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Conference contributions | 2020

Challenges and recent results in microalgae research

Meixner K. Challenges and recent results in microalgae research. 6th Central european biomass conference, 2020, Graz.

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Conference contributions | 2020

CleanAir by biomass

Sturmlechner R, Stressler H, Golicza L, Reichert G, Schwabl M, Höftberger E, Kelz J. CleanAir by biomass. 6th Central European Biomass Conference, 2020, Graz.

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Peer-reviewed publications | 2020

Combined influence of inorganics and transport limitations on the pyrolytic behaviour of woody biomass

Almuina-Villar H, Sommersacher P, Retschitzegger S, Anca-Couce A, Dieguez-Alonso A. Combined influence of inorganics and transport limitations on the pyrolytic behaviour of woody biomass. Chemical Engineering Transactions. 2020.80:73-78

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A deeper understanding and quantification on the influence of inorganic species on the pyrolysis process, combined with the presence of heterogeneous secondary reactions, is pursued in this study. Both chemical controlled and transport limited regimes are considered. The former is achieved in a thermogravimetric analyser (TGA) with fine milled biomass in the mg range, while the latter is investigated in a particle level reactor with spherical particles of different sizes. To account for the influence of inorganics, wood particles were washed and doped with KCl aqueous solutions, resulting in K concentrations in the final wood of around 0.5% and 5% on dry basis. Gas species and condensable volatiles were measured online with Fourier transform infrared (FTIR) spectroscopy and a non-dispersive infrared (NDIR) gas analyzer. The removal of inorganic species delayed the pyrolysis reaction to higher temperatures and lowered char yields. The addition of inorganics (K) shifted the devolatilization process to lower temperatures, increased char and water yields, and reduced CO production among others. Higher heating rates and temperatures resulted in lower char, water, and light condensable yields, but significantly higher CH4 and other light hydrocarbons, as well as CO. The increase in these yields can be attributed, at least in part, to the gas phase cracking reactions of the produced volatiles. Larger particle size increased the formation of char, CH4 and other light hydrocarbons, and light condensables for low and high pyrolysis temperatures, while reduced the release of CO2 and H2O. This novel data set allows to quantify the influence of each parameter and can be used as basis for the development of detailed pyrolysis models which can include both the influence of inorganics and transport limitations when coupled into particle models.


Peer Reviewed Scientific Journals | 2020

Consequential Life Cycle Assessment of energy generation from waste wood and forest residues: The effect of resource-efficient additives

Corona B, Shen L, Sommersacher P, Junginger M. Consequential Life Cycle Assessment of energy generation from waste wood and forest residues: The effect of resource-efficient additives. Journal of Cleaner Production 2020. 259:120948.

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Combustion of waste wood can cause slagging, fouling and corrosion which lead to boiler failure, affecting the energy efficiency and the lifetime of the power plant. Additivation with mineral and sulfur containing additives during waste wood combustion could potentially reduce these problems. This study aims at understanding the environmental impacts of using additives to improve the operational performance of waste wood combustion. The environmental profiles of four energy plants (producing heat and/or power), located in different European countries (Poland, Austria, Sweden and Germany), were investigated through a consequential life cycle assessment (LCA). The four energy plants are all fueled by waste wood and/or residues. This analysis explored the influences of applying different additives strategies in the four power plants, different wood fuel mixes and resulting direct emissions, to the total life cycle environmental impacts of heat and power generated. The impacts on climate change, acidification, particulate matter, freshwater eutrophication, human toxicity and cumulative energy demand were calculated, considering 1 GJ of exergy as functional unit. Primary data for the operation without additives were collected from the power plant operators, and emission data for the additives scenarios were collected from onsite measurements. A sensitivity analysis was conducted on the expected increase of energy efficiency. The analysis indicated that the use of gypsum waste, halloysite and coal fly ash decreases the environmental impacts of heat and electricity produced (average of 12% decrease in all impacts studied, and a maximum decrease of 121%). The decrease of impacts is mainly a consequence of the increase of energy generation that avoids the use of more polluting marginal technologies. However, impacts on acidification may increase (up to 120% increase) under the absence of appropriate flue gas cleaning systems. Halloysite was the additive presenting the highest benefits.


Peer Reviewed Scientific Journals | 2020

Control of biomass grate boilers using internal model control

Schörghuber C, Gölles M, Reichhartinger M, Horn M. Control of Biomass Grate Boilers using Internal Model Control. Control engineering practice. 2020.

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A new model-based control strategy for biomass grate boilers is presented in this paper. Internal model control is used to control four outputs of the plant and to achieve a control structure with fewer control parameters needing to be experimentally tuned. A nonlinear state–space model describing the essential behaviour of the biomass grate boiler is used for controller design. The inverse system dynamics representing the main part of internal model control are designed with the help of this model. In doing so the properties of differentially flat systems are used. Due to a time delayed input, the inverse system is determined only for three input output channels. The stabilization of the inverse system dynamics, however, is a challenging task. A stabilization method with the help of the time delayed input is suggested and a stability analysis is given. The new control strategy has only three parameters to be tuned, representing a major reduction of complexity in comparison to existing model-based approaches. Finally, experimental results of the implemented control strategy on representative biomass grate boiler with a nominal capacity of 180 kW are presented and compared to an existing model-based control strategy based on input output linearization. The experimental evaluation proves that it is possible to operate the biomass boiler in all load ranges with high efficiency and low pollutant emissions.


Peer Reviewed Scientific Journals | 2020

Correction to: Investigation of solid oxide fuel cell operation with synthetic biomass gasification product gases as a basis for enhancing its performance

Pongratz G, Subotić V, Schroettner H, Stoeckl B, Hochenauer C, Anca-Couce A, Scharler R. Correction to: Investigation of solid oxide fuel cell operation with synthetic biomass gasification product gases as a basis for enhancing its performance. Biomass Conversion and Biorefinery. 2020

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The authors want to acknowledge, that during the production of the final version of the publication the image for Figure 9 has been replaced with the image for Figure 12, however without changing the content of the paper. This issue is resolved in the current version of the publication.


Conference contributions | 2020

Customizing biomass as reducing agent in blast furnace steelmaking – Reduction potential and fluidization

Deutsch R, Strasser C, Martini S, Kienzl N. Customizing biomass as reducing agent in blast furnace steelmaking – Reduction potential and fluidization. 28th European Biomass Conference and Exhibition (oral presentation) 2020.

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The reduction of greenhouse gas emissions is an important issue for iron and steel industry. One possibility is to use biomass-based reducing agents, also called bioreducers, to replace at least partly the fossil reducer agents. In a first step woody biomass was treated in a lab-scale muffle furnace and afterwards ground with a ball mill. The powder characteristics were investigated in respect to the flow behavior. For a certain treatment temperature the particle size distribution and as well the flow behavior shows similarities to lignite. The next stage was to identify relations between powder characteristics and its fluidization behavior. A fluidization device was assembled and used to determine the minimum fluidization gas velocity for various bioreducer powders.


Conference contributions | 2020

Das neue Holzwärmeszenario "Holz ersetzt Heizöl"

Schmidl C, Reichert G. Das neue Holzwärmeszenario "Holz ersetzt Heizöl". World Sustainable Energy Days 2020, Wels, Austria (oral presentation). 2020.

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Peer Reviewed Scientific Journals | 2020

Decentralized heating grid operation: A comparison of centralized and agent-based optimization

Lichtenegger K, Leitner A, Märzinger T, Mair C, Moser A, Wöss D, Schmidl C, Pröll T. Decentralized heating grid operation: A comparison of centralized and agent-based optimization. Sustainable Energy, Grids and Networks. 2020;2020(21).

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Moving towards a sustainable heat supply calls for decentralized and smart heating grid solutions. One promising concept is the decentralized feed-in by consumers equipped with their own small production units (prosumers). Prosumers can provide an added value regarding security of supply, emission reduction and economic welfare, but in order to achieve this, in addition to advanced hydraulic control strategies also superordinate control strategies and appropriate market models become crucial.

In this article we study methods to find a global optimum for the local energy community or at least an acceptable approximation to it. In contrast to standard centralized control approaches, based either on expert rules or mixed integer linear optimization, we adopt an agent-based, decentralized approach that allows for incorporation of nonlinear phenomena. While studied here in small-scale systems, this approach is particularly attractive for larger systems, since with an increasing number of interacting units, the optimization problem becomes more complex and the computational effort for centralized approaches increases dramatically.

The agent-based optimization approach is compared to centralized optimization of the same prosumer-based setting as well as to a purely central setup. The comparison is based on the quality of the optimization solution, the computational effort and the scalability. For the comparison of these three approaches, three different scenarios have been set up and analysed for four seasons. In this analysis, no approach has emerged as clearly superior to the others; thus each of them is justified in certain situations.


Peer Reviewed Scientific Journals | 2020

Detailed experimental investigation of the spatially distributed gas release and bed temperatures in fixed-bed biomass combustion with low oxygen concentration

Archan G, Anca-Couce A, Gregorc J, Buchmayr M, Hochenauer C, Gruber J, Scharler R. Detailed experimental investigation of the spatially distributed gas release and bed temperatures in fixed-bed biomass combustion with low oxygen concentration. Biomass and Bioenergy. 2020;141:105725

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This publication focuses on the experimental investigation of a novel small-scale fuel flexible biomass combustion technology with a fixed-bed employing a low oxygen concentration. It was obtained through a low primary air ratio and the additional supply of recirculated flue gas. The plant was operated with spruce wood chips, which contained three different mass fractions of water, and miscanthus pellets. All relevant components of the released gas above the fixed-bed were measured, as well as the 3D bed temperature distribution. The balances confirmed a high experimental data consistency. Therefore, it was possible to determine the location of the four different conversion zones inside the fixed-bed: drying, pyrolysis, char gasification and char oxidation. The reduction of CO2 to CO in the char reduction zone worked efficiently across the entire grate area. Furthermore, the results showed that the water mass fraction of the fuel did not influence the dry product gas composition, but significantly affected the location for the release of pyrolysis products such as tars. It was found that the low oxygen concentration in the fixed-bed combined with flue gas recirculation was an effective method to reduce bed temperatures and therefore its inorganic emissions while significantly increasing feedstock flexibility. The investigations provided fundamental findings on the conversion and release behavior of the new technology under real operating conditions and are very useful for further experimental work and CFD simulations targeting the reduction of PM and NOX emissions.


Conference contributions | 2020

Detailed investigations of high terpene concetrations in biogas laboratory trials

Knoll L, Sumethberger-Hasinger M, Nussbaumer M, Dalnodar D, Loibner A, Drosg B. Detailed investigations of high terpene concetrations in biogas laboratory trials. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

Developing an adsorption-based gas cleaning system for a dual fluidized bed gasification process

Loipersböck J, Weber G, Rauch R, Hofbauer H. Developing an adsorption-based gas cleaning system for a dual fluidized bed gasification process.Biomass Conversion and Biorefinery. 2020.

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Biomass has the potential to make a major contribution to a renewable future economy. If biomass is gasified, a wide variety of products (e.g., bulk chemicals, hydrogen, methane, alcohols, diesel) can be produced. In each of these processes, gas cleaning is crucial. Impurities in the gas can cause catalyst poisoning, pipe plugging, unstable or poisoned end products, or harm the environment. Aromatic compounds (e.g., benzene, naphthalene, pyrene), in particular, have a huge impact on stable operation of syngas processes. The removal of these compounds can be accomplished by wet, dry, or hot gas cleaning methods. Wet gas cleaning methods tend to produce huge amounts of wastewater, which needs to be treated separately. Hot gas cleaning methods provide a clean gas but are often cost intensive due to the high operating temperatures and catalysts used in the system. Another approach is dry or semi-dry gas cleaning methods, including absorption and adsorption on solid matter. In this work, special focus was laid on adsorption-based gas cleaning for syngas applications. Adsorption and desorption test runs were carried out under laboratory conditions using a model gas with aromatic impurities. Adsorption isotherms, as well as dynamics, were measured with a multi-compound model gas. Based on these results, a temperature swing adsorption process was designed and tested under laboratory conditions, showing the possibility of replacing conventional wet gas cleaning with a semi-dry gas cleaning approach.


Conference Papers | 2020

Development and experimental validation of a linear state-space model for absorption heat pumping systems for model-based control strategies

Zlabinger S, Unterberger V, Gölles M, Horn M, Wernhart M, Rieberer R. Development and experimental validation of a linear state-space model for absorption heat pumping systems for model-based control strategies. International Sorption Heat Pump Conference 2020.

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Control strategies of absorption heat pumping systems (AHPS, comprising heat pumps and chillers) often
perform insufficiently well, since they usually do not explicitly consider the systems’ dynamics and crosscoupling effects. One promising approach to improve their performance is to apply model-based control strategies since they would allow for an explicit consideration of these system characteristics. Therefore, mathematically simple models of the system to be controlled are required. This contribution proposes a new approach for such a model for a H2O-LiBr AHPS. The model results from the linearization of a more complex, nonlinear simulation model, leading to a simple, but physically still meaningful linear state-space model structure. The experimental validation shows that the developed model describes the system’s dynamics and cross-coupling effects sufficiently well and indicates that it is suitable to serve as a basis for the development of a model-based control strategy for AHPS.


Conference contributions | 2020

Die Donau - Eine Chance für die Bioenergiebranche?

Dißauer C, Strasser C. Die Donau - Eine Chance für die Bioenergiebranche? 6th Central European Biomass Conference, 2020, Graz.

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Conference contributions | 2020

Dual fluidized bed steam gasification of biomass – the basic technology for a broad product portfolio

Kuba M. Dual fluidized bed steam gasification of biomass – the basic technology for a broad product portfolio. 6th Central European Biomass Conference (oral presentation). 2020.

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Conference Papers | 2020

Dynamische Simulation von Absorptionskälteanlagen – Dymola-Modell einer H2O/LiBr-Absorptionskälteanlage

Wernhart M, Rieberer R, Zlabinger S, Unterberger V, Gölles M. Dynamische Simulation von Absorptionskälteanlagen: Dymola-Modell einer H2O/LiBr-Absorptionskälteanlage. in Proc. Deutsche Kälte-Klima-Tagung 2020. Deutscher Kälte- und Klimatechnischer Verein e.V. 2020

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Absorptionskälteanlagen können einen wesentlichen Beitrag zur Verringerung von CO2-Emissionen leisten, wenn Wärme aus regenerativen Energieträgern oder Abwärme aus industriellen Prozessen zum Antrieb verwendet wird. Absorptionskälteanlagen weisen bereits jetzt eine hohe Effizienz auf, bei veränderlichen Betriebsbedingungen kann diese je nach vorhandenen Stellgliedern weiter gesteigert werden. Dazu werden im Rahmen des Forschungsprojektes „Heat Pumping Systems Control (HPC)“ zwei Absorptionskälteanlagen – eine mit der Stoffpaarung Ammoniak/Wasser (NH3/H2O) und eine mit der Stoffpaarung Wasser/Lithiumbromid (H2O/LiBr) – untersucht, um für unterschiedliche Anwendungen optimale Betriebsstrategien zu entwickeln. Zur Berücksichtigung der Zustandsänderungen in der Absorptionskälteanlage, werden dynamische Simulationsmodelle in der Modellierungssprache Modelica entwickelt und mit Messdaten validiert.

Im Rahmen dieses Konferenzbeitrags werden Komponentenmodelle für die NH3/H2O-Absorptionskälteanlage und Simulationsrechnungen bei veränderlichen Randbedingungen präsentiert, sowie ein Vergleich mit Messdaten diskutiert.


Peer Reviewed Scientific Journals | 2020

Effects of Pyrolysis Conditions and Feedstocks on the Properties and Gasification Reactivity of Charcoal from Woodchips

Phounglamcheik A, Wang L, Romar H, Kienzl N, Broström M, Ramser K, Skreiberg Ø, Umeki K. Effects of Pyrolysis Conditions and Feedstocks on the Properties and Gasification Reactivity of Charcoal from Woodchips. Energy and Fuels. 2020;34(7):8353-8365.

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Pyrolysis conditions in charcoal production affect yields, properties, and further use of charcoal. Reactivity is a critical property when using charcoal as an alternative to fossil coal and coke, as fuel or reductant, in different industrial processes. This work aimed to obtain a holistic understanding of the effects of pyrolysis conditions on the reactivity of charcoal. Notably, this study focuses on the complex effects that appear when producing charcoal from large biomass particles in comparison with the literature on pulverized biomass. Charcoals were produced from woodchips under a variety of pyrolysis conditions (heating rate, temperature, reaction gas, type of biomass, and bio-oil embedding). Gasification reactivity of produced charcoal was determined through thermogravimetric analysis under isothermal conditions of 850 °C and 20% of CO2. The charcoals were characterized for the elemental composition, specific surface area, pore volume and distribution, and carbon structure. The analysis results were used to elucidate the relationship between the pyrolysis conditions and the reactivity. Heating rate and temperature were the most influential pyrolysis parameters affecting charcoal reactivity, followed by the reaction gas and bio-oil embedding. The effects of these pyrolysis conditions on charcoal reactivity could primarily be explained by the difference in the meso- and macropore volume and the size and structural order of aromatic clusters. The lower reactivity of slow pyrolysis charcoals also coincided with their lower catalytic inorganic content. The reactivity difference between spruce and birch charcoals appears to be mainly caused by the difference in catalytically active inorganic elements. Contrary to pyrolysis of pulverized biomass, a low heating rate produced a higher specific surface area compared with a high heating rate. Furthermore, the porous structure and the reactivity of charcoal produced from woodchips were influenced when the secondary char formation was promoted, which cannot be observed in pyrolysis of pulverized biomass.


Conference contributions | 2020

Erneuerbare in Österreich - Die Marktdiffusion im Lichte der Klima- und Energieziele

Biermayr P, Leonhartsberger K, Dißauer C; Eberl M, Enigl M, Fechner H, Lukas Fischer L, Fürnsinn B, Moidl S, Schmidl C, Strasser C, Weiss W, Wonisch P, Wopienka E. Erneuerbare in Österreich - Die Marktdiffusion im Lichte der Klima- und Energieziele. EnInnov 2020, 16. Symposium Energieinnovation (oral presentation). 2020.

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Conference contributions | 2020

Evaluation of gas cleaning processes for the coupling of biomass gasification with Solid Oxide Fuel Cells (SOFC)

Martini S, Lagler J, Kienzl N, Tsiotsias T, Rettschitzegger S. Evaluation of gas cleaning processes for the coupling of biomass gasification with Solid Oxide Fuel Cells (SOFC). 6th Central European Biomass Conference (oral presentation). 2020.

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Peer Reviewed Scientific Journals | 2020

Evaluation of heat transfer models at various fluidization velocities for biomass pyrolysis conducted in a bubbling fluidized bed

von Berg L, Soria-Verdugo A, Hochenauer C, Scharler R, Anca-Couce A. Evaluation of heat transfer models at various fluidization velocities for biomass pyrolysis conducted in a bubbling fluidized bed. International Journal of Heat and Mass Transfer. 2020;160:120175

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Four different models for heat transfer to the particles immersed in a fluidized bed were evaluated and implemented into an existing single particle model. Pyrolysis experiments have been conducted using a fluidized bed installed on a balance at different temperatures and fluidization velocities using softwood pellets. Using a heat transfer model applicable for fluidized beds, the single particle model was able to predict the experimental results of mass loss obtained in this study as well as experimental data from literature with a reasonable accuracy. A good agreement between experimental and modeling results was found for different reactor temperatures and configurations as well as different biomass types, particle sizes – in the typical range of pellets - and fluidization velocities when they were higher than . However, significant deviations were found for fluidization velocities close to minimum fluidization. Heat transfer models which consider the influence of fluidization velocity show a better agreement in this case although differences are still present.


Conference Papers | 2020

Evaluation of the Transient Behaviour of a Fixed-Bed Biomass Gasifier for Demand-Oriented Electricity Production

Hollenstein C, Zemann C, Antolini D, Patuzzi F, Martini S, Baratieri M, Gölles M. Horn M. Evaluation of the Transient Behaviour of a Fixed-Bed Biomass Gasifier for Demand-Oriented Electricity Production. 28th European Biomass Conference & Exhibition. 6-9 July 2020.

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The majority of renewable energy technologies are volatile in nature. External factors such as weather conditions lead to fluctuations in their produced electricity and heat. This results in a demand either not being covered or dissatisfied since too much electricity and heat is produced in the energy system. Although energy storages can counteract these fluctuations, renewable energy technologies that are capable of producing energy on demand are needed as well. As such, technologies based on the thermochemical conversion of biomass are especially relevant as they are considered to be CO2-neutral. Although most existing implementations are based on combustion of biomass, fixed-bed biomass gasification is of growing relevance due to higher overall efficiencies and low pollutant emissions. Currently, fixed-bed biomass gasifiers are usually operated at steady-state operation to produce the maximum amount of energy possible. This contribution investigates, whether they can be used as a technology for demand-oriented electricity and heat production


Other publication | 2020

EVEmBi – Bestimmung von Methanemissionen aus Biogasanlagen und Reduktionsstrategien

Meixner K. EVEmBi – Bestimmung von Methanemissionen aus Biogasanlagen und Reduktionsstrategien. CEBC 2020

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Conference contributions | 2020

Experimental investigation of biomass based reducing agents for blast furnace ironmaking

Kienzl N, Strasser C, Deutsch R. Experimental investigation of biomass based reducing agents for blast furnace ironmaking. 6th Central European Biomass Conference (oral presentation). 2020.

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Conference Papers | 2020

Experimentally verified dynamic simulation model of a NH3/H2O-absorption refrigeration system

Wernhart M, Rieberer R, Zlabinger S, Unterberger V, Gölles M. Experimentally verified dynamic simulation model of a NH3/H2O-absorption refrigeration system. in Japan Society of Refrigerating and Air Conditioning Engineers, Hrsg., 14th IIR Gustav-Lorentzen Conference on Natural Fluids, GL 2020 - Proceedings. International Institute of Refrigeration. 2020. S. 103-109. (Refrigeration Science and Technology). https://doi.org/10.18462/iir.gl.2020.1145

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The operation characteristics of thermally driven absorption refrigeration systems (ARS) are strongly dependent on their hydraulic integration. Therefore, varying operating conditions of the hydraulic supply have a great influence on the behaviour of ARS and lead to dynamic operation, which can affect the efficiency and is largely unexplored so far. To enable a simple investigation of ARS integration considering their dynamic behaviour and to develop modern, efficiency-enhancing control strategies, dynamic simulation models of ARS are developed in Modelica Code.

In this paper, a dynamic simulation model of an ARS with the working pair ammonia/water (NH3/H2O) is presented. The parameterization and the physical correlations of selected components of the simulation model are described. Afterwards, the simulation model is verified by comparing simulation results with measurement data of the NH3/H2O-ARS. Finally, the capabilities of the simulation model are demonstrated by performing a simulation-based analysis of the temperature glide of the refrigerant in the evaporator.


Peer Reviewed Scientific Journals | 2020

Fate of Phosphorus in Fluidized Bed Cocombustion of Chicken Litter with Wheat Straw and Bark Residues

Häggström G, Fürsatz K, Kuba M, Skoglund N, Öhman M. Fate of Phosphorus in Fluidized Bed Cocombustion of Chicken Litter with Wheat Straw and Bark Residues. Energy and Fuels. 2020.34:1822-1829

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This study aims to determine the fate of P during fluidized bed co-combustion of chicken litter (CL) with K-rich fuels [e.g., wheat straw (WS)] and Ca-rich fuels (bark). The effect of fuel blending on phosphate speciation in ash was investigated. This was performed by chemical characterization of ash fractions to determine which phosphate compounds had formed and identify plausible ash transformation reactions for P. The ash fractions were produced in combustion experiments using CL and fuel blends with 30% CL and WS or bark (B) at 790–810 °C in a 5 kW laboratory-scale bubbling fluidized bed. Potassium feldspar was used as the bed material. Bed ash particles, cyclone ash, and particulate matter (PM) were collected and subjected to chemical analysis with scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) and X-ray diffraction. P was detected in coarse ash fractions only, that is, bed ash, cyclone ash, and coarse PM fraction (>1 μm); no P could be detected in the fine PM fraction (<1 μm). SEM–EDS analysis showed that P was mainly present in K–Ca–P-rich areas for pure CL as well as in the ashes from the fuel blends of CL with WS or B. In the WS blend, P was found together with Si in these areas. The crystalline compound containing P was hydroxyapatite in all cases as well as whitlockite in the cases of pure CL and WS blend, of which the latter compound has been previously identified as a promising plant nutrient. The ash fractions from CL and bark blend only contained P in hydroxyapatite. Co-combustion of CL together with WS appears to be promising for P recovery, and ashes with this composition could be further studied in plant growth experiments