TY - GEN A1 - Rakhi, Rakhi A1 - Schmidt, Heiko T1 - Using a Stochastic One-Dimensional Turbulence model to study Incomporessible Spatially Developing Turbulent Boundary Layers T2 - Proc. of the 11th International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, July 30 to August 2, 2019 Y1 - 2019 UR - http://www.tsfp-conference.org/proceedings/2019/273.pdf ER - TY - GEN A1 - Rakhi, Rakhi A1 - Shrestha, Krishna Prasad A1 - Günther, Vivien A1 - Mauß, Fabian T1 - Thermodynamic analysis to develop a detailed surface reaction mechanism T2 - Fuel Science - From Production to Propulsion, Aachen, Germany, May 2022 N2 - The reduction of greenhouse gasses such as CO2 and CH4 is becoming necessary due to global environmental problems. The reforming of light hydrocarbons is a particularly efficient process for producing synthesis gas, H2 and CO, from greenhouse gasses [1]. The steam reforming of methane is the most important method to produce syngas in industry by using a nickel catalyst. Nickel-based catalysts are the conventional catalysts in industrial applications due to their fast turnover rates, good availability, and low costs, however, limited by their tendency towards coke formation. In this study, a detailed surface reaction mechanism is developed for steam reform-ing of methane over nickel and results are compared with the reference data. Y1 - 2022 UR - https://www.researchgate.net/publication/361279412_Thermodynamic_analysis_to_develop_a_detailed_surface_reaction_mechanism ER - TY - GEN A1 - Rakhi, Rakhi A1 - Giri, Binod Raj A1 - Günther, Vivien A1 - Mauss, Fabian T1 - Investigation dry reforming of methane over nickel using a one‐dimensional model T2 - PAMM N2 - In the field of catalysis, dry reforming, that is, methane reforming with CO2, is in the focus due to growing environmental concerns about oil depletion and global warming with a desire to produce synthesis gas. However, this process can lead to the formation of carbon, which can cause catalyst deactivation, especially at industrial conditions. Nevertheless, the key to develop a more coke-resistant catalyst is a better comprehension of the reforming process at a molecular level. Regardless of all the investigations available in literature, the detailed path for the conversion of methane to syngas and carbon remains a controversial issue. Another problem in setting up a reaction mechanism is the difficulty to define the thermodynamic data for intermediate surface species and this leads to the development of thermodynamic consistent surface reaction mechanisms in literature where the thermodynamic data are not used to calculate the rate coefficients of the reverse reactions. Rather the Arrhenius parameters for the forward as well as backward reactions are explicitly given in the reaction mechanism to establish thermodynamic equilibrium. In this investigation, a kinetically consistent detailed surface reaction mechanism is developed which consists of 26 reversible reactions with the help of a one-dimensional model, LOGEcat. Our previous work constructs the basis of the present investigation. Further, a detailed sensitivity analysis of reversible reactions and reaction pathways is performed to understand the mechanism better. The mechanism is validated for dry reforming of methane over nickel catalyst, however, it can also be used for other processes, such as, steam reforming and partial oxidation. The mechanism is tested by comparing the simulation results with the literature experiments and simulations in a wide range of temperature. The new developed kinetically consistent surface reaction mechanism is able to accurately express the dry reforming of methane over the nickel catalyst for complete range of temperature and also provide a useful insight into the key rate determining steps. Y1 - 2023 UR - https://onlinelibrary.wiley.com/doi/pdf/10.1002/pamm.202300266 U6 - https://doi.org/10.1002/pamm.202300266 VL - 23 IS - 4 ER - TY - GEN A1 - Rakhi, Rakhi A1 - Giri, Binod Raj A1 - Günther, Vivien A1 - Mauss, Fabian T1 - Insight into the thermodynamic model for reforming of methane over nickel catalyst T2 - Proceedings of the 64th International Conference of Scandinavian Simulation Society, SIMS 2023 Västerås, Sweden, September 25-28, 2023 N2 - The reforming of light hydrocarbons to produce synthesis gas, H2 and CO, is an important intermediate for manufacturing valuable basic chemicals and synthesis fuels. In order to understand these reforming processes better, elementary step reaction mechanisms are developed. In the available literature, the surface reaction mechanisms are usually achieved with the help of reaction kinetic parameters without using the thermochemistry of the species referred to kinetic models due to the unavailability of the thermochemistry of the intermediate species involved in the multi-step reaction mechanism. In this work, investigations are made to obtain the thermochemistry of the intermediate species to establish thermodynamic equilibrium in order to develop a thermodynamic model for steam reforming of methane over nickel. The thermochemistry of the surface bound species is taken from different sources available in the literature and after that a detailed sensitivity analysis is performed to match the results with experiments. The simulation set up is adapted from the literature experiments given in [1]. The results produced with the one-dimensional tool using the thermodynamic model developed in the present investigation consisting of 21 reversible reactions are compared with the kinetic scheme with 42 irreversible reactions from reference simulation along with their experimental results. Both the models show some major differences in the reaction pathways which provides a useful insight into the key rate determining steps and needs further investigations. Y1 - 2023 UR - https://ecp.ep.liu.se/index.php/sims/article/view/766 U6 - https://doi.org/10.3384/ecp200025 SP - 192 EP - 197 ER - TY - GEN A1 - Mauss, Fabian A1 - Rakhi, Rakhi T1 - Numerical study of catalytic methanation reactions using a kinetic model T2 - SAE Technical Paper N2 - Even if huge efforts are made to push alternative mobility concepts, such as, electric cars (BEV) and fuel cell powered cars, the importance and use of liquid fuels is anticipated to stay high during the 2030s. The biomethane and synthetic natural gas (SNG) might play a major role in this context as they are raw material for chemical industry, easy to be stored via existing infrastructure, easy to distribute via existing infrastructure, and versatile energy carrier for power generation and mobile applications. Hence, biomethane and synthetic natural gas might play a major role as they are suitable for power generation as well as for mobile applications and can replace natural gas without any infrastructure changes. In this paper, we aim to understand the direct production of synthetic natural gas from CO2 and H2 in a Sabatier process based on a thermodynamic analysis as well as a multi-step kinetic approach. For this purpose, we thoroughly discuss CO2 methanation to control emission in order to maximize the methane formation and minimize the CO formation and to understand the complex methanation process. We have considered an equilibrium and kinetic modelling study on the NiO-SiO2 catalyst for methanation focusing on CO2 derived SNG. In this work, a comprehensive thermodynamic analysis of CO2 hydrogenation is preformed to define the optimum process parameters followed by the kinetic simulations. Further, the simulations can be performed at various conditions, for example, catalyst mass, mass flow, pressure, temperature etc. to optimize the methanation process. Y1 - 2024 U6 - https://doi.org/10.4271/2024-24-0022 SN - 0148-7191 IS - 2024-24-0022 ER - TY - GEN A1 - Verma, Rakhi A1 - Mauss, Fabian T1 - Equilibrium analysis for methanation focusing on CO₂ derived substitute natural gas T2 - Proceedings of the Second SIMS EUROSIM Conference on Modelling and Simulation, SIMS EUROSIM 2024 N2 - In this study the methanation of synthesis gas (syngas) is investigated with a focus on achieving maximum methane and minimum CO by full methanation of CO2. For this study, we have considered a comprehensive thermodynamics analysis of CO2 hydrogenation. This will help us to understand the thermodynamic behaviour of the reactions involved in the methanation process. We have discussed the behavior of the species, CO2, H2, CH4, and H2O at the equilibrium with temperature, pressure, and fuel ratio variation in order to get the desired output. The preliminary study will focus on selecting the optimum conditions (temperature, pressure, and H2/CO2 ratio) for performing the experiments and for catalyst development. Y1 - 2025 SN - 978-91-8075-984-7 U6 - https://doi.org/10.3384/ecp212.022 SN - 1650-3686 VL - 211 SP - 162 EP - 167 PB - Linköping University Electronic Press CY - Linköping ER -