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Peer Reviewed Scientific Journals | 2019

Single large wood log conversion in a stove: Experiments and modelling

Anca-Couce A, Caposciutti G, Gruber T, Kelz J, Bauer T, Hochenauer C, Scharler R. Single large wood log conversion in a stove: Experiments and modelling. Renewable Energy 2019.143:890-897.

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Natural draft wood log stoves for residential bioheat production are very popular due to the low fuel costs, the ecological aspect of a renewable energy source and the visual appeal of the flame. However, they have rather high pollutant emissions, specially of unburnt products. The description of large wood logs conversion in stoves needs to be improved to allow a process optimization which can reduce these emissions. The transient conversion of a single wood log in a stove is experimentally investigated with test runs quenching the log after defined time intervals and measuring the flue gas composition and temperatures in the log and stove. The experiments have been described with a volumetric single particle model, which predicts with good accuracy the log conversion until a time of around 30 min, when pyrolysis is almost ending. At that point, log fragmentation takes place and smaller fragments are detached from the log falling onto the bed of embers. Despite the increase in external surface area, char oxidation takes place at a moderate rate. This last stage of wood log conversion in a stove is the most challenging to model. Finally, preliminary recommendations are provided for reducing CO emissions in wood log stoves.


Conference contributions | 2019

Smart Logwood Boiler - A holistic approach for improving the efficiency of residential heating systems. 27th European Biomass Conference & Exhibition.

Zemann C, Deutsch M, Zlabinger S, Hofmeister G, Gölles M, Horn M. Smart Logwood Boiler - A holistic approach for improving the efficiency of residential heating systems. 27th European Biomass Conference & Exhibition. Lisbon. 2019. (Oral presentation, 27.05.2019).

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Conference contributions | 2019

Smart Logwood Boiler – A holistic approach for improving the efficiency of residential heating systems

Zemann C, Deutsch M, Zlabinger S, Hofmeister G, Gölles M, Horn M. Smart Logwood Boiler – A holistic approach for improving the efficiency of residential heating systems. 27th European Biomass Conference & Exhibition (Oral Presentation). May 2019.

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Conference contributions | 2019

Spectroscopic in situ methods for the evaluation of the active centers on ash-layered bed materials from gasification in a fluidized bed reactor

Chlebda D, Aziaba K, Janisch D, Kuba M, Hofbauer H, Łojewska J. Spectroscopic in situ methods for the evaluation of the active centers on ash-layered bed materials from gasification in a fluidized bed reactor. ICPS 2019

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Technical Reports | 2019

Synchronization of the gas production and utilization rates of a solid-to-gas process and a downstream gas-to-X process

Nigitz T, Gölles M, Aichernig C, Hofbauer H, Horn, M. Synchronization of the gas production and utilization rates of a solid-to-gas process and a downstream gas-to-X process. 21. Styrian Workshop on Automatic Control. 10 September 2019. Leitring/Wagna, Austria. (oral presentation)

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Conference contributions | 2019

Technology mapping of market-available small-scale combustion appliances

Feldmeier S, Wopienka E, Schwarz M, Pfeifer C. Technology mapping of market-available small-scale combustion appliances. 27th European Biomass Conference & Exhibition (Poster). 2019.

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A broad range of different biomass combustion appliances dedicated to domestic heating is available on the market. Depending on the technology the impact of varying properties of biomass fuels on slag formation and emission release may vary. Aspects as the design of the grate section and the selection of individual boiler components as well as operational settings determine the applicability of biomass fuels. Apart from fuel properties also the fuel load on the grate, residence time, air distribution and geometry of grate and combustion chamber affect the degree of slag formation and emission release. Technology indexes determined by means of constructional measures enable a systematic comparison and – in a further step – an assessment of combustion appliances. In this work specific technology indexes were specified and applied to compare technological aspects, which will prospectively allow investigating the technological influence on the combustion performance.


Conference contributions | 2019

Thermal Trouble: Challenges in Optimization and Evaluation of Thermal Energy Systems

Lichtenegger K, Unterberger V, Stadler M, Zellinger M, Carreras F, Moser A. Thermal Trouble: Challenges in Optimization and Evaluation of Thermal Energy Systems. IAPE 2019 : International Conference on Innovative Applied Energy (oral presentation). March 2019.

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Conference contributions | 2019

Time-dependent catalytic activation of inactive k-feldspar by layer formation during fluidized bed conversion with residual fuels

Wagner C, Hammerl C, Kuba M, Hofbauer H. Time-dependent catalytic activation of inactive k-feldspar by layer formation during fluidized bed conversion with residual fuels. 27th European Biomass Conference & Exhibition (Poster). May 2019.

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Olivine is currently used as bed material in dual fluidized bed steam gasification due to its catalytic activity towards the water-gas-shift (WGS) reaction and tar reforming. However, olivine contains traces of heavy metals which necessitate an expensive disposal of the accruing ash. The study of alternative bed materials for DFB steam gasification is therefore of major importance. The activity of a bed material is one important factor when classifying its suitability. Several alternative bed materials like quartz and K-feldspar are non-active when fresh but become activated during operation by interaction with the ash by forming layers. The focus of this work was therefore to quantify the initial activation of K-feldspar over the first operational hours as exemplary inactive bed material. Bed material samples from fluidized bed combustion were collected during operation. The fuels used were bark, chicken manure and a bark/chicken manure mixture. The obtained samples were sieved to 200 – 250 µm and tested in a micro-scale test-rig regarding the WGS reaction. A time-dependent activation of K-feldspar was observed marking a first step in better understanding the activation of bed materials.


Conference contributions | 2019

Towards the in house production of enzymes using processing waste

Weiss R, Nyanhongo G, Ortner M, Guebitz G.Towards the in house production of enzymes using processing waste. 15th International Conference on Renewable Resources and Biorefineries, Toulouse, FRANCE. June 2019.

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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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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 | 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.


Conference contributions | 2018

Adaptive forecasting methods for the prediction of future solar yield of solar thermal plants and heat demand of consumers

Unterberger V, Nigitz T, Luzzu M, Innerhofer P, Muschick D, Gölles M. Adaptive forecasting methods for the prediction of future solar yield of solar thermal plants and heat demand of consumers. 5th International Solar District Heating Conference SDH. Graz, Austria: 2018.

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Conference Papers | 2018

Adaptive Methods for Energy Forecasting of Production and Demand of Solar Assisted Heating Systems

Unterberger V, Nigitz T, Luzzu M, Muschick D, Gölles M. Adaptive Methods for Energy Forecasting of Production and Demand of Solar Assisted Heating Systems., Proceeding of Papers Vol1, p170-181 International conference on time series and forecasting, Granada, Spain, September 19-21, 2018.

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Scientific Journals | 2018

Adsorptive on-board desulfurization over multiple cycles for fuel-cell-based auxiliary power units operated by different types of fuels

Neubauer, R, Weinlaender C, Kienzl N, Bitschnau B, Schroettner H, Hochenauer C. Adsorptive on-board desulfurization over multiple cycles for fuel-cell-based auxiliary power units operated by different types of fuels. Journal of Power Sources. 1 May 2018, 385: 45-54.

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On-board desulfurization is essential to operate fuel-cell-based auxiliary power units (APU) with commercial fuels. In this work, both (i) on-board desulfurization and (ii) on-board regeneration performance of Ag-Al2O3 adsorbent is investigated in a comprehensive manner. The herein investigated regeneration strategy uses hot APU off-gas as the regeneration medium and requires no additional reagents, tanks, nor heat exchangers and thus has remarkable advantages in comparison to state-of-the-art regeneration strategies. The results for (i) show high desulfurization performance of Ag-Al2O3 under all relevant operating conditions and specify the influence of individual operation parameters and the combination of them, which have not yet been quantified. The system integrated regeneration strategy (ii) shows excellent regeneration performance recovering 100% of the initial adsorption capacity for all investigated types of fuels and sulfur heterocycles. Even the adsorption capacity of the most challenging dibenzothiophene in terms of regeneration is restored to 100% over 14 cycles of operation. Subsequent material analyses proved the thermal and chemical stability of all relevant adsorption sites under APU off-gas conditions. To the best of our knowledge, this is the first time 100% regeneration after adsorption of dibenzothiophene is reported over 14 cycles of operation for thermal regeneration in oxidizing atmospheres.


Conference Papers | 2018

Assessment of the Behaviour of a Commercial Gasification Plant During Load Modulation and Feedstock Moisture Variation: Preliminary results of the "Flexi-Fuel-Gas-Control" Project

Antolini D, Hollenstein C, Martini S, Patuzzi F, Zemann C, Felsberger W, Baratieri M, Gölles M. Assessment of the Behaviour of a Commercial Gasification Plant During Load Modulation and Feedstock Moisture Variation: Preliminary results of the "Flexi-Fuel-Gas-Control" Project. 7th International conference on Engineering for Waste and Biomass Valorisation. 2.-5. July 2018. Prague: Czech Republic.

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Peer Reviewed Scientific Journals | 2018

Catalytic Efficiency of Oxidizing Honeycomb Catalysts Integrated in Firewood Stoves Evaluated by a Novel Measuring Methodology under Real-Life Operating Conditions

Reichert G, Schmidl C, Haslinger W, Stressler H, Sturmlechner R, Schwabl M, Wöhler M, Hochenauer C. Catalytic Efficiency of Oxidizing Honeycomb Catalysts Integrated in Firewood Stoves Evaluated by a Novel Measuring Methodology under Real-Life Operating Conditions. Renewable Energy, March 2018;117:300-313.

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Catalytic systems integrated in firewood stoves represent a potential secondary measure for emission reduction. However, the evaluation of catalytic efficiency is challenging since measurements, especially for PM emissions, upstream an integrated catalyst are not possible. Therefore, a special test facility, called “DemoCat”, was constructed which enabled parallel measurements in catalytically treated and untreated flue gas. The catalytic efficiency for CO, OGC and PM emissions was investigated under real-life operating conditions including ignition and preheating. The results confirmed a significant emission reduction potential (CO: > 95%, OGC: > 60%, PM: ∼30%). The conversion rates of CO and OGC emissions correlated with the space velocity and the coated area of honeycomb carriers which represent key parameters for the integration design. A quick response of the catalytic effect of around 5–12 min after ignition was observed when reaching 250 °C flue gas temperature at the catalyst. Most effective CO and OGC emission conversion was evident during the start-up and burn-out phase of a firewood batch. This reveals an important synergy for primary optimization which focuses particularly on the stretched intermediate phase of a combustion batch. The catalytic effect on PM emissions, especially on chemical composition, needs further investigations.


Studien | 2018

CO2-Einsparungskosten

Analyse der Sektoren Mobilität und Wärmebereitstellung

Strasser C, Sturmlechner R, Schwarz M. CO2-Einsparungskosten.2018

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Dieser Bericht bietet eine ERhebung dero CO2e-Einsparungskosten außerhalb des ETS-Handels für den Bereich der Mobilität sowie der Wärmebereitstellung im häuslichen Sektor und Fern- und Nahwärme.


Peer Reviewed Scientific Journals | 2018

Cyanobacteria Biorefinery — Production of poly(3-hydroxybutyrate) with Synechocystis salina and utilisation of residual biomass

Meixner K, Kovalcik A, Sykacek E, Gruber-Brunhumer M, Zeilinger W, Markl K, Haas C, Fritz I, Mundigler N, Stelzer F, Neureiter M, Fuchs W, Drosg B. Cyanobacteria Biorefinery — Production of poly(3-hydroxybutyrate) with Synechocystis salina and utilisation of residual biomass. Journal of Biotechnology. 10 January 2018;265(10): 46-53

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Peer Reviewed Scientific Journals | 2018

Determination of off-gassing and self-heating potential of wood pellets - Method comparison and correlation analysis

Sedlmayer I, Arshadi M, Haslinger W, Hofbauer H, Larsson I, Lönnermark A, Pollex A, Schmidl C, Stelte W, Wopienka E, Bauer-Emhofer W. Determination of off-gassing and self-heating potential of wood pellets - Method comparison and correlation analysis. Fuel 2018;234:894-903.

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Several methods for identifying the phenomena of self-heating and off-gassing during production, transportation and storage of wood pellets have been developed in recent years. Research focused on the exploration of the underlying mechanisms, influencing factors or the quantification of self-heating or off-gassing tendencies. The present study aims at identifying a clear correlation between self-heating and off-gassing. Thus, different methods for determining self-heating and off-gassing potentials of wood pellets are compared. Therefore, eleven wood pellet batches from the European market were analyzed. For this investigation, three methods for the determination of self-heating, like isothermal calorimetry, oxi-press and thermogravimetric analysis, and four methods for off-gassing, like volatile organic compound (VOC) emissions measurements, gas phase analysis of stored pellets in a closed container by offline and by glass flask method and determination of fatty and resin acids content, were performed. Results were ranked according to the self-heating and off-gassing tendency providing a common overview of the analyzed pellets batches. Relations between different methods were investigated by Spearman’s correlation coefficient. Evaluation of the results revealed an equal suitability of offline and glass flask methods to predict off-gassing tendency and indicated a very significant correlation with isothermal calorimetry for the identification of self-heating tendency. The thermogravimetric analysis as well as the fatty and resin acids determination proved to be insufficient for the exclusive assessment of self-heating and off-gassing tendency, respectively.


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.

Peer Reviewed Scientific Journals | 2018

Experimental demonstration and validation of hydrogen production based on gasification of lignocellulosic feedstock

Loipersböck J, Luisser M, Müller S, Hofbauer H, Rauch R. Experimental demonstration and validation of hydrogen production based on gasification of lignocellulosic feedstock. 2018.2:61-73.

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The worldwide production of hydrogen in 2010 was estimated to be approximately 50 Mt/a, mostly based on fossil fuels. By using lignocellulosic feedstock, an environmentally friendly hydrogen production route can be established. A flow sheet simulation for a biomass based hydrogen production plant was published in a previous work. The plant layout consisted of a dual fluidized bed gasifier including a gas cooler and a dust filter. Subsequently, a water gas shift plant was installed to enhance the hydrogen yield and a biodiesel scrubber was used to remove tars and water from the syngas. CO2 was removed and the gas was compressed to separate hydrogen in a pressure swing adsorption. A steam reformer was used to reform the hydrocarbon-rich tail gas of the pressure swing adsorption and increase the hydrogen yield. Based on this work, a research facility was erected and the results were validated. These results were used to upscale the research plant to a 10 MW fuel feed scale. A validation of the system showed a chemical efficiency of the system of 60% and an overall efficiency of 55%, which indicates the high potential of this technology


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.