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Peer Reviewed Scientific Journals | 2017

CO/CO2 Ratio in biomass char oxidation

Anca-Couce A, Sommersacher P, Shiehnejadhesar A, Mehrabian R, Hochenauer C, Scharler R. CO/CO2 Ratio in biomass char oxidation. INFUB 2017, 11th European Conference on Industrial Furnace and Boilers. 18-21 April 2017, Albufeira, Portugal.

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The CO/CO2 release ratio obtained during char combustion of single biomass particles has been analysed in this work experimentally and by modelling. Experiments have been conducted with spruce, straw and Miscanthus pellets at different temperatures. Furthermore, these experiments have been modelled with a single particle model coupled with a CFD model of the single particle reactor. The results show that the CO/CO2 ratio strongly depends on the feedstock, being lower for spruce than for straw or Miscanthus. Furthermore, the most commonly employed correlations for this ratio in literature are not adequate, as they either under- or over-predict it.


Other publication | 2017

Comparison of selected firelighters for stoves from renewable and fossil fuels in terms of gaseous emissons

Matschegg D, Kirchhof JM, Golicza L, Schwabl M, Schmidl C. Comparison of selected firelighters for stoves from renewable and fossil fuels in terms of gaseous emissons. 5th Central European Biomass Conference (Poster). January 2017, Graz, Austria.

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Peer Reviewed Scientific Journals | 2017

CPFD simulations of an industrial-sized dual fluidized bed steam gasification system of biomass with 8 MW fuel input

Kraft S, Kirnbauer F, Hofbauer H. CPFD simulations of an industrial-sized dual fluidized bed steam gasification system of biomass with 8 MW fuel input. Applied Energy. 15 March 2017;190: 408-420.

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Dual fluidized bed (DFB) systems for biomass gasification consist of two connected fluidized beds with a circulating bed material in between. Inside such reactor systems, rough conditions occur due to the high temperatures and the movement of the bed material. Computational fluid dynamics calculations are a useful tool for investigating fluid dynamics inside such a reactor system. In this study, an industrial-sized DFB system was simulated with the commercial code CPFD Barracuda. The DFB system is part of the combined heat and power (CHP) plant at Güssing, situated in Austria, and has a total fuel input of 8 MWth. The model was set up according to geometry and operating data which allows a realistic description of the hot system in the simulation environment. Furthermore, a conversion model for the biomass particles was implemented which covers the drying and devolatilization processes. Homogeneous and heterogeneous reactions were considered. Since drag models have an important influence on fluidization behavior, four drag models were tested. It was found that the EMMS drag model fits best, with an error of below 20%, whereas the other drag models produced much larger errors. Based on this drag law, further simulations were conducted. The simulation model correctly predicts the different fluidization regimes and pressure drops in the reactor system. It is also able to predict the compositions of the product and flue gas, as well as the temperatures inside the reactor, with reasonable accuracy. Due to the results obtained, Barracuda seems suitable for further investigations regarding the fluid mechanics of such reactors.


Peer Reviewed Scientific Journals | 2017

Cyanobacterial PHA Production—Review of Recent Advances and a Summary of Three Years’ Working Experience Running a Pilot Plant

Troschl C, Meixner K, Drosg B. Cyanobacterial PHA Production—Review of Recent Advances and a Summary of Three Years’ Working Experience Running a Pilot Plant. Bioengineering. 28 March 2017;4(2), 26.

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Scientific Journals | 2017

Development and experimental validation of a water gas shift kinetic model for Fe-/Cr-based catalysts processing product gas from biomass steam gasification.

Kraussler M, Hofbauer H. Development and experimental validation of a water gas shift kinetic model for Fe-/Cr-based catalysts processing product gas from biomass steam gasification. Biomass Conversion and Biorefinery. Volume 7, Issue 2, 1 June 2017, Pages 153-165

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Peer Reviewed Scientific Journals | 2017

Effect of draught conditions and ignition technique on combustion performance of firewood roomheaters

Reichert G, Hartmann H, Haslinger W, Öhler H, Mack R, Schmidl C, Schön C, Schwabl M, Stressler H, Sturmlechner R, Hochenauer C. Effect of draught conditions and ignition technique on combustion performance of firewood roomheaters. Renewable Energy. 1 May 2017;105: 547-560.

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Firewood roomheaters are popular, widespread and important for reaching European CO2 emission targets. Since they contribute significantly to local air pollution, they have to be optimized towards minimal emission release, especially in real-life operation. Draught conditions and user behavior, particularly the ignition technique, significantly affect the emission and efficiency performance of firewood roomheaters. This study assessed the effects of the respective parameters experimentally. The results revealed a clear correlation between draught conditions and thermal efficiency. Increased draught conditions up to 48 Pa significantly decreased thermal efficiency by 6%–11% absolutely. However, for gaseous emissions no clear trend was observed. Accordingly, CO and OGC emissions increased at higher draught conditions for one tested roomheater by 30% and 60%, but decreased for two other tested roomheaters by 13%–45%. For PM emissions no effect of increased draught conditions was evident. Top-down ignition technique did not lead to a significant decrease of PM emissions compared to bottom-up ignition. In contrast, bottom-up ignition led to best thermal efficiencies. The use of either spruce or beech as kindling material revealed no significant relevance for the ignition performance.


Conference contributions | 2017

Effizienzsteigerung und Optimierung des Zusammenspiels von Scheitholzkessel, Pufferspeicher und Solaranlage durch die Verwendung mathematischer Modelle

Schulz J, Zemann C, Gölles M. Effizienzsteigerung und Optimierung des Zusammenspiels von Scheitholzkessel, Pufferspeicher und Solaranlage durch die Verwendung mathematischer Modelle. 5th Central European Biomass Conference (oral presentation). January 2017, Graz, Austria.

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Reviewed Conference Papers | 2017

Emission factor assessment for two firewood stoves in the autumn or spring season

Sturmlechner R, Stressler H, Schwabl M, Reichert G, Carlon E, Haslinger W, Schmidl C, Weissinger A. Emission factor assessment for two firewood stoves in the autumn or spring season. 25th International Conference on Modelling, Monitoring and Management of Air Pollution. 25-27 April 2017.

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This study analyses the emission factors of two firewood room heaters under testing conditions which emulate real life operation. A 6.5 kW stove with low heat storage capacity and high leakage rate (stove A) is compared with an 8 kW air-tight stove with high heat storage capacity (stove B). Thermal efficiency, carbon monoxide (CO) and organic gaseous compound (OGC) emissions, as well as the thermal heat losses (THL) during cool down phase were investigated in a series of laboratory tests. Furthermore, the influence of closing the air supply dampers at the end of the heating cycle was evaluated. Test results for the whole test cycle (including cool down phase) showed that stove A had CO emissions of 2633 mg/MJOutput and OGC emissions of 203 mg/MJOutput, while stove B had CO emissions of 2408 mg/MJOutput and OGC emissions of 109 mg/MJOutput, when air dampers were closed. It was also found that user behaviour has a critical influence on the stoves’ performance. Closing the air supply dampers at the end of the stove operation improved the efficiency by up to 5.0 percentage points. Furthermore, the duration of the cool down phase increased, as well as CO and OGC emissions decreased. As a matter of fact, measures to improve the user behaviour as for example user trainings and accurate manuals are of major importance in order to decrease emissions and increase efficiency of domestic heating appliances. Moreover, real life emission factors of other technologies should be established in order to develop a database which can be applied in air quality dispersion models.


Peer Reviewed Scientific Journals | 2017

Environmental trade-offs between residential oil-fired and wood pellet heating systems: forecast scenarios for Austria until 2030

Karner K, Kristöfel C, Enigl M, Strasser C, Schmid E. Environmental trade-offs between residential oil-fired and wood pellet heating systems: forecast scenarios for Austria until 2030. Renewable & Sustainable Energy Reviews. December 2017;80: 868-879.

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Conference contributions | 2017

ErgoS – Energierückgewinnung durch offene Sorption für Biomassefeuerungsanlagen

Höftberger E, Riepl R, Hebenstreit B, Golicza L, Paar EK, Goritschnig M, Zweiler R, Hochenauer C. ErgoS – Energierückgewinnung durch offene Sorption für Biomassefeuerungsanlagen. Güssing 17 Konferenz. March 2017, Güssing, Austria.

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Peer Reviewed Scientific Journals | 2017

Estimation of binary diffusion coefficients in supercritical water - A mini review

Kraft S, Vogel F. Estimation of binary diffusion coefficients in supercritical water - A mini review. Industrial & Engineering Chemistry Research. 26 April 2017;56(16): 4847-4855.

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Diffusion coefficients of various solutes in supercritical water, which were either measured or retrieved from Molecular Dynamics simulations, were reviewed. Diffusion coefficients of molecules relevant for supercritical water processes were calculated with correlations reported in the literature and compared to the values of reference data. For conditions well above the critical point of water the simple Stokes-Einstein equation predicts the diffusion coefficients with an accuracy better than 20%. For conditions near the critical point the Wilke-Chang correlation gives the most accurate results. Diffusion coefficients for typical molecules occurring in supercritical water processes such as O2, N2, CO, CO2, or CH4 are estimated to be in the range of 60 · 10⁻⁹ m²/s at 673 K and 30 MPa. For H2, for which no experimental data are available, much higher diffusion coefficients in the range of 250 · 10⁻⁹ m²/s seem plausible. The data set of binary diffusion coefficients in supercritical water, either determined experimentally or by Molecular Dynamics simulations, should be extended significantly to include more solutes, as well as higher temperatures and pressures.
 


Conference contributions | 2017

Evaluation of the Combustion Behaviour of Straw, Poplar and Maize in a Small-Scale Biomass Boiler

Kelz J, Zemann C, Muschick D, Krenn O, Hofmeister G, Weissinger A, Gölles M. & Hochenauer C. Evaluation of the Combustion Behaviour of Straw, Poplar and Maize in a Small-Scale Biomass Boiler. Proceedings 25th European Biomass Conference and Exhibition, 12-15 June 2017, Stockholm, Sweden. p. 1958-1966

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In order to evaluate the combustion behaviour of new biomass feedstocks such as short rotation coppice (poplar wood chips), fuels from agriculture (wheat straw pellets) and biomass residues (maize spindle grits), comprehensive test runs investigating both particulate matter (PM) and gaseous emissions were performed. A commercially available small-scale biomass boiler, especially designed to enable high fuel flexibility, was used for this evaluation. The combustion behaviour was determined for various boiler load conditions and primary air ratios while maintaining a constant total air ratio. Based on wet chemical analyses of the fuels, fuel indexes were calculated to deliver primary information on the combustion behaviour to be expected. During the test runs appropriate operating conditions were determined for these new biomass feedstocks in order to optimise combustion parameters and to minimise PM and gaseous emissions as well as to inhibit ash related problems (slagging, ash deposit formation and corrosion). The optimisation of operating conditions by primary measures showed a big potential for a stable boiler operation combined with reduced emissions. The findings provide the basis for a further development of combustion systems as well as control systems for the combustion of new biomass feedstocks.


Conference contributions | 2017

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

Feldmeier S, Wopienka E, Schwarz M. GrateAdvance - Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies. 5th Central European Biomass Conference, Workshop Highlights of Bioenergy Research 2017 (oral presentation). January 2017, Graz, Austria.

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Conference Papers | 2017

HCNG or hythane production from biomass steam gasification

Kraussler M, Priscak J, Hofbauer H. HCNG or hythane production from biomass steam gasification. 5th Central European Biomass Conference (oral presentation). January 2017, Graz, Austria.

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Other publication | 2017

Honeycomb catalysts integrated in firewood stoves - potentials and limitations

Reichert G, Haslinger W, Kirchhof JM, Schmidl C, Sedlmayer I, Schwabl M, Stressler H, Sturmlechner R, Wöhler M, Hochenauer C. Honeycomb catalysts integrated in firewood stoves - potentials and limitations. 5th Central European Biomass Conference (oral presentation). January 2017, Graz, Austria.

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Peer Reviewed Scientific Journals | 2017

Hydrogen production from biomass: The behavior of impurities over a CO shift unit and a biodiesel scrubber used as a gas treatment stage

Loipersböck J, Lenzi M, Rauch R, Hofbauer H. Hydrogen production from biomass: The behavior of impurities over a CO shift unit and a biodiesel scrubber used as a gas treatment stage. Korean Journal of Chemical Engineering. 22 June 2017; 1-6.

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Most of the hydrogen produced is derived from fossil fuels. Bioenergy2020+ and TU Wien have been working on hydrogen production from biomass since 2009. A pilot plant for hydrogen production from lignocellulosic feedstock was installed onsite using a fluidized bed biomass gasifier in Güssing, Austria. In this work, the behavior of impurities over the gas conditioning stage was investigated. Stable CO conversion and hydration of sulfur components could be observed. Ammonia, benzene, toluene, xylene (BTX) and sulfur reduction could be measured after the biodiesel scrubber. The results show the possibility of using a commercial Fe/Cr-based CO shift catalyst in impurity-rich gas applications. In addition to hydrogen production, the gas treatment setup seems to also be a promising method for adjusting the H2 to CO ratio for synthesis gas applications.


Technical Reports | 2017

IEA Bioenergy Task 39 Report on State of the Technology of Algae Bioenergy

Bacovsky D, Sonnleitner A, Laurens L, McMillan JD. IEA Bioenergy Task 39 Report on State of the Technology of Algae Bioenergy. 5th Central European Biomass Conference, Workshop Highlights of Bioenergy Research 2017 (oral presentation). January 2017, Graz, Austria.

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Conference Papers | 2017

Influence of Calcium-rich Coatings on the Catalytic Activity of Bed Materials in CO2-Gasification of Biomass

Kuba M, Kirnbauer F, Hofbauer H. Influence of Calcium-rich Coatings on the Catalytic Activity of Bed Materials in CO2-Gasification of Biomass. 24th European Biomass Conference & Exhibition (poster). June 2016, Amsterdam, Netherlands.

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Peer Reviewed Scientific Journals | 2017

Influence of coated olivine on the conversion of intermediate products from decomposition of biomass tars during gasification

Kuba M, Kirnbauer F, Hofbauer H. Influence of coated olivine on the conversion of intermediate products from decomposition of biomass tars during gasification. Biomass Conversion and Biorefinery. 1 March 2017;7(1): 11-21.

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Steam gasification of solid biomass in dual fluidized bed systems is a suitable technology for the production of chemicals, fuels for transportation, electricity, and district heating. Interaction between biomass ash and bed material leads to the development of Ca-rich bed particle layers. Furthermore, incomplete decomposition of biomass leads to the formation of tar components; among these are stable intermediate products such as 1H-indene and stable gaseous hydrocarbons such as methane. In this work, the influence of bed particle layers on the conversion of intermediate products such as 1H-indene and methane via steam reforming was investigated by conducting experiments in a lab-scale test rig. Satisfying conversion of 1H-indene into gaseous molecules (e.g., CO, CO2, H2) was achieved with used, layered olivine, whereas fresh olivine showed significantly poorer performance. Since steam reforming was connected to the water-gas-shift reaction for the tested hydrocarbons, investigations regarding carbon monoxide conversion in the presence of steam were conducted as well. Furthermore, a comparison of the influence of fresh and used bed material concerning the conversion of methane is presented, showing that methane is not affected by the bed material, independent of the presence of particle layers.
 


Peer Reviewed Scientific Journals | 2017

Influence of Heterogeneous Secondary Reactions during Slow Pyrolysis on Char Oxidation Reactivity of Woody Biomass

Anca-Couce A, Dieguez-Alonso A, Zobel N, Berger A, Kienzl N, Behrendt F. Influence of Heterogeneous Secondary Reactions during Slow Pyrolysis on Char Oxidation Reactivity of Woody Biomass. Energy and Fuels. 16 March 2017;31(3): 2335-2344.

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The influence of heterogeneous secondary reactions on char oxidation reactivity, which can take place during slow pyrolysis processes in a woody biomass particle, is analyzed in this study. To this end, the oxidative behavior of primary char produced in a thermobalance with initial wood masses of a few milligrams is compared to the behavior of char produced under conditions enhancing secondary reactions, i.e., large particle and bed sizes in fixed-bed reactors. The influence of the maximum conversion temperature, heating rate, and catalytic effect of inorganics is also studied to compare the effect of each parameter. Results show that a significant reduction in reactivity takes place when char is produced under conditions enhancing these secondary reactions during pyrolysis. The effect is of similar order as the effect as a result of thermal annealing at 900 °C or the catalytic effect of alkali and alkaline earth metals. Therefore, the presence of heterogeneous secondary reactions during pyrolysis should be taken into account in studies addressing biomass char reactivity. Furthermore, it is shown that the reduction of reactivity as a result of secondary reactions is related to neither the loss of oxygen-containing functional groups nor the potential blocking of pores, specially micropores, resulting from the formation of this secondary char. The explanation may, therefore, lie on the deactivation or blocking of active sites by the secondary char.


Peer Reviewed Scientific Journals | 2017

Influence of pellet length on performance of pellet room heaters under real life operation conditions

Wöhler M, Jaeger D, Reichert G, Schmidl C, Pelz SK. Influence of pellet length on performance of pellet room heaters under real life operation conditions. Renewable Energy. 1 May 2017;105: 66-75.

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Wood pellet combustion for heating is increasing in importance in Europe. However, the most commonly used heating appliances such as wood pellet stoves are responsible for emissions which could negatively affect human health. The emissions quality of pellet stoves is influenced by pellet properties and combustion phase characteristics. The goal of this study is to investigate the influence of pellet length on the performance of pellets stoves under real life operation conditions. Three softwood pellet samples were produced, differing only in length. Combustion tests with two different types of pellet stoves were performed in steady and non-steady combustion phases. Gaseous and particulate emissions as well as fuel mass flow were measured. Results show a reduced fuel mass flow (up to 36%) into the combustion chamber for long pellets compared to short pellets. The results of the combustion tests show a considerable influence of pellet length on the performance of both pellet stoves. For example, carbon monoxide emissions and particulate emissions of one stove in nominal load operation increased for long pellets compared to short pellets from 185 mg/m3 to 882 mg/m3, and from 27 mg/m3 to 37 mg/m3 respectively. Results also show a considerable influence of the combustion phase on the emissions level.


Conference Papers | 2017

Influence of sulfur components on the catalytic mixed alcohol synthesis based on wood gas derived from biomass steam

Binder, M., Rauch, R., Koch, M., Summers, M., Aichernig, C., and Hofbauer, H.: Influence of sulfur components on the catalytic mixed alcohol synthesis based on wood gas derived from biomass steam. In: Proceedings of the 25th European Biomass Conference and Exhibition, 12 - 15 June 2017, Stockholm, Sweden.

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Conference Papers | 2017

Innovative flexible grate solutions for future biomass combustion appliances

Feldmeier, S., Wopienka, E., Schwarz, M., Mehrabian Bardar, R.: Innovative flexible grate solutions for future biomass combustion appliances. (European Biomass Conference and Exhibition 2017, Stockholm).

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The energetic utilization of alternative fuels (short rotation coppice, miscanthus), agricultural by-products (straw, corn cobs) or biomass residues (nut shells, coffee grounds) becomes of increasing interest. Due to variations in fuel properties – and the ash content in particular – biomass fuels considerably influence the conditions in the combustion zone and especially in the fuel bed. Usually, state-of-the-art combustion appliances are optimized for a particular fuel quality and typically approved only for utilization of standardized wood pellets or wood chips. Research activities within the GrateAdvance project focus on fuel flexible grate technologies being capable of adapting conditions in the combustion zone by a systematic and targeted adjustment of grate parameters in order to minimize emissions and slagging problems, thus setting the basis for a new generation of biomass technologies. Moreover, a novel control concept will ensure optimal combustion conditions for any biomass fuel, and specifically adjust to relevant fuel properties.


Peer Reviewed Scientific Journals | 2017

Intelligent Heat Networks: First Results of an Energy-Information-Cost-Model

Lichtenegger K, Hoeftberger E, Schmidl C, Woess D, Proell T, Halmdienst C. Intelligent Heat Networks: First Results of an Energy-Information-Cost-Model. Sustainable Energy, Grids and Networks. September 2017;11: 1-12.

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Integrating additional renewable heat sources into district heating networks can have several beneficial effects, but it also requires more sophisticated control strategies than supply by only one central plant. In this article, we study the integration of prosumers (i.e. buildings which have both the capacity to produce and the need to consume energy, here heat) into heat distribution grids.

This study is performed with a simplified model, based on energy and information flows. The prosumers can act autonomously, based on a price communicated by the central heat plant. This price is determined based on the benefit for the network by additional heat feed-in and is regularly updated. This leads to an interlocking of a physical/technical and an economic feedback loop. The control parameters are optimized by using a stochastic optimization algorithm, based on simulation runs for one typical week in winter, spring and summer.

We compare the results with standard setups (heat network with only consumers, central heat generation and additional heat-producing building disconnected from the grid) and obtain an improvement concerning fuel consumption in most and concerning emissions in many situations. While economic benefits are achieved in most scenarios, it is a non-trivial task to construct a market model that distributes these benefits in a fair way between the central heat plant and the prosumers.


Peer Reviewed Scientific Journals | 2017

Investigations using a cold flow model of char mixing in the gasification reactor of a dual fluidized bed gasification plant

Kraft S, Kirnbauer F, Hofbauer H. Investigations using a cold flow model of char mixing in the gasification reactor of a dual fluidized bed gasification plant. Powder Technology. 1 July 2017;316: 687-696.

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This paper treats the mixing and movement of char in a dual fluidized bed (DFB) biomass gasification plant. In these plants such measurements are troublesome to perform, and so a cold flow model has been developed to investigate this topic. This cold flow model allows simulating the fluidization behaviour of the gasification reactor in the DFB plant in Güssing, Austria. The recirculation of the bed material is also possible, and can be easily controlled with a rotary valve. In the cold flow model, bronze is used as the bed material and polyethylene as the char. It is possible to take samples during operation to investigate the char concentration in the bed material recirculation stream. Experiments have shown that the char shows a flotsam behaviour since it is of low density. Furthermore, the investigations have shown that higher fluidization rates and higher bed material recirculation rates enhance the char mixing and increase the char concentration in the recirculation stream. It was found that doubling the overall char concentration in the system does not lead to a doubling of the char concentration in the bed material recirculation stream. Furthermore, the influence of the bed height in the gasification reactor was investigated. It was found that higher bed heights lead to lower char concentrations in the recirculation stream. These initial investigations revealed that much is still unknown about DFB plants, but the knowledge of the behaviour of the different types of particles in the bubbling bed of the gasification reactor helps to further improve and develop the DFB technology.


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