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Conference 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.


Other Presentations | 2018

Regelung verfahrens- und energietechnischer Anlagen. Zukünftige Möglichkeiten durch zunehmende Digitalisierung.

Gölles M. Regelung verfahrens- und energietechnischer Anlagen. Zukünftige Möglichkeiten durch zunehmende Digitalisierung. 6. Fachkolloquium, Effiziente und schadstoffarme Verbrennungstechnologien für Biomasse. Präseantion. 10.07.2018.

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Conference contributions | 2014

"BioCAT – Clean air technology for small-scale combustion systems"

Reichert G, Wöhler M, Schwabl M, Schmidl C, Aigenbauer S, Bachmaier H, Figl F, Hartmann H, Haslinger W, Kirchhof J, Stressler H, Sturmlechner R, Turowski P, Voglauer B. BioCAT – Clean air technology for small-scale combustion systems, 4. Central European Biomass Conference 2014, 15th-18th of January 2014, Graz, Austria. (oral presentation)

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Conference contributions | 2015

"Investigations on the catalytic activity of bed material coating regarding the water-gas-shift reaction and the steam reforming of model compounds for lighter and heavier hydrocarbons"

Kuba M, Havlik F, Kirnbauer F, Hofbauer H. Investigations on the catalytic activity of bed material coating regarding the water-gas-shift reaction and the steam reforming of model compounds for lighter and heavier hydrocarbons, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (oral presentation)

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Conference contributions | 2020

"Long-term verification of a new modular method for CO-lambda-optimisation"

Zemann C, Hammer F, Gölles M. Long-term verification of a new modular method for CO-lambda-optimisation. 6th Central European Biomass Conference CEBC 2020 (Oral Presentation). 2020.

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Technical Reports | 2017

2016 Survey of Non-Starch Alcohol and Renewable Hydocarbon Biofuels Producers

Warner E, Bacovsky D, Schwab A. 2016 Survey of Non-Starch Alcohol and Renewable Hydocarbon Biofuels Producers. 2016 Survey of Non-Starch Alcohol and Renewable Hydocarbon Biofuels Producers. February 2017.

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Peer Reviewed Scientific Journals | 2016

2250-h long term operation of a water gas shift pilot plant processing tar-rich product gas from an industrial scale dual fluidized bed biomass steam gasification plant

Kraussler M, Binder M, Hofbauer H. 2250-h long term operation of a water gas shift pilot plant processing tar-rich product gas from an industrial scale dual fluidized bed biomass steam gasification plant. International Journal of Hydrogen Energy. 27 April 2016;41(15): 6247-6258.

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Conference contributions | 2012

2nd Generation Biofuels from Biomass by steam gasification

Rauch R. 2nd Generation Biofuels from Biomass by steam gasification, 1. Nürnberger Fach-Kolloquium Methanisierung und Second Generation Fuels 2012, 29th-30th of May 2012, Nürnberg, Germany.

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Peer Reviewed Scientific Journals | 2011

A carbon-cycle-based stochastic cellular automata climate model

Lichtenegger K, Schappacher W. A carbon-cycle-based stochastic cellular automata climate model. International Journal of Modern Physics C. 2011;22(6):607-621.

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In this paper a stochastic cellular automata model is examined, which has been developed to study a "small" world, where local changes may noticeably alter global characteristics. This is applied to a climate model, where global temperature is determined by an interplay between atmospheric carbon dioxide and carbon stored by plant life. The latter can be released by forest fires, giving rise to significant changes of global conditions within short time.


Contributions to trade journals | 2009

A cell agglomeration algorithm for accelerating detailed chemistry. In: Combustion Theory and Modelling

Goldin GM, Ren Z, Zahirovic S. A cell agglomeration algorithm for accelerating detailed chemistry in CFD. Combustion Theory and Modelling. 2009;13(4):721-39.

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A cell agglomeration algorithm is proposed to mitigate the computational cost of incorporating detailed chemical kinetics in multi-dimensional Computational Fluid Dynamics (CFD) simulations. Cells that are close in species and energy composition space are agglomerated before calling the reaction integrator, substantially reducing the number of chemistry integrations. The algorithm is generalized and applicable to any reacting flow configuration, and the accuracy is fully controllable. A dynamic hash table is used to efficiently bin cells into high dimensional hyper-cubes in composition space. The method is applied to four different CFD simulations and the speed-up and incurred error are assessed for a range of agglomeration tolerances and table dimensions. The proposed approach exhibits up to an order of magnitude speed-up with a relatively moderate decrease in accuracy.


Reviewed Conference Papers | 2012

A CFD model for thermal conversion of thermally thick biomass particles

Mehrabian R, Zahirovic S, Scharler R, Obernberger I, Kleditzsch S, Wirtz S, et al. A CFD model for thermal conversion of thermally thick biomass particles. Fuel Process Technol. 2012;95:96-108.

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A one-dimensional model for the thermal conversion of thermally thick biomass particles is developed for the simulation of the fuel bed of biomass grate furnaces. The model can be applied for cylindrical and spherical particles. The particle is divided into four layers corresponding to the main stages of biomass thermal conversion. The energy and mass conservation equations are solved for each layer. The reactions are assigned to the boundaries. The model can predict the intra-particle temperature gradient, the particle mass loss rate as well as the time-dependent variations of particle size and density, as the most essential features of particle thermal conversion. When simulating the fuel bed of a biomass grate furnace, the particle model has to be numerically efficient. By reducing the number of variables and considering the lowest possible number of grid points inside the particle, a reasonable calculation time of less than 1 min for each particle is achieved. Comparisons between the results predicted by the model and by the measurements have been performed for different particle sizes, shapes and moisture contents during the pyrolysis and combustion in a single-particle reactor. The results of the model are in good agreement with experimental data which implies that the simplifications do not impair the model accuracy.


Conference contributions | 2019

A CFD-method for the analysis and optimization of the fixed bed conversion in biomass grate furnaces

Singer M, Gruber T, Mehrabian R, Scharler R. A CFD-method for the analysis and optimization of the fixed bed conversion in biomass grate furnaces. 27th European Biomass Conference & Exhibition (Poster). 2019.

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To optimize the combustion of biomass grate furnaces a sensitivity analysis is carried out by means of CFD simulation. The methodical procedure consists of a 3D packed bed biomass combustion model, which describes the most essential characteristics of the thermal conversion of biomass particles, such as the detailed consideration of drying, pyrolysis and char oxidation in parallel processes. Within the sensitivity analysis the following parameters have been investigated: distribution of false air, residence time of fuel on the grate and distribution of recirculated flue gas and primary air below the grate. To evaluate the influence of the varied parameters on the combustion process the focus lied on the position of the thermal conversion of the biomass and the CO at the outlet of the simulation domain. The results of the sensitivity analysis show a shift of the thermal conversion towards the grate end for increased false air as well as for reduced momentum of primary air/recirculated flue gas mixture. An increase of the fuel residence time leads to a shift of the thermal conversion towards the fuel inlet. Consequently a large region of the primary combustion zone is not used due to earlier release of CO inside the fuel bed.


Other Publications | 2018

A flexible low cost PV/EV microgrid controller concept based on a Raspberry Pi

Stadler M. A flexible low cost PV/EV microgrid controller concept based on a Raspberry Pi. Working Paper, Center for Energy and innovative Technologies (CET) and Bioenergy 2020+ GmbH, June 2018.

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Peer Reviewed Scientific Journals | 2017

A Generalization of Ackermann’s Formula for the Design of Continuous and Discontinuous Observers

Anca-Couce A, Sommersacher P, Scharler R. Online experiments and modelling with a detailed reaction scheme of single particle biomass pyrolysis. Journal of Analytical and Applied Pyrolysis. Available online 17 July 2017

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Detailed reaction schemes and experimental data for the online release of pyrolysis volatiles are required to gain a more fundamental understanding of biomass pyrolysis, which would in turn allow the process to be controlled in a more precise way and the development of more targeted applications. A detailed online characterisation of pyrolysis products has been conducted in single particle experiments with spruce pellets at different temperatures, obtaining a good closure of the elemental mass balances. The yields and online release of CO, CO2, H2O, CH4, other light hydrocarbons and total organic condensable species, as well as char yield and composition, can be predicted with a reasonable accuracy with the application of a single particle model, coupled with a detailed pyrolysis scheme, and a simple one-step scheme for tar cracking. In order to achieve it, improvements have been conducted in the pyrolysis scheme, mainly concerning the release of light hydrocarbons and char yield and composition. Deviations are still present in the different groups in which organic condensable species can be classified.


Conference Papers | 2019

A Generalization of Ackermann’s Formula for the Design of Continuous and Discontinuous Observers

Niederwieser H, Koch S, Reichhartinger M. A Generalization of Ackermann’s Formula for the Design of Continuous and Discontinuous Observers. 58th IEEE Conference on Decision and Control. 2019.

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This paper proposes a novel design algorithm for nonlinear state observers for linear time-invariant systems. The approach is based on a well-known family of homogeneous differentiators and can be regarded as a generalization of Ackermann's formula. The method includes the classical Luenberger observer as well as continuous or discontinuous nonlinear observers, which enable finite time convergence. For strongly observable systems with bounded unknown perturbation at the input the approach also involves the design of a robust higher order sliding mode observer. An inequality condition for robustness in terms of the observer gains is presented. The properties of the proposed observer are also utilized in the reconstruction of the unknown perturbation and robust state-feedback control


Peer Reviewed Scientific Journals | 2019

A generally applicable, simple and adaptive forecasting method for the short-term heat load of consumers

Nigitz T, Gölles M. A generally applicable, simple and adaptive forecasting method for the short-term heat load of consumers. Applied Energy 2019;241:73-81.

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Energy management systems aiming for an efficient operation of hybrid energy systems with a high share of different renewable energy sources strongly benefit from short-term forecasts for the heat-load. The forecasting methods available in literature are typically tailor-made, complex and non-adaptive. This work condenses these methods to a generally applicable, simple and adaptive forecasting method for the short-term heat load. From a comprehensive literature review as well as the analysis of measurement data from seven different consumers, varying in size and type, the ambient temperature, the time of the day and the day of the week are deduced to be the most dominating factors influencing the heat load. According to these findings, the forecasting method bases on a linear regression model correlating the heat load with the ambient temperature for each hour of the day, additionally differentiating between working days and weekend days. These models are used to predict the future heat load by using forecasts for the ambient temperature from weather service providers. The model parameters are continuously updated by using historical data for the ambient temperature and the heat load, i.e. the forecasting method is adaptive. Additionally, the current prediction error is used to correct the prediction for the near future. Due to their simplicity, all necessary steps of the forecasting method, the update of the model parameters, the prediction based on linear regression models and the correction, can be implemented and computed with little effort. The final evaluation with measurement data from all seven consumers investigated leads to a Mean Absolute Range Normalized Error (MARNE) of 2.9% on average, and proves the general applicability of the forecasting method. In summary, the forecasting method developed is generally applicable, simple and adaptive, making it suitable for the use in energy management systems aiming for an efficient operation of hybrid energy systems.


Peer Reviewed Scientific Journals | 2018

A higher-order generalization of the NPK-method.

Birkelbach F, Deutsch M, Flegkas S, Winter F, Werner A. A higher-order generalization of the NPK-method. Thermochimica Acta, 9 January 2018;661:27-33.

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A novel algorithm to identify the full kinetic model of solid state reactions according to the General Kinetic Equation is presented. It is a higher-order generalization of the Non-Parametric Kinetics method (NPK-method) and allows for the simultaneous identification of the conversion, temperature and pressure dependency from any combination of measurements. As a model-free identification method, it does not rely on a-priori assumptions about the kinetic model. The result vectors can be used to identify the kinetic parameters by means of model fitting for each variable independently.

The steps of the algorithm are described and its effectiveness is demonstrated by applying it to simulated datasets. The kinetic parameters could be recovered very accurately from the test data, also in the presence of noise.

Overall the higher order NPK-method is a very promising approach to derive kinetic models from experimental data with a minimum of a-priori assumptions about the reaction.


Peer Reviewed Scientific Journals | 2017

A hybrid of winddiesel technology with biomass-based Fischer-Tropsch synthesis

Nikparsa P, Rauch R, Mirzaei AA. A hybrid of winddiesel technology with biomass-based Fischer-Tropsch synthesis. Monatshefte für Chemie. 10 July 2017;1-10.

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The syngas mixture produced from biomass (bio-syngas) is characterized by a H2/CO molar ratio of 1.5 in this work, which is different from that of traditional syngas ratio of 2. Therefore a hybrid of winddiesel technology with bio-syngas conversion by Fischer–Tropsch synthesis (WD-FT) on a cobalt based catalyst was investigated, for the first time, using a slurry reactor. The result from feeding this technology is compared with the direct converting biomass derived synthetic gas to fuels via Fischer–Tropsch synthesis (BS-FT). Experiments were performed at different syngas composition (variation of H2/CO ratio), keeping the other parameters (temperature 230 °C; gas flow 5 Nm³/h, pressure 20 bar) constant. Comparison of the WD-FT with the BS-FT synthesis results displayed mass fraction of light hydrocarbons and higher catalytic stability and activity after 500 h. The olefin structures for the different product distributions, obtained from different reactions, are determined by ¹H NMR spectroscopy. Negligible amounts of iso-α-olefins were detected in the product of the WD-FT reaction. In the case of the alpha value, a slight change was observed between 0.93 and 0.92 for the BS-FT and WD-FT reaction.
 


Peer Reviewed Scientific Journals | 2020

A MILP-based modular energy management system for urban multi-energy systems: Performance and sensitivity analysis

Moser AGC, Muschick D, Gölles M, Nageler PJ, Schranzhofer H, Mach T et al. A MILP-based modular energy management system for urban multi-energy systems: Performance and sensitivity analysis. Applied Energy. 2020;2020(261). 114342.

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The continuous increase of (volatile) renewable energy production and the coupling of different energy sectors such as heating, cooling and electricity have significantly increased the complexity of urban energy systems. Such multi-energy systems (MES) can be operated more efficiently with the aid of optimization-based energy management systems (EMS). However, most existing EMS are tailor-made for one specific system or class of systems, i.e. are not generally applicable. Furthermore, only limited information on the actual savings potential of the usage of an EMS under realistic conditions is available. Therefore, this paper presents a novel modular modeling approach for an EMS for urban MES, which also enables the modeling of complex system configurations. To assess the actual savings potential of the proposed EMS, a comprehensive case study was carried out. In the course of this the influence of different user behavior, changing climatic conditions and forecast errors on the savings potential was analyzed by comparing it with a conventional control strategy. The results showed that using the proposed EMS in conjunction with supplementary system components (thermal energy storage and battery) an annual cost savings potential of between 3 and 6% could be achieved.


Conference contributions | 2020

A modular energy management system for multi-energy systems

Muschick D, Kaisermayer V, Moser A, Gölles M. A modular energy management system for multi-energy systems. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Contributions to trade journals | 2013

A new innovative CFD-based optimisation method for biomass combustion plants

Shiehnejadhesar A, Schulze K, Scharler R, Obernberger I. A new innovative CFD-based optimisation method for biomass combustion plants. Biomass Bioenergy. 2013;53:48-53.

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In this paper, the work on the development and test of a basic design tool for the automatic performance of parameter studies for the optimisation of biomass combustion plants is presented. The model consists of parameterisation and optimisation routines linked with an in-house developed empirical packed bed combustion model as well as gas phase CFD models especially adapted for biomass grate furnaces. To test and verify the routine developed, it has been applied to the optimisation of a 180 kWth pilot-scale grate furnace. The main focus was on the minimisation of CO emissions and the pressure loss by changing the diameter and angle of the secondary air nozzles. The simulation results show that the time of the optimisation process can be reduced considerably by the automatic routine developed and the evaluation of several independent design parameters is possible. This new procedure forms an important milestone towards automatic CFD-based furnace and boiler optimisations in the future. © 2013 Elsevier Ltd.


Conference Papers | 2017

A novel approach for the implementation of TORrefaction in Residential and COMmunal heating Boilers (TORRECOMB)

Kourkoumpa DS, Kienzl N, Isemin R, Strasser C, Nikolopoulus N, Margaritis N, Panagiotis G. A novel approach for the implementation of TORrefaction in Residential and COMmunal heating Boilers (TORRECOMB). 5th Central European Biomass Conference (Poster). January 2017, Graz, Austria.

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Scientific Journals | 2020

A novel production route and process optimization of biomass-derived paraffin wax for pharmaceutical application

Gruber H, Lindner L, Arlt S, Reichhold A, Rauch R, Weber G, Trimbach J, Hofbauer H. A novel production route and process optimization of biomass-derived paraffin wax for pharmaceutical application. Journal of Cleaner Production. 2020;275:124135

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The Biomass to Liquid (BtL) Fischer-Tropsch (FT) route converts lignocellulosic feedstock to renewable hydrocarbons. This, paper shows a novel production route for biomass-derived synthetic paraffin wax via gasification of lignocellulosic feedstock, Fischer-Tropsch synthesis (FTS) and hydrofining. The Fischer-Tropsch wax was fractionated, refined and analyzed with respect to compliance to commercial standards. The fractioned paraffin waxes were hydrofined using a commercial sulfide NiMo–Al2O3 catalyst and a trickle bed reactor. A parametric variation was performed to optimize the hydrofining process. It was shown that the produced medium-melt paraffin wax could fulfill the requirements for “Paraffinum solidum” defined by the European Pharmacopoeia (Ph. Eur). The high-melt wax fraction showed potential to be used as food packaging additive. Furthermore, the renewable wax was analyzed regarding PAH content and it was shown that the hydrofined wax was quasi-PAH-free.


Scientific Journals | 2019

A practical field trial to assess the potential of Sida hermaphrodita as a versatile, perennial bioenergy crop for Central Europe.

von Gehren P, Gansberger M, Pichler W, Weigl M, Feldmeier S, Wopienka E, Bochmann G. A practical field trial to assess the potential of Sida hermaphrodita as a versatile, perennial bioenergy crop for Central Europe. Biomass and Bioenergy 2019;122:99-108.

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Due to high biomass accumulation ability and multiple ecological benefits, the versatile, perennial bioenergy crop Sida hermaphrodita has sparked the interest of researchers in Central Europe. We assessed the crop's agronomy and bioenergy potential when grown under Austrian climate and soil conditions. A field trial was established in Austria, where the factors planting density and utilization strategy (thermal or biogas) were monitored for three growing seasons. Harvesting lignified biomass for thermal utilization at the end of the growing period resulted in higher dry matter yields than green biomass for biogas utilization which was harvested with a two-cut strategy. Due to lower costs but similar yield, a planting density of 1.77 plants m-2 is preferable over 2.66 plants m-2. The pelletizing process of the biomass was analyzed iteratively in 20 runs to optimize the energy efficiency and process stability while simultaneously increasing pellet durability. A simple drying step, disintegration with a pan grinder mill and pelletizing using a flat die pellet press resulted in stable, high quality pellets. Fuel characteristics of the biomass were favorable and all requirements to be categorized as solid biofuel were met, while combustion tests showed a good applicability of the produced pellets. When green biomass was used for biogas production, a significant drop in methane yield could be noted from the second growing season onward, indicating that older plants are less suitable for biogas production. Our results hint towards the potential of lignified S. hermaphrodita biomass to be used as a solid fuel for energy production.


Peer Reviewed Scientific Journals | 2021

A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds

Kuba M, Skoglund N, Öhman M, Hofbauer H. A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds.Fuel.2021.291:120214. https://doi.org/10.1016/j.fuel.2021.120214

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Bed material particle layer formation plays a significant role in thermo-chemical conversion of biomass. The interaction between biomass ash and bed material in fluidized bed conversion processes has been described for a variety of different applications and spans from fundamental research of formation mechanisms to effects of this layer formation on long-term operation in industrial-scale. This review describes the current state of the research regarding the mechanisms underlying layer formation and the positive influence of bed material particle layer formation on the operation of thermo-chemical conversion processes. Thus, the main focus lies on its effect on the catalytic activity towards gasification reactions and the impact on oxygen transport in chemical looping combustion. The review focuses on the most commonly investigated bed materials, such as quartz, feldspar or olivine. While the most relevant results for both the underlying mechanisms and the subsequently observed effects on the operation are presented and discussed, knowledge gaps where further research is necessary are identified and described.