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Conference contributions | 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 14th IIR-Gustav Lorentzen Conference on Natural Refrigerants. International Institute of Refrigeration. 2020

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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


Conference contributions | 2020

GrateAdvance - Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies

Barroso G, Essl M, Feldmeier S, Mehrabian R, Nussbaumer T, Öhman M, Reiterer T, Schwarz M, Shiehnejad-Hesar A, Wopienka E. GrateAdvance - Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies. 6th Central European Biomass Conference, 2020, Graz.

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Conference contributions | 2020

How to create value chains from different feedstocks

Enigl M, How to create value chains from different feedstocks. 6th Central Eurpean Biomass Conference, 22-254 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

Impact of residual fuel ash layers on the catalytic activation of K-feldspar regarding the water–gas shift reaction

Fürsatz K, Kuba M, Janisch D, Aziaba K, Hammerl C, Chlebda D, Łojewska J, Hofbauer H. Impact of residual fuel ash layers on the catalytic activation of K-feldspar regarding the water–gas shift reaction. Biomass Conversion and Biorefinery. 2020

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Interaction of biomass ash and bed materials in thermochemical conversion in fluidized beds leads to changes of the bed particle surface due to ash layer formation. Ash components present on the bed particle surface strongly depend on the ash composition of the fuel. Thus, the residual biomass used has a strong influence on the surface changes on bed particles in fluidized bed conversion processes and, therefore, on the catalytic performance of the bed material layers. Ash layer formation is associated with an increase in the catalytic activity of the bed particles in gasification and plays a key role in the operability of different biomass fuels. The catalytic activation over time was observed for K-feldspar used as the bed material with bark, chicken manure, and a mixture of bark and chicken manure as fuels. The changes on the bed material surfaces were further characterized by SEM/EDS and BET analyses. Raman, XPS, and XRD analyses were used to characterize the crystal phases on the bed material surface. An increase in surface area over time was observed for K-feldspar during the interaction with biomass ash. Additionally, a more inhomogeneous surface composition for fuels containing chicken manure in comparison to pure bark was observed. This was due to the active participation of phosphorus from the fuel ash in the ash transformation reactions leading to their presence on the particle surface. A decreased catalytic activity was observed for the same BET surface area compared to bark combustion, caused by the different fuel ash composition of chicken manure.


Peer Reviewed Scientific Journals | 2020

Increased efficiency of dual fluidized bed plants via a novel control strategy

Nigitz T, Gölles M, Aichernig C, Schneider S, Hofbauer H, Horn M. Increased efficiency of dual fluidized bed plants via a novel control strategy. Biomass & Bioenergy. 2020 Okt;141. 105688. https://doi.org/10.1016/j.biombioe.2020.105688

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Industrial plants using DFB biomass gasification are on the verge of profitability. These plants should be operated more economically in order to support the industrial applications for renewable technologies of this kind. Since some parts of such plants are typically difficult to control, a state-of-the-art control strategy is analyzed here in the context of its potential for increased economic efficiency. The DFB gasification plant “HGA Senden” in Ulm, Germany is considered on an exemplary basis here. A process analysis reveals a high potential in the synchronization of product gas generation and utilization. At the present time a relevant surplus of product gas is burned in an auxiliary boiler for synchronization purposes and regular manual adjustments at the fuel feed are necessary by the plant operators. For this synchronization a novel control strategy is developed that actuates the auxiliary boiler and the fuel feed simultaneously. The novel control strategy was experimentally validated for a period of over one month. Due to this long-term evaluation the fuel consumption was reduced by 5% and the manual adjustments of the fuel feed that were necessary on average every 30min were eliminated. As a result DFB gasification plants can be operated more economically by applying the novel control strategy for synchronization of product gas generation and utilization.


Conference contributions | 2020

Individual heat management in the living room

Schwabl M. Individual heat management in the living room. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference contributions | 2020

Influence of ash forming elements from biogenous residues on fluidized bed conversion processes

Fürsatz K, Influence of ash forming elements from biogenous residues on fluidized bed conversion processes. 6th Central Eurpean Biomass Conference, 22-24 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

Influence of bed materials on the performance of the Nong Bua dual fluidized bed gasification power plant in Thailand

Siriwongrungson V, Hongrapipat J, Kuba M, Rauch R, Pang S, Thaveesri J, Messner M, Hofbauer H. Influence of bed materials on the performance of the Nong Bua dual fluidized bed gasification power plant in Thailand. Biomass Conversion and Biorefinery. 2020;

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Bed materials and their catalytic activity are two main parameters that affect the performance of the dual fluidized bed (DFB) gasification system in terms of product gas composition and tar levels. Two sources of bed materials were used for the operation of a commercial DFB gasification system in Thailand, using woodchips as a biomass feedstock. One source of the bed materials was the calcined olivine which had been used in the Gussing Plant, Austria, and the other activated bed material was a mixture of fresh Chinese olivine and used Austrian olivine with additives of biomass ash, calcium hydroxide and dolomite. These bed materials were collected and analysed for morphological and chemical composition using a scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF). The product gas was cleaned in a scrubber to remove tars, from which the samples were collected for gravimetric tar analysis. Its composition data was automatically recorded at the operation site before it entered the gas engine. From the SEM, EDS and XRF analyses, calcium-rich layers around the bed materials were observed on the activated bed material. The inner layers of bed materials collected were homogeneous. Biomass ash, which was generally added to the bed materials, had significant calcium and potassium content. These calcium-rich layers of the bed materials, from the calcium hydroxide, biomass ash and dolomite, influenced system performance, which was determined by observing lower tar concentration and higher hydrogen concentration in the product gas.


Conference contributions | 2020

Integrating steam gasification into established infrastructure in the pulp and paper industry

Karl T, Integrating steam gasification into established infrastructure in the pulp and paper industry. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

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. 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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Solid oxide fuel cells represent a promising technology to increase the electrical efficiency of biomass-based combined-heat-power systems in comparison to state-of-the-art gas engines, additionally providing high temperature heat. To identify favorable fuel gas compositions for an efficient coupling with gasifiers at low degradation risk is of major importance to ensure stability, reliability, and durability of the systems used, thus increasing attractiveness of electricity production from biomass. Therefore, this study presents a comprehensive analysis on the influence of main gas components from biomass gasification on the performance and efficiency of a cell relevant for real application. An industrial-size electrolyte supported single cell with nickel/gadolinium-doped ceria anode was selected showing high potential for gasifier-solid oxide fuel cell systems. Beneficial gas component ratios enhancing the power output and electric efficiency are proposed based on the experimental study performed. Furthermore, the degradation stability of a SOFC fueled with a synthetic product gas representing steam gasification of woody biomass was investigated. After 500 h of operation under load at a steam-to-carbon ratio of 2.25 in the fuel gas, no performance or anode degradation could be detected.


Technical Reports | 2020

Investigation of the formation of coherent ash residues during fluidized bed gasification of wheat straw lignin

Priscak J, Fürsatz K, Kuba M, Skoglund N, Benedikt F, Hofbauer H. Investigation of the formation of coherent ash residues during fluidized bed gasification of wheat straw lignin. Energies. 2020;13(15):3935:

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Thermal conversion of ash-rich fuels in fluidized bed systems is often associated with extensive operation problems caused by the high amount of reactive inorganics. This paper investigates the behavior of wheat straw lignin—a potential renewable fuel for dual fluidized bed gasification. The formation of coherent ash residues and its impact on the operation performance has been investigated and was supported by thermochemical equilibrium calculations in FactSage 7.3. The formation of those ash residues, and their subsequent accumulation on the surface of the fluidized bed, causes temperature and pressure fluctuations, which negatively influence the steady-state operation of the fluidized bed process. This paper presents a detailed characterization of the coherent ash residues, which consists mostly of silica and partially molten alkali silicates. Furthermore, the paper gives insights into the formation of these ash residues, dependent on the fuel pretreatment (pelletizing) of the wheat straw lignin, which increases their stability compared to the utilization of non-pelletized fuel.


Conference contributions | 2020

Lessons Learned from Alternative Fuels Experience

Sonnleitner A. Lessons Learned from Alternative Fuels Experience. 6th Central European Biomass Conference, 22-24 January 2020, Graz

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Conference contributions | 2020

Long-term validation of a new modular approach for CO-lambda-optimization

Zemann C, Hammer F, Gölles M, Horn M. Long-term validation of a new modular approach for CO-lambda-optimization. 28th European Biomass Conference & Exhibition. 6-9 July 2020.

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Long Term Validation of a New Modular Approach for CO-Lambda-Optimization

The optimization of existing biomass boilers in terms of efficiency and pollutant emissions is essential for their continued economic and ecological viability in future energy systems. These improvements are typically achieved by constructive changes which are expensive and can require prolonged downtimes. A well-known method for optimizing biomass boilers in terms of efficiency and pollutant emissions without constructive changes is the so-called CO-lambda-optimization. While multiple approaches for CO-lambda-optimization have been presented in literature, they are still rarely used in real biomass boilers. This is partly due to the fact that these approaches do not meet the requirements associated with their long-term operation in real biomass boilers. This contribution presents a new and modular approach for the CO-lambda-optimization which is specifically designed to meet these requirements. Particular emphasis in this contribution is laid on the long-term validation of the presented approach for CO-lambda-optimization at a medium-scale fixed-bed biomass boiler.


Conference contributions | 2020

Microgrid Lab 100 % - R&D project for decentralized energy supply with biomass and other Distributed energy Resources

Aigenbauer S. Microgrid Lab 100 % - R&D project for decentralized energy supply with biomass and other Distributed energy Resources. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference contributions | 2020

Microgrid Lab 100% Testbed for the development of control algorithms for microgrids

Aigenbauer S, Microgrid Lab 100% Testbed for the development of control algorithms for microgrids. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

Model-based control of hydraulic heat distribution systems — Theory and application

Unterberger V, Muschick D, Loidl A, Poms U, Gölles M, Horn M. Model-based control of hydraulic heat distribution systems — Theory and application. Control Engineering Practice. 2020;2020(101).104464. https://doi.org/10.1016/j.conengprac.2020.104464

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With the share of renewable energy sources increasing in heating and hot water applications, the role of hydraulic heat distribution systems is becoming more and more important. This is due to the fact that in order to compensate for the often fluctuating behaviour of the renewables a flexible heat transfer must be ensured by these distribution systems while also taking the optimal operating conditions (mass flow, temperature) of the individual components into consideration. This demanding task can be accomplished by independently controlling the two physical quantities mass flow and temperature. However, since there exists an intrinsic nonlinear coupling between these quantities this challenge cannot be handled sufficiently by decoupled linear PI controllers which are currently state-of-the-art in the heating sector. For this reason this paper presents a model-based control strategy which allows a decoupled control of mass flow and temperature. The strategy is based on a systematic design approach from models described in this contribution, which are validated by commercially available components from which most of them can be parametrized by the data sheet. The control strategy is designed for a typical hydraulic configuration used in heating systems, which will allow the accurate tracking of the desired trajectories for mass flows, temperatures and consequently heat flows. The controllers are validated experimentally and compared to well-tuned state-of-the-art (PI) controllers in order to illustrate their superiority and prove their decoupling of the control of mass flow and temperature in real world applications.


Peer Reviewed Scientific Journals | 2020

Model-Based Estimation of the Flue Gas Mass Flow in Biomass Boilers. IEEE Transactions on Control Systems Technology.

Niederwieser H, Zemann C, Gölles M, Reichhartinger M. Model-Based Estimation of the Flue Gas Mass Flow in Biomass Boilers. IEEE Transactions on Control Systems Technology. 2020 August 31. doi: 10.1109/TCST.2020.3016404.

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Three estimators for the estimation of the flue gas mass flow in biomass boilers are presented and compared, namely a sliding-mode observer, a Kalman filter, and a so-called steady-state estimator. The flue gas mass flow is an important process variable in biomass boilers as it contains information about the supplied mass flows of air and decomposed fuel. It is also related to the generated heat flow. Furthermore, its knowledge may be exploited in model-based control strategies which allow one to keep pollutant emissions low, on the one hand, and to achieve high efficiency, on the other hand. However, due to fouling of the equipment over time, measurements and existing estimation methods are not suitable for long-term applications. The estimators proposed in this article are based on a dynamic model for gas tube heat exchangers. They are capable of handling the fouling of the heat exchanger and, additionally, they offer the possibility of monitoring the degree of fouling. By incorporating an additional differential pressure measurement and extending the aforementioned estimators, an improvement regarding the dynamic response and the estimation accuracy is achieved. The application of the estimators to real measurement data from both, a medium-scale and a small-scale biomass boiler, demonstrates their wide applicability.


Conference contributions | 2020

Model-based estimation of the flue gas mass flow in biomass furnaces

Niederwieser H. Model-based estimation of the flue gas mass flow in biomass furnaces. 6th Central European Biomass Conference. 22-24 January 2020, Graz.

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Other Presentations | 2020

Modern control strategies for biomass combustion systems in residential heating systems

Gölles M, Zemann C. Modern control strategies for biomass combustion systems in residential heating systems. At 6th Central European Biomass Conference IEA-Workshop: TASK 32. Oral Presenation. 23.01.2020.

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Conference contributions | 2020

Modern control strategies for biomass combustion systems in residential heating systems

Gölles M, Zemann C. Modern control strategies for biomass combustion systems in residential heating systems. 6th Central European Biomass Conference, 2020, Graz.

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Conference contributions | 2020

Modification of ash properties in fixed bed combustion systems

Sommersacher P, Retschitzegger S. Modification of ash properties in fixed bed combustion systems. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

Multi-stage model for the release of potassium in single particle biomass combustion

Anca-Couce A, Sommersacher P, Hochenauer C, Scharler R. Multi-stage model for the release of potassium in single particle biomass. Fuel. 2020:280:118569.

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The release of potassium during biomass combustion leads to several problems as the emissions of particle matter or formation of deposits. K release is mainly described in literature in a qualitative way and this work aims to develop a simplified model to quantitatively describe it at different stages. The proposed model has 4 reactions and 5 solid species, describing K release in 3 steps; during pyrolysis, KCl evaporation and carbonate dissociation. This release model is coupled into a single particle model and successfully validated with experiments conducted in a single particle reactor with spruce, straw and Miscanthus pellets at different temperatures. The model employs same kinetic parameters for the reactions in all cases, while different product compositions of the reactions are employed for each fuel, which is attributed to differences in composition. The proposed model correctly predicts the online release at different stages during conversion as well as the final release for each case.


Conference contributions | 2020

NOx Modelling and Emission Reduction

Eßl M, NOx Modelling and Emission Reduction. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Scientific Journals | 2020

Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid

Sedlmayer I, Bauer-Emhofer W, Haslinger W, Hofbauer H, Schmidl C, Wopienka E. Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid. Fuel Processing Technology 2020.198:106218.

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During transportation and storage of wood pellets various gases are formed leading to toxic atmosphere. Various influencing factors and measures reducing off-gassing have already been investigated. The present study aims at applying an antioxidant, acetylsalicylic acid (ASA), to reduce off-gassing from wood pellets by lowering wood extractives oxidation. Therefore, acetylsalicylic acid was applied in industrial and laboratory pelletizing processes. Pine and spruce sawdust (ratio 1:1) were pelletized with adding 0-0.8% (m/m) ASA. Glass flasks measurements confirmed off-gassing reduction by adding ASA for all wood pellets investigated.The biggest effect was achieved by adding 0.8% (m/m) ASA in the industrial pelletizing experiments where the emission of volatile organic compounds (VOCtot) was reduced by 82% and a reduction of carbon monoxide (CO) and carbon dioxide (CO2) emissions by 70% and 51%, respectively, could be achieved. Even an addition of 0.05% (m/m) ASA led to off-gassing reduction by >10%. A six week storage experiment to investigate the long-term effectivity of ASA addition revealed, that antioxidant addition was effective in reducing CO-, CO2- and VOCtot-release, especially during the first four weeks of the storage experiment, after which time the relative reduction effect was significantly decreased.