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Peer Reviewed Scientific Journals | 2015

Anaerobic digestion of thermal pretreated brewers' spent grains

Bochmann G, Drosg B, Fuchs W. Anaerobic digestion of thermal pretreated brewers' spent grains. Environmental Progress and Sustainable Energy. 2015;34(4):1092-6.

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Anaerobic digestion offers a good opportunity to degrade residues from breweries to biogas. To improve the anaerobic degradation process thermal pretreatment of brewers' spent grains (BSG) offers the opportunity to increase degradation rate and biogas yield. Aim of the work is to show the influence of the thermal pretreatment of BSG to anaerobic digestion. BSG were pretreated at different temperature levels from 100 to 200°C. The biogas production of thermally pretreated BSG lies between 30 and 40% higher than for untreated reference. The temperature of the pretreatment process has a significant influence on the degradation rate or gas yield, respectively. Up to a temperature of 160°C, the biogas yield rises. Temperatures over 160°C result in a slower degradation and decreasing biogas yield. Substrate with and without pretreatment gave a daily biogas yield of 430 and 389 Nm3 × kg-1 VS, respectively. Batch analysis of the biochemical methane potential gives a total methane yield of 409.8 Nm3 CH4 × kg-1 VS of untreated brewers' spent grains and 467.6 Nm3 CH4 × kg-1 VS of the pretreated samples. For pretreatment energy balance estimation has been carried out. Without any heat recovery demand is higher than the energy surplus resulting from pretreatment of BSG. With energy recovery by heat exchanger the net energy yield could be increased to 38.87 kWh × kg-1 FM or 8.81%. © 2015 American Institute of Chemical Engineers Environ Prog.


Peer Reviewed Scientific Journals | 2015

Application of an empirical model in CFD simulations to predict the local high temperature corrosion potential in biomass fired boilers.

Gruber T, Scharler R, Obernberger I. Application of an empirical model in CFD simulations to predict the local high temperature corrosion potential in biomass fired boilers. Biomass and Bioenergy. Volume 79, August 2015, Pages 145-154.

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To gain reliable data for the development of an empirical model for the prediction of the local high temperature corrosion potential in biomass fired boilers, online corrosion probe measurements have been carried out. The measurements have been performed in a specially designed fixed bed/drop tube reactor in order to simulate a superheater boiler tube under well-controlled conditions. The investigated boiler steel 13CrMo4-5 is commonly used as steel for superheater tube bundles in biomass fired boilers. Within the test runs the flue gas temperature at the corrosion probe has been varied between 625 °C and 880 °C, while the steel temperature has been varied between 450 °C and 550 °C to simulate typical current and future live steam temperatures of biomass fired steam boilers. To investigate the dependence on the flue gas velocity, variations from 2 m·s−1 to 8 m·s−1 have been considered. The empirical model developed fits the measured data sufficiently well. Therefore, the model has been applied within a Computational Fluid Dynamics (CFD) simulation of flue gas flow and heat transfer to estimate the local corrosion potential of a wood chips fired 38 MW steam boiler. Additionally to the actual state analysis two further simulations have been carried out to investigate the influence of enhanced steam temperatures and a change of the flow direction of the final superheater tube bundle from parallel to counter-flow on the local corrosion potential.


Conference contributions | 2015

Application of numerical modelling to biomass grate furnaces

Mehrabian R, Shiehnejadhesar A., Scharler R. Application of numerical modelling to biomass grate furnaces. Internation conference on advances in mechanical engineering, Istanbul 2015.

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The direct combustion of the biomass is the most advanced and mature technology in the field of energetic biomass utilisation. The legislations on the amount of emitted pollutants and the plant efficiency of biomass combustion systems are continually being restricted. Therefore constant improvement of the plant efficiency and emission reduction is required Numerical modelling is gaining increasing importance for the development of biomass combustion technologies. In this paper an overview about the numerical modelling efforts deal with the most relevant phenomena in biomass grate firing systems is given. The numerical modelling results in a deeper understanding of the underlying processes in biomass combustion plants. Therefore, it leads to a faster and safer procedure of development of a new technology.


Conference contributions | 2015

AshMelT Project Background – Why this work was necessary

Schwabl M, Wopienka E. AshMelT Workshop “AshMelT Project Background – Why this work was necessary” (held during de World Sustainable Energy Days 2015), 25th-27th of February, Wels, Austria, 2015.

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Other Presentations | 2015

Aspects of microalgal biomass as feedstock in biogas plants

Gruber M, Zohar E, Jerney J, Ludwig I, Bochmann G, Nussbaumer L, Montgomery L, Fuchs W, Drosg B, Schöpp T, Obbard JP. Aspects of microalgal biomass as feedstock in biogas plants, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Conference contributions | 2015

Ausbrandregelung durch zusätzliche Messung des Kohlenmonoxidgehalts im Rauchgas

Bischof J, Gölles M, Obernberger I, Baumbach G. Ausbrandregelung durch zusätzliche Messung des Kohlenmonoxidgehalts im Rauchgas. 27. Deutscher Flammentag. September 2015, Clausthal, Germany.

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Conference contributions | 2015

Benz(a)pyrene emission measurements in flue gas from residential biomass combustion appliances

Meier F, Schwabl M, Sedlmayer I, Kleinhappl M, Schmidl C, Haslinger W. Benz(a)pyrene emission measurements in flue gas from residential biomass combustion appliances, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Peer Reviewed Scientific Journals | 2015

Bioavailability of essential trace elements and their impact on anaerobic digestion of slaughterhouse waste

Ortner M, Rameder M, Rachbauer L, Bochmann G, Fuchs W. Bioavailability of essential trace elements and their impact on anaerobic digestion of slaughterhouse waste. Biochemical Engineering Journal. 15 July 2015;99:107-113.

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Conference contributions | 2015

Biomasse der Zukunft – Bioenergie der Zukunft?

Wopienka E. Biomasse der Zukunft – Bioenergie der Zukunft? Internationale Konferenz auf Schloss Weinzierl 2015, 29th of Januar 2015, Wieselburg, Austria.

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Conference Papers | 2015

Challenges toward model-based control for hybrid biomass-based heating systems

Unterberger V, Gölles M. Challenges toward model-based control for hybrid biomass-based heating systems. e-nova 2015. November 2015, Pinkafeld, Austria. Unterberger V, Gölles M. Challenges toward model-based control for hybrid biomass-based heating systems. Nachhaltige Gebäude, Graz. Leykam. 2015;10:393-404.

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Biomass boilers used for residential heating and hot water supply are typically combined with a buffer storage and solar collectors. However, the annual utilization rates typically achieved with such systems are far below those theoretically possible, which is mainly because of the often poor quality of both the individual control of the components as well as the high-level control of the entire system. The control strategies typically applied consist of simple decou-pled control circuits with linear controllers, which cannot deal with the mostly nonlinear and coupled behaviour of the components and thus do not ensure their reasonable interaction. The most appropriate approach to address these challenges is the application of model-based control techniques. Within the paper an overview of mathematical models suitable for control purposes, a simple to implement load forecasting method as well as control strate-gies for both the individual components and the entire system are presented. Future chal-lenges for a practical implementation of this novel approach are discussed in the outlook sec-tion.


Peer Reviewed Scientific Journals | 2015

Closing the Nutrient Cycle in Two-Stage Anaerobic Digestion of Industrial Waste Streams

Rachbauer L, Gabauer W, Scheidl S, Ortner M, Fuchs W, Bochmann G. Closing the Nutrient Cycle in Two-Stage Anaerobic Digestion of Industrial Waste Streams. Energy Fuels 2015;29(7):4052-4057.

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Industrial waste streams from brewing industries and distilleries provide a valuable but largely unused alternative substrate for biogas production by anaerobic digestion. High sulfur loads in the feed caused by acidic pretreatment to enhance bioavailability are responsible for H2S formation during anaerobic digestion. Microbiological oxidation of H2S provides an elegant technique to remove this toxic gas compound. Moreover, it allows for recovery of sulfuric acid, the final product of aerobic sulfide oxidation, as demonstrated in this study. Two-stage anaerobic digestion of brewer’s spent grains, the major byproduct in the brewing industry, allows for the release of up to 78% of total H2S formed in the first pre-acidification stage. Desulfurization of such pre-acidification gas in continuous acidic biofiltration with immobilized sulfur-oxidizing bacteria resulted in a maximum H2S elimination capacity of 473 g m–3 h–1 at an empty bed retention time of 91 s. Complete H2S removal was achieved at inlet concentrations of up to 6363 ppm. The process was shown to be very robust, and even after an interruption of H2S feeding for 10 days, excellent removal efficiency was immediately restored. A maximum sulfate production rate of 0.14 g L–1 h–1 was achieved, and a peak concentration of 4.18 g/L sulfuric acid was reached. Further experiments addressed the reduction of fresh water and chemicals to minimize process expenses. It was proven that up to 50% of mineral medium that is required in large amounts during microbiological desulfurization can be replaced by the liquid fraction of the digestate. The conducted study demonstrates the viability of microbial sulfur recovery with theoretical recovery rates of up to 44%.


Peer Reviewed Scientific Journals | 2015

Combustion related characterisation of Miscanthus peat blends applying novel fuel characterisation tools

Sommersacher P, Brunner T, Obernberger I, Kienzl N, Kanzian W. Combustion related characterisation of Miscanthus peat blends applying novel fuel characterisation tools. Fuel 2015;158:253-262.

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Conference contributions | 2015

Control of a Biomass-Furnace Based on Input-Output-Linearization

Schörghuber C, Reichhartinger M, Horn M, Gölles M, Seeber R. Control of a Biomass-Furnace Based on Input-Output-Linearization, European Control Conference 2015, 15th-17th of July 2015, Linz, Austria. p 3513-3518.

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Peer Reviewed Scientific Journals | 2015

Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant

Kuba M, He H, Kirnbauer F, Boström D, Öhman M, Hofbauer H. Deposit build-up and ash behavior in dual fluid bed steam gasification of logging residues in an industrial power plant. Fuel Processing Technology. 25 June 2015;139:33-41.

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A promising way to substitute fossil fuels for production of electricity, heat, fuels for transportation and synthetic chemicals is biomass steam gasification in a dual fluidized bed (DFB). Using lower-cost feedstock, such as logging residues, instead of stemwood, improves the economic operation. In Senden, near Ulm in Germany, the first plant using logging residues is successfully operated by Stadtwerke Ulm. The major difficulties are slagging and deposit build-up. This paper characterizes inorganic components of ash forming matter and draws conclusions regarding mechanisms of deposit build-up. Olivine is used as bed material. Impurities, e.g., quartz, brought into the fluidized bed with the feedstock play a critical role. Interaction with biomass ash leads to formation of potassium silicates, decreasing the melting temperature. Recirculation of coarse ash back into combustion leads to enrichment of critical fragments. Improving the management of inorganic streams and controlling temperature levels is essential for operation with logging residues.


Scientific Journals | 2015

Developing a simulation model for a mixed alcohol synthesis reactor and validation of experimental data in IPSEpro

Weber G, Di Giuliano A, Rauch R, Hofbauer H. Developing a simulation model for a mixed alcohol synthesis reactor and validation of experimental data in IPSEpro. Fuel Process Technology. 141:167-176, 2015.

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Peer Reviewed Scientific Journals | 2015

Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed

Shiehnejadhesar A, Mehrabian R, Scharler R, Obernberger I. Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed. Fuel Processing Technology. Volume 139, November 2015, Pages 142–158.

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State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the “porous” nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.


Conference contributions | 2015

Development of a briquette stove with a candle burning principle - characteristics and measurement results

Kirchhof J, Schmidl C, Moser W, Haslinger W. Development of a briquette stove with a candle burning principle - characteristics and measurement results, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Conference contributions | 2015

Development of a new test method for defining a real life thermal heat output of firewood stoves

Sturmlechner R, Aigenbauer S, Moser W, Schmidl C, Reichert G, Stressler H, Schwabl M, Haslinger W. Development of a new test method for defining a real life thermal heat output of firewood stoves, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Conference contributions | 2015

Development of a streak formation model for an improved prediction of gas phase combustion in biomass grate furnaces

Shiehnejadhesar A, Mehrabian R, Scharler R, Goldin GM, Obernberger I. Development of a streak formation model for an improved prediction of gas phase combustion in biomass grate furnaces, INFUB 10th European Conference on Industrial Furnace and Boilers 2015, 7th-10th of April 2015, Porto, Portugal.

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State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the “porous” nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.


Peer Reviewed Scientific Journals | 2015

Econometric analysis of the wood pellet market in Austria

Kristöfel C, Strasser C, Morawetz U, Schmid E. Econometric analysis of the wood pellet market in Austria. 12th International Conference On The European Energy Market, 20-22 May 2015. 20 August 2015, Lisbon, Portugal.

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Other Presentations | 2015

Effects of pretreatment and storage methods on biomethane potential of different microalgae in anaerobic digestion

Gruber M, Jerney J, Zohar E, Nussbaumer M, Hieger C, Bochmann G, Schagerl M, Obbard JP, Fuchs W, Drosg B. Effects of pretreatment and storage methods on biomethane potential of different microalgae in anaerobic digestion, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (oral presentation)

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Peer Reviewed Scientific Journals | 2015

Efficiency and operational behaviour of small-scale pellet boilers installed in residential buildings

Carlon E, Schwarz M, Golicza L, Verma VK, Prada A, Baratieri M, et al. Efficiency and operational behaviour of small-scale pellet boilers installed in residential buildings. Appl Energy 2015;155:854-865.

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Conference contributions | 2015

Emission Reduction of Firewood Stoves by Integrated Honeycomb Catalysts

Reichert G, Schmidl C, Schwabl M, Sedlmayer I, Stressler H, Sturmlechner R, Wöhler M, Haslinger W. Emission Reduction of Firewood Stoves by Integrated Honeycomb Catalysts, Word Sustainable Energy Days next 2015, 24th-27th of February 2015, Wels, Austria.

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Peer Reviewed Scientific Journals | 2015

Energy self-supply of large abattoir by sustainable waste utilisation based on anaerobic mono-digestion

Ortner M, Wöss D, Schumergruber A, Pröll T, Fuchs W. Energy self-supply of large abattoir by sustainable waste utilisation based on anaerobic mono-digestion. Applied Energy. 2015;143:460-471.

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Abattoirs have a large number of energy intensive processes. Beside energy supply, disposal costs of animal by-products (ABP) are the main relevant cost drivers. In this study, successful implementation of a new waste and energy management system based on anaerobic digestion is described. Several limitations and technical challenges regarding the anaerobic digestion of the protein rich waste material had to be overcome. The most significant problems were process imbalances such as foaming and floatation as well as high accumulation of volatile fatty acids and low biogas yields caused by lack of essential microelements, high ammonia concentrations and fluctuation in operation temperature. Ultimately, 85% of the waste accumulated during the slaughter process is converted into 2700 MW h thermal and 3200 MW h electrical energy in a biogas combined heat and power (CHP) plant. The thermal energy is optimally integrated into the production process by means of a stratified heat buffer. The energy generated by the biogas CHP-plant can cover a significant share of the energy requirement of the abattoir corresponding to 50% of heat and 60% of electric demand, respectively. In terms of annual cost for energy supply and waste disposal a reduction of 63% from 1.4 Mio € to about 0.5 Mio € could be achieved with the new system. The payback period of the whole investment is approximately 9 years. Beside the economic benefits also the positive environmental impact should be highlighted: a 79% reduction of greenhouse gas emissions from 4.5 Mio kg CO2 to 0.9 Mio kg CO2 annually was achieved. The realized concept received the Austrian Energy Globe Award and represents the first anaerobic mono-digestion process of slaughterhouse waste worldwide.


Other Presentations | 2015

Entwicklung eines modellbasierten Optimierungsalgorithmus für die Wärmeversorgung mit Biomassefeuerungen

Oberlechner, F. Entwicklung eines modellbasierten Optimierungsalgorithmus für die Wärmeversorgung mit Biomassefeuerungen, Master Thesis, Technische Universität Graz, Graz, Austria, 2015.

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Wärmeversorgungsanlagen von Gebäuden, bestehend aus Biomasse-Feuerung, Solarkollektoren, Pufferspeicher, Heizkreis und Warmwasserzapfstellen gewinnen aufgrund ihrer Nachhaltigkeit zunehmend an Bedeutung. In den letzten Jahren wurden insbesondere für eine effiziente Regelung der Biomasse-Feuerung sehr gute Konzepte entwickelt. Diese können jedoch zumeist aufgrund unzureichender, übergeordneter Systemregelungen nicht ihr volles Potential ausschöpfen. In ihrer primitivsten Ausführung schaltet eine Systemregelung die Biomasse-Feuerung anhand der Ladehöhe des Pufferspeichers aus und ein. Diese Art der Regelung hat unweigerlich viele Ein-/ Ausschaltvorgänge der Feuerung, sowie eine schlechte Ausnutzung des solaren Eintrags zur Folge. Insbesondere bei Biomasse-Feuerungen sind Ein-/ Ausschaltvorgänge äußerst unwirtschaftlich und führen zu stark erhöhten Schadstoffemissionen. Die häufigen Ein-/ Ausschaltvorgänge verursachen zusätzlich erhöhte Wartungs- und Betriebskosten und schlussendlich eine verkürzte Lebensdauer zahlreicher Komponenten. Um die Ein-/ Ausschaltvorgänge zu minimieren und den solaren Eintrag zu steigern, soll im Rahmen dieser Arbeit ein übergeordnetes, modellprädiktives Regelungskonzept für die gesamte Wärmeversorgungsanlage entwickelt werden. Nach einer theoretischen Einführung in gemischt-ganzzahlige Optimalsteuerungsprobleme sowie ausgewählter Lösungsmethoden werden Prädiktionsmodelle für alle Komponenten der Wärmeversorgungsanlage entwickelt. Aufbauend auf den mathematischen Modellen für die einzelnen Komponenten der Anlage wird eine nichtlineare modellprädiktive Regelung entwickelt. Diese berücksichtigt zusätzlich Wetterprognosen sowie die erwartete Lastabnahme und führt schlussendlich zu einer Minimierung des Brennstoffverbrauchs sowie der Anzahl der Ein-/ Ausschaltvorgänge. Den Abschluss der Arbeit bilden ausführliche Simulationsstudien mit unterschiedlichen Wetterszenarien sowie Vergleiche mit herkömmlichen Regelungsstrategien.