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![Ammonia synthesis based on different hydrogen sources. Reprinted with permission from [13]. Copyright 2008, Iowa State University.](publication/284816352/figure/fig2/AS:393250419560456@1470769614648/Ammonia-synthesis-based-on-different-hydrogen-sources-Reprinted-with-permission-from.png)
Ammonia synthesis based on different hydrogen sources. Reprinted with permission from [13]. Copyright 2008, Iowa State University.
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In a time of increasing concerns about the immense energy consumption and poor environmental performance of contemporary processes in the chemical industry, there is great need to develop novel sustainable technologies that enhance energy efficiency. There is abundant chemical literature on process innovations (laboratory-scale) around the plasma r...
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... synthesis via alternative energy sources has been conceptualized for both electricity and hydrogen production based on different technologies as shown in Figure 2 [13]. Although methane steam reforming is a more economically and energy efficient production technique of hydrogen, compared to hydrolysis or air separation, the latter can be proved feasible, if combined with renewable sources what have higher or comparable electricity generation efficiency as the conventional one. ...
Citations
... The utilization of high-frequency nanosecond pulsing for plasma production can optimize both the yield and energy efficiency of the plasma-assisted nitrogen fixation process. The three main components for the energy performance of the plasma-assisted nitrogen fixation process are, according to Anastasopoulou et al. [128], the integration of renewable energy, the power supply system and reactor, and the process design at the industrial scale. Few studies have been conducted on topics such as product separation, absorption, or process design as a whole; much of the research conducted to date has been on the reactor itself. ...
... A decentralized method with plasma assistance can better suit the needs of low capital costs, scale-down economics, and localized usage of abundant renewable resources rather than large-scale industrial fertilizer production. Parallel to technological development, an assessment of the technoeconomic viability and sustainability of the plasma-assisted nitrogen fixation process must be carried out [128,131,132]. This will provide suggestions for further improving process efficiency toward real applications. ...
Nitrogen fixation, the conversion of atmospheric nitrogen into biologically useful compounds, is crucial for sustaining biological processes and industrial productivity. Recent advances have explored plasma-assisted processes as an innovative approach to facilitate nitrogen fixation. This review offers a comprehensive summary of the development, current state of the art, and potential future applications of plasma-based nitrogen fixation. The analysis encompasses fundamental principles, mechanisms, advantages, challenges, and prospects associated with plasma-induced nitrogen fixation.
... In contrast, NTP reactors can be started up and shut down quickly due to low thermal inertia, which reduces the idle time and energy costs (Snoeckx and Bogaerts, 2017). However, the current energy efficiency of an NTP-based process is the main constriction for its industrial acceptance (Anastasopoulou et al., 2014). Experiments in dielectric discharge barrier reactors have obtained low energy yields up to 35.7 g NH 3 /kWh (Kim et al., 2017). ...
Haber-Bosch (HB) process, the main method for ammonia (NH3) production, contributes to near 2% of the global carbon emissions because the hydrogen input is obtained from fossil sources. NH3 production is concentrated in a few countries, adding emissions due to global distribution. Distributed plants next to farmers and fed by renewable energy can reduce these impacts, as well as NH3 storage, shortage risks, and price volatility. Distributed plants cannot reach low NH3 production costs as centralised plants, but they can be promoted by the environmental benefits of its products lifecycles. Therefore, life cycle assessments of NH3 production pathways and specific modelling for NH3 transport in Australia were performed, from cradle-to-site, to identify the influence of storage, transport, and energy sources in their environmental profiles. The carbon footprint of centralised production was up to 2.96 kg.CO2-eq/kg.NH3, from which 29.3% corresponded to transport. Local production demonstrated substantial avoided transport impacts and that CO2-eq can reach reductions over 100% when including co-product credits such as oxygen and carbon black. Local plants using electrolysers to supply mini-HB loops obtained rates of 0.12, −0.52, and −1.57 kg.CO2-eq/kg.NH3 using electricity from solar, wind, and biogas (other than manure) sources, respectively. The alternative using high temperature plasma reactor instead of electrolyser obtained its best rate of −0.65 kg.CO2-eq/kg using biogas different from manure. At farm electrolyser-based plants using novel non-thermal plasma reactors, considering potential energy yields and simplified NH3 separation technology, could reach a rate of −1.07 kg.CO2-eq/kg.NH3, using solar energy. Among the assessed pathways, the most notable impact was on freshwater eutrophication in the electrolyser-based plants generating reductions up to 290%, due to oxygen credits. Despite these results, the use of solar energy raises concerns on land use and terrestrial ecotoxicity due to the area needed for solar farms and the manufacture of their components.
... Non-thermal plasma based processes have been one of the most prominent alternatives studied over the past few years for artificial NF. 6,[19][20][21][22][23][24] Their unique non-equilibrium properties give them the potential to be theoretically less energy intensive than the HB process. 9 This is mainly related to the capability of plasmas to transfer energy from hot electrons specifically to other gas components through inelastic collisional interactions. ...
Nitrogen disproportionation i.e. its simultaneous conversion to compounds of higher (NOx) and lower (NH3) oxidation states in a N2 DC plasma-driven electrolysis process with a plasma cathode is investigated. This...
... Under this running condition, the energy efficiency was 554 mg/L/kWh (or 1.108 g-NO x /kWh for 2 L liquid treated) and the NO x concentration in the liquid reached 110.8 mg/L. This performance of the CFLPPD was much better than that of the existing liquid plasma reactors reported in past research, for which very low concentration of fixed nitrogen species in treated water (below 1 mg/L) was obtained with low energy efficiency [34]. ...
... As a matter of fact, the process is nowadays at the base of the sustenance of approximatively 40% of the planet population and it is still used as its dissociation yields of 15-20% [25,26], making it the most efficient way to dissociate nitrogen molecule. Despite these impressive achievements, to which it can be added that this process is regarded by many as one of the greatest inventions of the 20 th century, an alternative way of fixation is still the object of a number of studies, as the optimal experimental conditions of Haber-Bosch process require the presence of high temperatures and pressures (850 K and 2´10 7 Pa) and therefore of high energy expenses (0.48 MJ/mol NH3), consuming the 2% of world's total energy [23,25,[27][28][29][30]]. ...
... Besides the drastic experimental conditions, the already mentioned high energy costs of the latter are strictly connected with the use of fossil fuels and the consequences of their exploitation. Despite non-renewable energy sources are the only able to provide the necessary high energy densities to sustain the whole process, a side production of 3´10 11 kg of CO2 per year [27][28][29][30] is not an affordable cost in the light of a world whose population keeps growing at great pace. This is why sustainable technologies are becoming more attractive to do the job, with the most avant-garde and promising ones relying on metallo-complexes to perform homogeneous catalysis at ambient pressure [28] and the plasmas discharges. ...
The primary objective of this thesis is to understand the mechanisms of dissociation of nitrogen molecule in microwave plasmas under low pressure conditions (1 – 150 Pa), in order to develop an optimized N-atom sources. The first part of the thesis concerns the development of the methodology for measuring N-atom densities using Two-Photon Absorption Laser Induced Fluorescence in ns regime (ns-TALIF) for highly emissive plasmas, as encountered in this thesis. This methodology has been used to characterize two different microwave sources, namely a magnetized source working between 1 Pa to 20 Pa, and a non-magnetized source working between 20 Pa to 150 Pa, under stationary and pulsed operating modes. The dissociation under stationary operating conditions is mainly driven by electron-impact processes and the vibrational ladder mechanisms. However, the dissociation is strongly limited by the vibrational translational relaxation process with N-atoms which suppresses the non-equilibrium nature of the vibrational distribution function and makes it difficult to enhance the dissociation of nitrogen. The later part of the thesis is dedicated to study the enhancement of dissociation using pulsed plasmas. Firstly, unusual sharp changes called Surge and Crash in N-atom densities caused by the conversion between N-atom and its metastables N(2Do) and N(2Po) during the change in the phase of the MW power were demonstrated. Further, it was shown that pulsed operation of MW plasmas can effectively enhance the dissociation of N-atoms by fine-tuning the different process parameters such as duty cycle, pulsation frequency etc
... NTP has significantly lower theoretical limit of energy cost (EC), which is 2.5 times lower than the H-B process limit, for N 2 dissociation [11]. The reason for this is the presence of highly energetic electrons in NTPs producing highly reactive species and enabling thermodynamically unfavorable reactions [12]. ...
A pulsed microwave surfaguide discharge operating at 2.45 GHz was used for the conversion of molecular nitrogen into valuable compounds in several gas mixtures: N2:O2, N2:O2:CO2 and N2:CO2. The ro-vibrational absorption bands of the molecular species were monitored by a Fourier transform infrared apparatus in the post-discharge region in order to evaluate the relative number density of species, specifically NO production. The effects of specific energy input, pulse frequency, gas flow fraction, gas admixture and gas flow rate were studied for better understanding and optimization of the NO production yield and the corresponding energy cost (EC). By both the experiment and modelling, a highest NO yield is obtained at N2:O2 (1:1) gas ratio in N2:O2 mixture. The NO yield reveals a small growth followed by saturation when pulse repetition frequency increases. The energy efficiency start decreasing after the energy input reaches about 5 eV/molec, whereas the NO yield rises steadily at the same time. The lowest EC of about 8 MJ mol-1 corresponding to the yield and the energy efficiency of about 7% and 1% are found, respectively, in an optimum discharge condition in our case.
... 234 project. [234][235][236][237][238][239][240] These studies revealed that plasma-based fertiliser production of nitric acid, under the best assumptions (recycling, energy recovery), could have a better environmental profile than the conventional process. 234 In terms of energy resources, the plasmaassisted fertilizer production is efficient in incorporating (local) renewable power supplies (solar, wind, etc.). ...
... 241 Apart from the aforementioned advantages, capital costs and energy costs are not yet in the range of a good industrial process. 238 For example, a plasma-assisted fertilizer production plant (10 t/d, with 6% NO yield) using the local solar and wind energy resources in Kenya would cost up to 155 and 312 million $, respectively. 235 Plasma-made nitric acid is calculated to be about 4 times more costly than conventionally made in terms of life-cycle costs. ...
To enhance crop efficiency and meet the growing global demands for food, a new agri-tech revolution has recently been triggering. Engineered nanomaterials have potential of lessening environmental impact and making...
... In terms of the plasma-assisted nitrogen fixation, there is only one comprehensive life cycle assessment study been conducted for an ex-ante process design of a small-scale plasma-assisted nitric acid production (Anastasopoulou, Butala, Lang, Hessel, & Wang, 2016). Although the incorporation of renewable energy sources into the plasma-assisted ammonia synthesis has been discussed in certain research studies (Anastasopoulou, Wang, Hessel, & Lang, 2014;Peng et al., 2016), a complete industrial process design that will enable a preliminary environmental assessment, and an economic appraisal at a later stage, of this novel process has not been yet developed. Based on these facts, the present research study aims at addressing this knowledge gap by proposing a small-scale industrial process design of the plasma-assisted ammonia and conducting a comparative life cycle assessment against the traditional production routes with the view to determining areas for potential improvement that will render an enhanced environmental performance of the plasma process. ...
The importance of ammonia in the fertilizer industry has been widely acknowledged over the past decades. In view of the upcoming increase of world population and, in turn, food demand, its production rate is likely to increase exponentially. However, considering the high dependence on natural resources and the intensive emission profile of the contemporary ammonia synthesis route, as well as the rigid environmental laws being enforced at a global level, the need to develop a sustainable alternative production route becomes quite imperative. A novel approach toward the synthesis of ammonia has been realized by means of non‐thermal plasma technology under ambient operating conditions. Because the given technology is still under development, carrying out a life cycle assessment (LCA) is highly recommended as a means of identifying areas of the chemical process that could be potentially improved for an enhanced environmental performance. For that purpose, in the given research study, a process design for a small‐scale plasma‐assisted ammonia plant is being proposed and evaluated environmentally for specific design scenarios against the conventional ammonia synthesis employing steam reforming and water electrolysis for hydrogen generation. On the basis of the LCA results, the most contributory factor to the majority of the examined life cycle impact categories for the plasma‐assisted process, considering an energy efficiency of 1.9 g NH3/kWh, is the impact of the power consumption of the plasma reactor with its share ranging from 15% to 73%. On a comparative basis, the plasma process powered by hydropower has demonstrated a better overall environmental profile over the two benchmark cases for the scenarios of a 5% and 15% NH3 yield and an energy recovery of 5% applicable to all examined plasma power consumption values.
... 2,3 As a result, the environmental impact of N 2 fixation processes can only be improved by considering new, innovative approaches, which are very different from the Haber−Bosch process. 6,7 Among several solutions, such as electrolysis, biological nitrogen fixation, and catalytic conversion under ambient pressure, the use of nonequilibrium plasmas seems very promising. 8 Nonequilibrium plasmas enable high energy electrons to forcefully interact with the stable NN bond, while the bulk gas can remain close to room temperature. ...
Plasma is gaining increasing interest for N2 fixation, being a flexible, electricity-driven alternative for the current conventional fossil fuel-based N2 fixation processes. As the vibrational-induced dissociation of N2 is found to be an energy-efficient pathway to acquire atomic N for the fixation processes, plasmas that are in vibrational non-equilibrium seem promising for this application. However an important challenge in using non-equilibrium plasmas lies in preventing vibrational-translational (VT) relaxation processes, in which vibrational energy crucial for N2 dissociation is lost to gas heating. We present here both experimental and modeling results for the vibrational and gas temperature in a µs pulsed microwave (MW) N2 plasma, showing how power pulsing can suppress this unfavorable VT relaxation and achieve a maximal vibrational non-equilibrium. Through matching our kinetic model to experimental data, we demonstrate that pulsed plasmas take advantage of the long time scale on which VT processes occur, yielding a very pronounced non-equilibrium over the whole N2 vibrational ladder. Additionally, the effect of pulse parameters like the pulse frequency and pulse width are investigated, demonstrating that the advantage of pulsing to inhibit VT relaxation diminishes for high pulse frequencies (around 7000 kHz) and long power pulses (above 400 µs). As all regimes studied here demonstrate a clear vibrational non-equilibrium while only requiring a limited power-on time, a pulsed plasma does seem very interesting for energy-efficient vibrational excitation.
... Plant-wide process modelling of plasma-assisted processes at large scale can be used as a tool to (1) identify challenges arising from the integration of plasma reactors with existing downstream processing systems and cost drivers that should be further optimized, and (2) estimate total energy requirements. Nonetheless, works in this field are rather limited and are not relevant to ethylene production [13][14][15][16]. ...
The electrification of the petrochemical industry, imposed by the urgent need for decarbonization and driven by the incessant growth of renewable electricity share, necessitates electricity-driven technologies for efficient conversion of fossil fuels to chemicals. Non-thermal plasma reactor systems that successfully perform in lab scale are investigated for this purpose. However, the feasibility of such electrified processes at industrial scale is still questionable. In this context, two process alternatives for ethylene production via plasma-assisted non-oxidative methane coupling have conceptually been designed based on previous work of our group namely, a direct plasma-assisted methane-to-ethylene process (one-step process) and a hybrid plasma-catalytic methane-to-ethylene process (two-step process). Both processes are simulated in the Aspen Plus V10 process simulator and also consider the technical limitations of a real industrial environment. The economically favorable operating window (range of operating conditions at which the target product purity is met at minimum utility cost) is defined via sensitivity analysis. Preliminary results reveal that the hybrid plasma-catalytic process requires 21% less electricity than the direct one, while the electric power consumed for the plasma-assisted reaction is the major cost driver in both processes, accounting for ~75% of the total electric power demand. Finally, plasma-assisted processes are not economically viable at present. However, future decrease in electricity prices due to renewable electricity production increase can radically affect process economics. Given that a break-even electricity price of 35 USD/MWh (without considering the capital cost) is calculated for the two-step plasma process and that current electricity prices for some energy intensive industries in certain countries can be as low as 50 USD/MWh, the plasma-assisted processes may become economically viable in the future.
