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“Carbon bed post-plasma to enhance the CO2 conversion and remove O2 from the product stream”. Girard-Sahun F, Biondo O, Trenchev G, van Rooij G, Bogaerts A, Chemical Engineering Journal 442, 136268 (2022). http://doi.org/10.1016/j.cej.2022.136268
Abstract: CO2 conversion by plasma technology is gaining increasing interest. We present a carbon (charcoal) bed placed after a Gliding Arc Plasmatron (GAP) reactor, to enhance the CO2 conversion, promote O/O2 removal and in crease the CO fraction in the exhaust mixture. By means of an innovative (silo) system, the carbon is constantly supplied, to avoid carbon depletion upon reaction with O/O2. Using this carbon bed, the CO2 conversion is enhanced by almost a factor of two (from 7.6 to 12.6%), while the CO concentration even increases by a factor of three (from 7.2 to 21.9%), and O2 is completely removed from the exhaust mixture. Moreover, the energy ef ficiency of the conversion process drastically increases from 27.9 to 45.4%, and the energy cost significantly drops from 41.9 to 25.4 kJ.L− 1. We also present the temperature as a function of distance from the reactor outlet, as well as the CO2, CO and O2 concentrations and the temperature in the carbon bed as a function of time, which is important for understanding the underlying mechanisms. Indeed, these time-resolved measurements reveal that the initial enhancements in CO2 conversion and in CO concentration are not maintained in our current setup. Therefore, we present a model to study the gasification of carbon with different feed gases (i.e., O2, CO and CO2 separately), from which we can conclude that the oxygen coverage at the surface plays a key role in determining the product composition and the rate of carbon consumption. Indeed, our model insights indicate that the drop in CO2 conversion and in CO concentration after a few minutes is attributed to deactivation of the carbon bed, due to rapid formation of oxygen complexes at the surface.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 15.1
DOI: 10.1016/j.cej.2022.136268
Additional Links: UA library record; WoS full record; WoS citing articles
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“Carbon bed post-plasma to enhance the CO2 conversion and remove O2 from the product stream”. Girard-Sahun F, Biondo O, Trenchev G, van Rooij G, Bogaerts A, Chemical Engineering Journal 442, 136268 (2022). http://doi.org/10.1016/j.cej.2022.136268
Abstract: CO2 conversion by plasma technology is gaining increasing interest. We present a carbon (charcoal) bed placed after a Gliding Arc Plasmatron (GAP) reactor, to enhance the CO2 conversion, promote O/O2 removal and in crease the CO fraction in the exhaust mixture. By means of an innovative (silo) system, the carbon is constantly supplied, to avoid carbon depletion upon reaction with O/O2. Using this carbon bed, the CO2 conversion is enhanced by almost a factor of two (from 7.6 to 12.6%), while the CO concentration even increases by a factor of three (from 7.2 to 21.9%), and O2 is completely removed from the exhaust mixture. Moreover, the energy ef ficiency of the conversion process drastically increases from 27.9 to 45.4%, and the energy cost significantly drops from 41.9 to 25.4 kJ.L− 1. We also present the temperature as a function of distance from the reactor outlet, as well as the CO2, CO and O2 concentrations and the temperature in the carbon bed as a function of time, which is important for understanding the underlying mechanisms. Indeed, these time-resolved measurements reveal that the initial enhancements in CO2 conversion and in CO concentration are not maintained in our current setup. Therefore, we present a model to study the gasification of carbon with different feed gases (i.e., O2, CO and CO2 separately), from which we can conclude that the oxygen coverage at the surface plays a key role in determining the product composition and the rate of carbon consumption. Indeed, our model insights indicate that the drop in CO2 conversion and in CO concentration after a few minutes is attributed to deactivation of the carbon bed, due to rapid formation of oxygen complexes at the surface.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 15.1
DOI: 10.1016/j.cej.2022.136268
Additional Links: UA library record; WoS full record; WoS citing articles
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“Effusion nozzle for energy-efficient NOx production in a rotating gliding arc plasma reactor”. Van Alphen S, Ahmadi Eshtehardi H, O'Modhrain C, Bogaerts J, Van Poyer H, Creel J, Delplancke M-P, Snyders R, Bogaerts A, Chemical Engineering Journal 443, 136529 (2022). http://doi.org/10.1016/j.cej.2022.136529
Abstract: Plasma-based NOx production is of interest for sustainable N2 fixation, but more research is needed to improve its performance. One of the current limitations is recombination of NO back into N2 and O2 molecules immediately after the plasma reactor. Therefore, we developed a novel so-called “effusion nozzle”, to improve the performance of a rotating gliding arc plasma reactor for NOx production, but the same principle can also be applied to other plasma types. Experiments in a wide range of applied power, gas flow rates and N2/O2 ratios demonstrate an enhancement in NOx concentration by about 8%, and a reduction in energy cost by 22.5%. In absolute terms, we obtain NOx concentrations up to 5.9%, at an energy cost down to 2.1 MJ/mol, which are the best values reported to date in literature. In addition, we developed four complementary models to describe the gas flow, plasma temperature and plasma chemistry, aiming to reveal why the effusion nozzle yields better performance. Our simulations reveal that the effusion nozzle acts as very efficient heat sink, causing a fast drop in gas temperature when the gas molecules leave the plasma, hence limiting the recombination of NO back into N2 and O2. This yields an overall higher NOx concentration than without the effusion nozzle. This immediate quenching right at the end of the plasma makes our effusion nozzle superior to more conventional cooling options, like water cooling In addition, this higher NOx concentration can be obtained at a slightly lower power, because the effusion nozzle allows for the ignition and sustainment of the plasma at somewhat lower power. Hence, this also explains the lower energy cost. Overall, our experimental results and detailed modeling analysis will be useful to improve plasma-based NOx production in other plasma reactors as well.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 15.1
DOI: 10.1016/j.cej.2022.136529
Additional Links: UA library record; WoS full record; WoS citing articles
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“Catalyst-free single-step plasma reforming of CH4 and CO2 to higher value oxygenates under ambient conditions”. Wang Y, Chen Y, Harding J, He H, Bogaerts A, Tu X, Chemical Engineering Journal 450, 137860 (2022). http://doi.org/10.1016/j.cej.2022.137860
Abstract: Direct conversion of CH4 and CO2 to liquid fuels and chemicals under mild conditions is appealing for biogas conversion and utilization but challenging due to the inert nature of both gases. Herein, we report a promising plasma process for the catalyst-free single-step conversion of CH4 and CO2 into higher value oxygenates (i.e., methanol, acetic acid, ethanol, and acetone) at ambient pressure and room temperature using a water-cooled dielectric barrier discharge (DBD) reactor, with methanol being the main liquid product. The distribution of liquid products could be tailored by tuning the discharge power, reaction temperature and residence time. Lower discharge powers (10–15 W) and reaction temperatures (5–20 ◦ C) were favourable for the production of liquid products, achieving the highest methanol selectivity of 43% at 5 ◦ C and 15 W. A higher discharge power and reaction temperature, on the other hand, produced more gaseous products, particularly H2 (up to 26% selectivity) and CO (up to 33% selectivity). In addition, varying these process parameters (discharge power, reaction temperature and residence time) resulted in a simultaneous change in key discharge properties, such as mean electron energy (Ee), electron density (ne) and specific energy input (SEI), all of which are essential determiners of plasma chemical reactions. According to the results of artificial neural network (ANN) models, the relative importance of these process parameters and key discharge indicators on reaction performance follows the order: discharge power > reaction temperature > residence time, and SEI > ne > Ee, respectively. This work provides new insights into the contributions and tuning mechanism of multiple parameters for optimizing the reaction performance (e.g., liquid production) in the plasma gas conversion process.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 15.1
DOI: 10.1016/j.cej.2022.137860
Additional Links: UA library record; WoS full record; WoS citing articles
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“Plasma activation of methane for hydrogen production in a N2 rotating gliding arc warm plasma : a chemical kinetics study”. Zhang H, Wang W, Li X, Han L, Yan M, Zhong Y, Tu X, Chemical engineering journal 345, 67 (2018). http://doi.org/10.1016/J.CEJ.2018.03.123
Abstract: In this work, a chemical kinetics study on methane activation for hydrogen production in a warm plasma, i.e., N-2 rotating gliding arc (RGA), was performed for the first time to get new insights into the underlying reaction mechanisms and pathways. A zero-dimensional chemical kinetics model was developed, which showed a good agreement with the experimental results in terms of the conversion of CH4 and product selectivities, allowing us to get a better understanding of the relative significance of various important species and their related reactions to the formation and loss of CH4, H-2, and C2H2 etc. An overall reaction scheme was obtained to provide a realistic picture of the plasma chemistry. The results reveal that the electrons and excited nitrogen species (mainly N-2(A)) play a dominant role in the initial dissociation of CH4. However, the H atom induced reaction CH4+ H -> CH3+ H-2, which has an enhanced reaction rate due to the high gas temperature (over 1200 K), is the major contributor to both the conversion of CH4 and H-2 production, with its relative contributions of > 90% and > 85%, respectively, when only considering the forward reactions. The coexistence and interaction of thermochemical and plasma chemical processes in the rotating gliding arc warm plasma significantly enhance the process performance. The formation of C-2 hydrocarbons follows a nearly one-way path of C2H6 -> C2H4 -> C2H2, explaining why the selectivities of C-2 products decreased in the order of C2H2 > C2H4 > C2H6.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.216
Times cited: 25
DOI: 10.1016/J.CEJ.2018.03.123
Additional Links: UA library record; WoS full record; WoS citing articles
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