Reactor Design, Modelling and Process Intensification for Ammonia Synthesis

Rossetti, Ilenia

doi:10.1007/978-3-030-35106-9_2

Cited by 16 publications

(12 citation statements)

References 60 publications

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“…CO is usually converted through the water–gas shift reaction and to a higher conversion through methanation or methanolation, while the other gases are usually removed by adsorption (e.g., pressure swing adsorption) or condensation in liquid nitrogen. Details on the integrated hydrogen production and purification steps can be deepened elsewhere . An example of the block diagram for processes from natural gas is reported in Figure , which exemplifies a scheme based on the steam reforming of natural gas .…”

Section: Synthesismentioning

confidence: 99%

Review on Ammonia as a Potential Fuel: From Synthesis to Economics

et al. 2021

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Ammonia, a molecule that is gaining more interest as a fueling vector, has been considered as a candidate to power transport, produce energy, and support heating applications for decades. However, the particular characteristics of the molecule always made it a chemical with low, if any, benefit once compared to conventional fossil fuels. Still, the current need to decarbonize our economy makes the search of new methods crucial to use chemicals, such as ammonia, that can be produced and employed without incurring in the emission of carbon oxides. Therefore, current efforts in this field are leading scientists, industries, and governments to seriously invest efforts in the development of holistic solutions capable of making ammonia a viable fuel for the transition toward a clean future. On that basis, this review has approached the subject gathering inputs from scientists actively working on the topic. The review starts from the importance of ammonia as an energy vector, moving through all of the steps in the production, distribution, utilization, safety, legal considerations, and economic aspects of the use of such a molecule to support the future energy mix. Fundamentals of combustion and practical cases for the recovery of energy of ammonia are also addressed, thus providing a complete view of what potentially could become a vector of crucial importance to the mitigation of carbon emissions. Different from other works, this review seeks to provide a holistic perspective of ammonia as a chemical that presents benefits and constraints for storing energy from sustainable sources. State-of-the-art knowledge provided by academics actively engaged with the topic at various fronts also enables a clear vision of the progress in each of the branches of ammonia as an energy carrier. Further, the fundamental boundaries of the use of the molecule are expanded to real technical issues for all potential technologies capable of using it for energy purposes, legal barriers that will be faced to achieve its deployment, safety and environmental considerations that impose a critical aspect for acceptance and wellbeing, and economic implications for the use of ammonia across all aspects approached for the production and implementation of this chemical as a fueling source. Herein, this work sets the principles, research, practicalities, and future views of a transition toward a future where ammonia will be a major energy player.

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Section: Synthesismentioning

confidence: 99%

Review on Ammonia as a Potential Fuel: From Synthesis to Economics

et al. 2021

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“…Ammonia can be produced through natural sources, such as gas exchange with the atmosphere, chemical and biochemical degradation of N-containing substances, and the excretion by biota [6]. Commercially, NH 3 is synthesized by the so-called Haber-Bosch process [7,8], which is extensively used as a basis for the production of a vast variety of chemicals, such as fertilizers, explosives, nitric acid, and polyamides. This represents a method for the fixation, i.e., activation of atmospheric nitrogen, and considering that 85% of 146 million ton per year of the ammonia produced worldwide is used for fertilizers production [8], one may appreciate the magnitude of admission of this nutrient in the environment, particularly in surface or ground waters.…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic Selective Oxidation of Ammonia in a Semi-Batch Reactor: Unravelling the Effect of Reaction Conditions and Metal Co-Catalysts

et al. 2021

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Photocatalysis has been used for the oxidation of ammonia/ammonium in water. A semibatch photoreactor was developed for this purpose, and nanostructured TiO2-based materials, either commercial P25 or prepared by flame spray pyrolysis (FSP), were used as catalysts. In the present work, we investigated the effect of (i) metal co-catalysts, (ii) pH, and (iii) ammonia concentration on the efficiency of oxidation and on the selectivity to the undesired overoxidation byproduct, i.e., nitrites and nitrates. Several metals were added to both titania samples, and the physicochemical properties of every sample were studied by XRD, BET, and UV-Vis spectroscopy. The pH, which was investigated in the range of 2.5–11.5, was the most important parameter. The optimum pH values, resulted as 11.5 and 4.8 for P25 and FSP respectively, matching the best compromise between an acceptable conversion and a limited selectivity toward nitrite and nitrate formation. For both titania samples (P25 and FSP), ammonia conversion vs. nitrite and nitrate formation were highly dependent on the pH. At pH ≥ 9, the initial rate of photooxidation was high, with selective formation of overoxidized byproducts, whereas, at a more acidic pH, the conversion was lower, but the selectivity toward nitrogen formation was higher. P25 samples added with noble metal co-catalysts (0.1 mol% Ag, Au, Pd, Pt) at pH = 11.5 remarkably increased the selectivity to nitrite and nitrate, while, in the case of FSP samples (pH = 4.8), the co-catalysts increased the selectivity toward N2 with respect to the unpromoted catalyst and also the conversion in the case of Au and Pt. Reactivity was discussed, leading to the proposing of a mechanism that correlates the activity with either surface adsorption (depending of the surface charge of the catalyst and on pH) or the homogeneous reactivity of oxidizing species.

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“…The catalysts selected are a commercial Fe-based (from wustite) catalyst, tested preliminarily in our labs, and a Ru/C-based catalyst developed by our research group a few years ago and transferred to a company for development. ,,− Detailed characterization of the materials are reported in previous publications, specifically in refs , − .…”

Section: Models and Methodsmentioning

confidence: 99%

“…Ammonia synthesis from gaseous nitrogen and hydrogen is a well-known reaction and established process, but its huge importance and very demanding reaction conditions have resulted in ongoing research studies for one century . The overall energetic balance and carbon dioxide footprint of the process depend, respectively, on the primary sources of nitrogen and hydrogen .…”

Section: Introductionmentioning

confidence: 99%

Process Intensification for Ammonia Synthesis in Multibed Reactors with Fe-Wustite and Ru/C Catalysts

Tripodi

Conte

Rossetti

2021

Ind. Eng. Chem. Res.

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An ammonia synthesis loop is designed using two different catalysts, namely, a Fe-based one from a wustite precursor and a Ru/C sample. Previously established kinetic models have been used and implemented in a process simulator to investigate different feeding and quenching arrangements. A different array of series and parallel reactive stages is then proposed and optimal conditions for the feeding strategy and catalyst loading are discussed. It is found that loading the last reacting stages with Ru/C (instead of Fewustite) always improved the ammonia yield when other conditions were fixed. Different feed-splitting, intercooling, and quenching options were tried to verify their effect on the heat duty of the reactor and the interplay between this aspect and the ammonia product fraction. Adopting mixed catalyst configuration allowed considerable energy savings both as lower duty for the recycle loop compressor and decreased heat exchange needs, boosting process intensification as one of the primary challenges for this reaction.

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Reactor Design, Modelling and Process Intensification for Ammonia Synthesis

Cited by 16 publications

References 60 publications

Review on Ammonia as a Potential Fuel: From Synthesis to Economics

Review on Ammonia as a Potential Fuel: From Synthesis to Economics

Photocatalytic Selective Oxidation of Ammonia in a Semi-Batch Reactor: Unravelling the Effect of Reaction Conditions and Metal Co-Catalysts

Process Intensification for Ammonia Synthesis in Multibed Reactors with Fe-Wustite and Ru/C Catalysts

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