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Peer Reviewed Scientific Journals | 2021

Analysis of H2S-related short-term degradation and regeneration of anode- and electrolyte supported solid oxide fuel cells fueled with biomass steam gasifier product gas

Pongratz G, Subotić V, Schroettner H, Hochenauer C, Skrzypkiewicz M, Kupecki J, Anca-Couce A, Scharler R. Analysis of H2S-related short-term degradation and regeneration of anode- and electrolyte supported solid oxide fuel cells fueled with biomass steam gasifier product gas. Energy.2021.218:119556.

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Using solid oxide fuel cells in biomass gasification based combined heat and power production is a promising option to increase electrical efficiency of the system. For an economically viable design of gas cleaning units, fuel cell modules and further development of suitable degradation detection methods, information about the behavior of commercially available cell designs during short-term poisoning with H2S can be crucial. This work presents short-term degradation and regeneration analyses of industrial-relevant cell designs with different anode structure and sulfur tolerance fueled with synthetic product gas from wood steam gasification containing 1 to 10 ppmv of H2S at 750°C and 800°C. Full performance regeneration of both cell types was achieved in all operating points. The high H2O content and avoided fuel depletion may have contributed to a lower performance degradation and better regeneration of the cells. A strong influence of the catalytically active anode volume on poisoning and regeneration behavior was quantified, thereby outlining the importance of considering the anode structure besides the sulfur tolerance of the anode material. Hence, cells with less sulfur tolerant anode material but larger anode volume might outperform cells less sensitive to sulfur in the case of an early detection of a gas cleaning malfunction.


Peer Reviewed Scientific Journals | 2021

Bioenergy technologies, uses, market and future trends with Austria as a case study

Anca-Couce A, Hochenauer C, Scharler R. Bioenergy technologies, uses, market and future trends with Austria as a case study. Renewable and Sustainable Energy Reviews.2021;135:110237.

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The current bioenergy uses and conversion technologies as well as future trends for the production of heat, power, fuels and chemicals from biomass are reviewed. The focus is placed in Austria, which is selected due to its high bioenergy utilization, providing 18.4% of the gross energy final consumption in 2017, and its strong industrial and scientific position in the field. The most common bioenergy application in Austria is bioheat with 170 PJ in 2017 mainly obtained from woody biomass combustion, followed by biofuels with 21 PJ and bioelectricity with 17 PJ. Bioheat has a stable market, where Austrian manufacturers of boilers and stoves have a strong position exporting most of their production. Future developments in bioheat production should go in the line of further reducing emissions, increasing feedstock flexibility and coupling with other renewables. For bioelectricity and biofuels, the current framework does not promote the growth of the current main technologies, i.e. combined heat and power (CHP) based on biomass combustion or biogas and first generation biofuels. However, an increase in all bioenergy uses is required to achieve the Austrian plan to be climate neutral in 2040. The current initiatives and future possibilities to achieve this increase are presented and discussed, e.g. mandatory substitution of old oil boilers, production of biomethane and early commercialization of CHP with a high efficiency or demonstration of advanced biofuels production based on gasification.


Peer Reviewed Scientific Journals | 2021

Categorization of small-scale biomass combustion appliances by characteristic numbers

Feldmeier S, Schwarz M, Wopienka E, Pfeifer C. Categorization of small-scale biomass combustion appliances by characteristic numbers. Renewable Energy. 2021.163:2128-2136.

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The market offers a broad range of different combustion appliances dedicated to residential heating with biomass. The effect of fuel properties on the formation of slag and emissions varies and the technology influences the impact to a certain extent. The applicability of biomass fuels is not only determined by operational settings but also by the design of boiler components as grate area and combustion chamber. Aspects as the fuel load on the grate, residence time, geometry of grate and combustion chamber design, as well as feeding and de-ashing influence the extent of slag formation and emission release. The determination of characteristic numbers by means of constructional measures allows a systematic comparison and - in a further step - an assessment/categorization of combustion technologies. After conducting a boiler survey relevant parameters regarding grate, combustion chamber, feeding, and ash removal were gathered. Characteristic numbers were specified in order to compare technological aspects. The results of this study allow the investigation of the influence of the combustion technology on the performance. They will assist the systematic and targeted design of small-scale boilers and the optimization of combustion appliances in future, especially when it comes to fuel-flexibility.


Peer Reviewed Scientific Journals | 2021

Combustion of poultry litter and mixture of poultry litter with woodchips in a fixed bed lab-scale batch reactor

Katsaros G, Sommersacher P, Retschitzegger S, Kienzl N, Tassou SA, Pandey DS. Combustion of poultry litter and mixture of poultry litter with woodchips in a fixed bed lab-scale batch reactor. Fuel. 2021.286.119310.

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Experiments have been conducted in a batch fixed bed lab-scale reactor to investigate the combustion behaviour of three different biomass fuels, poultry litter (PL), blend of PL with wood chips (PL/WC) and softwood pellets (SP). Analysis of the data gathered after completion of the test runs, provided useful insights about the thermal decomposition behaviour of the fuels, the formation of N gaseous species, the release of ash forming elements and the estimation of aerosol emissions. It was observed that the N gaseous species are mainly produced during the devolatilisation phase. Hydrogen cyanide (HCN) was the predominant compound in the case of SP combustion, whereas ammonia (NH3) displayed the highest concentration during the combustion of PL and blend (PL/WC). With reference to ash forming elements, the release rates of potassium (K) and sodium (Na) range between 15–50% and 20–37% respectively, whereas the release rate of sulphur (S) falls between 54–92%. Chlorine (Cl) presents very high release rate for all tested fuels acquiring values greater than 85%, showing the volatile nature of the specific compound. The maximum potential of aerosol emissions was estimated based on the calculation of ash forming elements. In particular, during PL combustion the maximum aerosol emissions were observed, 2806 mg/Nm3 (dry flue gas, 13 vol% O2), mainly influenced by the release rate of K in the gas phase. Fuel indexes for the pre-evaluation of combustion related challenges such as NOx emissions, potential for aerosols formation, corrosion risk, and ash melting behaviour have also been investigated.


Peer Reviewed Scientific Journals | 2021

Digestate as Sustainable Nutrient Source for Microalgae—Challenges and Prospects

Bauer L, Ranglová K, Masojidek J, Drosg B, Meixner K. Digestate as Sustainable Nutrient Source for Microalgae—Challenges and Prospects. Applied Sciences. 2021.11(3):1056

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The interest in microalgae products has been increasing, and therefore the cultivation industry is growing steadily. To reduce the environmental impact and production costs arising from nutrients, research needs to find alternatives to the currently used artificial nutrients. Microalgae cultivation in anaerobic effluents (more specifically, digestate) represents a promising strategy for increasing sustainability and obtaining valuable products. However, digestate must be processed prior to its use as nutrient source. Depending on its composition, different methods are suitable for removing solids (e.g., centrifugation) and adjusting nutrient concentrations and ratios (e.g., dilution, ammonia stripping). Moreover, the resulting cultivation medium must be light-permeable. Various studies show that growth rates comparable to those in artificial media can be achieved when proper digestate treatment is used. The necessary steps for obtaining a suitable cultivation medium also depend on the microalgae species to be cultivated. Concerning the application of the biomass, legal aspects and impurities originating from digestate must be considered. Furthermore, microalgae species and their application fields are essential criteria when selecting downstream processing methods (harvest, disintegration, dehydration, product purification). Microalgae grown on digestate can be used to produce various products (e.g., bioenergy, animal feed, bioplastics, and biofertilizers). This review gives insight into the origin and composition of digestate, processing options to meet requirements for microalgae cultivation and challenges regarding downstream processing and products.


Peer Reviewed Scientific Journals | 2021

Effect of biomass fuel ash and bed material on the product gas composition in DFB steam gasification

Fürsatz K, Fuchs J, Benedikt F, Kuba M, Hofbauer H. Effect of biomass fuel ash and bed material on the product gas composition in DFB steam gasification. Energy. 2021.219:119650.

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Gasification is a thermochemical process that transforms carbonaceous matter into a gaseous secondary energy carrier, referred to as product gas. This product gas can be used for heat and power generation but also for syntheses. One possible gasification technology suitable for further synthesis is dual fluidised bed (DFB) steam gasification. The H2:CO ratio, which determines the suitability of the product gas for further synthesis, is influenced by the catalytic activity inside the gasification reactor. Eleven DFB steam gasification experiments were performed comparing the catalytic activity for various bed material and fuel combinations. The bed materials used were K-feldspar, fresh and layered olivine, and limestone, and the fuels gasified were softwood, chicken manure, a bark–chicken manure mixture and a bark-straw-chicken manure mixture. The water-gas-shift (WGS) equilibrium deviation was used to evaluate the catalytic activity inside the gasification reactor. It was shown that both the fuel ash and bed material have an effect on the catalytic activity during gasification. Scanning electron microscopy and energy dispersive X-ray spectrometry showed the initial layer formation for experiments with ash-rich fuels. Isolated WGS experiments were performed to further highlight the influence of bed material, fuel ash and fuel ash layers on the WGS equilibrium.


Peer Reviewed Scientific Journals | 2021

Optimal planning of thermal energy systems in a microgrid with seasonal storage and piecewise affine cost functions

Mansoor M, Stadler M, Zellinger M, Lichtenegger K, Auer H, Cosic A. Optimal planning of thermal energy systems in a microgrid with seasonal storage and piecewise affine cost functions. Energy. 2021:215;119095.

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The optimal design of microgrids with thermal energy system requires optimization techniques that can provide investment and scheduling of the technology portfolio involved. In the modeling of such systems with seasonal storage capability, the two main challenges include the low temporal resolution of available data and the non-linear cost versus capacity relationship of solar thermal and heat storage technologies. This work overcomes these challenges by developing two different optimization models based on mixed-integer linear programming with objectives to minimize the total energy costs and carbon dioxide emissions. Piecewise affine functions are used to approximate the non-linear cost versus capacity behavior. The developed methods are applied to the optimal planning of a case study in Austria. The results of the models are compared based on the accuracy and real-time performance together with the impact of piecewise affine cost functions versus non-piecewise affine fixed cost functions. The results show that the investment decisions of both models are in good agreement with each other while the computational time for the 8760-h based model is significantly greater than the model having three representative periods. The models with piecewise affine cost functions show larger capacities of technologies than non-piecewise affine fixed cost function based models.


Peer Reviewed Scientific Journals | 2021

Steam gasification of biomass – Typical gas quality and operational strategies derived from industrial-scale plants

Larsson A, Kuba M, Berdugo Vilches T, Seemann M, Hofbauer H, Thunman H. Steam gasification of biomass – Typical gas quality and operational strategies derived from industrial-scale plants. Fuel Processing Technology. 2021.212:106609.

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Steam gasification enables the thermochemical conversion of solid fuels into a medium calorific gas that can be utilized for the synthesis of advanced biofuels, chemicals or for heat and power production. Dual fluidized bed (DFB) gasification is at present the technology applied to realize gasification of biomass in steam environment at large scale. Few large-scale DFB gasifiers exist, and this work presents a compilation and analysis of the data and operational strategies from the six DFB gasifiers in Europe. It is shown that the technology is robust, as similar gas quality can be achieved despite the differences in reactor design and operation strategies. Reference concentrations of both gas components and tar components are provided, and correlations in the data are investigated. In all plants, adjusting the availability and accessibility to the active ash components (K and Ca) was the key to control the gas quality. The gas quality, and in particular the tar content of the gas, can conveniently be assessed by monitored the concentration of CH4 in the produced gas. The data and experience acquired from these plants provide important knowledge for the future development of the steam gasification of biomass.


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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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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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.


Conference contributions | 2020

Advanced biomass CCHP (BIO-CCHP) based on gasification, SOFC and cooling machines

Lagler J, Martini S. Advanced biomass CCHP (BIO-CCHP) based on gasification, SOFC and cooling machines. 6th Central European Biomass Conferenc, 2020, Graz.

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Conference Papers | 2020

Advanced modular process analysis tool for biomass-based Chemical Looping systems

Steiner T, Schulze K, Scharler R. Advanced modular process analysis tool for biomass-based Chemical Looping systems. 3RD DOCTORAL COLLOQUIUM BIOENERGY. 2020.

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In order to limit global warming to 1.5 °C compared to the pre-industrial temperature level, zero net CO2 emissions are needed on a global scale until 2050. A Chemical Looping (CL) process represents a technological system which is CO2-negative when using biomass as fuel and thus can substantially contribute to this target. In principle, the process uses a metal oxide as oxygen carrier material (OC) which is cyclically oxidized by air or steam and reduced by the fuel. Without air as the direct oxygen source for fuel conversion, high calorific product gases or pure carbon dioxide in case of combustion are obtained after the condensation of water vapor, which can then be stored or further utilized.
Within the funded project ”BIO-LOOP”, different Chemical Looping processes (for example combustion, gasification, hydrogen production) and reactors (fixed bed, fluidized bed) are investigated numerically and experimentally. An advanced process analysis tool based on mass and energy balances of the system considered will be presented. It provides data about the specific internal and external streams, process conditions and efficiencies. Within the analysis tool, various independent modular units describe individual process steps, e.g. mixing, chemical reaction or splitting. These components can be adjusted, combined and interconnected according to the flow chart of the system. The process model represents the first step towards a flexible Chemical Looping reactor simulation toolbox to analyze various process scenarios. Emphasis is put on the flexibility regarding the fuels and oxygen carriers, their conversion and possible process variations. The tool developed will support upcoming CFD modeling and further economic considerations.


Conference contributions | 2020

Advanced Test Methods for Pellet Stoves

Reichert G, Schmidl C. Advanced Test Methods for Pellet Stoves. 6th Central European Biomass Conference, 2020, Graz.

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Conference contributions | 2020

Advanced Test Methods for Pellet Stoves – A Technical Review

Reichert G, Schwabl M, Schmidl C. Advanced Test Methods for Pellet Stoves – A Technical Review. 6th Central European Biomass Conference (oral presentation) 2020.

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Third party testing of direct heating appliances fueled with pellets has been established in many countries worldwide. The main goals are ensuring operation safety and a minimum level of performance of the products prior to market implementation. This kind of approval procedure for new products requires testing standards, certified testing bodies and a legal framework defining minimum requirements for specified performance parameters which are assessed in the respective standards.

While the overall targets are quite similar for all countries having set-up such procedures, the practical implementation of these targets in the national/international testing standards is remarkably different. This applies to both, the way of operating the appliance during the testing and the measurements performed during the testing.

Furthermore several industries were requested recently to modify their product standards towards more realistic operating conditions. The most famous example is car industry, but this request may also apply to biomass heating systems.

 


Peer Reviewed Scientific Journals | 2020

Alkaline Ethanol Oxidation Reaction on Carbon Supported Ternary PdNiBi Nanocatalyst using Modified Instant Reduction Synthesis Method

Cermenek B, Genorio B, Winter T, Wolf S, Connell JG, Roschger M, Letofsky-Papst I, Kienzl N, Bitschnau B, Hacker V. Alkaline Ethanol Oxidation Reaction on Carbon Supported Ternary PdNiBi Nanocatalyst using Modified Instant Reduction Synthesis Method. Electrocatalysis. 2020.11:203-204.

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Direct ethanol fuel cells (DEFC) still lack active and efficient electrocatalysts for the alkaline ethanol oxidation reaction (EOR). In this work, a new instant reduction synthesis method was developed to prepare carbon supported ternary PdNiBi nanocatalysts with improved EOR activity. Synthesized catalysts were characterized with a variety of structural and compositional analysis techniques in order to correlate their morphology and surface chemistry with electrochemical performance. The modified instant reduction synthesis results in well-dispersed, spherical Pd85Ni10Bi5 nanoparticles on Vulcan XC72R support (Pd85Ni10Bi5/C(II-III)), with sizes ranging from 3.7 ± 0.8 to 4.7 ± 0.7 nm. On the other hand, the common instant reduction synthesis method leads to significantly agglomerated nanoparticles (Pd85Ni10Bi5/C(I)). EOR activity and stability of these three different carbon supported PdNiBi anode catalysts with a nominal atomic ratio of 85:10:5 were probed via cyclic voltammetry and chronoamperometry using the rotating disk electrode method. Pd85Ni10Bi5/C(II) showed the highest electrocatalytic activity (150 mA⋅cm−2; 2678 mA⋅mg−1) with low onset potential (0.207 V) for EOR in alkaline medium, as compared to a commercial Pd/C and to the other synthesized ternary nanocatalysts Pd85Ni10Bi5/C(I) and Pd85Ni10Bi5/C(III). This new synthesis approach provides a new avenue to developing efficient, carbon supported ternary nanocatalysts for future energy conversion devices.


Conference contributions | 2020

Anaerobic Digestion Optimization for Biogas and Biomethane Production

Ionel I, Drosg B. Anaerobic Digestion Optimization for Biogas and Biomethane Production. 28th European Biomass Conference and Exhibition (oral presentation) 2020.

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Peer Reviewed Scientific Journals | 2020

Applicability of Torrefied Sunflower Husk Pellets in Small and Medium Scale Furnaces

Kienzl N, Margaritis N, Isemin R, Zaychenko V, Strasser C, Kourkoumpas DS, Grammelis P, Klimov D, Larina O, Sytchev G, Mikhalev A. Applicability of Torrefied Sunflower Husk Pellets in Small and Medium Scale. Waste and Biomass Valorization. 2020;275:122882.

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The aim of this paper is to test the applicability of upgraded agricultural biomass feedstock such as torrefied sunflower husks during combustion in small and medium heating applications. Sunflower husk is formed in large quantities at enterprises producing sunflower oil and can be used as biofuel. However, big problems arise due to the low bulk density of husks and the rapid growth of ash deposits on the heating surfaces of boilers. In order to solve these problems, it was proposed to produce pellets from husks, and to subject these pellets to torrefaction. After torrefaction, net calorific value was increased by 29% while the risk of high temperature corrosion of boilers was reduced. Signs of ash softening neither occurred in combustion of raw nor in combustion of torrefied sunflower husk pellets. High aerosol emissions, already present in raw sunflower husk pellets, could not be mitigated by torrefaction. First combustion results at medium scale furnaces indicated that sunflower husk pellets (both raw and torrefied) in a commercial boiler < 400 kW, operated in a mode with low primary zone temperatures (< 850 °C), meet current emission limits. Regarding the future upcoming emission limits according to the European Medium Combustion Plant Directive, additional measures are required in order to comply with the dust limits.


Scientific Journals | 2020

Aqueous phase reforming of pilot-scale Fischer-Tropsch water effluent for sustainable hydrogen production

Zoppi G, Pipitone G, Gruber H, Weber G, Reichhold A, Pirone R, Bensaid S. Aqueous phase reforming of pilot-scale Fischer-Tropsch water effluent for sustainable hydrogen production. Catalysis Today.2020.

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Fischer-Tropsch (FT) synthesis produces an aqueous stream containing light oxygenates as major by-product. The low carbon concentration of the organics makes its thermal recovery unprofitable. Thus, novel processes are needed to utilize this waste carbon content. In this work, the aqueous phase reforming of the wastewater obtained from a 15 kWth Fischer-Tropsch plant was explored as a promising process to produce hydrogen at mild temperatures. The FT product water was firstly characterized and afterward subjected to the reforming at different reaction temperatures and time, using a platinum catalyst supported on activated carbon. It was observed that, besides activity, the selectivity towards hydrogen was favored at higher temperatures; equally, increasing the reaction time allowed to obtain the total conversion of most molecules found in the solution, without decreasing the selectivity and reaching a plateau at 4 hours in the hydrogen productivity. In order to get more insights into the reaction mechanism and product distribution derived from the APR of FT product water, several tests were performed with single compounds, finding characteristic features. The importance of the position of the hydroxyl group in the molecule structure was highlighted, with secondary alcohols more prone to dehydrogenation pathways compared to primary alcohols. Moreover, no interference among the substrates was reported despite the mixture is constituted by several molecules: in fact, the results obtained with the real FT product water were analogous to the linear combination of the single compound tests. Finally, the reuse of the catalyst showed no appreciable deactivation phenomena.


Conference contributions | 2020

BIOCHAR - Reaction kinetics under gasification conditions by experimental tests with TGA

Lagler J, Martini S, Kienzl N, Loder A. BIOCHAR - Reaction kinetics under gasification conditions by experimental tests with TGA. 6th Central European Biomass Conference. 2020. Graz.

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Conference contributions | 2020

Biochar’s reaction kinetics under gasification conditions by experimental tests with TGA

Lagler J, Martini S, Kienzl N, Loder A. Biochar’s reaction kinetics under gasification conditions by experimental tests with TGA. 6th Central European Biomass Conference (poster). 2020.

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During the last years biomass evolved into one of the most important energy sources in Central Europe. Depending on the atmosphere, different types of thermochemical processes can be differentiated: pyrolysis, gasification and combustion, whereas pyrolysis operates without any oxygen in the atmosphere, combustion with the highest ratio of oxygen. Depending on the conversion technology and conversion conditions, different products can be generated: heat, cooling power and electrical power, liquid, gaseous and solid products, such as hydrogen, FT-fuels and biochar.
This work focuses on the valorisation of solid side products of gasification based biomass CHP-systems to increase ecologic and economic benefit. Depending on the conversion process of biomass into producer gas this solid residue consists mainly of ash or of so called biochar with high carbon content. Increasing the amount of biochar leads to a decrease of producer gas, but, with the high market potential of biochar, the economic benefits increase. According to its characteristics (e.g. purity, surface structure) different applications can be addressed and therefore different prices can be achieved. Therefore, extended research on biochar treatment processes and related reaction kinetics of biochar is from crucial importance for the development and optimisation of downstream upgrading processes in order to reach the desired quality of the biochar. In the past, such considerations of utilising side products, like biochar, have not been in the centre of attention during the design phase of gasification reactors. Therefore, the establishment of a finishing-treatment of biochar extracted from a gasification process is under investigation. The focus of this paper lies on the reaction kinetics of biochar activation itself and not the primary material (biomass). In order to derivate correlations between reaction kinetics and atmosphere compositions as well as temperature, experimental test runs are conducted with a Thermogravimetric Analyser (TGA) including a steam furnace, which enables studies of mass and energy changes under defined absolute humidity. To produce applicable and reliable data, the limitations of the TGA-test-setup are evaluated with examinations on variations of sample mass, bulk density, particle size distribution and the gas flow. On this basis the test design is defined with certain specifications on the sample preparation and a constant flow velocity. The investigated biochar taken out the gasification process is dried, milled and sieved for the TGA-tests. The main part is devoted to conduct a detailed investigation changing the content of moisture (H2O) and carbon dioxide (CO2) as well as the temperature. The tests are operated at a temperature range between 700 and 1000°C, H2O-concentrations from 0 to 80 vol% and CO2-concentrations also in the range of 0 to 80 vol%. These systematic experimental variations provide the basis for a model of the reaction kinetics of biochar under different boundary conditions. The data is to be evaluated via the generic model including temperature and the partial pressures of CO2 and H2O. Afterwards it will be matched with conventional models (e.g. Arrhenius plot, linear regression models) to determine their suitability. One of those models was used in the paper of Ollero et al, where the influence of CO2 on the reaction kinetics of olive residue was investigated. 1First results show that the reaction rate of biochar is much lower than the one of olive residue. Effects of treatment conditions on the surface properties are investigated by taking out the treated samples after a defined treatment period at a defined mass loss and subsequent surface analysis (BET, pore size/volume distribution) of the samples. In first BET surface analysis, the treatments of biochar with vapour lead to a surface of approximately 1000m²/g whereas the original sample has a BET surface lower than 150m²/g. This finding leads to the question how the reaction kinetics of a treatment process influences the surface change. The obtained data is taken as basis for developing an upgrading process for biochar to a high value product of the gasification process. In order to prove the suitability of TGA-tests for identifying optimised treatment conditions, further research shall demonstrate the correlation of the lab-scale TGA-results with experiences of pilot scale tests.
 


Conference contributions | 2020

Biofuels for transport decarbonisation Country specific assessment for Finland, Sweden, Germany, USA and Brazil

Matschegg D, Biofuels for transport decarbonisation Country specific assessment for Finland, Sweden, Germany, USA and Brazil. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference contributions | 2020

Biological Methanation Processes

Drosg B, Wellinger A. Biological Methanation Processes. 28th European Biomass Conference and Exhibition (oral presentation) 2020.

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Peer Reviewed Scientific Journals | 2020

Biomass pyrolysis TGA assessment with an international round robin

Anca-Couce A, Tsekos C, Retschitzegger S, Zimbardi F, Funke A, Banks S, Kraia T, Marques P, Scharler R, de Jong W, Kienzl N. Biomass pyrolysis TGA assessment with an international round robin.Fuel.2020;276:118002.https://doi.org/10.1016/j.fuel.2020.118002

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The large variations found in literature for the activation energy values of main biomass compounds (cellulose, hemicellulose and lignin) in pyrolysis TGA raise concerns regarding the reliability of both the experimental and the modelling side of the performed works. In this work, an international round robin has been conducted by 7 partners who performed TGA pyrolysis experiments of pure cellulose and beech wood at several heating rates. Deviations of around 20 – 30 kJ/mol were obtained in the activation energies of cellulose, hemicellulose and conversions up to 0.9 with beech wood when considering all experiments. The following method was employed to derive reliable kinetics: to first ensure that pure cellulose pyrolysis experiments from literature can be accurately reproduced, and then to conduct experiments at different heating rates and evaluate them with isoconversional methods to detect experiments that are outliers and to validate the reliability of the derived kinetics and employed reaction models with a fitting routine. The deviations in the activation energy values for the cases that followed this method, after disregarding other cases, were of 10 kJ/mol or lower, except for lignin and very high conversions. This method is therefore proposed in order to improve the consistency of data acquisition and kinetic analysis of TGA for biomass pyrolysis in literature, reducing the reported variability.