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Scientific Journals | 2018

Development of a compact technique to measure benzo(a)pyrene emissions from residential wood combustion, and subsequent testing in six modern wood boilers

Klauser F, Schwabl M, Kistler M, Sedlmayer I, Kienzl N, Weissinger A, Schmidl C, Haslinger W, Kasper-Giebl A. Development of a compact technique to measure benzo(a)pyrene emissions from residential wood combustion, and subsequent testing in six modern wood boilers. Biomass and Bioenergy. April 2018, 111: 288-300.

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Polycyclic aromatic hydrocarbons (PAHs) are emitted during incomplete combustion of organic materials and are particularly harmful to human health. As a representative of PAHs, Benzo(a)pyrene (BaP) is restricted by the European Union to an annual average value of 1 ng m−3 in ambient air. This threshold is significantly exceeded during the heating season in various regions. Residential wood combustion furnaces are considered to be a major source for BaP pollution.

In this research, a compact sampling method for BaP measurements was validated. Afterwards, the method was used to assess emissions from modern automatic wood boilers, in order to obtain a detailed knowledge of BaP emissions from residential wood combustion furnaces.

It was demonstrated that, for a wide range of BaP concentrations, sampling from the hot flue gas of residential wood combustors can be carried out effectively over a simple quartz filter, after proper dilution with cold purified air. Highest BaP emissions from the investigated boilers occurred during start, with a mean concentration value of 6.3 μg m-3. All values refer to standard conditions (273.15 °C, 100 kPa) and to an O2 volume fraction of 13% in the dry flue gas. The lowest concentrations occurred during full load operation (mean value 73 ng m-3 at STP). It was found that, amongst all flue gas compounds analysed, elemental carbon is the parameter most closely related to BaP. This work demonstrates, at optimal operating conditions, modern automatic wood boilers have potentially lowest BaP emission concentrations amongst residential wood combustion furnaces.


Peer Reviewed Scientific Journals | 2018

Emission characterisation of modern wood stoves under real-life oriented operating conditions

Klauser F, Carlon E, Kistler M, Schmidl C, Schwabl M, Sturmlechner R, Haslinger W, Kasper-Giebl A. Emission characterisation of modern wood stoves under real-life oriented operating conditions. Atmospheric Environment 2018;192:257-266.

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The quality of emission inventories substantially bases on the reliability of used emission factors (EFs). In this work EFs were studied according to recently published characterization methods, called “beReal”, reflecting real life operating conditions in Europe. EFs for four pellet stoves and nine firewood appliances (roomheaters and cookers) of carbon monoxide (CO), organic gaseous compounds (OGC), nitrogen oxides, total solid particles (TSP) of hot and of diluted flue gas, total, elemental and organic carbon (TC, EC, OC) and benzo(a)pyrene were determined.

CO, OGC, TSPs, TC, EC and OC emissions from firewood appliances were significantly higher than for pellet stoves, indicating the high relevance of classifying appliances according to the operation type. TSP sampled from diluted flue gas at 40 °C (28 mg MJ−1 to 271 mg MJ−1 based on fuel input) was higher than TSP sampled from hot flue gas (21 mg MJ−1 to 70 mg MJ−1). This reveals the high relevance of sampling conditions for the determination of real life emissions. Benzo(a)pyrene emissions scattered over a wide range (0.5 μg MJ−1 to 129.8 μg MJ−1) indicating high sensitivity to unfavorable combustion conditions. Therefore a higher number of experimentally determined emissions factors could improve the reliability of EFs for inventories. CO emissions measured in beReal tests were substantially higher than official type tests, thus showing that type testing results provide limited information for the determination of real life emissions.

A systematic evaluation of EFs with defined real life methods like beReal would substantially improve the reliability of emission inventories.


Peer Reviewed Scientific Journals | 2018

Evaluation of the Potential for Efficiency Increase by the Application of Model-Based Control Strategies in Large-Scale Solar Thermal Plants

Unterberger V, Lichtenegger K, Innerhofer P, Gerardts B, Gölles M. Evaluation of the Potential for Efficiency Increase by the Application of Model-Based Control Strategies in Large-Scale Solar Thermal Plants. International Journal of Contemporary ENERGY. 2018; 4(1): 549-559.

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This paper presents a systematic evaluation procedure to estimate the potential for performance improvement by applying model-based control strategies in large-scale thermal plants. The evaluation is performed separately for the low-level control which is in charge of the temperatures in the collector fields and for the high-level control which defines the general mode of operation of a plant. In order to evaluate the potential for the low-level control, simulation studies have been carried out, based on the assumption that the individual flows through the collector fields can be controlled separately. This can be achieved by an advanced model-based control which makes use of motor-driven control valves at the inlets of the collector fields. The potential of the high-level control has been evaluated by energy calculations based on measurement data from a typical large-scale solar thermal plant. The evaluation finally identified a potential for efficiency increase in the range of 8% for the low- level control and about 3% for the high-level control.

Scientific Journals | 2018

Experimental parametric study in industrial-scale dual fluid bed gasification of woody biomass: Influences on product gas and tar composition

Kuba M, Hofbauer H. Experimental parametric study in industrial-scale dual fluid bed gasification of woody biomass: Influences on product gas and tar composition. Biomass and Bioenergy. 2018, 115: 35-44.

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Tar measurements at two industrial-scale DFB gasification plants showed clear trends regarding the influence of the above mentioned parameters on the product gas and tar composition. Since data was gathered during tar measurement campaigns over the course of four years the density of information in industrial-scale was increased significantly. As different operation points, e.g. different capacities of the power plant, are included in the consideration, the verisimilitude is comparably high.

It was shown, that reducing the operation temperature leads to an increase of the total tar amounts. However, while the concentration of the tar compounds benzofuran, styrene, and 1H-indene was increased when lowering the temperature, the concentration of naphthalene was decreased. These results were in good correlation with previous work from lab-scale investigations. The temperature did not have a measureable influence on the concentration of the tar compounds anthracene and ace-naphthalene, which was against former experience from lab-scale. The concentration of those larger PAHs anthracene and ace-naphthalene was more dominantly influenced by the bed height in the gasification reactor. Increasing the bed height led to a decrease of the concentration of larger PAHs while it did not have a distinctive influence on benzofuran, styrene, and 1H-indene.

The reactor design was identified as an influencing effect, due to the presence of a moving bed section above the inclined wall, where no fluidization is ensured. Thus, additional fluidization nozzles were installed to reduce the effect of the inclined wall. Finally, two operation points for optimized long-term operation were derived from the results.


Scientific Journals | 2018

Experiments and modelling of NOx precursors release (NH3 and HCN) in fixed-bed biomass combustion conditions

Anca-Couce A, Sommersacher P, Evic N, Mehrabian R, Scharler R. Experiments and modelling of NOx precursors release (NH3 and HCN) in fixed-bed biomass combustion conditions. Fuel. 2018, 222: 529-537.

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There is a need to reduce NOx emissions, which can only be achieved through a detailed understanding of the mechanisms for their formation and reduction. In this work the release of the NOx precursors, NH3 and HCN, for different fuels is experimentally analysed and modelled in typical fixed-bed combustion conditions. It is shown that NH3 and HCN are released during the main devolatilization phase and the NH3/HCN ratio increases for fuels with a higher nitrogen content. A simplified two-steps model for their release is presented. The model can predict with a reasonable accuracy the release for fuels with a low nitrogen content, however deviations are present for fuels with a high nitrogen content, which probably arise due to a reduction of NH3 and HCN taking place already in the bed.


Scientific Journals | 2018

Hydrogen production within a polygeneration concept based on dual fluidized bed biomass steam gasification

Kraussler M, Binder M, Schindler P, Hofbauer H. Hydrogen production within a polygeneration concept based on dual fluidized bed biomass steam gasification. Biomass and Bioenergy. April 2018, 111: 320-329.

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Dual fluidized bed biomass steam gasification generates a high calorific, practically nitrogen-free product gas with a volumetric H2 content of about 40%. Therefore, this could be a promising route for a polygeneration concept aiming at the production of valuable gases (for example H2), electricity, and heat. In this paper, a lab-scale process chain, based on state of the art unit operations, which processed a tar-rich product gas from a commercial dual fluidized bed biomass steam gasification plant, is investigated regarding H2 production within a polygeneration concept. The lab-scale process chain employed a water gas shift step, two gas scrubbing steps, and a pressure swing adsorption step. During the investigations, a volumetric H2 concentration of 99.9% with a specific H2 production of 30 g kg−1 biomass was reached. In addition, a valuable off-gas stream with a lower heating value of 7.9 MJ m−3 was produced. Moreover, a techno-economic assessment shows the economic feasibility of such a polygeneration concept, if certain feed in tariffs for renewable electricity and H2 exist. Consequently, these results show, that the dual fluidized bed biomass steam gasification technology is a promising route for a polygeneration concept, which aims at the production of H2, electricity, and district heat.


Scientific Journals | 2018

Impact of Oxidizing Honeycomb Catalysts Integrated in Firewood Stoves on Emissions under Real-Life Operating Conditions

Reichert G, Schmidl C, Haslinger W, Stressler H, Sturmlechner R, Schwabl M, Wöhler M, Hochenauer C. Impact of Oxidizing Honeycomb Catalysts Integrated in Firewood Stoves on Emissions under Real-Life Operating Conditions. Fuel Processing Technology. 2018; 117: 300-313.

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Catalytic systems integrated in firewood stoves represent a secondary measure for emission reduction. This study evaluates the impact on emissions of two types of honeycomb catalysts integrated in different firewood stoves. The tests were conducted under real-life related testing conditions. The pressure drop induced by the catalyst's carrier geometry affects primary combustion conditions which can influence the emissions. A negative primary effect reduces the catalytic efficiency and has to be considered for developing catalyst integrated solutions. However, a significant net emission reduction was observed. The ceramic catalyst reduced CO emissions by 83%. The metallic catalyst reduced CO emissions by 93% which was significantly better compared to the ceramic catalyst. The net emission reduction of OGC (~30%) and PM (~20%) was similar for both types of catalysts. In most cases, the “Ecodesign” emission limit values, which will enter into force in 2022 for new stoves, were met although the ignition and preheating batches were respected. PM emission composition showed a lower share of elemental (EC) and organic carbon (OC) with integrated catalyst. However, no selectivity towards more reduction of EC or OC was observed. Further investigations should evaluate the long term stability under real-life operation in the field and the effect of the catalyst on polycyclic aromatic hydrocarbon (PAH) emissions.


Scientific Journals | 2018

Improving exploitation of chicken manure via two-stage anaerobic digestion with an intermediate membrane contactor to extract ammonia

Wang X, Gabauer W, Li Z, Ortner M, Fuchs W. Improving exploitation of chicken manure via two-stage anaerobic digestion with an intermediate membrane contactor to extract ammonia. Bioresource Technology 2018;368:811-814.

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This study describes a modified process of ammonia release through pre-hydrolysis – ammonia removal via membrane contactor – methanization for counteracting ammonia inhibition in anaerobic digestion of chicken manure. In the pre-hydrolysis step, ammonia was rapidly released within the first 3–5 days. 78%-83% of the total nitrogen was finally converted into total ammonia/ammonium (TAN) with volatile fatty acids concentration of approximately 300 g/kg·VS. In the ammonia removal process, diluting the hydrolyzed chicken manure to 1:2, the TAN could be reduced to 2 g/kg in 21 h when pH was increased to 9. The final BMP test of chicken manure verified that lower TAN concentration (decreased to 2 g/kg) significantly reduced inhibitory effects, obtaining a high methane yield of 437.0 mL/g·VS. The investigations underlined several advantages of this modified process.


Peer Reviewed Scientific Journals | 2018

Influence of drag laws on pressure and bed material recirculation rate in a cold flow model of an 8 MW dual fluidized bed system by means of CPFD

Kraft S, Kirnbauer F, Hofbauer H. Influence of drag laws on pressure and bed material recirculation rate in a cold flow model of an 8 MW dual fluidized bed system by means of CPFD. Particuology, February 2018;36:70-81.

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A cold flow model of an 8 MW dual fluidized bed (DFB) system is simulated using the commercial computational particle fluid dynamics (CPFD) software package Barracuda. The DFB system comprises a bubbling bed connected to a fast fluidized bed with the bed material circulating between them. As the hydrodynamics in hot DFB plants are complex because of high temperatures and many chemical reaction processes, cold flow models are used. Performing numerical simulations of cold flows enables a focus on the hydrodynamics as the chemistry and heat and mass transfer processes can be put aside. The drag law has a major influence on the hydrodynamics, and therefore its influence on pressure, particle distribution, and bed material recirculation rate is calculated using Barracuda and its results are compared with experimental results. The drag laws used were energy-minimization multiscale (EMMS), Ganser, Turton–Levenspiel, and a combination of Wen–Yu/Ergun. Eleven operating points were chosen for that study and each was calculated with the aforementioned drag laws. The EMMS drag law best predicted the pressure and distribution of the bed material in the different parts of the DFB system. For predicting the bed material recirculation rate, the Ganser drag law showed the best results. However, the drag laws often were not able to predict the experimentally found trends of the bed material recirculation rate. Indeed, the drag law significantly influences the hydrodynamic outcomes in a DFB system and must be chosen carefully to obtain meaningful simulation results. More research may enable recommendations as to which drag law is useful in simulations of a DFB system with CPFD.


Technical Reports | 2018

Modellbasierte Regelung und Elektrofilterintegration zur schadstoffarmen Verbrennung alternativer Biomassebrennstoffe

Muschick D, Zemann C, Kelz J, Hofmeister G, Gölles M. Modellbasierte Regelung und Elektrofilterintegration zur schadstoffarmen Verbrennung alternativer Biomassebrennstoffe. FFG, Energieforschungsprogramm 1. Ausschreibung. 2018.

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Other Presentations | 2018

Modular Energy Management Systems for future cross-sectoral energy systems

Muschick D, Moser A, Stadler M, Gölles M. Modular Energy Management Systems for future cross-sectoral energy systems. World Sustainable Energy Days 2018.

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Conference contributions | 2018

Modular optimization-based energy management framework for cross-sectoral energy networks

Muschick D, Gölles M, Moser A. Modular optimization-based energy management framework for cross-sectoral energy networks. 5th International Solar District Heating Conference SDH. Graz, Austria: 2018. (Poster)

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Other Presentations | 2018

Modulares Energiemanagementsystem für sektorübergreifende Energiesysteme

Muschick D, Moser A, Stadler M, Gölles M. Modulares Energiemanagementsystem für sektorübergreifende Energiesysteme. 15. Symposiums Energieinnovation; Februar 2018.

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Conference contributions | 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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Scientific Journals | 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.


Scientific Journals | 2018

Tackling ammonia inhibition for efficient biogas production from chicken manure: Status and technical trends in Europe and China

Fuchs W, Wang X, Gabauer W, Ortner M, Li Z. Tackling ammonia inhibition for efficient biogas production from chicken manure: Status and technical trends in Europe and China (Review). Renewable and Sustainable Energy Reviews 2018;97:186-199.

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The increased global consumption of chicken products has resulted in the generation of huge amounts of manure. Numerous studies emphasized the large potential of this waste as an untapped source of renewable energy through anaerobic digestion (AD). However, intrinsic difficulties, in particular the high N content, induce instable process conditions, including the accumulation of intermediates, and foaming, which reduces methane yields. Such issues limit the widespread application of this energy-rich substrate for biogas production. The process inhibition by ammonia is usually prevented by reducing the concentration of chicken manure through dilution or by operating the plant considerably below its theoretical reactor capacity. However, this process compromises process efficiency, thereby increasing capital investments and operational costs. Another option to achieve optimal process performance is co-digestion with less N-rich materials. However, co-digestion also has its limitations due to the frequent unavailability of sufficient amounts of C-rich substrates. A series of promising technical solutions have been developed to overcome the aforementioned bottlenecks. Examples include stripping or membrane extraction as means to reduce ammonia concentration in the fermenter. Several full-scale plants employing ammonia removal techniques have been installed recently. Latest research also investigated the use of additives, such as zeolites and trace elements, as well as bioaugmentation, to mitigate ammonia inhibition. The current study reviews the state of technology as well as recent achievements and perspectives. It provides an overview of the different approaches to remove ammonia from AD-process and presents practical examples from China and Europe.


Technical Reports | 2018

The Green P - Nutzung von städtischen Verkehrsflächen für die Produktion von Biomasse

Lichtenegger K, Meixner K, Riepl R, Schipfer F, Zellinger M. The Green P - Nutzung von städtischen Verkehrsflächen für die Produktion von Biomasse. BMVIT, Schriftenreihe 25/2018.

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Peer Reviewed Scientific Journals | 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.


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