Publikationen

Conference presentations and posters | 2013

Production of mixed alcohols from biomass-derived synthesis gas using a sulfidized molybdenum catalyst

Weber G, Rauch R, Hofbauer H. Production of mixed alcohols from biomass-derived synthesis gas using a sulfidized molybdenum catalyst, International Conference on Polygeneration Strategies 2013, 3th-5th of September 2013, Vienna, Austria. Weber G, Rauch R, Hofbauer H. Production of mixed alcohols from biomass-derived synthesis gas using a sulfidized molybdenum catalyst, International Conference on Polygeneration Strategies 2013, 3th-5th of September 2013, Vienna, Austria. (peer reviewed)

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Conference presentations and posters | 2015

Production of high purity hydrogen from biomass-derived synthesis gas using dual fluidised bed gasification technology

Loipersböck J., Rehling B., Rauch R., Hofbauer H. Production of high purity hydrogen from biomass-derived synthesis gas using dual fluidised bed gasification technology, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (oral presentation)

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Conference presentations and posters | 2017

Production of Fuel Ethanol and Higher Alcohols from Biomass Residue

Summers M, Liao C, Hoffman M, Hart M, Seiser R, Neimann U, Cattolica R, Rauch R, Binder M. Production of Fuel Ethanol and Higher Alcohols from Biomass Residue. 25th European Biomass Conference & Exhibition (oral presentation). June 2017, Stockholm, Sweden.

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Reports | 2016

Production of advanced biofuels

Bacovsky D. Production of advanced biofuels. Nationaler Workshop Biotreibstoffe. September 2016.

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Conference presentations and posters | 2020

Product flexibility from biomass steam gasification applying gas upgrading and synthesis processes

Binder M, Product flexibility from biomass steam gasification applying gas upgrading and synthesis processes. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference presentations and posters | 2012

Processing Options Of Heavy Fractions From MBT Plants

Meirhofer M, Ragoßnig AM, Sommer M. Processing Options Of Heavy Fractions From MBT Plants, ISWA Annual Congress Florence 2012, 17th-19th of September 2012, Florence, Italy. (peer reviewed)

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Heavy fractions resulting from mechanical treatment stages of Mechanical Biological Treatment (MBT) plants are posing very specific demands with regard to further treatment/disposal as they contain a high portion of inert material as well as a high portion of high calorific components. Based on the current Austrian legal situation (landfill ordinance: max. Higher Calorific Value (HCV) for MBT-fractions to be landfilled = 6,600 kJ/kg DM) this waste stream cannot be landfilled but must be thermally treated. In economic terms it is desirable to separate high calorific from inert waste components in order to allow for a material specific routing taking advantage of the difference in the costs for the downstream treatment / disposal.
In this conference contribution results of extensive processing experiments with the heavy fraction from the mechanical stage of the MBT plant of Umweltdienst Burgenland in Oberpullendorf, Austria, are presented. Experiments have been conducted with three different sensor-based automatic sorting systems (NIR – Multiplexer, NIR – Spectral Imaging, X-Ray transmission) as well as two density based processing technologies (wet treatment with a jigger, dry treatment with a cross flow air separation device). In addition a rotary shredder, which allows selective crushing, followed by screening has been investigated.
The performance of the processing options have been evaluated by characterizing the resulting product streams by means of manual sorting in order to evaluate purity and yield achieved by the respective treatment options. In addition to that chemical and physical parameters relevant for further treatment / disposal steps for the resulting product streams have been analysed. The inert fraction has been evaluated regarding the landfilling on a mass waste landfill on one hand and on a C&D waste landfill on the other hand. The high calorific product stream has been evaluated with regard to its thermal utilization.
Complementing the technical evaluation of the processing options an economical assessment of the processing options looked at including the economical implications of the resulting changes in the routing of the waste streams has been conducted.

Conference presentations and posters | 2012

Processing Options Of Heavy Fractions From MBT Plant

Meirhofer M, Ragoßnig AM, Sommer M. Processing Options Of Heavy Fractions From MBT Plant, ISWA Annual Congress Florence 2012, 18th of September 2012, Florence, Italy.

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Other Publications | 2021

Probenahmen, Messung, Behandlung von Chrom VI in Holzaschen

Retschitzegger S. Probenahmen, Messung, Behandlung von Chrom VI in Holzaschen. 23. Österreichischer Biomassetag & Heizwerke-Betreibertag. September 2021.

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Other Publications | 2019

Primäre und sekundäre Verbesserungen an einem Biomassekessel für Agrarbrennstoffe

Zemann C, Kelz J, Muschick D, Retschitzegger S, Gölles M. Primäre und sekundäre Verbesserungen an einem Biomassekessel für Agrarbrennstoffe. 10. Fachgespräch: Partikelabscheider in häuslichen Feuerungen. 20. März 2019 (2019). [online]. (Tagungsreader, 15). Leipzig: DBFZ. 168 S.

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ie Biomasseverbrennung spielt eine zentrale Rolle bei der Bereitstellung von Wärme aus erneuerbaren Energieträgern. Konventionelle Biomasse-Brennstoffe werden jedoch aufgrund einer steigenden Anzahl stofflicher Verwertungsmöglichkeiten, wie z.B. der Umwandlung in Chemikalien, teurer und schwieriger zugänglich. Agrarbrennstoffe, die bisher nur selten oder gar nicht in Biomasse-Kleinfeuerungen eingesetzt wurden, stellen eine vielversprechende Alternative zu konventionellen Brennstoffen dar. Diese Agrarbrennstoffe, wie zum Beispiel Kurzumtrieb, Maisspindeln oder Stroh sind kostengünstig und in ausreichender Menge vorhanden. Der Einsatz von Agrarbrennstoffen in konventionellen Biomasse-Kleinfeuerungen ist jedoch aufgrund stark variierender Brennstoffeigenschaften mit erhöhten Anforderungen an das Verbrennungssystem verbunden. Erhöhte N, S, Cl, Alkalimetall- und Aschegehalte sowie niedrigere Aschenschmelzpunkte können zu aschebedingten Problemen (Ascheschmelze, Ascheablagerung und Korrosion) sowie erhöhten Konzentrationen von gasförmigen (CO, NOx, HCl und SOx) und partikelförmigen Emissionen bei der Verbrennung führen.

Ziel der in diesem Beitrag präsentierten Arbeiten war die Erhöhung die Brennstoffflexibilität einer handelsüblichen Biomasse-Kleinfeuerung um damit eine Verbrennung von Agrarbrennstoffen mit niedrigen Schadstoffemissionen und einem hohen Wirkungsgrad zu ermöglichen. Hierzu wurde eine modellbasierte Regelung entwickelt, welche insbesondere eine gezielte Einstellung des Luftverhältnisses in der Primärverbrennungszone ermöglicht und damit das Risiko der Ascheschmelze reduziert und Schadstoffmissionen verringert. Soft-Sensoren bestimmen relevante Brennstoffeigenschaften während des Betriebs, welche von der modellbasierten Regelung zur automatischen Anpassung an geänderte Brennstoffeigenschaften genutzt werden. Die modellbasierte Regelung wurde um eine CO-lambda-Optimierung ergänzt, welche auf Basis von Messwerten des Restsauerstoffgehalts und der CO-Emissionen den Wirkungsgrad der Verbrennung maximiert und gleichzeitig die Schadstoffemissionen verringert. Zur weiteren Verringerung von partikelförmigen Schadstoffemissionen wurde ein am Markt verfügbarer Elektrofilter adaptiert und nach dem Wärmeübertrager der Biomasse-Kleinfeuerung angebracht.

Dieses Verbrennungssystem wurde durch umfassende Testläufe mit begleitenden Emissionsmessungen sowie Brennstoff-, Staub- und Ascheanalysen bewertet. Der Einsatz der modellbasierten Regelung führte zu einem stabileren Betrieb bei allen Leistungen und für alle Brennstoffe. Der Elektrofilter zeigte sehr zufriedenstellende Abscheidegrade für alle untersuchten Brennstoffe und Anlagenleistungen. Dadurch konnte die Brennstoffflexibilität der handelsüblichen Biomasse-Kleinfeuerung erhöht und die Verbrennung von Agrarbrennstoffen ermöglicht werden.

 

Conference presentations and posters | 2020

Primary- and Secondary Measures for Manually Fired Stoves – An Overview

Reichert G. Primary- and Secondary Measures for Manually Fired Stoves – An Overview. 6th Central European Biomass Conference - KeepWarm/CleanAir workshop (oral presentation). 2020.

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Conference presentations and posters | 2020

Primary- and Secondary Measures for Manually Fired Stoves - An Overview

Reichert G. Primary- and Secondary Measures for Manually Fired Stoves - An Overview. 6th Central European Biomass Conference, 2020, Graz.

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Conference presentations and posters | 2009

Primary measures for low-emission residential wood combustion – comparison of old with optimised modern systems

Brunner T, Obernberger I, Scharler R. Primary measures for low-emission residential wood combustion – comparison of old with optimised modern systems, 17th European Biomass Conference 2009, 29th of June-3rd of July 2009, Hamburg, Germany.

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Conference presentations and posters | 2014

Price cointegration in the Austrian wood fuel market,

Kristöfel C, Morawetz UB, Schmid E, Strasser C. Price cointegration in the Austrian wood fuel market, 22nd European Biomass Conference 2014, 23rd-26th of June 2014, Hamburg, Germany. p 1330-1335.

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The wood fuel market is connected to the forest­based industry in various ways: the sawmill by­ products such as sawdust and wood chips are usually used as raw material in the panel, pulp and paper industry and are increasingly pelletized to supply the energy commodity market. Hence, the question arises whether or not prices of these woody biomass commodities are integrated. Threshold cointegration and asymmetric error correction models are used to analyze the price dynamics between roundwood, wood pellets and sawmill by­ products. Results indicate that a statistical significant price transmission between sawmill by­products and wood pellets, but wood pellet and roundwood prices are not integrated. The price transmission between wood pellets and sawdust as well as wood chips is asymmetric. The Granger Causality test reveals that the prices of sawdust and wood chips depend on the price of wood pellets.

Conference presentations and posters | 2021

Price cointegration in the Austrian sawmill industry with a focus on by-products

Fuhrmann M, Dißauer C, Strasser C, Schmid E. Price cointegration in the Austrian sawmill industry with a focus on by-products. 29th European Biomass Conference and Exhibition, EUBCE 2021. 26-29 April 2021.

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Conference presentations and posters | 2023

Predictive control of biomass and biogas-based CHPs at the intersection between the electricity grid and heating networks – Improving electricity market participation through optimization and demand side management

Muschick D, Kaisermayer V, Moser A, Gölles M. Predictive control of biomass and biogas-based CHPs at the intersection between the electricity grid and heating networks – Improving electricity market participation through optimization and demand side management. 7. Mitteleuropäische Biomassekonferenz: CEBC 2023. 20. Jan 2023. Oral presentation.

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Peer reviewed papers | 2020

Prediction of slag related problems during fixed bed combustion of biomass by application of a multivariate statistical approach on fuel properties and burner technology

Rebbling A, Näzelius IL, Schwabl M, Feldmeier S, Schön C, Dahl J, Haslinger W, Boström D, Öhman M, Boman C. Prediction of slag related problems during fixed bed combustion of biomass by application of a multivariate statistical approach on fuel properties and burner technology. Biomass and Bioenergy 2020.137:105557.

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Slag is related to the melting properties of ash and is affected by both the chemical composition of the fuel ash and the combustion parameters. Chemical analysis of slag from fixed bed combustion of phosphorus-poor biomass show that the main constituents are Si, Ca, K, O (and some Mg, Al, and Na), which indicates that the slag consists of different silicates. Earlier research also points out viscosity and fraction of the ash that melts, as crucial parameters for slag formation. To the authors’ knowledge, very few of the papers published to this day discuss slagging problems of different pelletized fuels combusted in multiple combustion appliances. Furthermore, no comprehensive classification of both burner technology and fuel ash parameters has been presented in the literature so far. The objective of the present paper was therefore to give a first description of a qualitative model where ash content, concentrations of main ash forming elements in the fuel and type of combustion appliance are related to slagging behaviour and potential operational problems of a biomass fuel in different small- and medium scale fixed bed appliances.

Based on the results from the combustion of a wide range of pelletized biomass fuels in nine different burners, a model is presented for amount of slag formed and expected severity of operational problems. The model was validated by data collected from extensive combustion experiments and it can be concluded that the model predicts qualitative results.

Conference presentations and posters | 2012

Prediction of biomass ash melting behaviour – correlation between the data obtained from thermodynamic equilibrium calculations and simultaneous thermal analysis (STA)

Evic N, Brunner T, Oberberger I. Prediction of biomass ash melting behaviour – correlation between the data obtained from thermodynamic equilibrium calculations and simultaneous thermal analysis (STA), 20th European Biomass Conference 2012, 18th-22nd of June 2012, Milano, Italy. p 807-813.

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Conference presentations and posters | 2019

Practical example: manufacturers’ data vs data from ecoinvent database – a comparison of LCI and LCA

Rixrath D, Wartha C, Enigl M, Strasser C, Piringer G. Practical example: manufacturers’ data vs data from ecoinvent database – a comparison of LCI and LCA. 15. Minisymposium Verfahrenstechnik MU Leoben (Poster). 2019.

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The aim of this work is to analyze biogenic residues and to test
them for their suitability as feedstocks for hydrothermal
liquefaction (HTL). Green waste, sewage sludge, micelles,
leftovers and organic waste were analyzed and tested. All
experiments were carried out in an autoclave at 350 °C with a
holding time of 15 minutes under an inert argon atmosphere. After
the experiments the yields of the gas, aqueous, biocrude and solid
phase were determined together with lipid contents, heating values
and elemental composition of the raw materials and biocrude
samples. Biocrude yields are of specific interest for a future
commercial use of the HTL-process. In this study we achieved
biocrude yields between 9.43% (green waste) and 34.28%
(leftovers).

Peer reviewed papers | 2018

Power to fuels: Dynamic modeling of a Slurry Bubble Column Reactor in lab-scale for Fischer Tropsch synthesis under variable load of synthesis gas

Seyednejadian S, Rauch R, Bensaid S, Hofbauer H, Weber G, Saracco G. Power to fuels: Dynamic modeling of a Slurry Bubble Column Reactor in lab-scale for Fischer Tropsch synthesis under variable load of synthesis gas. Apllied Sciences. 2018, 8(4): 514.

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This research developed a comprehensive computer model for a lab-scale Slurry Bubble Column Reactor (SBCR) (0.1 m Dt and 2.5 m height) for Fischer–Tropsch (FT) synthesis under flexible operation of synthesis gas load flow rates. The variable loads of synthesis gas are set at 3.5, 5, 7.5 m3/h based on laboratory adjustments at three different operating temperatures (483, 493 and 503 K). A set of Partial Differential Equations (PDEs) in the form of mass transfer and chemical reaction are successfully coupled to predict the behavior of all the FT components in two phases (gas and liquid) over the reactor bed. In the gas phase, a single-bubble-class-diameter (SBCD) is adopted and the reduction of superficial gas velocity through the reactor length is incorporated into the model by the overall mass balance. Anderson Schulz Flory distribution is employed for reaction kinetics. The modeling results are in good agreement with experimental data. The results of dynamic modeling show that the steady state condition is attained within 10 min from start-up. Furthermore, they show that step-wise syngas flow rate does not have a detrimental influence on FT product selectivity and the dynamic modeling of the slurry reactor responds quite well to the load change conditions.

Other papers | 2020

Power Systems in the context of district heating and cooling networks as an integrated energy system approach -Regulations and Business Cases within the IEA DHC Annex TS3

Kneiske T, Kallert A, Cronbach D, Yu Y, Schmidt D, Johannsen R, Sorknæs P, Muschick D, Ianakiev A, Svensson I, Schmidt R, Terreros O, Widl E. Power Systems in the context of district heating and cooling networks as an integrated energy system approach - Regulations and Business Cases within the IEA DHC Annex TS3. 48. CIGRE conference 2020. July 2020.

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Integrated energy systems 1 couples power systems, district heating and cooling (DHC), and gas grids, thereby enabling the storage and distribution of energy across different infrastructure types. Supply and demand follow different patterns in these different domains, which can lead to synergies in generation, storage and consumption, if planned and managed as one energy system. An integrated approach has the potential to increase reliability, flexibility and supply safety and efficiency. Moreover, network coupling increases local utilization of renewables, avoiding problems in the distribution networks, as well as transmission losses. In addition, hybrid energy networks are a promising opportunity to manage and mitigate temporal imbalances of supply and demand in energy systems with a high share of volatile renewables, mainly PV and wind energy. The IEA DHC Annex TS3 provides a holistic approach for designing and assessing hybridization schemes, focusing on the district heating and cooling (DHC) networks and considering both technical (system configuration, operational strategy) and strategic aspects (business models, regulatory frame). These aspects will be discussed within the framework of the IEA DHC Annex TS3 in order to promote the benefits of DHC networks in an integrated energy system. Furthermore we can establish a common direction for the development and implementation of hybrid energy concepts. The IEA DHC Annex TS3 will connect existing national and international projects and thus benefit from interdisciplinary experience and exchange. The primary result of the IEA DHC Annex TS3 will be a guidebook including:  Analyses of available technologies and synergies / application areas  An overview of international case studies including simulation scenarios 1 Different alternative notations can be found in literature, e.g. multi-energy networks, hybrid energy networks, sector coupling, multi-domain networks, cross energy systems. However, since no standard definition is available, those notations are used synonymously.

Other papers | 2016

Possibility of industrial scale BioH2 production from product gas in existing dual fluidized bed biomass gasification plant

Jovanovic A, Stamenkovic M, Nenning L, Rauch R. Possibility of industrial scale BioH2 production from product gas in existing dual fluidized bed biomass gasification plant. 4th International Symposium on Environment Friendly Energies and Applications, EFEA 2016. 18 November 2016, Belgrade, Serbia.

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Conceptual solution of production of pure renewable hydrogen from wood gas or product derived from the commercial biomass steam gasification plant Güssing, Austria was carried out. The proposed process of product gas upgrading consisted of tree basic operations: (I) catalyzed water-gas shift (WGS) reaction, (II) gas drying and cleaning in a wet scrubber and (III) hydrogen purification by pressure swing adsorption. The tail gas or adsorbate can be used like fuel for gas engine for electrical energy production or like a boiler fuel for hot water-heat production.

Conference presentations and posters | 2009

Possibilities of Ash Utilisation from Biomass Combustion Plants

Obernberger I, Supancic K. Possibilities of Ash Utilisation from Biomass Combustion Plants, 17th European Biomass Conference 2009, 29th of June-3rd of July 2009, Hamburg, Germany. p 2373-2384.

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Other papers | 2017

Polygeneration of hydrogen and a gas mixture composed of H2 and CH4 via sorption enhanced reforming of biomass

Kraussler M, Priscak J, Benedikt F, Hofbauer H. Polygeneration of hydrogen and a gas mixture composed of H2 and CH4 via sorption enhanced reforming of biomass. 25th European Biomass Conference & Exhibition (oral presentation). June 2017, Stockholm, Sweden.

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Conference presentations and posters | 2010

PM emissions from old and modern biomass combustion systems and their health effects

Kelz J, Brunner T, Obernberger I, Hirvonen M, Javala P. PM emissions from old and modern biomass combustion systems and their health effects, 18th European Biomass Conference and Exhibition 2010, 3rd-7th of May 2010, Lyon, France. p 1231-1243.

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Reports | 2021

Planung zellularer Energiesysteme

Teil 1: Effektive integrierte Investitions- und Betriebsplanung von Energiezellen

VDE Verband der Elektrotechnik e.V. Energietechnische Gesellschaft (ETG)

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In einem zellularen Energiesystem wird die physikalische Balance zwischen Energieangebot und -nachfrage so weit als möglich bereits auf regionaler, lokaler Ebene hergestellt. Der zentrale Baustein dabei ist die Energiezelle. Sie kann Energie in Form von Wärme, Elektrizität oder Gas aufnehmen und/oder Elektrizität und Wärme (z. B. aus erneuerbaren Energien) selbst erzeugen, um so den eigenen Wärme- und Elektrizitätsbedarf zu decken. Energieüberschüsse können (elektrisch und/oder thermisch) gespeichert oder anderen Zellen im Nahbereich oder einem Energieversorger zur Verfügung gestellt werden. Ein Energiezellenmanagement kann in Koordination mit Nachbarzellen den Ausgleich von Erzeugung und Verbrauch über alle vorhandenen Energieformen organisieren.
Die Planung und der Betrieb zellularer Energiesysteme ist eine komplexe Aufgabe, da eine Vielzahl von dezentralen Energietechnologien, verschiedenste Ziele und auch Entscheidungsträger berück-sichtigt werden müssen.
Der vorliegende VDE Impuls beschreibt als ersten Schritt die Planung einer Energiezelle, welche mit Energieversorgern interagieren kann. Er ist der Auftakt einer Reihe weiterer Veröffentlichungen zur detaillierten Planung von Energiezellen und zellularen Energiesystemen.

Peer reviewed papers | 2019

Planning and implementation of bankable microgrids

Stadler M, Nasle A. Planning and implementation of bankable microgrids. The Electricity Journal 2019. 32:24-29.

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Currently, many Microgrid projects remain financially uncertain and not bankable for institutional investors due to major challenges in existing planning and design methods that require multiple, complex steps and software tools.

Existing techniques treat every Microgrid project as a unique system, resulting in expensive, non-standardized approaches and implementations which cannot be compared. That is, it is not possible to correlate the results from different planning methods performed by different project developers and/or engineering companies.

This very expensive individual process cannot guarantee financial revenue streams, cannot be reliably audited, impedes pooling of multiple Microgrid projects into a financial asset class, nor does it allow for wide-spread and attractive Microgrid and Distributed Energy Resource projects deployment.

Thus, a reliable, integrated, and streamlined process is needed that guides the Microgrid developer and engineer through conceptual design, engineering, detailed electrical design, implementation, and operation in a standardized and data driven approach, creating reliable results and financial indicators that can be audited and repeated by investors and financers.

This article describes the steps and methods involved in creating bankable Microgrids by relying on an integrated Microgrid planning software approach that unifies proven technologies and tested planning methods, researched and developed by the United States National Laboratory System as well as the US Department of Energy, to reduce design times.

Peer reviewed papers | 2019

Photoautotrophic production of poly-hydroxybutyrate – First detailed cost estimations

Panuschka S, Drosg B, Ellersdorfer M, Meixner K, Fritz I. Photoautotrophic production of poly-hydroxybutyrate – First detailed cost estimations. Algal Research 2019.41:101558.

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Political, economic and ecological reasons have recently been leading to efforts to replace fossil hydrocarbons and their products in a sustainable way. In order to replace fossil-based polymers, photoautotrophically produced polyhydroxybutryrates (PHBs), which are intracellular carbon storage products of nutrient-deprived microorganisms, seem to be a promising, biobased and biodegradable alternative. Although laboratory and pilot scale experiments have already been performed, no economic evaluation has been carried out so far. Consequently, valid claims on PHB production costs and the influence of different parameters, such as intracellular PHB-content, choice of cultivation system or location, cannot be made. In this study potential demonstration plants, equipped with different photoautotrophic cultivation systems and located at two sites, were designed to identify key parameters for a successful economic realization and implementation. Material and energy balances were determined to reveal specific PHB production costs for four different scenarios. Raw material and operating supply costs, expenditures for plant construction and operation as well as product amounts were determined using literature data for specified results from laboratory and pilot scale experiments. The lowest calculated PHB production price (24 € kg−1) accomplished in a thin-layer-system plant located in Southern Europe with 60% PHB-content of the produced biomass is significantly higher than the current market price of heterotrophically produced PHB. The most important cost factors in all scenarios are cultivation and harvesting costs accounting for 62 to 72% of the total specific production costs, followed by maintenance costs with a cost share of 11 to 14%. Therefore, the choice of a suitable cultivation system is the key driving factor for an economic PHB-production due to the currently high investment costs for photosynthetic biomass production systems. Specific production costs for a Southern compared to a Central European location amount to almost half of the costs.

Reports | 2022

PHB Producing Cyanobacteria Found in the Neighborhood— Their Isolation, Purification and Performance Testing

Meixner K, Daffert C, Bauer L, Drosg B, Fritz I. PHB Producing Cyanobacteria Found in the Neighborhood— Their Isolation, Purification and Performance Testing. 2022.9:178

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Cyanobacteria are a large group of prokaryotic microalgae that are able to grow photo-autotrophically by utilizing sunlight and by assimilating carbon dioxide to build new biomass. One of the most interesting among many cyanobacteria cell components is the storage biopolymer polyhydroxybutyrate (PHB), a member of the group of polyhydroxyalkanoates (PHA). Cyanobacteria occur in almost all habitats, ranging from freshwater to saltwater, freely drifting or adhered to solid surfaces or growing in the porewater of soil, they appear in meltwater of glaciers as well as in hot springs and can handle even high salinities and nutrient imbalances. The broad range of habitat conditions makes them interesting for biotechnological production in facilities located in such climate zones with the expectation of using the best adapted organisms in low-tech bioreactors instead of using “universal” strains, which require high technical effort to adapt the production conditions to the organism‘s need. These were the prerequisites for why and how we searched for locally adapted cyanobacteria in different habitats. Our manuscript provides insight to the sites we sampled, how we isolated and enriched, identified (morphology, 16S rDNA), tested (growth, PHB accumulation) and purified (physical and biochemical purification methods) promising PHB-producing cyanobacteria that can be used as robust production strains. Finally, we provide a guideline about how we managed to find potential production strains and prepared others for basic metabolism studies.

Conference presentations and posters | 2020

PHB from cyanobacteria - Why phototrophic biotechnology is interesting for Europe.

Fritz I, Drosg B, Meixner K, Daffert C, Troschl C, Silvestrini L. PHB from cyanobacteria - Why phototrophic biotechnology is interesting for Europe. Eurobiotech 2020. 24-26 September 2020.

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Other papers | 2016

Phase Sewparation Behaviour of FAME and Water

Bardolf R, Thoma C, Bosch K, Rauch R, Hofbauer H. Phase Sewparation Behaviour of FAME and Water. 24th European Biomass Conference & Exhibition (poster). June 2016, Amsterdam, Netherlands.

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Other Publications | 2019

Pflanzenkohle-Design - Beeinflussung der Kohleeigenschaften durch gezielte Prozessführung in der Herstellung

Martini S. Pflanzenkohle-Design - Beeinflussung der Kohleeigenschaften durch gezielte Prozessführung in der Herstellung. Big Biochar Day No 3. September 2019.

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Conference presentations and posters | 2014

Performances of a non-sulfided CoMo/SiO2-Al2O3 hydrocracking catalyst used in BtL Technology

Sauciuc A, Ganea R, Dumitrescu L, Rauch R, Hofbauer H. Performances of a non-sulfided CoMo/SiO2-Al2O3 hydrocracking catalyst used in BtL Technology, 4th International Symposium on Gasification and its Applications (iSGA-4) 2014, 2nd-5th of September 2014, Vienna, Austria.

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Peer reviewed papers | 2017

Performance of a water gas shift unit processing tar-rich product gas from a commercial dual fluidized bed biomass steam gasification plant which operates at partial load

Kraussler M, Binder M, Hofbauer H. Performance of a water gas shift unit processing tar-rich product gas from a commercial dual fluidized bed biomass steam gasification plant which operates at partial load. International Journal of Oil, Gas and Coal Technology. 2017;14(1-2): 32-48.

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In this paper, the performance of a water gas shift unit processing product gas from a commercial dual fluidised bed biomass steam gasification plant is studied. The experiments were carried out during a partial load operation of the gasification plant. In order to investigate a water gas shift process, a water gas shift unit, located at the site of the gasification plant in Oberwart, Austria, was used. The water gas shift unit consisted of three reactors in series filled with a commercial Fe'Cr-based catalyst and was operated with tar-rich product gas. No performance decrease of the water gas shift unit was observed during the partial load operation of the gasification plant. Furthermore, a CO conversion of 92% and a GCMS tar reduction of about 30% were reached. In addition, it was found that partial load operation of the gasification plant did not negatively affect the performance of the water gas shift unit.

Other papers | 2015

Performance of a Water Gas Shift Unit Processing Product Gas from Biomass Steam Gasification

Kraussler M, Binder M, Fail S, Rauch R, Bosch K, Hackel M, Hofbauer H. Performance of a Water Gas Shift Unit Processing Product Gas from Biomass Steam Gasification. 23rd European Biomass Conference & Exhibition (oral presentation). June 2015, Vienna, Austria.

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Other papers | 2015

Performance of a water gas shift pilot plant processing tar-rich product gas from a commercial biomass steam gasification plant operating at partial load conditions

Kraussler M, Binder M, Hofbauer H. Performance of a water gas shift pilot plant processing tar-rich product gas from a commercial biomass steam gasification plant operating at partial load conditions. International Bioenergy Exhibition and Asian Bioenergy Conference 2015. October 2015, Shanghai, China.

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Peer reviewed papers | 2015

Performance of a water gas shift pilot plant processing product gas from an industrial scale biomass steam gasification plant

Kraussler M, Binder M, Fail S, Bosch K, Hackel M, Hofbauer H. Performance of a water gas shift pilot plant processing product gas from an industrial scale biomass steam gasification plant. Biomass and Bioenergy. 4 August 2015;89:50-57.

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In this paper, the performance of a commercial Fe/Cr based catalyst for the water gas shift reaction was investigated. The catalyst was used in a water gas shift pilot plant which processed real product gas from a commercial biomass steam gasification plant with two different qualities: extracted before and extracted after scrubbing with a rapeseed methyl ester gas scrubber. The performance of the WGS pilot plant regarding these two different gas qualities was investigated. For this reason, extensive chemical analyses were carried out. CO, CO2, CH4, N2, O2, C2H6, C2H4, and C2H2 and H2S, COS, and C4H4 S were measured. In addition, GCMS tar and NH3 analyses were performed. Furthermore, the catalyst's activity was observed by measuring the temperature profiles along the reactors of the water gas shift pilot plant. During the 200 h of operation with both product gas qualities, no catalyst deactivation could be observed. A CO conversion up to 93% as well as a GCMS tar reduction (about 28%) along the water gas shift pilot plant was obtained. Furthermore, a specific H2 production of 63 g H2 per kg biomass (dry and ash free) was reached with both product gas qualities. No significant performance difference could be observed.

Other papers | 2013

Performance of a pellet boiler fired with agricultural fuels

Carvalho L, Wopienka E, Pointner C, Lundgren J, Verma VK, Haslinger W, et al. Performance of a pellet boiler fired with agricultural fuels. Appl Energy. 2013;104:286-96.

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The increasing demand for woody biomass increases the price of this limited resource, motivating the growing interest in using woody materials of lower quality as well as non-woody biomass fuels for heat production in Europe. The challenges in using non-woody biomass as fuels are related to the variability of the chemical composition and in certain fuel properties that may induce problems during combustion. The objective of this work has been to evaluate the technical and environmental performance of a 15. kW pellet boiler when operated with different pelletized biomass fuels, namely straw (Triticum aestivum), Miscanthus (Miscanthus× giganteus), maize (Zea mays), wheat bran, vineyard pruning (from Vitis vinifera), hay, Sorghum (Sorghum bicolor) and wood (from Picea abies) with 5% rye flour. The gaseous and dust emissions as well as the boiler efficiency were investigated and compared with the legal requirements defined in the FprEN 303-5 (final draft of the European standard 303-5). It was found that the boiler control should be improved to better adapt the combustion conditions to the different properties of the agricultural fuels. Additionally, there is a need for a frequent cleaning of the heat exchangers in boilers operated with agricultural fuels to avoid efficiency drops after short term operation. All the agricultural fuels satisfied the legal requirements defined in the FprEN 303-5, with the exception of dust emissions during combustion of straw and Sorghum. Miscanthus and vineyard pruning were the best fuels tested showing comparable emission values to wood combustion. © 2012 Elsevier Ltd.

Other papers | 2017

Performance of a mixed alcohol synthesis lab-scale process chain operated with wood gas from dual fluidized bed biomass steam gasification

Binder M, Weber G, Rauch R, Hofbauer H. Performance of a mixed alcohol synthesis lab-scale process chain operated with wood gas from dual fluidized bed biomass steam gasification. 5th Central European Biomass Conference (Poster). January 2017, Graz, Austria.

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Conference presentations and posters | 2018

Performance improvement of model-based control strategies in large-scale solar plants and its implementation details

Innerhofer P, Unterberger V, Luidolt P, Lichtenegger K, Gölles M. Performance improvement of model-based control strategies in large-scale solar plants and its implementation details. 5th International Solar District Heating Conference SDH. Graz, Austria: 2018.

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Other papers | 2013

Performance improvement of dual fluidized bed gasifiers by temperature reduction: The behavior of tar species in the product gas

Kirnbauer F, Wilk V, Hofbauer H. Performance improvement of dual fluidized bed gasifiers by temperature reduction: The behavior of tar species in the product gas. Fuel. 2013;108:534-42.

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To meet the aims of the worldwide effort to reduce greenhouse gas emissions, product gas from biomass steam gasification in DFB (dual fluidized bed) gasification plants can play an important role for the production of electricity, fuel for transportation and chemicals. Using a catalytically active bed material, such as olivine, brings advantages concerning tar reduction in the product gas. Experience from industrial scale gasification plants showed that a modification of the olivine occurs during operation due to the interaction of the bed material with ash components from the biomass and additives. This interaction leads to a calcium-rich layer on the bed material particles which influences the gasification properties and reduces tar concentration in the product gas. In this paper, the influence on the gasification performance, product gas composition and tar formation of a reduction of the gasification temperature are studied. A variation of the gasification temperature from 870 °C to 750 °C was carried out in a 100 kW pilot plant. A reduction of the gasification temperature down to 750 °C reduces the concentration of hydrogen and carbon monoxide in the product gas and increases the concentration of carbon dioxide and methane. The product gas volume produced per kg of fuel is reduced at lower gasification temperatures but the calorific value of the product gas increases. The volumetric concentration of tars in the product gas increases slightly until 800 °C and nearly doubles when decreasing the gasification temperature to 750 °C. The tars detected by gas chromatography-mass spectrometry (GCMS) were classified into substance groups and related to the fuel input to the gasifier and showed a decrease in naphthalenes and polycyclic aromatic hydrocarbons (PAHs) and an increase in phenols, aromatic compounds and furans when reducing the gasification temperature. The comparison with results from an earlier study, where the gasification properties of unused fresh olivine were compared with used olivine, underlines the importance of a long retention time of the bed material in the gasifier, ensuring the formation of a calcium-rich layer in the bed material. © 2012 Elsevier Ltd. All rights reserved.

Other papers | 2019

Performance evaluation of an electrostatic precipitator in a small-scale biomass boiler by using different biomass feedstocks

Kelz J, Zemann C, Muschick D, Hofmeister G, Gölles M. & Retschitzegger S. Performance evaluation of an electrostatic precipitator in a small-scale biomass boiler by using different biomass feedstocks. Proceedings 27th European Biomass Conference and Exhibition, 27-31 May 2019, Lisbon, Portugal.1932-1938.

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In order to evaluate the performance of an electrostatic precipitator (ESP), comprehensive test runs investigating both particulate matter (PM) and gaseous emissions were performed by using softwood pellets as well as alternative biomass feedstocks such as short rotation coppice (poplar) and biomass residues (maize). An ESP was directly integrated in a commercially available small-scale biomass boiler. Based on wet chemical analyses of the fuels, so-called fuel indexes were calculated to deliver primary information on the expected combustion behaviour. The overall aim was to determine appropriate operating conditions, to optimise combustion parameters in order to minimise PM and gaseous emissions as well as to inhibit ash related problems. This was done by an efficient combination of primary (air staging in combination with an innovative control system) and secondary measures (integration of an ESP) and showed an enormous potential for both, a stable plant operation and reduced PM emissions. Thus the findings provide the basis for developing a fuel flexible, low emission and highly efficient biomass boiler in the sector of small-scale combustion systems.

Peer reviewed papers | 2020

Performance Comparison between Two Established Microgrid Planning MILP Methodologies Tested On 13 Microgrid Projects

Stadler M, Pecenak Z, Mathiesen P, Fahy K, Kleissl J. Performance Comparison between Two Established Microgrid Planning MILP Methodologies Tested On 13 Microgrid Projects. Energies.2020;13:446

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Mixed Integer Linear Programming (MILP) optimization algorithms provide accurate and clear solutions for Microgrid and Distributed Energy Resources projects. Full-scale optimization approaches optimize all time-steps of data sets (e.g., 8760 time-step and higher resolutions), incurring extreme and unpredictable run-times, often prohibiting such approaches for effective Microgrid designs. To reduce run-times down-sampling approaches exist. Given that the literature evaluates the full-scale and down-sampling approaches only for limited numbers of case studies, there is a lack of a more comprehensive study involving multiple Microgrids. This paper closes this gap by comparing results and run-times of a full-scale 8760 h time-series MILP to a peak preserving day-type MILP for 13 real Microgrid projects. The day-type approach reduces the computational time between 85% and almost 100% (from 2 h computational time to less than 1 min). At the same time the day-type approach keeps the objective function (OF) differences below 1.5% for 77% of the Microgrids. The other cases show OF differences between 6% and 13%, which can be reduced to 1.5% or less by applying a two-stage hybrid approach that designs the Microgrid based on down-sampled data and then performs a full-scale dispatch algorithm. This two stage approach results in 20–99% run-time savings.

Other papers | 2008

Pelletfeuerungen mit thermoelektrischer Stromerzeugung

Friedl G, Moser W, Griesmayr S. Pelletfeuerungen mit thermoelektrischer Stromerzeugung, 10. Holzenergiesymposium 2008, 12th of September, Zürich, Swiss.

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Other Publications | 2014

Pellet off-gassing during storage: The impact of storage conditions and type of source material

Meier, F. Pellet off-gassing during storage: The impact of storage conditions and type of source material, Master Thesis, University of Natural Resources and Life Sciences Vienna, Vienna, Austria, 2014.

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Conference presentations and posters | 2012

Particulate matter emissions from small-scale biomass combustion systems – characterisation and primary measures for emission reduction

Brunner T. Particulate matter emissions from small-scale biomass combustion systems – characterisation and primary measures for emission reduction, IEA Bioenergy Conference 2012, 13th-15th of November 2012, Vienna, Austria.

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Peer reviewed papers | 2017

Particulate emissions from modern and old technology wood combustion induce distinct time-dependent patterns of toxicological responses in vitro.

Happo MS, Hirvonen MR, Uski O, Kasurinen S, Kelz J, Brunner T, Obernberger I, Jalava PI. Particulate emissions from modern and old technology wood combustion induce distinct time-dependent patterns of toxicological responses in vitro. Toxicology in Vitro. Volume 44, October 2017, Pages 164-171

Toxicology in Vitro.

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Toxicological characterisation of combustion emissions in vitro are often conducted with macrophage cell lines, and the majority of these experiments are based on responses measured at 24 h after the exposure. The aim of this study was to investigate how significant role time course plays on toxicological endpoints that are commonly measured in vitro. The RAW264.7 macrophage cell line was exposed to PM1 samples (150 μg/ml) from biomass combustion devices representing old and modern combustion technologies for 2, 4, 8, 12, 24 and 32 h. After the exposure, cellular metabolic activity, cell membrane integrity, cellular DNA content, DNA damage and production of inflammatory markers were assessed. The present study revealed major differences in the time courses of the responses, statistical differences between the studied samples mostly limiting to differences between modern and old technology samples. Early stage responses consisted of disturbances in metabolic activity and cell membrane integrity. Middle time points revealed increases in chemokine production, whereas late-phase responses exhibited mostly increased DNA-damage, decreased membrane integrity and apoptotic activity. Altogether, these results implicate that the time point of measurement has to be considered carefully, when the toxicity of emission particles is characterised in in vitro study set-ups.

Conference presentations and posters | 2015

Parameter Study with Sulfidized Molybdenum Catalyst for Mixed Alcohol Synthesis with Biomass-Derived Synthesis Gas

Weber G, Rauch R, Hofbauer H. Parameter Study with Sulfidized Molybdenum Catalyst for Mixed Alcohol Synthesis with Biomass-Derived Synthesis Gas, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (oral presentation)

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Conference presentations and posters | 2023

Overview on flexible bioenergy options and implementation

Thrän D, Mäki E, Lange N, Hennig C, Schmieder U, Schildhauer T, Kiel J, Kroon P, Schipfer F, Philbrook A, Andersson K, Higa C, Gölles M. Overview on flexible bioenergy options and implementation. 7. Mitteleuropäische Biomassekonferenz: CEBC 2023. 20. Jan 2023. Oral presentation.

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Conference presentations and posters | 2016

Overview on advanced biofuels technologies

Bacovsky D. Overview on advanced biofuels technologies. Bioenergy Australia 2016. November 2016, Brisbane, Australia.

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Peer reviewed papers | 2013

Overview of Forestry and Wood Fuel Supply Chains in Austria; Investment Costs and Profitability of Biomass Heating Plants in Austria; Business Models from Austria Covering the Entire Wood Heat Supply Chain

Otepka P, Kristöfel C, Strasser C, et al. Guidebook on Local Bioenergy Supply Based on Woody Biomass. Overview of Forestry and Wood Fuel Supply Chains in Austria; Investment Costs and Profitability of Biomass Heating Plants in Austria; Business Models from Austria Covering the Entire Wood Heat Supply Chain. ISBN 978-1-938681-98-1. 2013:2-36;57-112.

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Peer reviewed papers | 2019

Overview obstacle maps for obstacle‐aware navigation of autonomous drones

Pestana J, Maurer M, Muschick D, Hofer M, Fraundorfer F. Overview obstacle maps for obstacle-aware navigation of autonomous drones. Journal of Field Robotics 2019.

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Achieving the autonomous deployment of aerial robots in unknown outdoor environments using only onboard computation is a challenging task. In this study, we have developed a solution to demonstrate the feasibility of autonomously deploying drones in unknown outdoor environments, with the main capability of providing an obstacle map of the area of interest in a short period of time. We focus on use cases where no obstacle maps are available beforehand, for instance, in search and rescue scenarios, and on increasing the autonomy of drones in such situations. Our vision‐based mapping approach consists of two separate steps. First, the drone performs an overview flight at a safe altitude acquiring overlapping nadir images, while creating a high‐quality sparse map of the environment by using a state‐of‐the‐art photogrammetry method. Second, this map is georeferenced, densified by fitting a mesh model and converted into an Octomap obstacle map, which can be continuously updated while performing a task of interest near the ground or in the vicinity of objects. The generation of the overview obstacle map is performed in almost real time on the onboard computer of the drone, a map of size urn:x-wiley:15564959:media:rob21863:rob21863-math-0001 is created in urn:x-wiley:15564959:media:rob21863:rob21863-math-0002, therefore, with enough time remaining for the drone to execute other tasks inside the area of interest during the same flight. We evaluate quantitatively the accuracy of the acquired map and the characteristics of the planned trajectories. We further demonstrate experimentally the safe navigation of the drone in an area mapped with our proposed approach.

Peer reviewed papers | 2017

Overcoming the bottlenecks of anaerobic digestion of olive mill solid waste by two-stage fermentation

Stoyanova E, Lundaa T, Bochmann G, Fuchs W. Overcoming the bottlenecks of anaerobic digestion of olive mill solid waste by two-stage fermentation. Environmental Technology (United Kingdom). 16 February 2017;38(4): 394-405.

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Conference presentations and posters | 2015

Outlook for the Project: Future Application and Development of the AshMelT methods

Schwabl M, Wopienka E. AshMelT Workshop “Outlook for the Project: Future Application and Development of the AshMelT methods” (held during de World Sustainable Energy Days 2015), 25th-27th of February, Wels, Austria, 2015.

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Conference presentations and posters | 2020

Optimizing of a hydrogen production plant by optimization of the CO2 removal step

Loipersböck J. Optimizing of a hydrogen production plant by optimization of the CO2 removal step. 6th Central European Biomass Conference (oral presentation) 2020.

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Hydrogen production in 2010 was estimated to 50 Mt/a. 96 % of today’s hydrogen is produced by converting fossil fuels in thermochemical processes. As main conversion technology steam reforming of natural gas and naphtha has been established. Hydrogen is mainly used in refineries, for ammonia production and in several chemical production plants. Hydrogen is also seen as a promising alternative energy carrier for the transport sector. Therefor an increasing demand on hydrogen over the next years can be assumed.  
To substitute fossil produced hydrogen several renewable hydrogen routes have been established. Beside electrolysis of water also steam reforming of biogas, methane pyrolysis and gasification technologies have been developed. This work will focus on hydrogen production based on dual fluidized bed gasification of biomass.  
Dual fluidized bed gasification gives the possibility to establish a renewable hydrogen production route and substitute fossil fuels. A hydrogen production plant consisting of a dual fluidized bed gasifier, a water gas shift stage, a CO2 removal, a pressure swing adsorption and a steam reformer were erected and operated over 1000 h. The gathered data was validated and a model for up-scaling was developed. A benchmark size of 10 MW fuel input power was used as base for economic estimations. As described in previous work an overall efficiency of 55 % can be achieved, which is comparable to alternative technologies. Compared to other renewable routes, hydrogen production based on dual fluidized bed gasification gives the possibility of a fuel flexible system for continuous hydrogen production.  
Hydrogen production derived by DFB gasification of wood is a reliable process, which needs to be optimized due to economic reasons. Special attention has to be paid on the CO2 removal, to obtain an economic efficient process.  
In this study a parameter variation of the CO2 removal, which consists of absorption and desorption column, was done. Mono-ethanol-amine (MEA) was used as a solvent. One focus of the experimental investigations was the desorption at low temperatures to gain the possibility of using temperature levels which are common in district heat grids. For the experiments real synthesis gas with impurities was used. Over the gas cleaning steps of the hydrogen production plant, impurities were removed and hydrogen content was increased. To increase the efficiency of the CO2 removal and further the hydrogen production, a parameter study was done. A good correlation between separation efficiency and desorption temperature could be observed.  
Economics were calculated comparing natural gas steam reforming, electrolysis and hydrogen production based dual fluidized bed gasification. First results show a high potential for establishing the BioH2 plant as a commercial production plant. An economic plant operation with wood chips can be achieved at plant sizes of 20-30 MW fuel input power. A switch to lower quality biomass can reduce the economic feasible plant size even further.  
Keywords: hydrogen, up-scaling, economics, CO2 removal

Other Publications | 2023

Optimized Planning of Microgrids and Smart Energy Communities

Aigenbauer S, Stadler M, Liedtke P, Sturmlechner R, Maier C, Mansoor M, Oberbauer C, Alavi F, Houben N, Haas R. Optimized Planning of Microgrids and Smart Energy Communities. BEST Center Day. 28 June 2023

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Microgrids generate and store energy for self consumption (electricity, heating, cooling, etc.). Decentralized and renewable generation and storage technologies, as well as energy strategies increase efficiency, resilience, grid stability, independency of imports, sustainability, and climate neutrality.

Other Publications | 2018

Optimization of Heating, Electricits and Cooling Services in a Microgrid to Increase the Efficiency and Reliability

Lichtenegger K, Stadler M, Moser A, Zellinger M, Muschick D, Gölles M, Steinlechner M, Ayoub T, Gerardts B. Optimization of Heating, Electricits and Cooling Services in a Microgrid to Increase the Efficiency and Reliability. PoserGen Europe Wien, 20. Juni 2018

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We briefly review the general concept and expected market potential of microgrids, then discuss the
optimization challenges associated with planning local cross-sectorial energy systems. A fair technology-
neutral approach to this optimization task leads to a hard problem, which has to be tackled with
advanced methods of mathematical optimization.
The power of this approach is illustrated in a case study, concerning the replacement of heating systems
in an alpine valley. In this case study we see both the potential for cost reduction and for the reduction
of CO2 emissions by an integrated planning approach

Peer reviewed papers | 2015

Optimization of a 50 MW bubbling fluidized bed biomass combustion chamber by means of computational particle fluid dynamics

Kraft S, Kuba M, Kirnbauer F, Bosch K, Hofbauer H. Optimization of a 50 MW bubbling fluidized bed biomass combustion chamber by means of computational particle fluid dynamics. Biomass and Bioenergy. 4 August 2015;89:31-39.

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An efficient utilization of biomass fuels in power plants is often limited by the melting behavior of the biomass ash, which causes unplanned shutdowns of the plants. If the melting temperature of the ash is locally exceeded, deposits can form on the walls of the combustion chamber. In this paper, a bubbling fluidized bed combustion chamber with 50 MW biomass input is investigated that severely suffers deposit build-up in the freeboard during operation. The deposit layers affect the operation negatively in two ways: they act as an additional heat resistance in regions of heat extraction, and they can come off the wall and fall into the bed and negatively influence the fluidization behavior. To detect zones where ash melting can occur, the temperature distribution in the combustion chamber is calculated numerically using the commercial CPFD (computational particle fluid dynamics) code, Barracuda Version 15. Regions where the ash melting temperature is exceeded are compared with the fouling observed on the walls in the freeboard. The numerically predicted regions agree well with the observed location of the deposits on the walls. Next, the model is used to find an optimized operating point with fewer regions in which the ash melting temperature is exceeded. Therefore, three cases with different distributions of the inlet gas streams are simulated. The simulations show if the air inlet streams are moved from the freeboard to the necking area above the bed a more even temperature distribution is obtained over the combustion chamber. Hence, the areas where the ash melting temperatures are exceeded are reduced significantly and the formation of deposits in the optimized operational mode is much less likely.

Conference presentations and posters | 2020

Optimization based planning of energy systems

Zellinger M, Optimization based planning of energy systems. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Other Publications | 2019

Optimization Based Design and Control of Distributed Energy Resources and Microgrids

Stalder M, Optimization Based Design and Control of Distributed Energy Resources and Microgrids. LetsCluster, Lighthouse Summit in the heart of Europe: Smart Energy Generation - Management - Optimization, Smart Home / Building, Interface to the Smart Grid, Microgrids, Electric Grid of the Future, Sector Linking, Graz, Österreich, 25 - 27 März 2019

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Conference presentations and posters | 2014

Optimising the heating system of a low energy house

Rimoldi M, Carlon E. Optimising the heating system of a low energy house, Word Sustainable Energy Days next 2014, 26th-28th of February 2014, Wels, Austria.

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Other papers | 2017

Optimisation of the post-consumer and demolition wood supply and value chain

Dißauer C, Kienzl N, Kunter A, Meirhofer M, Pointner C, Schwarzbauer P, Sommersacher P, Strasser C, Wellacher M. Optimisation of the post-consumer and demolition wood supply and value chain. 5th Central European Biomass Conference (Poster). January 2017, Graz, Austria.

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Other Publications | 2017

Optimisation of continuous gas fermentation by immobilisation of acetate-producing Acetobacterium woodii.

Steger, F, Rachbauer L, Windhagauer M, Montgomery LFR, Bochmann G. Optimisation of continuous gas fermentation by immobilisation of acetate-producing Acetobacterium woodii. Anaerobe. Available online 22 June 2017

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Peer reviewed papers | 2017

Optimisation of continuous gas fermentation by immobilisation of acetate-producing Acetobacterium woodi

Steger, F, Rachbauer L, Windhagauer M, Montgomery LFR, Bochmann G. Optimisation of continuous gas fermentation by immobilisation of acetate-producing Acetobacterium woodi. Anaerobe. August 2017;46: 96-103

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Conference presentations and posters | 2010

Optimisation of biomass grate furnaces with a new 3D packed bed combustion model - on example of a small-scale underfeed stoker furnace

Mehrabian R, Scharler R, Weissinger A, Obernberger I. Optimisation of biomass grate furnaces with a new 3D packed bed combustion model - on example of a small-scale underfeed stoker furnace, 18th European Biomass Conference and Exhibition 2010, 3rd-7th of May 2010, Lyon, France. p 1175-1183.

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The design and optimisation of a biomass grate furnace requires accurate and efficient models for the
combustion process on the grate as well as the turbulent reactive flow in the combustion chamber. Computational Fluid Dynamics (CFD) have been successfully applied for gas phase combustion. However, no numerical models for the biomass packed bed combustion, which can be used as engineering design tools, are commercially available at present. This paper presents an innovative 3D CFD model for biomass packed bed combustion consisting of an Euler-Granular model for hydrodynamics of gas-particle multiphase flow and a thermally thin particle model for combustion of biomass particles. Modelling the particle trajectories and the thermal conversion of each particle in the bed constitutes the simulation of the entire bed combustion. The simulation of a small-scale underfeed stoker furnace of KWB has been successfully performed by the application of the new packed bed combustion model. The positions of the drying, pyrolysis and char burnout zones in the fuel bed as well as the temperature distribution among the particles seem to be plausible and could be confirmed by observations. Furthermore, a good qualitative agreement concerning the flue gas temperatures measured by thermocouples at different positions in the combustion chamber, and CO emissions measured at boiler outlet could be achieved. The new packed bed model provides the advantages of considering the release profiles of species and energy from the fuel bed close to reality and enables to consider the chemical compositions, size and physical properties of the fuel particles as well as the influence of primary air
distribution and grate motion on the particle trajectories.

Other Publications | 2008

Optimierung einer biomassebefeuerten 10 kWth-Mikro-Kraft-Wärme-Kopplung mit Thermoelektrischem Generator

Lohr, M. Optimierung einer biomassebefeuerten 10 kWth-Mikro-Kraft-Wärme-Kopplung mit Thermoelektrischem Generator, Master Thesis, Fachhochschule Oberösterreich, Wels, Austria, 2008.

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The availability of energy is important to our every day lives. Biomass-fuelled heating systems are comfortable and reach an efficiency form over 90 %. With a thermoelectric generator (TEG) it’s possible to convert a part of the heat directly into electrical power and so become self sufficient from electicity. The purpose of this thesis was to optimise an existing prototype of a combined heat and power (CHP) plant based on a pellet heating system and a thermoelectric generator. Balancing the energy flows, especially the losses, was also part of the thesis.
Tests with the prototype were done. Some with the originial prototype, some with additional insulation and some with preheating the combustion air. To examine the part load behaviour, tests were done at 10, 7 and 4 kW fuelheat input.
By insulating the TEG the performance rose from 153 W to 174 W. The insulation and the preheating of the combustion air from room temperature to 350 degree lead to an power output from 194 watt. All at 10 kW fuellheat input. Finally the following conclusions can be drawn: For the series product it is recommended to optimize the insulation of the TEG. As the preheating of the combustion air didn’t lead to the expected effects it should be left out.

Other Publications | 2013

Optimierung des Emissionsverhaltens eines Ofens mittels primären und sekundären Maßnahmen am Beispiel des Scheitholzofens

Rieger, B. Optimierung des Emissionsverhaltens eines Ofens mittels primären und sekundären Maßnahmen am Beispiel des Scheitholzofens, Master Thesis, Fachochschule Technikum Wien, Vienna, Austria, 2013.

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The use of biomass in manually charged room heating appliances to cover the domestic heating demand has traditionally been of a high percentage in the European Union. As a result of continued or even increased use of firewood stoves, the enhancement of available stoves is a declared objective of the European Union.
Therefore, an example-optimization of the firewood stove Stûv 16/78-in (available on the European market) was performed in preparation of this paper. There was a primary- and a secondary optimization carried out to quantify the potential of optimization. When optimizing, the gas and particulate emissions was considered. The operating behavior were measured and evaluated by performing combustion experiments on a specially designed test rig.
The primary optimization is divided into five sub-steps. Each Step was quantified by gas analysis. The achieved reduction of particulate emissions was measured before and after the entire primary optimization.
In comparison to the delivery condition it was possible to reduce the CO emissions to one quarter and the particulate emissions from 100 mg / mn³ to 39 mg / mn³ over the course of the primary optimization.
As a secondary optimization, a Catalyst was implemented. The used catalyst is a solid-state catalyst in the modification of a heterogeneous supported catalyst in the shape of honeycomb, which is marketed by Clariant International Ltd. under the name "EnviCat ® Longlife Plus". The catalytically active materials platinum and palladium are used.
After a strictly implemented primary optimizations, a further reduction to half of emissions was achieved by the integration of the catalyst even though a bypass of 20 % had to be integrated to ensure the operating safety.

Reports | 2022

Optimiertes Regelungs- und Betriebsverhalten thermisch aktivierter Gebäude zukünftiger Stadtquartiere (ÖKO-OPT-AKTIV)

Muschick D, Kaisermayer V, Moser A, Gölles M, Heimrath R, Brandl D, Mach T, Ribas-Tugores C, Ramschak T, Oswald S, Polster M, Lackner F, Eibisberger K, Nebel M. Optimiertes Regelungs- und Betriebsverhalten thermisch aktivierter Gebäude zukünftiger Stadtquartiere (ÖKO-OPT-AKTIV). Stadt der Zukunft 6. Ausschreibung. BMK. Schriftenreihe 60/2023. Jänner, 2022. Deutsch, 76 Seiten.

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Peer reviewed papers | 2021

Optimal planning of thermal energy systems in a microgrid with seasonal storage and piecewise affine cost functions

Mansoor M, Stadler M, Zellinger M, Lichtenegger K, Auer H, Cosic A. Optimal planning of thermal energy systems in a microgrid with seasonal storage and piecewise affine cost functions. Energy. 2021:215;119095.

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The optimal design of microgrids with thermal energy system requires optimization techniques that can provide investment and scheduling of the technology portfolio involved. In the modeling of such systems with seasonal storage capability, the two main challenges include the low temporal resolution of available data and the non-linear cost versus capacity relationship of solar thermal and heat storage technologies. This work overcomes these challenges by developing two different optimization models based on mixed-integer linear programming with objectives to minimize the total energy costs and carbon dioxide emissions. Piecewise affine functions are used to approximate the non-linear cost versus capacity behavior. The developed methods are applied to the optimal planning of a case study in Austria. The results of the models are compared based on the accuracy and real-time performance together with the impact of piecewise affine cost functions versus non-piecewise affine fixed cost functions. The results show that the investment decisions of both models are in good agreement with each other while the computational time for the 8760-h based model is significantly greater than the model having three representative periods. The models with piecewise affine cost functions show larger capacities of technologies than non-piecewise affine fixed cost function based models.

Peer reviewed papers | 2020

Optimal operation of residential heating systems with logwood boiler, buffer storage and solar thermal collector

Zemann C, Deutsch M, Zlabinger S, Hofmeister G, Gölles M, Horn M. Optimal operation of residential heating systems with logwood boiler, buffer storage and solar thermal collector. Biomass and Bioenergy, 2020,140:105622.

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Modern central heating systems with logwood boilers are comprised of the boiler, a buffer storage and solar thermal collectors. Conventional control strategies for these heating systems do not coordinate the utilization of all components. This can lead to a sub-optimal operation of the entire heating system resulting in a loss of efficiency and increased pollutant emissions. This contribution presents a control strategy which considers all components of the heating system including the user and forecasts for the solar yield and heat demand. It determines and carries out an optimal operating strategy that improves the user utility and maximizes the heating system efficiency while also ensuring a clean and efficient combustion. The control strategy continuously learns the user behavior and instructs the user when to refill the logwood boiler and how much fuel to use. The new control strategy was verified through test runs performed at an experimental setup consisting of a commercially available logwood boiler with a nominal capacity of 28 kW , two buffer storages with a capacity of 1.5 m3 each and a heating device with a thermal output of up to 12 kW simulating a solar thermal collector. During these test runs, the CO emissions were reduced 93.6 %by in the main combustion phase, 7.1 % more solar yield was utilized, the buffer losses were reduced by - 16.9 % and the overall efficiency was increased by 3.1 % . Thus, the application of this control strategy resulted in a significantly improved user utility and heating system efficiency.

Other Publications | 2021

Optimal operation of cross-ownership district heating and cooling networks

Muschick D, Kaisermayer V, Gölles M, Horn M.Optimal operation of cross-ownership district heating and cooling networks. 20th European Roundtable on Sustainable Consumption and Production. 9. Sep 2021. Graz. Oral Presentation.

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Peer reviewed papers | 2023

Optimal dispatch of a multi-energy system microgrid under uncertainty: a renewable energy community in Austria

Houben N, Cosic A, Stadler M, Mansoor M, Zellinger M, Auer H, Ajanovic A, Haas R. Optimal dispatch of a multi-energy system microgrid under uncertainty: a renewable energy community in Austria. Applied Energy. 1 May 2023.337:120913

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Microgrids can integrate variable renewable energy sources into the energy system by controlling flexible assets locally. However, as the energy system is dynamic, an effective microgrid controller must be able to receive feedback from the system in real-time, plan ahead and take into account the active electricity tariff, to maximize the benefits to the operator. These requirements motivate the use of optimization-based control methods, such as Model Predictive Control to optimally dispatch flexible assets in microgrids. However, the major bottleneck to achieve maximum benefits with these methods is their predictive accuracy. This paper addresses this bottleneck by developing a novel multi-step forecasting method for a Model Predictive Control framework. The presented methods are applied to a real test-bed of a renewable energy community in Austria, where its operational costs and CO2 emissions are benchmarked with those of a rule-based control strategy for Flat, Time-of-Use, Demand Charge and variable energy price tariffs. In addition, the impact of forecast errors and electric battery capacity on energy community operational savings are examined. The key results indicate that the proposed controller can outperform a rule-based dispatch strategy by 24.7% in operational costs and by 8.4% in CO2 emissions through optimal operation of flexibilities if it has perfect foresight. However, if the controller is deployed in a realistic environment, where forecasts for electrical load and PV generation are required, the same savings are reduced to 3.3% for cost and 7.3% for CO2, respectively. In such environments, the proposed controller performs best in highly dynamic tariffs such as Time-of-Use and Real-time pricing rates, achieving real cost savings of up to 6.3%. These results show that the profitability of optimization-based control of microgrids is threatened by forecast errors. This motivates future research on control strategies that compensate for forecast errors in real-world operation and more accurate forecasting methods.

Reports | 2021

OptEnGrid Optimal integration of heat, electricity and gas systems to increase efficiency and reliability

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OptEnGrid is a cross-sectoral multi-energy system optimization tool for the optimal planning and dispatch of the Distributed Energy Resource (DER) technologies in smart- and microgrids. The methodology of OptEnGrid considers an optimization model which is based on Mixed-Integer Linear Programming (MILP) framework. The following sub-sections provide more details about the energy flow and system optimization inside OptEnGrid and the choice of the optimization over simulation

Other Publications | 2023

Operational optimization and error detection in biomass boilers by model based monitoring: methods and practice

Zemann C, Niederwieser H, Gölles M. Operational optimization and error detection in biomass boilers by model based monitoring: methods and practice. 7. Mitteleuropäische Biomassekonferenz: CEBC 2023. 20. Jan 2023. Oral presentation.

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One of the main tasks for operators of medium- and large-scale biomass boilers is the continuous operational monitoring of these plants in order to assess their performance, detect errors and identify possibilities for operational optimization. However, due to the high complexity of this task, errors are frequently detected too late or not at all, which can lead to even more costly secondary errors. In addition, possibilities for optimization remain unused in many existing plants, resulting in unnecessary pollutant emissions and low efficiencies.
To assist operators in performing this task and to achieve a high level of automation, methods for the automated, model-based monitoring of such plants have been focus of recent research activities. In this contribution, we will discuss the numerous possibilities provided by the application of such methods in a practical context. For this purpose, we present selected results from previous activities, demonstrating how methods for model-based monitoring were applied at combustion plants and used to enable automated error detection and support operational optimization.


Exemplary result 1: We developed a soft-sensor which accurately estimates the non-measurable internal state of heat exchangers and implemented it at a large-scale combustion plant with a nominal capacity of 38.2 MW. This soft-sensor uses a dynamic mathematical model of the heat exchanger in combination with measured data to determine a new estimate for the heat exchanger’s internal state every second. Based on this estimate, the soft-sensor accurately detects fouling and determines the non-measurable flue gas mass flow in real time. The estimated flue gas mass flow was used in a model-based control strategy which resulted in significant improvements of the combustion plant’s operational behaviour and load modulation capabilities. These results are discussed in this contribution.


Exemplary result 2: We developed a method for the real-time estimation of non-measurable fuel properties, i.e. chemical composition, bulk density, lower heating value, in biomass boilers. These estimates were subsequently used in a model-based control strategy and enabled the improvement of the biomass boiler’s fuel flexibility. Results of this estimator achieved for different biomass fuels, e.g. poplar wood chips, corncob grits and standard wood pellets, are discussed in this contribution.
On the basis of these selected results, it will be examined which possibilities arise from the use of methods for model-based monitoring in biomass boilers and also how these results can be extended to other technologies such as biomass gasifiers.

Peer reviewed papers | 2021

Operation of coupled multi-owner district heating networks via distributed optimization

Kaisermayer V, Muschick D, Horn M, Gölles M. Operation of coupled multi-owner district heating networks via distributed optimization. Energy Reports. 2021 Okt;7(Suppl. 4):273-281. https://doi.org/10.1016/j.egyr.2021.08.145

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The growth of district heating and cooling (DHC) networks introduces the possibility of connecting them with neighbouring networks. Coupling networks can save costs by reducing operating hours of peak load or backup boilers, or free up production capacity for network expansion. Optimization-based energy management systems (EMS) already provide operators of individual DHC networks with solutions to the unit commitment and economic dispatch problem. They are especially useful for complex networks with multiple producers and integrated renewable energy sources, where incorporating forecasts is important. Time-dependent constraints and network capacity limitations can easily be considered. For coupled networks, a centralized optimization would provide a minimum with respect to an objective function which can incorporate fuel costs, operational costs and costs for emissions. However, the individual coupled networks are generally owned by different organizations with competing objectives. The centralized solution might not be accepted, as each company aims to optimize its own objective. Additionally, all data has to be shared with a centralized EMS, and it represents a single point of failure. A decentralized EMS may therefore be a better choice in a multi-owner setting. In this article, a novel decentralized EMS is presented that can handle multi-owner structures with cooperative and non-cooperative coupling. Each local EMS solves its own optimization problem, and an iterative Jacobi-style algorithm ensures consensus among the networks. The distributed EMS is compared to a centralized EMS based on a representative real-world example consisting of three coupled district heating networks operated by two companies.

Other Publications | 2021

Operation of Coupled Multi-Owner District Heating Networks via Distributed Optimization

Muschick D, Gölles M, Kaisermayer V, Horn M. Operation of Coupled Multi-Owner District Heating Networks via Distributed Optimization.17th International Symposium on District Heating and Cooling. Nottingham Trent University, Nottingham, United Kingdom. 7. Sep 2021. Oral Presentation. [online]

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The simultaneous operation of multiple connected heating networks can be handled by optimization techniques. However, a global optimum might not represent a good operating strategy if the networks belong to different owners and thus might habe competing interests. An approach from game theory then needs to be applied, which finds a generalized Nash equilibrium instead.

Conference presentations and posters | 2012

Operation Experience & Developments at Industrial Plants with Dual‐Fluid Gasification

Hofbauer H. Operation Experience & Developments at Industrial Plants with Dual‐Fluid Gasification, 20th European Biomass Conference 2012, 18th-22nd of June 2012, Milano, Italy.

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Conference presentations and posters | 2013

Operation characteristics of a bulk catalyst in a test stand under similar conditions to a firewood stove

Wöhler M, et al. Operation characteristics of a bulk catalyst in a test stand under similar conditions to a firewood stove, Word Sustainable Energy Days next 2013, 27th-28th of February 2013, Wels, Austria.

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Conference presentations and posters | 2015

Operation and Efficiency of a Wood-Pellet Fired 5 KWel Stirling

Aigenbauer S, Schnetzinger R, Höftberger E, Schmidl C, Haslinger W. Operation and Efficiency of a Wood-Pellet Fired 5 KWel Stirling, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Other Publications | 2013

Online-Monitoring von Korrosionsvorgängen in Biomasse-befeuertenAnlagen

Bernsteiner, C. Online-Monitoring von Korrosionsvorgängen in Biomasse-befeuertenAnlagen, Master Thesis, Technische Universität Graz, Graz, Austria, 2013.

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Für den ökonomisch und ökologisch effizienteren Betrieb von Dampfkesselanlagen ist die Untersuchung von Korrosionsvorgängen in Wärmetauschern, verursacht durch das Rauchgas aus einer Biomasse-Feuerung, notwendig. Daher wurden bei Bioenergy 2020+ kurzzeitige Korrosionsversuche im Umfang von 300h Betriebszeit an einem Wärmetauscherstahl 13CrMo4-5 mit einer ONLINE-Korrosionssonde der Firma Corrmoran GmbH für die Erstellung eines empirischen Korrosionsmodells durchgeführt. Als Brennstoffe dienten Waldhackgut, Weizenstrohpellets und Altholz. Die Messung benötigt eine Ionen leitende Deckschicht, die sich erst am Beginn des Versuchs aufbaut. Aufgrund der fehlenden Deckschicht wird daher zu Beginn der Messung der Korrosionsleitwert unterschätzt. Daraus ergeben sich systematische Messfehler. Ziel dieser Arbeit war die Eruierung des Zusammenhanges zwischen Messfehler und Versuchszeit. Dabei stellten sich zwei systematische Messfehler als relevant heraus: •Die Abzehrrate ist zum Korrosionsleitwert proportional. Daher wird die Abzehrrate während der Eingangsphase der Messung unterschätzt. •Die Abzehrrate berechnet sich aus dem Korrosionsleitwert, multipliziert mit einem Kalibrierungsfaktor. Dabei ergibt sich der Kalibrierungsfaktor aus dem Verhältnis des gesamten korrosionsbedingten Materialverlustes über die gesamte Versuchsdauer, dividiert durch den über denselben Zeitraum integrierten Korrosionsleitwert. Aufgrund des zu Beginn unterschätzten Korrosionsleitwertes wird der Kalibrierungsfaktor und somit die Abzehrrate, berechnet aus dem reproduzierbaren Signal, überschätzt. Die Literaturrecherche zeigte, dass die Kinetik bei der Hochtemperaturkorrosion bei konstant gehaltenen korrosionsrelevanten Parametern einen linearen, parabolischen oder paralinearen Verlauf einnehmen kann. Die kleinstmögliche Abzehrrate und somit der kleinstmögliche Korrosionsleitwert zu Beginn der Messung ergibt sich bei der Annahme eines linearen Verlaufs, welcher die möglicherweise erhöhten Abzehrraten der Initialkorrosion nicht mitberücksichtigt. Aus dieser Annahme konnte der kleinstmögliche Korrekturfaktor cmin berechnet werden. Dazu mussten die Daten bei konstant gehaltenen Parametern gefiltert und daraus der zeitlich integrierte Korrosionsleitwert PL,Messung gebildet werden. Das Verhältnis von PL,Messung mit einem über die gesamte Versuchszeit konstant angenommenen zeitlich integrierten Korrosionsleitwertes PL,linear ergibt den Korrekturfaktor, der multipliziert mit den ursprünglich bei gleichen Parametern bestimmten Abzehrraten eine neue Abzehrrate k(t)neu ergibt. Der Vergleich mit den Ergebnissen eines Langzeitversuches unter ähnlichen Betriebsbedingungen in einem Biomasse-Heizkraftwerk zeigte dadurch eine Verbesserung der Abweichung der Kurzzeitversuche von 125% auf 55%. Aufgrund der Parametervariationen sowie der Temperaturschwankungen, verursacht durch Ein- und Ausschaltvorgänge der Anlage, haben die bei konstanten Parametern bestimmten Korrekturfaktoren für die durchgeführten Versuche nur bedingt Gültigkeit. Daher wurde in einem weiteren Schritt ein Korrekturfaktor cmin,var bestimmt, welcher alle Daten der Versuchsserie berücksichtigt. Dazu wurde das Signal der Eingangsphase durch ein gleichlanges reproduzierbares Signal, gemessen unter denselben Bedingungen am Ende der Versuchsserien, ersetzt. Es ergibt sich aus dem Verhältnis der zeitlich integrierten Korrosionsleitwerte PL,Messung der Originalkurve zu PL,idealisiert des idealisierten Verlaufs der Korrekturfaktor cmin,var. Dieser hat aufgrund der Berücksichtigung aller gesammelten Daten für alle bei den Versuchen bestimmten Abzehrraten Gültigkeit. Durch cmin,var konnte eine Reduktion der Abweichung auf 110% erreicht werden. Diese wird auf die im Gegensatz zur Langzeitmessung im Biomasse-Heizkraftwerk unterschiedliche Versuchsmethode sowie auf den unbekannten Einfluss der möglicherweise erhöhten Abzehrraten der Initialkorrosion zurückgeführt.  

Peer reviewed papers | 2020

Online determination of potassium and sodium release behaviour during single particle biomass combustion by FES and ICP-MS

Paulauskas R, Striūgas N, Sadeckas M, Sommersacher P, Retschitzegger S, Kienzl N. Online determination of potassium and sodium release behaviour during single particle biomass combustion by FES and ICP-MS. Science of the Total Environment. 2020;746:141162.

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This study focuses on the determination of alkali release from wood and straw pellets during combustion. The aim is to expand the knowledge on the K and Na release behaviour and to adopt chemiluminescence-based sensors for online monitoring of alkali detection which can be applied for the prevention of fouling formation in low quality biomass combustion plants. Flame emission spectrometry (FES) was used for optical detection of chemiluminescence spectra of K and Na using optical bandpass filters mounted on an ICCD (Intensified Charge Coupled Device) camera. FES data were verified by additional experiments with a single particle reactor (SPR) coupled with an inductively coupled plasma mass spectrometer (ICP-MS). Using both techniques, the release profiles of K and Na during a single pellet combustion at 1000 °C were determined and obtained K* and Na* emission intensities directly correlated with the results from the ICP-MS. It was determined that the emission intensity of alkali radicals depends on alkali concentrations in the samples and K and Na radical emission intensities increase with increasing alkali amounts in the samples. The ICP-MS data revealed that the release of K and Na mainly takes place during the stage of devolatilization. During devolatilization, almost all potassium and sodium are released from wood samples, while only 65–90% of K and 74–90% of Na are released from straw samples. Based on the results, the flame emission spectroscopy technique is capable to fully detect released alkali metals in the gas phase during combustion and proves a possibility to use flame emission sensors for monitoring the release of alkali species from biomass during combustion processes.

Peer reviewed papers | 2024

On the characteristic polynomial of the dynamic matrix of linear time-invariant multivariable systems in Luenberger's canonical forms

Niederwieser H, Reichhartinger M. On the characteristic polynomial of the dynamic matrix of linear time-invariant multivariable systems in Luenberger's canonical forms. Automatica. April 2024.162:11532

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This article presents a general representation of the characteristic polynomial of the dynamic matrix for multivariable systems in Luenberger’s canonical forms. The characteristic polynomial is given by means of the determinant of a polynomial matrix of substantially lower order. Therein, the polynomial coefficients of the single elements are the coefficients of the corresponding blocks of the dynamic matrix. The proposed representation of the characteristic polynomial can be helpful for the design of state-feedback controllers and state observers which is demonstrated by a numerical example.

Other Publications | 2016

On site monitoring and dynamic simulation of a low energy house heated by a pellet boiler

Carlon E, Schwarz M, Prada A, Golicza L, Verma V, Baratieri M, Gasparella A, Haslinger W, Schmidl C. On site monitoring and dynamic simulation of a low energy house heated by a pellet boiler. 15 March 2016;116: 296-306.

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Prefabricated low energy houses are becoming increasingly popular thanks to their low cost and high energy performance. Heating systems installed in these houses should be optimally designed and controlled, to ensure thermal comfort for the whole heating season.

This study presents the on-site monitoring and dynamic simulation of a low energy house heated by a pellet boiler via a floor heating system. The house combines a lightweight envelope, a heat distribution system with a high thermal inertia and a biomass-based heat supply. The one-year monitoring campaign allowed to closely investigate the system's response to the heat demand. Moreover, a coupled simulation of the house and its heating and hot water supply system was set-up, calibrated, and validated against measured indoor temperature profiles and energy consumptions. Root mean square deviations between simulated and measured indoor temperature were in the range 0.4–0.8 K, while simulated energy consumptions fulfilled the criteria of the ASHRAE 14-2002 Guideline. As monitoring data evidenced the importance of better managing the high thermal inertia of the floor heating system, two improved control strategies were tested in the simulation environment and evaluated in terms of thermal comfort, pellet consumption and efficiency of the pellet boiler.

Peer reviewed papers | 2020

Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid

Sedlmayer I, Bauer-Emhofer W, Haslinger W, Hofbauer H, Schmidl C, Wopienka E. Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid. Fuel Processing Technology 2020.198:106218.

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During transportation and storage of wood pellets various gases are formed leading to toxic atmosphere. Various influencing factors and measures reducing off-gassing have already been investigated. The present study aims at applying an antioxidant, acetylsalicylic acid (ASA), to reduce off-gassing from wood pellets by lowering wood extractives oxidation. Therefore, acetylsalicylic acid was applied in industrial and laboratory pelletizing processes. Pine and spruce sawdust (ratio 1:1) were pelletized with adding 0-0.8% (m/m) ASA. Glass flasks measurements confirmed off-gassing reduction by adding ASA for all wood pellets investigated.The biggest effect was achieved by adding 0.8% (m/m) ASA in the industrial pelletizing experiments where the emission of volatile organic compounds (VOCtot) was reduced by 82% and a reduction of carbon monoxide (CO) and carbon dioxide (CO2) emissions by 70% and 51%, respectively, could be achieved. Even an addition of 0.05% (m/m) ASA led to off-gassing reduction by >10%. A six week storage experiment to investigate the long-term effectivity of ASA addition revealed, that antioxidant addition was effective in reducing CO-, CO2- and VOCtot-release, especially during the first four weeks of the storage experiment, after which time the relative reduction effect was significantly decreased.

Conference presentations and posters | 2014

Off-gassing –Safety issues related with emissions from wood pellets along the pellet supply chain

Emhofer W, et al. Pellets Workshop ” Off-gassing –Safety issues related with emissions from wood pellets along the pellet supply chain” (held held during the Central European Biomass Conference 2014), 15th-18th of January, Graz, Austria, 2014.

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Conference presentations and posters | 2014

Off-gassing – Safety issues related with harmful emissions from wood pellets

Emhofer W. Second International Workshop on Pellet Safety “Off-gassing – Safety issues related with harmful emissions from wood pellets”, 5th of May, Fügen, Austria, 2014.

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Peer reviewed papers | 2012

Odor, gaseous and PM 10 emissions from small scale combustion of wood types indigenous to central Europe

Kistler M, Schmidl C, Padouvas E, Giebl H, Lohninger J, Ellinger R, et al. Odor, gaseous and PM 10 emissions from small scale combustion of wood types indigenous to central Europe. Atmos Environ. 2012;51:86-93.

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In this study, we investigated the emissions, including odor, from log wood stoves, burning wood types indigenous to mid-European countries such as Austria, Czech Republic, Hungary, Slovak Republic, Slovenia, Switzerland, as well as Baden-Württemberg and Bavaria (Germany) and South Tyrol (Italy). The investigations were performed with a modern, certified, 8 kW, manually fired log wood stove, and the results were compared to emissions from a modern 9 kW pellet stove. The examined wood types were deciduous species: black locust, black poplar, European hornbeam, European beech, pedunculate oak (also known as “common oak”), sessile oak, turkey oak and conifers: Austrian black pine, European larch, Norway spruce, Scots pine, silver fir, as well as hardwood briquettes. In addition, “garden biomass” such as pine cones, pine needles and dry leaves were burnt in the log wood stove. The pellet stove was fired with softwood pellets.

The composite average emission rates for log wood and briquettes were 2030 mg MJ−1 for CO; 89 mg MJ−1 for NOx, 311 mg MJ−1 for CxHy, 67 mg MJ−1 for particulate matter PM10 and average odor concentration was at 2430 OU m−3. CO, CxHy and PM10 emissions from pellets combustion were lower by factors of 10, 13 and 3, while considering NOx – comparable to the log wood emissions. Odor from pellets combustion was not detectable. CxHy and PM10 emissions from garden biomass (needles and leaves) burning were 10 times higher than for log wood, while CO and NOx rise only slightly. Odor levels ranged from not detectable (pellets) to around 19,000 OU m−3 (dry leaves). The odor concentration correlated with CO, CxHy and PM10. For log wood combustion average odor ranged from 536 OU m−3 for hornbeam to 5217 OU m−3 for fir, indicating a considerable influence of the wood type on odor concentration.

Conference presentations and posters | 2009

Nutzungsgradsteigerung bei Pelletsfeuerungen

Friedl G. Nutzungsgradsteigerung bei Pelletsfeuerungen, 9. Industrieforum Pellets 2009, 7th-9th of October 2009, Stuttgart, Germany.

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Conference presentations and posters | 2019

Nutrient recovery by digestate processing

Drosg B, Fuchs W. Nutrient recovery by digestate processing. Second COASTAL Biogas conference (Roskilde, Denmark). Nov 2019.

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Reports | 2015

Nutrient recovery by biogas digestate processing

Drosg B, Fuchs W, Al Seadi T, Madsen M, Linke B. Nutrient recovery by biogas digestate processing. IEA Bioenergy (2015): 7-11

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Other papers | 2020

Numerical simulation of fuel nitrogen conversion and NOx emissions in biomass boilers with advanced air staging technology

Essl M, Schulze K, Scharler R. Numerical simulation of fuel nitrogen conversion and NOx emissions in biomass boilers with advanced air staging technology. 3RD DOCTORAL COLLOQUIUM BIOENERGY. 2020

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The increased biomass utilization leads to the need of an efficient and flexible usage of available sources. Therefore, it is necessary to combust low-cost biogenic residues, which inherently have higher nitrogen contents that lead to increased NOx emissions. In order to tackle this issue a new combustion technology with double air staging and flue gas recirculation is under development. The technology also features an increased fuel bed height and very low oxygen concentrations in the fuel bed to reduce fuel bed temperatures. This work focuses on the CFD simulation of the formation and reduction of NOx emissions of in a small scale boiler (35 kWth). Compared to previously applied models, major modification concerning the heat and mass transfer in the fuel bed as well as the subsequent conversion in the freeboard were made. The fuel bed is modelled via representative fuel particles with a Lagrangian approach and a thermally thick particle model considering intra-particle
gradients. Due to the increased fuel bed height and the relatively low oxygen concentration the formation and cracking of tars has to be considered in the simulation. This heavily influences the formation and reduction of NOx and its precursors. The fuel bound nitrogen is released via the particle model in the form of NO during char burnout and via a lumped tar species during pyrolysis. The cracking of the lumped tar species is modelled via two global gas phase reactions that releases the NOx precursors NH3 and HCN. The cracking reactions are added to a skeletal reaction mechanism with 28 species and 102 reactions that includes the fate of the N species. The simulation results are compared to experimental data from test runs with spruce wood chips and Miscanthus pellets as fuels. The comparison showed good agreement for the test runs with wood chips, where the temperature distribution inside the fuel bed and the released species above the fuel bed were predicted well. The test runs with Miscanthus showed a greater deviation between the measured and simulated values. For both fuels the NOx reduction that was experimentally observed in the secondary combustion zone could not be predicted with reasonable agreement. Therefore, it is necessary to further investigate the cracking of the tars and the subsequent formation of the NOx precursors. The presented work forms the basis for further improvements of the numerical models and subsequently the optimization of the new technology.

Conference presentations and posters | 2019

Numerical simulation and experimental analysis of a novel small scale biomass grate firing system

Eßl M, Mehrabian R, Shiehnejad-Hesar A, Kelz J, Feldmeier S, Reiterer T, Anca-Couce A, Robert Scharler R. Numerical simulation and experimental analysis of a novel small scale biomass grate firing system. 27th European Biomass Conference & Exhibition (Poster). May 2019.

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The presented grate firing system is a patented small scale screw burner, which is designed for high fuel flexibility. This work focuses on the numerical modelling of the boiler via CFD simulations. The in-house developed CFD models use an Euler – Lagrange approach to predict the thermal degradation of the fuel particles and the subsequent gas-phase reactions. The CFD models are validated with experimental data from a representative measurement campaign where the boiler is operated with softwood pellets and the composition of the flue gas is measured in the primary and secondary combustion zone as well as the boiler outlet. The simulation results agree well with the data acquired in the measurement campaigns.
Keywords: CFD, simulation, combustion, small scale application, wood pellet

 

Other papers | 2015

Numerical modelling of biomass grate furnaces with a particle based model

Mehrabian R, Shiehnejadhesar A, Scharler R, Obernberger I. Numerical modelling of biomass grate furnaces with a particle based model, INFUB 10th European Conference on Industrial Furnace and Boilers 2015, 7th-10th of April 2015, Porto, Portugal.

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Other Publications | 2023

Numerical investigation of reaction mechanisms on NOx emissions from biomass combustion with enhanced reduction

Eßl M, Schulze K. Numerical investigation of reaction mechanisms on NOx emissions from biomass combustion with enhanced reduction. BEST Center Day. 28 June 2023

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With the increasing demand for lower emissions and innovative combustion technologies, it is necessary to have a reaction mechanisms that is accurate as well as computationally affordable for geometry and process optimization using computational fluid dynamics (CFD). The objective of this work is to explore the applicability of several reaction mechanisms in predicting NOx emissions from various combustion systems. This work focuses on the selection of suitable mechanisms from literature (see Table 1) in a full scale 3D model for the prediction of NOX especially for furnaces with low oxygen concentration in the fuel bed and enhanced reduction zones.

Peer reviewed papers | 2019

NPK 2.0: Introducing tensor decompositions to the kinetic analysis of gas–solid reactions

Birkelbach F, Deutsch M, Flegkas S, Winter F, Werner A. NPK 2.0: Introducing tensor decompositions to the kinetic analysis of gas–solid reactions. Int J Chem Kinet. 2019;1–11.

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A method for deriving kinetic models of gas–solid reactions for reactor and process design is presented. It is based on the nonparametric kinetics (NPK) method and resolves many of its shortcomings by applying tensor rank‐1 approximation methods. With this method, it is possible to derive kinetic models based on the general kinetic equation from any combination of experiments without additional a priori assumptions. The most notable improvements over the original method are that it is computationally much simpler and that it is not limited to two variables. Two algorithms for computing the rank‐1 approximation as well as a tailored initialization method are presented, and their performance is assessed. Formulae for the variance estimation of the solution values are derived to improve the accuracy of the model identification and to provide a tool for diagnosing the quality of the kinetic model. The methods effectiveness and performance are assessed by applying it to a simulated data set. A Matlab implementation is available as Supporting Information.

Conference presentations and posters | 2020

NOx Modelling and Emission Reduction

Eßl M, NOx Modelling and Emission Reduction. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Other papers | 2017

Novel concepts for CO2 utilisation to produce value added products

Sonnleitner A, Dißauer C, Martini S, Drosg B, Meixner K, Rachbauer L, Lazarova Z, Herwig C, Kinger G, Kofler I, Strasser C. Novel concepts for CO2 utilisation to produce value added products. 5th Central European Biomass Conference (Poster). January 2017, Graz, Austria.

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Other papers | 2017

Nitrogen Assessment in Small Scale Biomass Heating Systems

Enigl M, Strasser C, Hochbichler E, Schmidl C. Nitrogen Assessment in Small Scale Biomass Heating Systems. 25th European Biomass Conference & Exhibition (Poster). June 2017, Stockholm, Sweden.

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Other Publications | 2010

Niedertemperatur Drehrohrpyrolyse als Vorschaltprozess für die Co-Verbrennung von unkonventionellen Brennstoffen in thermischen Anlagen

Kern, S. Niedertemperatur Drehrohrpyrolyse als Vorschaltprozess für die Co-Verbrennung von unkonventionellen Brennstoffen in thermischen Anlagen, Master Thesis, Technische Universität Wien, Vienna, Austria, 2010.

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Peer reviewed papers | 2019

New experimental evaluation strategies regarding slag prediction of solid biofuels in pellet boilers

Schön C, Feldmeier S, Hartmann H, Schwabl M, Dahl J, Rathbauer J, Vega-Nieva D, Boman C, Öhman M, Burvall J. New experimental evaluation strategies regarding slag prediction of solid biofuels in pellet boilers. Energy & Fuels. 2019.33:11985-11995

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Pellet boilers and pellet stoves are widely used for heat production. But in most cases, only specific wood pellets with a low ash content are approved due to the increased risk of slagging and limited deashing capacity. The ash fusion test (AFT), according to prCEN/TS 15370-1, is currently the only standard method for the prediction of slagging. This method is not feasible for all biomass fuel types, since sometimes the characteristic temperatures cannot be determined or the characteristic shapes do not occur for temperature determination. Furthermore, the method is costly and requires complex instrumental infrastructure. Hence, a demand for more expressive or more rapid methods to characterize slag formation potential of fuels is often claimed. Based on a literature study, four such laboratory test methods were chosen, partly adapted, and then experimentally investigated. These methods included thermal treatment of the fuel itself or the ashes of the fuel and were the rapid slag test, CIEMAT, the slag analyzer, and the newly developed pellet ash and slag sieving assessment (PASSA) method. Method performance was practically assessed using 14 different biomass fuel pellets, which were mainly from different assortments of wood, but also herbaceous or other nonwoody fuels. The results from the tests with these four alternative methods were evaluated by comparing to both results from standard AFT and results from full-scale combustion tests performed over a maximum of 24 h. Seven different pellet boilers were assessed, of which one boiler was used to apply all 14 test fuels. According to the granulometric ash analysis (i.e., the ratio of >1 mm-fraction toward total ash formed), the sensitivity of the new test methods to depict slagging phenomena at a suitable level of differentiation was assessed. Satisfactory conformity of the boiler ash assessment (reference) was found for both, the slag analyzer and the PASSA method. The latter may, in particular, be seen as a promising and relatively simple low-input procedure, which can provide more real-life oriented test results for fixed-bed combustion. The standardized AFT could, however, not sufficiently predict the degree of slag actually formed in the reference boiler, particularly when only wood fuels are regarded.

Conference presentations and posters | 2013

New concepts for converting renewable electricity to transportation fuels by CO2 gasification

Rauch R. New concepts for converting renewable electricity to transportation fuels by CO2 gasification, 1st International Industrial Seminar Messer Benelux 2013, 18th of April 2013, Antwerp, Belgium.

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