The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Hermann Hofbauer - One of the best experts on this subject based on the ideXlab platform.
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Effect of biomass fuel ash and bed material on the product gas composition in DFB steam Gasification
Energy, 2021Co-Authors: Katharina Fürsatz, Florian Benedikt, Josef Fuchs, Matthias Kuba, Hermann HofbauerAbstract:Abstract 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.
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A kinetic model of carbonation and calcination of limestone for sorption enhanced reforming of biomass
International Journal of Greenhouse Gas Control, 2019Co-Authors: Josef Fuchs, J C Schmid, Stefan Müller, Hermann HofbauerAbstract:Abstract The dual fluidized bed steam Gasification process aims for the production of a nitrogen-free product gas via a steam blown Gasification Reactor and an air blown combustion Reactor. Limestone as bed material enables the in-situ removal of carbon dioxide from the Gasification Reactor and therefore hydrogen contents in the product gas up to 75 vol.-%db can be gained (sorption enhanced reforming). Thereby, the limestone experiences cycles of carbonation (CaO + CO2 ->CaCO3) and calcination (CaCO3 ->CaO + CO2). Typically, kinetics are of great relevance for heterogeneous gas-solid reactions. Thus, the influence of both, kinetics of carbonation and calcination, on the SER process is investigated and a model of the SER process is established. The theoretical results are compared to those experimentally gathered and show good accordance for low to medium cycle rates of the bed material. The calcination reaction is identified as limiting step during the process due to insufficient residence time and an unfavorable temperature profile in the combustion Reactor.
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Dual fluidized bed steam Gasification: Change of product gas quality along the Reactor height
Energy, 2019Co-Authors: Anna Magdalena Mauerhofer, J C Schmid, Josef Fuchs, Stefan Müller, Florian Benedikt, Hermann HofbauerAbstract:Abstract The impact of the counter-current column of the Gasification Reactor of a 100 kWth dual fluidized bed steam Gasification pilot plant on the product gas quality was investigated. Through the advanced design of the Gasification Reactor by operating the lower part as bubbling bed and the upper part as counter-current column, the gas-solid interactions between downward flowing hot bed material particles with upwards flowing product gas could be enhanced. This was realized by equipping the counter-current column with constrictions, which increase the residence time and the bed material hold-up. Thus, the conversion efficiency of the fuel including the tar was improved. For the investigations three different experimental campaigns converting softwood pellets using a mixture of olivine and limestone (50/50 wt.-%), a mixture of feldspar and limestone (50/50 wt.-%), and 100 wt.-% quartz as bed materials were conducted. Higher H2 contents and lower contents of higher hydrocarbons could be detected along the height of the counter-current column. Especially heavy tar compounds could be reduced significantly. These two effects are explained by enhanced water gas shift and steam reforming reactions. In case of catalytically inactive quartz, only thermal effects are available and therefore lower effects on tar reduction could be obtained.
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The behavior of biomass and char particles in a dual fluidized bed Gasification system
Powder Technology, 2018Co-Authors: Stephan Kraft, Matthias Kuba, Hermann HofbauerAbstract:Abstract Biomass Gasification in fluidized beds is a complex process in which particles occur in a wide range of size and density. In this paper, the mixing behavior of the char, biomass and bed material in a Gasification Reactor of a typical dual fluidized bed (DFB) system was investigated in a cold flow model. Experiments with ternary mixtures were performed in which the size and the density of the used particles were varied. For the experiments, a cold flow model was constructed with a full bed material recirculation loop, similar to DFB systems. Experiments revealed that at low fluidization velocities, the smaller char particles and biomass particles occur more preferentially in the bed material recirculation stream. If the fluidization velocities are increased, this tendency diminishes. Furthermore, the experiments showed that the mass fraction of biomass particles in the recirculation stream is always higher than that of the lighter char particles. It is also shown that the current design of the Gasification Reactor in DFB systems is not optimal. A way to overcome this issue in existing plants is presented.
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Investigations using a cold flow model of char mixing in the Gasification Reactor of a dual fluidized bed Gasification plant
Powder Technology, 2017Co-Authors: Stephan Kraft, Friedrich Kirnbauer, Hermann HofbauerAbstract:Abstract 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 Gussing, 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.
Jane H. Davidson - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of a prototype molten salt solar Gasification Reactor
Solar Energy, 2017Co-Authors: Brandon J. Hathaway, Jane H. DavidsonAbstract:Abstract In the present work, a prototype molten salt solar Gasification Reactor was demonstrated at the 2.2 kW scale using simulated concentrated solar radiation. The molten alkali carbonate salt offers the benefits of improved heat transfer, catalysis of Gasification, reduced production of tars, and thermal stability for transient solar input. Utilizing cellulose as feedstock and carbon dioxide as oxidizer, the Reactor achieved a solar efficiency of 30% and converted 47% of the carbon in a continuous process at 1218 K. Based on an energy balance on the Reactor, we project efficiencies approaching 55% with future improvements to the Reactor.
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Development of a Molten Salt Reactor for Solar Gasification of Biomass
Energy Procedia, 2014Co-Authors: Brandon J. Hathaway, David B. Kittelson, Jane H. DavidsonAbstract:Abstract Solar Gasification has the benefits of maximizing the yield of synthesis gas from Gasification of biomass and other carbonaceous feed stock and storing solar energy in chemical form. The University of Minnesota has developed a 3kWth prototype solar Gasification Reactor in which biomass is converted to synthesis gas within a molten carbonate salt. The salt serves as a catalyst for Gasification, ensures effective transfer of heat to the reactants, and provides thermal storage to ensure steady operation. This paper describes the Reactor concept and provides an overview of the design process.
Brandon J. Hathaway - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of a prototype molten salt solar Gasification Reactor
Solar Energy, 2017Co-Authors: Brandon J. Hathaway, Jane H. DavidsonAbstract:Abstract In the present work, a prototype molten salt solar Gasification Reactor was demonstrated at the 2.2 kW scale using simulated concentrated solar radiation. The molten alkali carbonate salt offers the benefits of improved heat transfer, catalysis of Gasification, reduced production of tars, and thermal stability for transient solar input. Utilizing cellulose as feedstock and carbon dioxide as oxidizer, the Reactor achieved a solar efficiency of 30% and converted 47% of the carbon in a continuous process at 1218 K. Based on an energy balance on the Reactor, we project efficiencies approaching 55% with future improvements to the Reactor.
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Development of a Molten Salt Reactor for Solar Gasification of Biomass
Energy Procedia, 2014Co-Authors: Brandon J. Hathaway, David B. Kittelson, Jane H. DavidsonAbstract:Abstract Solar Gasification has the benefits of maximizing the yield of synthesis gas from Gasification of biomass and other carbonaceous feed stock and storing solar energy in chemical form. The University of Minnesota has developed a 3kWth prototype solar Gasification Reactor in which biomass is converted to synthesis gas within a molten carbonate salt. The salt serves as a catalyst for Gasification, ensures effective transfer of heat to the reactants, and provides thermal storage to ensure steady operation. This paper describes the Reactor concept and provides an overview of the design process.
Tobias Proll - One of the best experts on this subject based on the ideXlab platform.
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Cold flow model investigations of the countercurrent flow of a dual circulating fluidized bed gasifier
Biomass Conversion and Biorefinery, 2012Co-Authors: J C Schmid, Christoph Pfeifer, Hannes Kitzler, Tobias Proll, Hermann HofbauerAbstract:A novel fluidized bed Gasification concept with enhanced gas–particle interaction combining two circulating fluidized bed Reactors is proposed. Cold flow model results show the feasibility of the concept with regard to fluid dynamics. The aim of the design is to generate a nitrogen (N_2) free product gas with low tars and fines contents. Therefore, the system is divided into an air/combustion and a fuel/Gasification Reactor. Two gas streams are obtained separately. The two Reactors are interconnected via loop seals to assure the global circulation of bed material and to avoid gas leakages from one Reactor to the other. The global circulation rate is driven by the gas velocity in the air/combustion Reactor. Furthermore, the fuel/Gasification Reactor itself is a circulating fluidized bed with the special characteristic of almost countercurrent flow conditions for the gas phase and bed material particles. By simple geometrical modifications, it is possible to achieve well-mixed flow conditions in the fuel/Gasification Reactor along the full height. The gas velocity and the geometrical properties in the fuel/Gasification Reactor are chosen in such a way that the entrainment of coarse particles is low at the top. Due to the dispersed downward movement of the bed material particles and the feedstock input at defined locations of the fuel/Gasification Reactor, no volatiles are produced in the upper regions and the problems of insufficient gas phase conversion and high tar contents are avoided.
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a new dual fluidized bed gasifier design for improved in situ conversion of hydrocarbons
2011Co-Authors: J C Schmid, Christoph Pfeifer, Hannes Kitzler, Tobias Proll, Hermann HofbauerAbstract:A new fluidized bed gasifier with increased gas-solid interaction combining two circulating fluidized bed Reactors is proposed. The aim of the design is to generate a nitrogen (N2) free product gas with low tars and fines content. Therefore the system is divided into an air/combustion and a fuel/Gasification Reactor. Two gas streams are separately gained. The two Reactors are interconnected via loop seals to assure the global circulation of bed material. The global circulation rate is driven by the gas velocity in the air/combustion Reactor. Furthermore the fuel/Gasification Reactor itself is a circulating fluidized bed but with the special characteristic of almost countercurrent flow conditions for gas phase and solids. By simple geometrical modifications it is possible to achieve well mixed flow conditions in the fuel/Gasification Reactor along the full height. The gas velocity and the geometrical properties in the fuel/Gasification Reactor are chosen in such a way that solids' entrainment of coarse particles is low at the top. Due to the dispersed downward movement of the solids, no volatiles are produced in the upper part of the fuel Reactor and the problems of insufficient gas phase conversion and high tar content are avoided. Cold flow model results show the fluid dynamic feasibility of the novel dual circulating fluidized bed concept.
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h2 rich syngas by selective co2 removal from biomass Gasification in a dual fluidized bed system process modelling approach
Fuel Processing Technology, 2008Co-Authors: Tobias Proll, Hermann HofbauerAbstract:A process model of dual fluidized bed Gasification is presented based on mass- and energy balances. The model further covers the evaluation of thermodynamic equilibrium states. The Gasification is investigated for the special case that CaO/CaCO3 is used as bed material allowing selective transport of CO2 from the Gasification Reactor to the combustion Reactor by repeated carbonation and calcination. Experimental data are used to determine the model parameters. An empirical approach towards the kinetics of fuel conversion allows prediction of process behaviour at varied fuel water content. The selective transport of CO2 results in high H2 contents in the produced syngas. The lower operating temperatures in the Gasification Reactor increase the efficiency of energy conversion. The results are in agreement with experimental data and show the thermodynamic limitations of the technology.
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h2 rich syngas by selective co2 removal from biomass Gasification in a dual fluidized bed system process modelling approach
Fuel Processing Technology, 2008Co-Authors: Tobias Proll, Hermann HofbauerAbstract:A process model of dual fluidized bed Gasification is presented based on mass- and energy balances. The model further covers the evaluation of thermodynamic equilibrium states. The Gasification is investigated for the special case that CaO/CaCO3 is used as bed material allowing selective transport of CO2 from the Gasification Reactor to the combustion Reactor by repeated carbonation and calcination. Experimental data are used to determine the model parameters. An empirical approach towards the kinetics of fuel conversion allows prediction of process behaviour at varied fuel water content. The selective transport of CO2 results in high H2 contents in the produced syngas. The lower operating temperatures in the Gasification Reactor increase the efficiency of energy conversion. The results are in agreement with experimental data and show the thermodynamic limitations of the technology.
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H2 rich syngas by selective CO2 removal from biomass Gasification in a dual fluidized bed system — Process modelling approach
Fuel Processing Technology, 2008Co-Authors: Tobias Proll, Hermann HofbauerAbstract:A process model of dual fluidized bed Gasification is presented based on mass- and energy balances. The model further covers the evaluation of thermodynamic equilibrium states. The Gasification is investigated for the special case that CaO/CaCO3 is used as bed material allowing selective transport of CO2 from the Gasification Reactor to the combustion Reactor by repeated carbonation and calcination. Experimental data are used to determine the model parameters. An empirical approach towards the kinetics of fuel conversion allows prediction of process behaviour at varied fuel water content. The selective transport of CO2 results in high H2 contents in the produced syngas. The lower operating temperatures in the Gasification Reactor increase the efficiency of energy conversion. The results are in agreement with experimental data and show the thermodynamic limitations of the technology.
Thomas Kempka - One of the best experts on this subject based on the ideXlab platform.
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tops technology options for coupled underground coal Gasification and co2 capture and storage
Energy Procedia, 2014Co-Authors: Sevket Durucan, Thomas Kempka, Anna Korre, Matthew Idiens, Krzysztof Stanczyk, Krzysztof Kapusta, Anna Rogutdabrowska, Karlheinz Wolf, Paul L Younger, Simon ZavsekAbstract:The TOPS project takes a radical and holistic approach to coupled UCG-CCS, and thus the site selection criteria for the coupled processes, considering both geological, reservoir and process engineering aspects and different end-uses of the produced synthetic gas in order to optimise the whole value chain. In particular, the experimental research carried out utilises a newly constructed high pressure Gasification Reactor investigating several prospective options of UCG technology implementations. Integrated research addresses field based technology knowledge gaps, such as cavity progression and geomechanics, potential groundwater contamination and subsidence impacts, together with research into process engineering solutions in order to assess the role/impact of site specific factors and selected reagents on the operability of given CO2 emission mitigation options. Ultimately, research aims to minimise the need for on-site CO2 storage capacity as well as maximising the economic yield of UCG through value added end products.
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coupled hydro thermal analysis of underground coal Gasification Reactor cool down for subsequent co2 storage
Energy Procedia, 2013Co-Authors: Vasilis Sarhosis, Dongmin Yang, Yong Sheng, Thomas KempkaAbstract:The present study investigates the time dependency of a UCG (Underground Coal Gasification) Reactor cool down process by comparing natural cool down with forced cooling driven by water flushing. The convective heat transport out of the UCG Reactor was calculated using an analytical approach coupled to a numerical heat flow model of the geology surrounding the UCG Reactor. Our results show that forced cooling by water flushing at flow velocities of 1 m/s can decrease the required time to retain initial in-situ temperature conditions by a factor of more than 300.