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Peer-reviewed publications | 2014

Economics and price risks in international pellet supply chains

Ehrig R, Behrendt F, Wörgetter M, Strasser C. Economics and price risks in international pellet supply chains. International Pellet Supply Chains. ISBN 978-3-319-07015-5. 2014.

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Conference contributions | 2014

Efficiency criteria for pellet heating systems

Schmidl C. Efficiency criteria for pellet heating systems, European Pellet Conference 2014, 26th-28th of February 2014, Wels, Austria.

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Peer Reviewed Scientific Journals | 2014

Efficient anaerobic mono-digestion of N-rich slaughterhouse waste: Influence of ammonia, temperature and trace elements

Ortner M, Leitzinger K, Skupien S, Bochmann G, Fuchs W. Efficient anaerobic mono-digestion of N-rich slaughterhouse waste: Influence of ammonia, temperature and trace elements. Bioresour Technol. 2014;174:222-32.

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Three mono-digestion experiments treating slaughterhouse waste with high TKN concentration (~11. g/kg) were applied in lab-scale at mesophilic and psychrophilic conditions to study the impact of high ammonia concentrations and additives. Precipitation of sulphur by addition of ferrous chloride did not influence process behaviour, whereas supplementation of trace elements significantly improved process stability by reducing volatile fatty acid concentration towards zero.The limit of NH4-N concentration causing a rise of VFAs to 19,000mg/l and reduction of methane by 25% was found between 7.7 and 9.1g/kg which correspond to NH3 concentrations of 830-1060mg/l.Psychrophilic operation (25°C) lowered inhibitory NH3 concentration to 140mg/l, but process performance was stable only at low OLR of 0.4kgVS/m3d.Robust performance at highest possible NH4-N concentration (7.7g/kg), low VFA accumulation and satisfying methane yield of about 280Nm3/t COD was observed at OLR of 2.5kgVS/m3d at 37°C. © 2014 Elsevier Ltd.


Conference contributions | 2014

Emissions from Biomass Boilers - The State of the Art

Schwabl M. Emissions from Biomass Boilers - The State of the Art, Wood Heating Conference, Newcastle 2015, 21st of November 2014, Newcastle, England.

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Conference contributions | 2014

Empirical analysis of biomass and energy price volatility

Kristöfel C, Strasser C, Morawetz U, Schmid E. Empirical analysis of biomass and energy price volatility. Schriften der GEWISOLA. 2014;49:385-386. (peer reviewed) (visual presentation)

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The current debate on biomass price volatility mainly refers to increased market dynamics and integration as well as renewable energy policy intervention. Higher price volatility leads to additional costs that are often transmitted along the supply chain to the final consumers. We empirically analyze whether or not price volatility of woody biomass commodities has increased in recent years. Results indicate that the price volatility of some woody biomass
commodities has increased, but it is still lower than of fossil fuels.


Contributions to trade journals | 2014

Experimental and modeling study of catalytic steam reforming of methane mixture with propylene in a packed bed reactor

Sadooghi P, Rauch R. Experimental and modeling study of catalytic steam reforming of methane mixture with propylene in a packed bed reactor. Int J Heat Mass Transfer. 2014;78:515-21.

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Producer gas from biomass gasification contains mainly hydrogen, carbon dioxide, carbon monoxide, methane and some other low molecular hydrocarbons like propylene. This paper reports mathematical simulation and experimental study of steam reforming of methane mixture with propylene in a packed bed reactor filled with nickel based catalysts. Due to the high heat input through the reformer tube wall and the endothermic reforming reactions, a two-dimensional pseudo-heterogeneous model that takes into account the diffusion reaction phenomena in gas phase as well as inside the catalyst particles has been used to represent temperature distribution and species concentration within the reactor. Steam reforming of propylene is faster and more selective than methane and it is shown that addition of propylene to the methane steam mixture reduces the conversion of methane. The obtained results play a key role in optimization and design of a commercial reactor. © 2014 Elsevier Ltd. All rights reserved.
 


Other Presentations | 2014

Fermentation of biomass from micro algae

Gruber M, Zohar E, Jerney J, Bochmann G, Obbard JP, Schagerl M, Fuchs W, Drosg B. Fermentation of biomass from micro algae, 4th Central European Biomass Conference 2014, 15th-18th of January 2014, Graz, Austria.

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Other Presentations | 2014

H2S and NH3 tolerance of acidophilic sulfur-oxidizing bacteria

Rachbauer L, Lorber G, Ortner M, Bochmann G. H2S and NH3 tolerance of acidophilic sulfur-oxidizing bacteria, 4th Central European Biomass Conference 2014, 15th-18th of January 2014, Graz, Austria.

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Conference contributions | 2014

Hydroprocessing and Catalytic Cracking of Fischer-Tropsch Biowaxes to Biokerosene

Rauch R, Jovcic M, Aichernig C, Ililopoulou E, Heracleous E, Lapppas AA. Hydroprocessing and Catalytic Cracking of Fischer-Tropsch Biowaxes to Biokerosene, Processing Technologies for the Forest and Biobased Products Industries PTF BPI 2014, 24th-25th of September 2014, Kuchl, Austria.

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Conference contributions | 2014

Impact of firebed temperature on PM1 formation in a small-scale biomass furnace

Gehrig M, Pelz S, Thorwarth H, Haslinger W, Jaeger D. Impact of firebed temperature on PM1 formation in a small-scale biomass furnace, International Aerosol Conference 2014, 31st of August-5th of September 2014, Busan, Korea.

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Conference contributions | 2014

Improvement of the accuracy of short-term corrosion probe measurements by addition of a mass loss probe

Retschitzegger S, Brunner T, Obernberger I. Improvement of the accuracy of short-term corrosion probe measurements by addition of a mass loss probe, Proc. of the Conference Impacts of Fuel Quality on Power Production and Environment 2014, 26th-31st of October 2014, Snowbird, USA.

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Conference contributions | 2014

Improving small scale combustion systems for better air quality

Schmidl C, Moser W, Reichert G. Improving small scale combustion systems for better air quality, TERMICA DA BIOMASSE E QUALITÀ DELL’ARIA 2014, 25th of June 2014, Udine, Italy.

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Contributions to trade journals | 2014

Integrating mitigation and adaptation into development: The case of Jatropha curcas in sub-Saharan Africa

Muys B, Norgrove L, Alamirew T, Birech R, Chirinian E, Delelegn Y, et al. Integrating mitigation and adaptation into development: The case of Jatropha curcas in sub-Saharan Africa. GCB Bioenergy. 2014;6(3):169-71.

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Contributions to trade journals | 2014

Integration von Oxidationskatalysatoren in Holzöfen

Reichert G, Schmidl C. Integration von Oxidationskatalysatoren in Holzöfen, 13. Holzenergiesymposium 2014, 12th of September 2014, Zürich, Schweiz. pp 77-92. (peer reviewed)

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Batch-wise operated wood stoves for room heating purposes are popular and widespread in Europe. Beside economic and ecological reasons they are also very important for reaching the European CO2 emission targets. However, since they contribute significantly to harmful gaseous as well as particulate emissions, they have to be optimized towards clear emission reduction in real life operation. Catalysts integrated in wood stoves can significantly contribute to reach this target. The results of this study showed an emission reduction potential of
integrated ceramic and metallic honeycomb catalysts of around 30 % to 99 %. Thereby the highest reduction potential was investigated for CO emissions (reduction rate 75 % to 99 %), followed by reductions of VOC emissions (reduction rate 40 % to 60 %) and reductions of PM emissions of around 30 % to 40 %. Long term tests and safety test series lead to the conclusion that integrated catalysts have to be cleaned regularly in order to prevent blocking and to guarantee optimal reduction performance.


Other Presentations | 2014

Integration von Thermogeneratoren in einen Scheitholzofen zur Eigenstromversorgung der automatischen Luftklappenregelung

Mair, C. Integration von Thermogeneratoren in einen Scheitholzofen zur Eigenstromversorgung der automatischen Luftklappenregelung, Diploma Thesis, Technische Universität Wien, Vienna, Austria, 2014.

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Conference contributions | 2014

Kinetic scheme and heat of reaction of biomass pyrolysis and torrefaction considering charring reactions.

Anca-Couce A, Mehrabian R, Scharler R, Obernberger I. Kinetic scheme and heat of reaction of biomass pyrolysis and torrefaction considering charring reactions, 20th International Analytical and Applied Pyrolysis Conference (PYRO2014), 19th-22nd of May 2014, Birmingham, United Kingdom.

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Contributions to trade journals | 2014

Kinetic scheme of biomass pyrolysis considering secondary charring reactions

Anca-Couce A, Mehrabian R, Scharler R, Obernberger I. Kinetic scheme of biomass pyrolysis considering secondary charring reactions. Energy Conversion and Management. 2014;87:687-96.

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A widely applicable kinetic scheme for pyrolysis is still missing. In this work an adaptation of the mechanistic scheme developed by Ranzi et al. (2008) for pyrolysis of small ash free biomass particles is proposed. The scheme is modified to include secondary char formation reactions, which are relevant for particles of a certain thickness, and sugar formation is avoided due to the catalytic effect of alkali metals in biomass. The predictions of the adapted scheme are compared to experimental data from the literature of pyrolysis in fixed beds of particles with a size of around 1 cm. It is shown that the adaptation improves the prediction of the final char yield and its CHO composition and also the yields of the main groups of volatiles, as carbonyls + alcohols, sugars and water vapor. © 2014 Elsevier Ltd. All rights reserved.


Contributions to trade journals | 2014

Kinetic scheme to predict product composition of biomass torrefaction

Anca-Couce A, Mehrabian R, Scharler R, Obernberger I. Kinetic scheme to predict product composition of biomass torrefaction [Internet]; 2014 [cited 2015 Aug 12]. Available from: www.scopus.com.

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A kinetic scheme for the prediction of product composition of torrefaction is presented in this work. The scheme is based on a pyrolysis scheme for fast pyrolysis of small ash free biomass particles and was adapted to consider the presence of secondary char formation reactions, the inhibition of sugar formation due to the catalytic effect of alkali metals in biomass, as well as the typical hemicellulose structure of hardwoods. The torrgas composition predicted by the model is compared to experimental data of torrefaction in a lab-scale packed bed reactor. It is shown that the adapted model is able to predict the yields of the main volatile groups, i.e., permanent gases, light and heavy condensable species and the yields of the several groups in which condensable species were classified based on their structure, i.e., carbonyls and alcohols, furans, phenolics as well as water vapour. Copyright © 2014,AIDIC Servizi S.r.l.


Conference contributions | 2014

Low energy houses heated by biomass boilers: optimization of the heating system control strategy by means of dynamic simulation

Carlon E, Schwarz M, Schmidl C, Baratieri M, Gasparella A, Haslinger W. Low energy houses heated by biomass boilers: optimization of the heating system control strategy by means of dynamic simulation, 3rd International High Performance Buildings Conference at Purdue 2014, 14th-17th of July 2014, Purdue, USA. (peer reviewed)

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Other Presentations | 2014

Microalgae as source of biogas: Anaerobic digestion of un- and pre-treated biomass

Gruber M, Zohar E, Jerney J, Nussbaumer M, Ludwig I, Hieger C, Bromberger P, Bochmann G, Obbard JP, Schagerl M, Fuchs W, Drosg B. Microalgae as source of biogas: Anaerobic digestion of un- and pre-treated biomass, Algae Networking Event 2014, 11th of September 2014, Dürnrohr, Austria. (oral presentation)

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Contributions to trade journals | 2014

Model based control of a small-scale biomass boiler

Gölles M, Reiter S, Brunner T, Dourdoumas N, Obernberger I. Model based control of a small-scale biomass boiler. Control Engineering Practice. 2014;22(1):94-102. https://doi.org/10.1016/j.conengprac.2013.09.012

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Because of increased efforts to reduce CO2 emissions a significant step in the development of small-scale (residential) biomass boilers for space heating has been achieved in recent years. Currently, the full potential for low-emission operation at high efficiencies, which is in principle possible due to optimized furnace geometries as well as combustion air staging strategies, cannot be exploited since there is still the need to enhance the controllers applied. For this reason, a model based control strategy for small-scale biomass boilers was developed and successfully implemented in a commercially available system. Thereby, appropriate mathematical models were developed for all relevant parts of the furnace and connected to an overall model subsequently used for the control unit design. The resulting controller is based on the input–output linearization and the state variables are estimated by an extended Kalman filter. Finally, the new control was implemented at a commercially available small-scale biomass boiler and the experimental verification showed a significant improvement of the operating behaviour in comparison to the conventional control.


Contributions to trade journals | 2014

Model based control of the secondary air massflow of biomass furnaces [Modellbasierte Regelung des Sekundärluftmassenstromes bei Biomasse-Feuerungsanlagen]

Schörghuber C, Gölles M, Dourdoumas N, Obernberger I. Model based control of the secondary air massflow of biomass furnaces. At-Automatisierungstechnik. 2014;62(7):487-99.

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To influence the combustion process of modern biomass furnaces specifically the combustion-controller determines the necessary mass flows. The gaseous mass flows can be adjusted by fans and flaps. To ensure the desired overall performance of the furnace the mass flows need to be set by inner control loops respectively. Within the work described in this paper a model based approach for the control design of the inner control loop is presented exemplarily for the secondary air supply. Thereby a flatness-based feedforward control will be designed by means of an appropriate model. © 2014 Oldenbourg Wissenschaftsverlag GmbH.


Conference contributions | 2014

Model based optimization of a combined biomass-solar thermal system

Stift F, Hartl M, Ferhatbegović T, Aigenbauer S, Simetzberger A. Model based optimization of a combined biomass-solar thermal system. Energy Procedia. 2014;48:681-688. (peer reviewed)

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Other Presentations | 2014

Modellierung und Regelung eines Pufferspeichers in Kombination mit einer Biomassefeuerung

Hemmer, J. Modellierung und Regelung eines Pufferspeichers in Kombination mit einer Biomassefeuerung, Master Thesis, Technische Universität Graz, Graz, Austria, 2014.

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Die vorliegende Arbeit widmet sich der Herleitung mathematischer Simulationsmodelle eines Pufferspeichers, eines Solarkollektors sowie eines Plattenwärmeübertragers. Dabei wird das Simulationsmodell des Pufferspeichers anhand eines am Markt verfügbaren Pufferspeichers entwickelt. Die mathematischen Beschreibungen der Simulationsmodelle basieren auf einer partiellen Differentialgleichung zur Beschreibung der Wärmeübertragung in einem durchströmten zylindrischen Rohr. Nach dem Erhalt der mathematischen Modelle werden diese mit einem impliziten Lösungsverfahren numerisch gelöst. Anschließend werden die experimentell zu ermittelnden Parameter des Pufferspeichermodells anhand gezielt durchgeführter Versuche bestimmt. Nach dem Ermitteln der Parameter wird das Simulationsmodell des Pufferspeichers mit einem weiteren Versuch experimentell verifiziert. Schlussendlich bildet das mathematische Modell des Pufferspeichers den untersuchten Pufferspeicher sehr zufriedenstellend ab, womit ein Simulationsmodell vorliegt, das gezielte Untersuchungen ohne aufwändige Versuche ermöglicht. Abschließend wird eine Regelung für die Wärmeübertragung aus dem Solarkollektor in den Pufferspeicher entwickelt. Dabei werden zwei in der Praxis übliche Verfahren untersucht. Bei der ersten Variante erfolgt die Übertragung der Wärme in den Pufferspeicher über ein im Pufferspeicher integriertes Solarregister. Bei der zweiten Variante erfolgt die Übertragung der Wärme über einen Plattenwärmeübertrager vom Wasser-Frostschutzgemisch auf Wasser, welches dann direkt in den Pufferspeicher eingespeist wird. Als Reglerstruktur wird in beiden Fällen ein Standard-Regelkreis mit einer statischen Vorsteuerung verwendet. Anhand von Simulationsstudien werden zunächst die Parameter des PI-Reglers festgelegt und in weiterer Folge die mit der jeweiligen Variante resultierenden Temperaturverläufe des Wassers im Pufferspeicher untersucht und gegenübergestellt. Dabei stellt sich heraus, dass die Temperatur des Wassers im Pufferspeicher, bei gleich bleibender Strahlungsstromdichte der Solarstrahlung Igauf den Solarkollektor, die gewünschte Solltemperatur bei Wärmeübertragung mittels Plattenwärmeübertrager schneller erreicht, als bei Wärmeübertragung durch das Solarregister. Darüber hinaus ermöglicht die Verwendung des Plattenwärmeübertragers eine Schichtung der Temperatur des Wassers im Pufferspeicher und somit eine Speicherung der Wärme auf einen höheren Temperaturniveau.


Reviewed Conference Papers | 2014

Multi-physics modelling of packed bed biomass combustion

Mehrabian R, Shiehnejadhesar A, Scharler R, Obernberger I. Multi-physics modelling of packed bed biomass combustion. Fuel. 2014;122:164-78.

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A transient 3D model for two main zones, namely the fuel bed and the freeboard, of biomass packed bed combustion systems was developed. It integrates the models for the biomass conversion sub-processes and solves the governing equations for the gas and solid phase and their interactions. The intra-particle gradients are included by considering the biomass particles as thermally thick particles. The shrinkage of the packed bed and the variations of the bed porosity due to the uneven consumption of the fuel are taken into account. Detailed kinetic mechanisms are used for the simulation of homogeneous gas phase reactions. To verify the model and to increase the understanding of packed bed combustion, laboratory-scale fixed-bed batch experiments have been performed in a reactor with 9.5 cm diameter and 10 cm length. The model performance was extensively validated with gas phase measurements (CO, CO2, CH4, H2, H2O and O2) above the fuel bed, temperatures at different heights in the bed and in the freeboard, and the propagation rate of reaction front. The simulation results are in a good agreement with the measured values. © 2014 Elsevier Ltd. All rights reserved.