@misc{KurnatowskaFradetMehlhoseetal., author = {Kurnatowska, Michalina and Fradet, Quentin and Mehlhose, Sven and Riedel, Uwe}, title = {Influence of various conditions on the course of the reduction of iron oxide with hydrogen in thermogravimetric studies}, series = {2nd ESTEP Hydrogen Conference, 2022-11-29 - 2022-12-01, Versailles, France.}, journal = {2nd ESTEP Hydrogen Conference, 2022-11-29 - 2022-12-01, Versailles, France.}, abstract = {The reduction of iron oxide with hydrogen is a widely studied research topic with increasing interest for several reasons. One of them is the growing demand for steel in the world and the CO2 emissions caused by its production. Hydrogen direct reduction is a very promising solution to green steelmaking and has the highest potential to reduce CO2 emissions. The direct reduction process is commonly associated with the reduction of pellets in shaft furnaces. But novel technologies, such as fluidized beds or entrained-flow reactors, which reduce directly iron ore fines must be further developed as they can reach much higher energy efficiencies. A second motivation to study the reduction of iron oxide with H2 is the growing need for fossil fuel-free energy carriers. Green hydrogen can be used to reduce iron oxide powders; the reduced iron, featuring high energy density, could serve as an energy carrier in "green" power plants. Both topics are in the scope of our research, dealing with thermogravimetric analyses of the reduction of iron oxide powders with hydrogen.}, language = {en} } @misc{LindnerBraunUnkhoffNaumannetal., author = {Lindner, Fabian and Braun-Unkhoff, Marina and Naumann, Clemens and Kathrotia, Trupti and K{\"o}hler, Markus and Riedel, Uwe}, title = {An experimental speciation study on the pyrolysis and oxidation of the oxygenated fuels DME, OME1, and OME2 in a single pulse shock tube}, series = {11th European Combustion Meeting (ECM), 2023-04-26 - 2023-04-28, Rouen, France}, journal = {11th European Combustion Meeting (ECM), 2023-04-26 - 2023-04-28, Rouen, France}, language = {en} } @misc{FradetKurnatowskaRiedel, author = {Fradet, Quentin and Kurnatowska, Michalina and Riedel, Uwe}, title = {Thermochemical reduction of iron oxide powders with hydrogen: review of selected thermal analysis studies}, series = {Thermochimica Acta}, volume = {726}, journal = {Thermochimica Acta}, publisher = {Elsevier BV}, issn = {0040-6031}, doi = {10.1016/j.tca.2023.179552}, pages = {15}, language = {en} } @misc{NgũgĩRichterBraunUnkhoffetal., author = {Ngũgĩ, John Mbũrũ and Richter, Sandra and Braun-Unkhoff, Marina and Naumann, Clemens and Riedel, Uwe}, title = {A study on fundamental combustion properties of trimethyl orthoformate: experiments and modeling}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {145}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {2}, publisher = {ASME International}, issn = {0742-4795}, doi = {10.1115/1.4055828}, abstract = {Trimethyl orthoformate (TMOF: HC(OCH3)3) has recently been examined as a viable biofuel. TMOF is a branched isomer of oxymethylene ether-2 (OME2) that, due to its high oxygen content and lack of direct carbon-carbon bonds, considerably reduces the formation of soot particles. To meet the challenges of a more flexible and sustainable power generation, a detailed understanding of its combustion properties is essential for its safe and efficient utilization, neat or in blends. In this work, two fundamental combustion properties of TMOF were studied: (i) Auto-ignition of TMOF/synthetic air mixtures (φ = 1.0; diluted 1:5 with N2) using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) Laminar burning velocities of TMOF/air mixtures using the cone angle method at ambient and elevated pressures of 3 and 6 bar. Furthermore, the impact of TMOF addition to a gasoline surrogate (PRF90) on ignition delay times was studied using the shock tube method at φ = 1.0, 1:5 dilution with N2, T = 900-2000}, language = {en} } @misc{HernandezKathrotiaMethlingetal., author = {Hernandez, Astrid Ramirez and Kathrotia, Trupti and Methling, Torsten and Braun-Unkhoff, Marina and Riedel, Uwe}, title = {An upgraded chemical kinetic mechanism for ISO-Octane Oxidation: prediction of polyaromatics formation in Laminar Counterflow Diffusion Flames}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {145}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {6}, publisher = {ASME International}, issn = {0742-4795}, doi = {10.1115/1.4056096}, pages = {8}, abstract = {Iso-octane is widely recognized as a prominent candidate to represent the oxidation of iso-alkanes within jet fuel and gasoline surrogates. This work evaluated a chemical kinetic mechanism for iso-octane focusing on the model's capability to predict the formation of polycyclic aromatic hydrocarbons (PAHs). As the model is intended to be further coupled with soot models, the chemical kinetic mechanism must supply good predictability of the formation and consumption of PAHs considered as major soot precursors. A first validation of the iso-octane submodel as incorporated within ESTiMatE-Mech, using experimental data from literature, reveals the need to improve the submodel. Considerable deviations were observed in the prediction of the PAHs, although concentration profiles of major species and fundamental combustion properties, here ignition delay time and laminar flame speed, were accurately predicted. Through rate of production and sensitivity analyses of the mechanism, nine reactions were identifie}, language = {en} } @misc{AliMehlhoseFradetetal., author = {Ali, Mohammed Liaket and Mehlhose, Sven and Fradet, Quentin and Riedel, Uwe}, title = {An experimental and CFD study of the iron ore fixed bed structure and its influence on the direct reduction process}, series = {Proceedings of the 14th European Conference on Industrial Furnaces and Boilers}, journal = {Proceedings of the 14th European Conference on Industrial Furnaces and Boilers}, abstract = {The current circumstances of global warming, improved energy efficiency, and the higher suitability of Direct Reduced Iron (DRI) in Electric Arc Furnaces (EAF) for steel production necessitate a transition in the iron and steelmaking process from the traditional blast furnace/basic oxygen furnace to the more sustainable and eco-friendly direct reduction process. This reduction can be effectively studied in a fixed bed configuration, which bridges the gap between fundamental investigations on a single pellet and industrial shaft furnaces. While an average porous media model may be used to simulate the fixed bed reactor, this approach fails to account for the impact of intra- and inter-pellet fluid dynamics as well as heat and mass transfer. To accurately represent the geometric structure of iron ore pellet beds, an experimental construction must be accompanied by a particle-resolved CFD model. This article is divided into successive steps. The first step consists in the experimental construction of iron ore beds with different pellet size distributions (10-12.5 mm and 12.5-16 mm) and of the calculation of the bulk bed porosity and radial average bed porosity. The discrete element method (DEM) is further used to computationally reconstruct random packed beds of 0.5 kg industrial pellets based on the experimental data of pellet size distributions. A 3D domain is created using particle position data from the previous step, and pellets and voids are meshed at different refinement levels. Finally, CFD simulations are carried out to investigate the reduction of iron oxide pellets using H2 as a reducing gas in a fixed bed, considering available experimental data for model validation. The effect of three different bed structures on the overall conversion degree of iron ore is examined. This approach allows for successful modeling of a fixed bed using experimental input and investigation into the potential effects of the bed structure on the overall conversion during the direct reduction of the iron ore pellets.}, language = {en} } @article{NeumannFradetScholtisseketal., author = {Neumann, Jannik and Fradet, Quentin and Scholtissek, Arne and Dammel, Frank and Riedel, Uwe and Dreizler, Andreas and Hasse, Christian and Stephan, Peter}, title = {Thermodynamic assessment of an iron-based circular energy economy for carbon-free power supply}, series = {Applied Energy}, volume = {368}, journal = {Applied Energy}, publisher = {Elsevier BV}, issn = {0306-2619}, doi = {10.1016/j.apenergy.2024.123476}, pages = {23}, language = {en} } @misc{AliMehlhoseFradetetal., author = {Ali, Mohammed Liaket and Mehlhose, Sven and Fradet, Quentin and Riedel, Uwe}, title = {Particle-resolved computational modeling of hydrogen-based direct reduction of iron ore pellets in a fixed bed. Part II: Influence of the pellet sizes and shapes}, series = {International Journal of Hydrogen Energy}, volume = {86}, journal = {International Journal of Hydrogen Energy}, publisher = {Elsevier BV}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2024.08.384}, pages = {1401 -- 1413}, language = {en} } @misc{AliFradetRiedel, author = {Ali, Mohammed Liaket and Fradet, Quentin and Riedel, Uwe}, title = {Particle-resolved computational modeling of hydrogen-based direct reduction of iron ore pellets in a fixed bed. Part I: Methodology and validation}, series = {International Journal of Hydrogen Energy}, volume = {87}, journal = {International Journal of Hydrogen Energy}, publisher = {Elsevier BV}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2024.09.028}, pages = {332 -- 343}, language = {en} } @misc{WernerNaumannBraunUnkhoffetal., author = {Werner, Fabienne and Naumann, Clemens and Braun-Unkhoff, Marina and K{\"o}hler, Markus and Riedel, Uwe}, title = {Revealing H-abstraction reactions with oxygenated fuels using shock tube experiments with ARAS}, series = {26th International Symposium on Gas Kinetics and Related Phenomena - GK2022}, journal = {26th International Symposium on Gas Kinetics and Related Phenomena - GK2022}, language = {en} } @misc{SchlichtingMethlingOsswaldetal., author = {Schlichting, Samuel and Methling, Torsten and Oßwald, Patrick and Zinsmeister, Julia and Riedel, Uwe and K{\"o}hler, Markus}, title = {Numerical prediction of research octane numbers via a quasi-dimensional two-zone cylinder model}, series = {Applications in Energy and Combustion Science}, volume = {11}, journal = {Applications in Energy and Combustion Science}, publisher = {Elsevier BV}, issn = {2666-352X}, doi = {10.1016/j.jaecs.2022.100079}, pages = {11}, language = {en} } @misc{RichterKukkadapuWestbrooketal., author = {Richter, Sandra and Kukkadapu, Goutham and Westbrook, Charles K. and Braun-Unkhoff, Marina and Naumann, Clemens and K{\"o}hler, Markus and Riedel, Uwe}, title = {A combined experimental and modeling study of combustion properties of an isoparaffinic alcohol-to-jet fuel}, series = {Combustion and Flame}, volume = {240}, journal = {Combustion and Flame}, publisher = {Elsevier BV}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2022.111994}, pages = {15}, language = {en} } @misc{NgũgĩRichterBraunUnkhoffetal., author = {Ngũgĩ, John Mbũrũ and Richter, Sandra and Braun-Unkhoff, Marina and Naumann, Clemens and Riedel, Uwe}, title = {A study on fundamental combustion properties of oxymethylene ether-1, the primary reference fuel 90, and their blend: experiments and modeling}, series = {Combustion and Flame}, volume = {243}, journal = {Combustion and Flame}, publisher = {Elsevier BV}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2022.111996}, pages = {14}, language = {en} } @misc{RamirezHernandezKathrotiaMethlingetal., author = {Ramirez Hernandez, Astrid and Kathrotia, Trupti and Methling, Torsten and Braun-Unkhoff, Marina and Riedel, Uwe}, title = {An upgraded chemical kinetic mechanism for ISO-Octane Oxidation: prediction of polyaromatics formation in Laminar Counterflow Diffusion Flames}, series = {Volume 2: Coal, Biomass, Hydrogen, and Alternative Fuels; Controls, Diagnostics, and Instrumentation; Steam Turbine}, journal = {Volume 2: Coal, Biomass, Hydrogen, and Alternative Fuels; Controls, Diagnostics, and Instrumentation; Steam Turbine}, publisher = {American Society of Mechanical Engineers}, isbn = {978-0-7918-8598-7}, doi = {10.1115/GT2022-83053}, abstract = {Iso-octane is widely recognized as a prominent candidate to represent the oxidation of iso-alkanes within jet fuel and gasoline surrogates. This work evaluated a chemical kinetic mechanism for iso-octane focusing on the model's capability to predict the formation of polycyclic aromatic hydrocarbons (PAHs). As the model is intended to be further coupled with soot models, the chemical kinetic mechanism must supply good predictability of the formation and consumption of PAHs considered as major soot precursors. A first validation of the iso-octane sub-model as incorporated within ESTiMatE-Mech, using experimental data from literature, reveals the need to improve the sub-model. Considerable deviations were observed in the prediction of the PAHs, although concentration profiles of major species and fundamental combustion properties such as ignition delay time and laminar flame speed were accurately predicted. Through rate of production and sensitivity analyses of the mechanism, nine reactions were identified to have a strong influence in the (over)prediction of the PAHs. These reactions have been modified based on information gathered from literature resulting in an updated version of the mechanism called ESTiMatE-Mech_mod. Simulation results with this modified mechanism showed that this updated mechanism is now capable of predicting well the targeted PAHs, while retaining the good initial prediction of the major species concentration profiles as well as of laminar flame speeds and ignition delay times.}, language = {en} } @misc{NgũgĩRichterBraunUnkhoffetal., author = {Ngũgĩ, John Mbũrũ and Richter, Sandra and Braun-Unkhoff, Marina and Naumann, Clemens and Riedel, Uwe}, title = {A study on fundamental combustion properties of trimethyl orthoformate: experiments and modeling}, series = {Volume 2: Coal, Biomass, Hydrogen, and Alternative Fuels; Controls, Diagnostics, and Instrumentation; Steam Turbine}, journal = {Volume 2: Coal, Biomass, Hydrogen, and Alternative Fuels; Controls, Diagnostics, and Instrumentation; Steam Turbine}, publisher = {American Society of Mechanical Engineers}, isbn = {978-0-7918-8598-7}, doi = {10.1115/GT2022-83029}, abstract = {Trimethyl orthoformate (TMOF: HC(OCH3)3) has recently been examined as a viable biofuel. TMOF is a branched isomer of oxymethylene ether-2 (OME2) that, due to its high oxygen content and lack of direct carbon-carbon bonds, considerably reduces the formation of soot particles. To meet the challenges of a more flexible and sustainable power generation, a detailed understanding of its combustion properties is essential for its safe and efficient utilization, neat or in blends. In this work, two fundamental combustion properties of TMOF were studied: (i) Auto-ignition of TMOF / synthetic air mixtures (φ = 1.0; diluted 1:5 with N2) using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) Laminar burning velocities of TMOF / air mixtures using the cone angle method at ambient and elevated pressures of 3 and 6 bar. Furthermore, the impact of TMOF addition to a gasoline surrogate (PRF90) on ignition delay times was studied using the shock tube method at φ = 1.0, 1:5 dilution with N2, T = 900-2}, language = {en} } @misc{FradetAliRiedel, author = {Fradet, Quentin and Ali, Mohammed Liaket and Riedel, Uwe}, title = {Development of a porous solid model for the direct reduction of iron ore pellets}, series = {steel research international}, volume = {93}, journal = {steel research international}, number = {12}, issn = {1869-344X}, doi = {10.1002/srin.202200042}, pages = {10}, language = {en} } @misc{FradetKuhnDeutschmannetal., author = {Fradet, Quentin and Kuhn, Carola and Deutschmann, Olaf and Riedel, Uwe}, title = {Towards carbon-free energy carriers: kinetics of the thermochemical reduction/oxidation of iron oxide/iron}, series = {18th International Conference on Numerical Combustion}, journal = {18th International Conference on Numerical Combustion}, abstract = {ron and its oxides are at the center of an innovative carbon-free chemical energy cycle within the Clean Circles research association. Energy can be stored within iron particles through the thermochemical reduction of iron oxide using green hydrogen; the stored energy is then released through the dust-firing of iron. Accurate kinetics models of both thermochemical processes are of prime importance for the design and operation of industrial systems. While the high-temperature oxidation of iron is a novel topic of research, many kinetic studies were already conducted on reducing iron oxide or iron ore. However, the discrepancies between studies are manifest, that it is in terms of reaction models, kinetic parameters, or even in terms of species involved. One of the issues is the simplicity of the mathematical models employed, based on linearization techniques of a limited number of thermogravimetric analysis (TGA) curves. The present work will tackle the kinetics of the thermochemical reduction/oxidation of iron oxide/iron utilizing the leastsquare method, allowing for a direct comparison between experiments and modeling. The experiments supporting the modeling will originate both from the literature and from our own measurements and will be of various types: isothermal TGA, TGA with linear heating rates, temperature-programmed reduction and X-ray diffractions. The influence of parameters, such as the particle size distribution or porosity, on the kinetics will be discussed.}, language = {en} } @misc{AliFradetRiedel, author = {Ali, Mohammed Liaket and Fradet, Quentin and Riedel, Uwe}, title = {Kinetic mechanism development for the direct reduction of single hematite pellets in H2/CO atmospheres}, series = {steel research international}, volume = {93}, journal = {steel research international}, number = {12}, publisher = {Wiley}, issn = {1611-3683}, doi = {10.1002/srin.202200043}, pages = {12}, abstract = {Increasing interest in the direct reduction process of iron ore has revived investigations on gaseous and heterogeneous iron oxides' kinetics. Despite extensive studies on the reduction of iron oxides with pure hydrogen or syngas, the development of a generic reduction mechanism for iron oxides is still lacking. The conventional shrinking core model hardly distinguishes between transport and reaction processes, leading to biases or even errors in the kinetic models. In the present study, a porous solid model, which solves mass balances of the individual gas-phase species and solid ones assuming spherical symmetry, is used for developing a heterogeneous kinetic mechanism accounting for different iron oxidation stages (Fe2O3, Fe3O4, FeO). It also accounts for carbon accumulation and cementite formation to model the carburization phenomena when using carbon-containing reducing agents like syngas. The proposed generic mechanism successfully reproduces 49 experimental data sets from the literature for single iron}, language = {en} }