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  • 201.
    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.

  • 202.
    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).

  • 203.
    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.

  • 204.
    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.

  • 205.
    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.

  • 206.
    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)
  • 207. 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.

  • 208. Öhman, Marcus
    et al.
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Grimm, Alejandro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Kofod-Hansen, Marie
    Minskade askrelaterade driftsproblem genom inblandning av torv i åkerbränslen2010Report (Other academic)
    Abstract [sv]

    Resultaten visar att inblandning av typisk starrbaserad bränntorv i salix och rörflen med låg askhalt ger positiva effekter vad avser bäddagglomerering och beläggningsbildning/(korrosion) i pannors konvektionsdelar redan vid relativt låga inblandningsgrader (15 vikts-% på TS basis). En starrbaserad bränntorv med relativt högt Ca/Si förhållande bör väljas för sameldning med salix i rosteranläggningar för att inte öka slaggningsrisken. Samma torvtyp kan också i rosteranläggningar nyttjas i sameldning med rörflen med låg askhalt (relativt låga inblandningsgrader räcker) och vetehalm (höga inblandningsgrader krävs) för att reducera slaggningsrisken. Vid val av torvslag för att maximera de ovanstående positiva effekterna vid förbränning kan därför en allmän rekommendation göras att torvar med hög askhalt (starrinnehållande torv), och gärna med högt inslag av svavel, ger de bästa sameldningsegenskaperna med det tilläget att vid rostereldning bör en torv med relativt högt Ca/Si förhållande väljas (gärna upp mot 1 på vikts-% basis).

  • 209.
    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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