the multivariate data analysis was that two factors were the most important for explaining the variation in the response variable; the particle size and a polymerization parameter called level.

  • 68. Wang, Huijiao
    et al.
    Mustafa, Majid
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yu, Gang
    Östman, Marcus
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cheng, Yi
    Wang, Yujue
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Oxidation of emerging biocides and antibiotics in wastewater by ozonation and the electro-peroxone process2019In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 235, p. 575-585Article in journal (Refereed)
    Abstract [en]

    This study investigated the abatement of a number of antimicrobials frequently detected in municipal wastewater by conventional ozonation and a recently developed ozone-based advanced oxidation process, the electro-peroxone (E-peroxone) process. A synthetic water and a real secondary wastewater effluent were spiked with fourteen antimicrobials, including antibiotics and biocides, and then treated by the two processes. The results show that most of the antibiotics investigated (e.g., ofloxacin, trimethoprim, norfloxacin, and ciprofloxacin) readily react with ozone (O3) and could therefore be efficiently eliminated from the water matrices by direct O3 oxidation during both processes. In contrast, most of the biocides tested in this study (e.g., clotrimazole, pentamidine, bixafen, propiconazole, and fluconazole) were only moderately reactive, or non-reactive, with O3. Therefore, these biocides were removed at considerably lower rate than the antibiotics during the two ozone-based processes, with hydroxyl radical (OH) oxidation playing an important role in their abatement mechanisms. When compared with conventional ozonation, the E-peroxone process is defined by the in situ electrogeneration of hydrogen peroxide, which considerably enhances the transformation of O3 to OH. As a result, the E-peroxone process significantly accelerated the abatement of biocides and required a considerably shorter treatment time to eliminate all of the tested compounds from the water matrices than conventional ozonation. In addition, the E-peroxone process enhanced the contributions of OH fractions to the abatement of moderately ozone reactive benzotriazoles. These results demonstrate that the E-peroxone process holds promise as an effective tertiary treatment option for enhancing the abatement of ozone-resistant antimicrobials in wastewater.

  • 69.
    Werner, Kajsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nils, Skoglund
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Albers, Eva
    Chalmers University of Technology.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Co-combustion of Miscanthus and Calcium Rich Brown Macroalgae2016In: 22nd International Conference of Impacts of Fuel Quality on Power Production, Prague, Czech Republic, September 19-23, 2016, 2016Conference paper (Refereed)
    Abstract [en]

    The high ash content and varying ash composition from aquatic biomass is often mentioned as problematic if used for thermal energy conversion. This paper suggests a fuel design approach where detailed information on ash composition is the starting point for mixing and using fuels considered to be difficult. The procedure is demonstrated on brown macroalgae grown for biorefinery purposes in sea water. The fuel fingerprint (concentrations of the main ash forming elements) showed an interesting profile with very high Ca content together with significant amounts of Mg, K, Na, Cl, S, and also some minor contributions from Si and P. After careful considerations, it was concluded that this specific alga would be suitable for co-combustion with a silicone rich biofuel that would typically require some additive to avoid ash melting. One such fuel is Miscanthus. The aim of this study was to evaluate and compare algae as a renewable source of Ca with mineral CaCO3 to reduce the risk of alkali silicate melt formation in combustion of the energy crop Miscanthus. The Miscanthus was co-pelletized with algal biomass and CaCO3, both at Ca/(K+Na) molar ratios of 1.5 and 3.0, and combusted in a bubbling fluidized bed. in. The ash reactions were assessed by analyzing samples from bed, deposit probe, cyclone, and particulate matter with SEM-EDS and P-XRD. The results showed that Ca from the algae reacted with the Miscanthus ash, forming less problematic silicate ash fractions. At the low combustion temperatures used (< 720°C) stable CaSO4 was formed, capturing some of the S that would otherwise have been available for alkali sulfation. Comparing the Ca rich algae with adding pure CaCO3 to the Miscanthus pellets indicated that the Ca in the algae ash was more prone to react with the K-silicate, and thereby more efficiently preventing ash melting.

  • 70.
    Werner, Kajsa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Piotrowska, Patrycja
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Gentili, Francesco
    Swedish University of Agricultural Sciences.
    Holmlund, Mattias
    Swedish University of Agricultural Sciences, SLU.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Characterization of Thermochemical Fuel Properties of Microalgae and Cyanobacteria2014Conference paper (Other academic)
  • 71.
    Wänglund, Josefin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Undersökning av SNCR som rökgasreningsmetod för att reducera utsläpp av NOx: En utredning gjord på SCA Östrands massafabrik2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    På SCA Östrands massafabrik i Timrå produceras två olika typer av pappersmassa,blekt sulfatmassa och kemitermomekanisk massa (CTMP). Idag produceras ungefär 430 000 ton blekt sulfatmassa och 95 000 ton CTMP per år. Just nu pågåren om- och nybyggnation av sulfatmassalinjen inom projektet Helios. Målet med projektet är att under 2018 ta i drift en fabrik med en kapacitet att producera 900 000 ton blekt sulfatmassa per år. I och med utbyggnaden har fabriken fått en ny miljödom (som ett resultat av verksamhetstillståndsansökan) med villkor attförhålla sig till. I miljödomen presenteras ett antal olika villkor; utredningsvillkor, utsläppsvillkor och riktvärden. Ett av villkoren är ett utredningsvillkor som gäller utredning av rökgasreningstekniken SNCR (selektiv icke-katalytisk reduktion) för att rena rökgaserna från fabrikens ångproducerande enheter, barkpannan (ÅP1)och sodapannan (SP6), från NOx. Syftet med examensarbetet var att i ett första steg i utredningen av utredningsvillkoret undersöka möjligheterna till att använda SNCR som rökgasrening på ÅP1 för att rena rökgaserna från NOx.

    För att utreda möjligheterna att använda SNCR på ÅP1 gjordes temperaturmätningar av rökgaserna i pannans övre del och en temperaturprofil över pannan bestämdes. Vidare undersöktes olika metoder av SNCR och andra sekundära rökgasreningsmetoder i en litteraturstudie och i en undersökning av marknaden som bland annat innehöll referensbesök på anläggningar med olika SNCR-system.En grov kostnadsmässig analys genomfördes också genom att beräkna teoretiskautsläppsmängder för de nya förutsättningarna efter Helios, NOx-avgiften och kemikalieförbrukningen i ett hypotetiskt fall där SNCR installeras.

    Under de förutsättningar som temperaturmätningarna gjordes framkom det att det inte är möjligt att använda sig av SNCR för att reducera NOx-utsläppen från ÅP1. Mätningarna visade dock att det är möjligt att använda SNCR som reningsmetod vid laster högre än 72 ton ånga/h om det finns ett linjärt samband mellan last(ton ånga/h) och rökgastemperaturen.

  • 72.
    Åberg, Katarina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Biomass conversion through syngas-based biorefineries: thermochemical process integration opportunities2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The replacement of fossil resources through renewable alternatives is one way to mitigate global climate change. Biomass is the only renewable source of carbon available for replacing oil as a refining feedstock. Therefore, it needs to be utilized not just as a fuel but for both biochemical and thermochemical conversion through biorefining. Optimizing and combining various conversion processes using a system perspective to maximize the valorization, biomass usage, and environmental benefits is of importance. This thesis work has evaluated the integration opportunities for various thermochemical conversion processes within a biorefinery system.

    The aim for all evaluated concepts were syngas production through gasification or reforming. Two potential residue streams from an existing biorefinery were evaluated as gasification feedstocks, thereby combining biochemical and thermochemical conversion. Torrefaction as a biomass pretreatment for gasification end-use was evaluated based on improved feedstock characteristics, process benefits, and integration aspects. A system concept, “Bio2Fuels”, was suggested and evaluated for low-temperature slow pyrolysis as a way to achieve simultaneous biomass refinement and transport driven CO2 negativity.

    Syngas was identified as a very suitable intermediate product for residue streams from biochemical conversion. Resulting syngas composition and quality showed hydrolysis residue as suitable gasification feedstock, providing some adjustments in the feedstock preparation. Gasification combined with torrefaction pretreatment demonstrated reduced syngas tar content. The co-gasification of biogas and wood in a FBG was successfully demonstrated with increased syngas H2/CO ratio compared to wood gasification, however high temperatures (≥1000°C) were required for efficient CH4 conversion. The demonstrated improved feedstock characteristics for torrefied biomass may facilitate gasification of biomass residue feedstocks in a biorefinery. Also, integration of a torrefaction unit on-site at the biorefinery or off-site with other industries could make use of excess low-value heat for the drying step with improved overall thermal efficiency. The Bio2Fuels concept provides a new application for slow pyrolysis. The experimental evaluation demonstrated significant hydrogen and carbon separation, and no significant volatilization of ash-forming elements (S and Cl excluded)  in low-temperature (<400°C) pyrolysis. The initial reforming test showed high syngas CH4 content, indicating the need for catalytic reforming.

    The collective results from the present work indicate that the application of thermochemical conversion processes into a biorefinery system, making use of by-products from biochemical conversion and biomass residues as feedstocks, has significant potential for energy integration, increased product output, and climate change mitigation.

  • 73.
    Åberg, Katarina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Syngas production by integrating thermal conversion processes in an existing biorefinery2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of carbon from fossil-based resources result in changes in the earth’s climate due to emissions of greenhouse gases. Biomass is the only renewable source of carbon that may be converted to transportation fuels and chemicals, markets now fully dominated by traditional oil supply. The biorefinery concept for upgrading and refinement of biomass feedstocks to value-added end-products has the potential to mitigate greenhouse gas emissions and replace fossil products. Most biorefineries use biochemical conversion processes and may have by-product streams suitable as feedstocks for thermal conversion and production of syngas. Further synthesis to value-added products from the syngas could increase the product output from the biorefinery.

    The application of thermal conversion processes integrated into an existing biorefinery concept has been evaluated in this licentiate thesis work. Two by-product streams; hydrolysis (lignin) residue from an ethanol plant and biogas from wastewater treatment, have been investigated as gasification/reforming feedstocks. Also, the pre-treatment method torrefaction has been evaluated for improved gasification fuel characteristics and integration aspects. A new process and system concept (Bio2Fuels) with potential carbon negative benefits has been suggested and evaluated as an alternative route for syngas production by separating biomass into a hydrogen rich gas and a carbon rich char product.

    The evaluation demonstrated that hydrolysis residue proved a suitable feedstock for gasification with respect to syngas composition. Biogas can be further reformed to syngas by combined biomass gasification and methane reforming, with promising results on CH4 conversion rate and increased H2/CO ratio at temperatures ≥1000°C. The pre-treatment method torrefaction was demonstrated to improve fuel qualities and may thus significantly facilitate entrained flow gasification of biomass residue streams. Also, integration of a torrefaction plant at a biorefinery site could make use of excess heat for drying the raw material before torrefaction. The Bio2Fuels concept was evaluated and found feasible for further studies.

    The application of thermal conversion processes into an existing biorefinery, making use of by-products and biomass residues as feedstocks, has significant potential for energy integration, increased product output as well as for climate change mitigation.

  • 74.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Borén, Eleonora
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hydrogen and carbon separation by low-temperature slow pyrolysis of biomass: experimental validationManuscript (preprint) (Other academic)
    Abstract [en]

    Previous work have indicated that slow pyrolysis may be used to separate hydrogen and carbon in a biomass feedstock into different product fractions. The hydrogen predominantly ends up in the pyrolysis gas fraction, whereas the carbon is mainly retained in the char. A system concept was suggested using low-temperature slow pyrolysis to achieve; a) transportation fuel/chemical production from the volatilized fraction, and b) potential carbon negativity by sequestering the carbon from the biochar fraction after use for electricity and/or heat production. The present work aimed to identify important process parameters, validate the hydrogen and carbon separation potential, and identify a potential process optimum for spruce wood slow pyrolysis. The process temperature was shown as the most important factor influencing the hydrogen and carbon pyrolysis gas yields, whereas the residence time factor only showed significant influence on the product yields for the shorter residence times. All experiments demonstrated significant hydrogen and carbon separation to gas and char respectively, particularly for lower process temperatures. An optimum process operation temperature was not found but from an industrial perspective, the suggested preferable temperature interval lies within the lowtemperature pyrolysis range (350-400°C), just above high temperature torrefaction (~300°C).

  • 75.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Khwaja, Salik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pilot scale experimental validation of the Bio2fuels low-temperature slow pyrolysis system conceptManuscript (preprint) (Other academic)
    Abstract [en]

    The “Bio2Fuels” concept previously suggested may potentially achieve a transport driven carbon negativity by use of a combination of; low-temperature slow pyrolysis/high-temperature torrefaction; gas reforming; fuel synthesis; coal replacement by the solid bio-coal stream; and CCS of the resulting flue gases. The initial pre-treatment process suggested may potentially exhibit several advantages and may well facilitate an appealing and cost-efficient conversion system. The present work was comprised of pilot-scale pyrolysis experiments on softwood pellets using a continuous auger screw torrefaction/pyrolysis reactor for validation of the process in the temperature range of 300-425°C. All products were analyzed for composition and the pyrolysis gas (permanent gases + bio-oil) was sampled for particulate matter, permanent gas and bio-oil composition. The volatilization propensity of ash-forming elements was analyzed based on alkali deposits on impactor plates with SEM analysis and ICP-AES analysis of the bio-oil. The volatilization of sulfur and chlorine was also evaluated via char retainment. In addition, an initial test run of thermal pyrolysis gas reforming was performed by operating the thermal oxidation burner in gasification/reforming mode. The results showed that the hydrogen and oxygen in the biomass feedstock were volatilized at lower temperatures than the feedstock carbon, with the desired resulting hydrogen/carbon separation into pyrolysis gas and biochar, but also enrichment of oxygen in the pyrolysis gas. The hydrogen pyrolysis gas yield was >75% for pyrolysis temperatures ≥375°C and the corresponding carbon gas yield ranged from 50% to 63%. Most of the hydrogen in the pyrolysis gas was bound in the bio-oil as water and various hydrocarbons. No significant volatilization of alkali elements was observed through either analysis method. The most abundant permanent gas formed was CO2 and with a CH4 concentration of about 9%vol. The thermal reforming experiments also demonstrated a high CH4 syngas concentration, strongly indicating the need for a catalytic reforming process.

  • 76.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindh, Ingemar
    Bioendev AB.
    Kollberg, Kristoffer
    Sigma Industry.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Torrefaction and gasification of lignocellulosic hydrolysis residue from bio-ethanol productionManuscript (preprint) (Other academic)
    Abstract [en]

    Production of lignocellulosic ethanol through hydrolysis (acid or enzymatic) combined with fermentation generate a large amount of residue consisting of mainly lignin and un-ydrolyzed cellulose. The significant amount of energy retained in this residue require further conversion as a measure to ensure economic viability for the total process. Thermal conversion of the hydrolysis residue through gasification for syngas production would improve the fuel yield in addition to the overall plant efficiency. Also, torrefaction of various biomass feedstocks has been shown to significantly improve biomass fuel characteristics in addition to having substantial positive effect on the energy consumption of the particle size reduction. The present work was an evaluation of hydrolysis residue and torrefied hydrolysis residue as gasification feedstocks in a bench-scale fluidized bed gasifier, based on syngas composition, particle formation, tar production and volatilization behavior. In addition, the effects of torrefaction on hydrolysis residue material characteristics were separately evaluated, including the influence of the process parameters on milling energy consumption and morphology. All torrefaction data was fitted to multiple linear regression models with good reproducibility and fit. The results confirm the previously reported improved feedstock characteristics resulting from torrefaction of biomass, however residence time was proved the most influential process parameter on the torrefaction severity, most likely derived from the lack of hemicellulose in the residue. The resulting syngas composition and quality indicated that both non-torrefied and torrefied hydrolysis residue were suitable gasification feedstocks. The hydrolysis residue product gas had elevated tar concentration but the torrefied residue demonstrated a significant reduction in the tar content (particularly the heavy tar components), compared to both raw hydrolyis residue and the wood reference feedstock. Hence, torrefaction may significantly reduce tar related problems in downstream equipment/processes.

  • 77.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Low-temperature slow pyrolysis of biomass for H2-enriched syngas production and carbon negativityManuscript (preprint) (Other academic)
    Abstract [en]

    To optimally utilize biomass resources as feedstock for fuels and chemicals production as well as for a potential substantial carbon sink, a dedicated process and system concept is suggested. The desired outcome of the process is a hydrogen-enriched pyrolysis gas and a carbon-enriched char, also retaining the ash-forming elements. To obtain a transport-driven large-scale CO2 negative system, the char is suggested as co-firing fuel in a facility with carbon capture and storage technology. In the present work, the basis for this Bio2Fuels separation concept was evaluated by 1) analysis of previously published empirical data for pyrolysis, and 2) chemical equilibrium calculations. The former analysis indicated on the potential for a significant separation of H and C to the pyrolysis gas and char respectively, with ~80% of the hydrogen and 40-60% of the carbon from the raw feedstock present in the pyrolysis gas product. Based on analyzed thermochemical driving forces, most of the ash-forming elements can be expected to be retained in the char, and an ash and alkali-free gas may be achieved at temperatures below 500°C. In addition, chemical equilibrium modelling of the pyrolysis gas reforming demonstrated a significantly increased H2/CO ratio in the syngas compared to gasification of the raw biomass.

  • 78.
    Åberg, Katarina
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Pommer, Linda
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordin, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Syngas production by combined biomass gasification and in-situ methane reformingManuscript (preprint) (Other academic)
  • 79. Ögren, Yngve
    et al.
    Sepman, Alexey
    Qu, Zhechao
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wiinikka, Henrik
    Comparison of measurement techniques for temperature and soot concentration in premixed, small-scale burner flames2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 10, p. 11328-11336Article in journal (Refereed)
    Abstract [en]

    Optical and intrusive measurement techniques for temperature and soot concentration in hot reacting flows were tested on a small-scale burner in fuel-rich, oxygen-enriched atmospheric flat flames produced to simulate the environment inside an entrained flow reactor. The optical techniques comprised two-color pyrometry (2C-PYR), laser extinction (LE), and tunable diode laser absorption spectroscopy (TDLAS), and the intrusive methods included fine-wire thermocouple thermometry (TC) and electrical low pressure impactor (ELPI) particle analysis. Vertical profiles of temperature and soot concentration were recorded in flames with different equivalence and O2/N2 ratios. The 2C-PYR and LE data were derived assuming mature soot. Gas temperatures up to 2200 K and soot concentrations up to 3 ppmv were measured. Close to the burner surface, the temperatures obtained with the pyrometer were up to 300 K higher than those measured by TDLAS. Further away from the burner, the difference was within 100 K. The TC-derived temperatures were within 100 K from the TDLAS results for most of the flames. At high signal-to-noise ratio and in flame regions with mature soot, the temperatures measured by 2C-PYR and TDLAS were similar. The soot concentrations determined with 2C-PYR were close to those obtained with LE but lower than the ELPI results. It is concluded that the three optical techniques have good potential for process control applications in combustion and gasification processes. 2C-PYR offers simpler installation and 2D imaging, whereas TDLAS and LE provide better accuracy and dynamic range without calibration procedures.

  • 80.
    Österlund, Patrik
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Förändrat körsätt av sodapannan2014Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    The student thesis has been carried out for five weeks at Smurfit Kappa Kraftliner in Piteå. The project assigned was to perform a change in their driving behaviour of the combustion air to the recovery boiler and eventually minimize problems with dust departure. The method of the experiments was to close the 1,1 MPa steam and only inject 0,3 MPa steam to the air preheater before injection into the recovery boiler. The purpose of the thesis was to analyse the experiments and evaluate if there are any negative consequences to run the plant with only 0,3 MPa steam. The computer program WinMops was used to evaluate how the facility had been running earlier in the year and then compare this with the results of the experimental runs.

    The purpose of the recovery boiler is to recover chemicals by burning black liquor and to produce overheated steam to the turbines. The control and driving style of the recovery boiler is important for the black liquor combustion to be optimal. The combustion depends on the composition of the black liquor and the combustion air that is added. With the right amount of air and in the right places, you can control how well the combustion will be depending on the composition of the black liquor. Therefore, the combustion air is inserted to the recovery boiler at four different levels.

    Combustion tests were performed on two occasions, 24 hours each, and resulted in many negative consequences. The degree of reduction of green liquor and outgoing steam quantity was reduced. The amount of air into the boiler increased when the air pressure went down as the temperature of the combustion air was lowered from 170°C to 132°C. Increased amount of air in the boiler led to increased amount of fumes, which had a negative effect on the dust departure.

    The conclusion from this study is that the problems of high dust departure continued even with the changed driving behaviour of the combustion air. The conditions for combustion experiments have not been optimal when a number of breakdowns occurred in the steam network. The results probably had become more reliable with longer trial periods because the black liquor composition varies from day to day. 

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