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![Detailed physical characteristics of ammonia [34,35].](publication/342175152/figure/tbl1/AS:905624686690306@1592929159687/Detailed-physical-characteristics-of-ammonia-34-35_Q320.jpg)
Ammonia is considered to be a potential medium for hydrogen storage, facilitating CO2-free energy systems in the future. Its high volumetric hydrogen density, low storage pressure and stability for long-term storage are among the beneficial characteristics of ammonia for hydrogen storage. Furthermore, ammonia is also considered safe due to its high...
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... ammonia production system from any primary source, such as natural gas, is considered complex, as it includes many combined processes. Figure 2 shows the schematic diagram of conventional ammonia production from natural gas. The system consists of different processes: steam reformation, the water-gas shift reaction, CO 2 removal, syngas purification, and ammonia synthesis and separation. ...
Context 2
... ammonia production system from any primary source, such as natural gas, is considered complex, as it includes many combined processes. Figure 2 shows the schematic diagram of conventional ammonia production from natural gas. The system consists of different processes: steam reformation, the water-gas shift reaction, CO2 removal, syngas purification, and ammonia synthesis and separation. ...
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Today, three phenomena are developing into critical global problems, requiring urgent attention from leaders all over the world. The first of these is the increase in carbon dioxide (CO 2 ) emissions due to the escalated use of coal, resulting in the gradual increase of the Earth’s average temperature. The second is the continually diminishing foss...
Citations
... [1][2][3][4] The transition to a H 2 -based energy sector would require innovative ways of producing, storing, and transporting the H 2 gas to where it is required. [5][6][7] In particular, the transportation of H 2 has proven to be challenging because it is expensive and unsafe to transport pressurised H 2 gas over long distances, and challenging to liquify the gas due to its very low boiling point (ca. À 253°C). ...
... Therefore, one of the proposed strategies is to store and/or transport hydrogen as a liquid of different chemical identity (e. g., ammonia and hydrocarbons). [5][6][7] Hydrocarbons are the long-standing primary sources of H 2 and several technologies (e. g., steam reforming and the watergas-shift (WGS) reaction) have been established to convert hydrocarbons to H 2 (and other carbon-based gases). [7] For example, liquid methanol is regarded as the simplest and most suitable form of storing and transporting hydrogen. ...
Polymer electrolyte membrane fuel cells (PEMFCs) are the core technology of the steadily growing hydrogen (H2) economy as they can convert chemical energy, in the form of H2, to electrical energy. If the H2 is derived from (green) hydrocarbons, via steam reforming and the water‐gas‐shift reaction, then it would contain small amounts of carbon monoxide (CO, 0.5–2 %), among other gases. CO poisons the platinum‐based anode catalyst in the PEMFC, and the current recommendation is to decrease its concentration to below 0.01 % (or 100 ppm) in the H2‐rich PEMFC feed. The preferential oxidation of CO (CO‐PrOx) is a promising strategy for decreasing the CO concentration, and base metal oxide catalysts have shown great potential in this regard. However, such catalysts tend to undergo physicochemical changes that cause undesirable catalytic activity and selectivity changes. This review discusses the different base metal oxide catalysts that have been evaluated in CO‐PrOx, while paying special attention to the various in situ and operando techniques that have been used to monitor the physicochemical changes of base metal oxides during operation. We conclude the review by highlighting the recent and possible future attempts of circumventing the undesired physicochemical changes of base metal oxides during CO‐PrOx.
... Ammonia (NH 3 ), whose previous main use has been as a fertilizer for agriculture, has recently attracted attention as a potential option for supplying hydrogen as an alternative low-CO 2 reductant. Ammonia is an attractive hydrogen carrier compared to liquid H 2 and LOHC (e.g., methylcyclohexane, 12H-N-ethylcarbazole, 18H-dibenzyltoluene) suitable for long-distance transport, as hydrogen constitutes 17.6 wt.% of ammonia [18][19][20]. Among all hydrogen carriers, ammonia is the easiest to be liquefied by pressurizing at -33 °C at 1 atm (10 bar at room temperature) compared with liquid H 2 , which must be liquefied at − 252.9 °C, at the same pressure, resulting in significant energy usage [16,19]. ...
... Ammonia is an attractive hydrogen carrier compared to liquid H 2 and LOHC (e.g., methylcyclohexane, 12H-N-ethylcarbazole, 18H-dibenzyltoluene) suitable for long-distance transport, as hydrogen constitutes 17.6 wt.% of ammonia [18][19][20]. Among all hydrogen carriers, ammonia is the easiest to be liquefied by pressurizing at -33 °C at 1 atm (10 bar at room temperature) compared with liquid H 2 , which must be liquefied at − 252.9 °C, at the same pressure, resulting in significant energy usage [16,19]. Liquid ammonia also has a 1.5 to 1.7 times higher volumetric hydrogen density than liquid H 2 , which is 120 kg-H 2 /m 3 in liquid ammonia compared to 70 kg-H 2 /m 3 in liquid H 2 [15]. ...
... Liquid ammonia also has a 1.5 to 1.7 times higher volumetric hydrogen density than liquid H 2 , which is 120 kg-H 2 /m 3 in liquid ammonia compared to 70 kg-H 2 /m 3 in liquid H 2 [15]. As well, the density of gaseous ammonia is lower than air (0.769 kg/m 3 compared to 1.225 kg/m 3 ) ensuring it dissipates rapidly in air at atmospheric pressure leading to lower risk of explosion in the case of leakages [19]. Moreover, at current production rates of hydrogen, ammonia may be considered as an excellent alternative hydrogen carrier because of its availability in larger quantities, reaching a worldwide production rate of up to 180 million tons NH 3 (see Fig. 1b) [21] making it the world's second most-produced chemical. ...
The steel industry is one of the main contributors to global greenhouse gas emissions, responsible for about 7 to 9% of the world’s total output. The steel sector is under pressure to move toward net-zero emissions by reducing its consumption of coke as the main method of reducing iron-rich feed materials to iron. Due to its well-developed synthesis process, high supply chain, straightforward handling technologies, and highly developed long-standing infrastructure, ammonia has the potential to become a replacement for coke as a future iron ore reductant. This work reviews previous research on ammonia direct reduction of iron oxides and the possible formation of iron nitrides. A thermodynamic assessment using FactSage 8.2 thermochemical software was carried out examining the behavior of ammonia gas as the reductant upon heating, detailed evaluations of the stable phases present under different reaction conditions and using different feed materials, and the formation and stability of iron nitride phases. The results suggest that the reduction of hematite with ammonia occurs in two steps below 570 °C and three steps above 570 °C. The ratio of Fe 2 O 3 /NH 3 was predicted to affect the reduction reactions by promoting a greater reduction degree and simultaneously lowering the initial temperature needed for reduction, while the excess gas concentration can suppress FeO formation. A predominance area diagram was developed showing the main areas of stable phases as a function of the partial pressure of NH 3 and temperature. The formation of iron nitrides during the process was predicted and these were not expected to cause issues for the formation of iron due to their instability under the conditions studied. This analysis can be used to inform further experimental studies regarding ammonia reduction of iron oxide.
Graphical Abstract
... As a carbon-free alternative fuel, ammonia is recognized as a potential fuel for achieving zero carbon emissions in transportation for the following reasons: ammonia is a good hydrogen carrier [2][3][4][5]; ammonia has the third highest volumetric energy density, surpassed only by gasoline and liquefied petroleum gas (LPG) [6,7]; ammonia is the most cost-effective fuel per gigajoule (GJ) when stored onboard [8]; the storage, transportation, and distribution of liquid ammonia are notably accessible, safe and mature [9][10][11][12]; ammonia can be used as an internal combustion engine fuel [13][14][15][16]. ...
Ammonia, known as a good hydrogen carrier, shows great potential for use as a zero-carbon fuel for vehicles. However, both the internal combustion engine (ICE) and the proton exchange membrane fuel cell (PEMFC), the currently available engines used by the vehicle, require hydrogen decomposed from ammonia. On-board hydrogen production is an energy-intensive process that significantly reduces system efficiency. Therefore, energy recovery from the system's residual heat is essential to promote system efficiency. ICEs and FCs require different amounts of hydrogen, and they produce residual heat of different quality and quantity, so the system efficiency is not only determined by the engine operating point, but also by the measures and ratios of residual heat recovery. To thoroughly understand the relationships between system energy efficiency and system configuration as well as system parameters, this paper takes three typical power systems with different configurations as our objects. Models of three systems are set up for system energy efficiency analysis, and carry out simulations under different conditions to conduct system output power and energy efficiency. By analyzing the simulation results, the factors that most significantly impact the system efficiency are identified, the guidelines for system design and parameter optimization are proposed.
... One of the most difficult challenges to the adoption of the hydrogen-based economy is hydrogen storage [6]. In-vehicle hydrogen storage systems must meet strict requirements for gravimetric and volumetric energy densities due to their constrained capacity and permitted weight [7,8]. ...
In this study, activated carbon (AC) obtained from waste hazelnut shell and halloysite nanotube (HNT) were used to prepare HNT-AC support material by hydrothermal method. CoNi/HNT-AC catalyst was synthesized by reducing Co and Ni on HNT-AC by chemical reduction method. CoNi/HNT-AC has been characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption–desorption, elemental mapping, and transmission electron microscopy (TEM) methods. The optimum reaction conditions for hydrogen generation through NaBH4 hydrolysis on CoNi/HNT-AC catalyst were determined using response surface methodology (RSM). The proposed quadratic model for NaBH4 hydrolysis on CoNi/HNT-AC was found to be statistically significant with a correlation coefficient of 0.96. Under the optimum reaction conditions of 40.76 mg catalyst, 0.18 M NaBH4, and 8.64 wt% NaOH, the hydrogen generation rate (HGR) and activation energy (Ea) were obtained as 1114.16 mL/gcat. min. and 24.15 kj/mol, respectively.
Graphical Abstract
... Systems for storing hydrogen safely and effectively until it is required for energy production or other uses are made up of a number of essential components [110][111][112]. These elements ( Table 2) are essential [113][114][115][116][117][118][119][120][121][122] to guaranteeing the hydrogen storage system's dependability and integrity. ...
As a case study on sustainable energy use in educational institutions, this study examines the design and integration of a solar–hydrogen storage system within the energy management framework of Kangwon National University’s Samcheok Campus. This paper provides an extensive analysis of the architecture and integrated design of such a system, which is necessary given the increasing focus on renewable energy sources and the requirement for effective energy management. This study starts with a survey of the literature on hydrogen storage techniques, solar energy storage technologies, and current university energy management systems. In order to pinpoint areas in need of improvement and chances for progress, it also looks at earlier research on solar–hydrogen storage systems. This study’s methodology describes the system architecture, which includes fuel cell integration, electrolysis for hydrogen production, solar energy harvesting, hydrogen storage, and an energy management system customized for the needs of the university. This research explores the energy consumption characteristics of the Samcheok Campus of Kangwon National University and provides recommendations for the scalability and scale of the suggested system by designing three architecture systems of microgrids with EMS Optimization for solar–hydrogen, hybrid solar–hydrogen, and energy storage. To guarantee effective and safe functioning, control strategies and safety considerations are also covered. Prototype creation, testing, and validation are all part of the implementation process, which ends with a thorough case study of the solar–hydrogen storage system’s integration into the university’s energy grid. The effectiveness of the system, its effect on campus energy consumption patterns, its financial sustainability, and comparisons with conventional energy management systems are all assessed in the findings and discussion section. Problems that arise during implementation are addressed along with suggested fixes, and directions for further research—such as scalability issues and technology developments—are indicated. This study sheds important light on the viability and efficiency of solar–hydrogen storage systems in academic environments, particularly with regard to accomplishing sustainable energy objectives.
... In addition to blending with hydrocarbon fuels, ammonia blending with hydrogen gas has great application potential. The use of hydrogen gas as a combustion promoter can completely eliminate carbon emissions from the engine, as hydrogen can be produced through ammonia decomposition, avoiding the need for bulky hydrogen storage containers [22][23][24][25][26]. Comotti et al. [27] successfully separated hydrogen gas from ammonia gas using a catalytic cracking reactor and demonstrated that adding hydrogen gas improved engine operation stability. ...
Ammonia is a very promising alternative fuel for internal combustion engines, but there are some disadvantages, such as difficulty in ignition and slow combustion rate when ammonia is used alone. Aiming to address the problem of ammonia combustion difficulty, measures are proposed to improve ammonia combustion by blending hydrogen. A one-dimensional turbocharged ammonia-hydrogen engine simulation model was established, and the combustion model was corrected and verified. Using the verified one-dimensional model, the effects of different ratios of hydrogen to ammonia, different rotational speeds and loads on the combustion performance are investigated. The results show that the ignition delay and combustion duration is shortened with the increase of the hydrogen blending ratio. The appropriate amount of hydrogen blending can improve the brake’s thermal efficiency. With the increase in engine speed, increasing the proportion of hydrogen blending is necessary to ensure reliable ignition. In conclusion, the ammonia-hydrogen fuel engine has good combustion performance, but it is necessary to choose the appropriate hydrogen blending ratio according to the engine’s operating conditions and requirements.
... Through a techno-economic analysis, it has been determined that ammonia is the most cost-effective fuel when compared to conventional options such as gasoline, natural gas, liquefied petroleum gas, methanol, and hydrogen [23]. Ammonia production and its use processes in the energy sector are shown in Figure 3 [24]. Ammonia is frequently generated through the Haber-Bosch process, which was created in the early 1900s and continues to be used today, despite its high expenses and energy requirements. ...
... Ammonia, as a result, displays decreased radiation heat transfer, which is essential during combustion and heat transfer processing. Furthermore, ammonia has a significantly lower maximum laminar burning velocity of 0.07 m/s, in contrast to methane (0.37 m/s), propane (0.43 m/s), and hydrogen (2.91 m/s) [24]. Additionally, vehicle performance running on these innovative fuels may pose limitationswhere although there has been progress made using hydrogen fuel cells, durability advancements, cost reduction measures, and efficiency remain imperative needs. ...
This study investigates the potential of hydrogen and ammonia, as alternatives for transportation fuels to tackle urgent issues concerning greenhouse gas emissions and air quality in the worldwide transportation sector. By examining studies and technological progresses, we evaluate the feasibility of transitioning to these energy options. Through an investigation of production methods, energy efficiency, environmental consequences, and infrastructure requirements, we present both the advantages and disadvantages of using hydrogen and ammonia as fuel substitutes. We spotlight production techniques such as electrolysis and renewable energy sources that could significantly decrease carbon emissions and air pollutants. Nonetheless, key challenges such as expanding infrastructure, cost-effectiveness, and safety considerations need to be resolved for adoption. Drawing on findings from research and industry developments, this article contributes to publications on transportation solutions while proposing avenues for research efforts and policy initiatives. Existing challenges and limitations are also discussed in details. In conclusion, this research underscores the significance of research endeavors and policy backing to unlock the potential of hydrogen and ammonia as sustainable transportation fuels underscoring their role in mitigating environmental impacts and promoting global sustainability objectives.
... Previous research has indicated that ammonia combustion has some drawbacks, such as low reactivity, slow burning, a limited flammability range, high autoignition temperature, and the high NOx emissions [17,25,26]. Ammonia's adiabatic flame temperature is lower than that of hydrogen and natural gas, recorded at 1800 °C (3272 °F), compared to 2110 °C (3812 °F) and 1950 °C (3542 °F), respectively. ...
... Although stoichiometric combustion of ammonia does not produce NOx, real-world conditions can lead to the formation of nitrogen-containing radicals and subsequent NOx emissions [28]. However, mature NOx removal technologies, such as selective catalytic reduction (SCR), can mitigate these emissions [29], and interestingly, ammonia from the fuel might be used in this process [26]. The risk of unburned ammonia is also a concern due to its toxicity [28], and ammonia can cause corrosion in materials, requiring careful material selection [24]. ...
Ammonia is emerging as a viable alternative to fossil fuels in combustion systems, aiding in the reduction of carbon emissions. However, its use faces challenges, including NOx emissions and low flame speed. Innovative approaches and technologies have significantly advanced the development and implementation of ammonia as a zero-carbon fuel. This review explores current advancements in using ammonia as a fuel substitute, highlighting the complexities that various systems need to overcome before reaching full commercial maturity in support of practical decarbonising global strategies. Different from other reviews, this article incorporates insights of various industrial partners currently working towards green ammonia technologies. The work further addresses fundamental complexities of ammonia combustion, crucial for its practical and industrial implementation in various types of equipment.
... When releasing hydrogen in ammonia, a step-wise decomposition step is followed. The sequence starts with ammonia adsorption on the metal, followed by ammonia dehydrogenation and the recombinative desorption of nitrogen and hydrogen (Aziz, Wijayanta, and Nandiyanto 2020;Valera-Medina et al. 2021). While ammonia handling is well documented, the use of this energy carrier has not been widely adopted for energy harvesting, as the necessary technology is yet to mature (Table 16.3). ...
... Ammonia contains high amount of hydrogen, i.e., 17.65% on a mass basis. Moreover, liquid ammonia carries 70% more hydrogen content on volume basis as compared to liquid hydrogen (Aziz et al. 2020). The storage of hydrogen requires enormously high (Kojima 2017) pressure, i.e., about 700 bar in the gaseous phase, and extremely low temperature, i.e., 20 K (−253 °C) in the liquid phase. ...
Humans contemporarily depend on fossil fuels for most of their energy needs which however is depleting at an alarming rate, forcing researchers to search for alternate and sustainable ways. The potential of ammonia and hydrogen as carbon-free fuels in energy systems is very promising. Hydrogen is the cleanest fuel presently available. The use of hydrogen in internal combustion engines, however, is constrained due to its low density, shorter flame-quenching distance, and complex storage and infrastructure. Ammonia is a hydrogen energy carrier (17.65% hydrogen by weight) with high hydrogen energy density, and it has a well-established storage/transportation infrastructure, and thus has the potential to mitigate the challenges faced due to hydrogen storage, distribution, and infrastructure drawback. Green ammonia produced from renewable sources can also contribute to carbon-neutrality targets. Using ammonia as a single fuel in an internal combustion engine faces several challenges due to its high auto-ignition temperature (~930 K), low flame velocity, slow chemical kinetics, and high unburnt ammonia emissions. Ammonia utilization in IC engines could be improved by enhancing the fuel quality, incorporating physical modifications in the engines (compression ratio, fuel injection strategies, etc.). This chapter discusses the key aspects of conventional and green ammonia production, highlighting the world energy outlook and a detailed literature study on the engine characteristics and challenges for ammonia-fueled engines with a due note on strategies for improving ammonia utilization and the possible enormous impact on various energy sector segments.
