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Concept

Ammoniac

Résumé

L'ammoniac est un composé chimique de formule (du groupe générique des nitrures d'hydrogène). Dans les conditions normales de température et de pression, c'est un gaz noté gaz. Il est incolore et irritant, d'odeur piquante à faible dose ; il brûle les yeux et les poumons en concentration plus élevée. Il est industriellement produit par le procédé Haber-Bosch à partir de diazote et de dihydrogène. C'est l'un des composés les plus synthétisés au monde, utilisé comme réfrigérant, et pour la synthèse de nombreux autres composés (dont un grand tonnage d'engrais). C'est aussi un solvant liquide en usage pur, à et , soit . L'auto-ionisation de l'ammoniac liquide est très faible, caractérisée par une constante de dissociation ionique K = [NH] [NH] qui vaut environ à . Dans le solvant protique liquide, le cation ammonium NH est l'acide le plus fort alors que l'anion amide NH est la base la plus forte. Son doublet électronique en fait à la fois une base, un nucléophile, un ligand et u

Source officielle

https://fr.wikipedia.org/wiki/Ammoniac

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Unités associées (9)

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Concepts associés (502)

L'azote est l'élément chimique de numéro atomique 7, de symbole N (du latin nitrogenium). C'est la tête de file du groupe des pnictogènes. Dans le langage courant, l'azote désigne le corps simple N

L'eau est une substance chimique constituée de molécules . Ce composé, très stable, mais aussi très réactif, est un excellent solvant à l'état liquide. Dans de nombreux contextes, le terme eau est e

Le chlore est l'élément chimique de numéro atomique 17, de symbole Cl. C'est le plus commun des halogènes. Le chlore est abondant dans la nature, son dérivé le plus important est le sel de table ou

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Cours associés (40)

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Séances de cours associées (88)

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The thermo-environomic assessment of the industrial production of ammonia has been investigated in this project. Thermodynamic models for the ammonia synthesis were developed on the flowsheeting software Vali based on the techniques used at LENI. Several process configurations were evaluated for the steam-methane reforming and the biomass gasification processes. Optimized values for key performance indicators were obtained based on sensitivity analysis and multi-objective optimization with respect to maximizing the energy yield while minimizing capital investment and carbon dioxide emissions. Life cycle assessment was performed on the optimized process configuration in order to address the possible process GWP reduction. Energy yields of 65.6% and 50.6%, respectively for the SMR and biomass processes have been obtained with process costs of 201.2 and 330.1 USD/MWh. Associated with literature data, the optimized process designs developed in this project allow to assess the potential of a biomass feedstock for ammonia as transportation fuel.

2012

Chargement

Investigation of the Electrochemical Destruction of X-ray Contrast Media using Boron-‐Doped Diamond Electrodes (BDD)

Guillaume Tissot

Iodinated X-ray contrast media (ICM) are persistent micropollutants in wastewater, which come mainly from hospital activities. Currently, there is no efficient method of treatment for this class of compounds, which leads to their increased presence in surface water and drinking water. In this work we propose to treat directly ICM in urine, meaning at high concentration, by electrochemical oxidation process using BDD electrodes. In a first step of the project, determination of the reactivity of Iohexol towards electrochemical oxidation in inactive electrolyte was performed. In subsequent iohexol electrolysis experiment the electrolyte composition was gradually modified until electrolysis of Iohexol in fresh urine. Obtained results were compared with those predicted by adjusted kinetic model of COD elimination. Model is based on the kinetic of the electrochemical oxidation is controlled by diffusion, and it was demonstrated, in this work, that this is also the case for the electrochemical oxidation of Iohexol. This methodology permits to determine interference that urine components such as chloride and ammonia have on the electrochemical oxidation. The obtained results showed that 99% of Iohexol present in the electrolyte and at least 85% of the initial COD elimination can be achieved with an efficiency close to 100%, even in fresh urine. Investigation of the main constituents of urine showed that chloride has a positive effect on the process efficiency due to both catalytic and no‐catalytic action (oxidation of organics compounds, via electrogenereted active chlorine, close to the electrode or in the bulk). On the contrary ammonia has no effect on the efficiency if it is present alone, and negative effect if chloride is also present (certainly due to chloramine formation). Nevertheless, at high concentration of ICM, the effect of chloride and ammonia is negligible as experiment in fresh urine demonstrated. As expected, the reaction of hydroxyl radical with Iohexol is non-specific. Preliminary identifications of transformation products by UPLC-MS showed that electrochemical oxidation can lead to nucleus attack (deiodination) or side chain attack unselectively. In addition, deiodination by cathodic reduction under mass transfer control is also possible according to these UPLC‐MS results, and by the kinetic of Iohexol elimination. At an elimination of 85% COD in treated urine only a very low concentration of pollutant remain. Ecotoxicity and biodegradability analyses were performed with the treated urine at this point. Toxicity assays showed some ecological toxicity towards environment; biodegradability test didn’t show clear biodegradation. Finally, operating cost analysis for a possible installation using electrochemical oxidation process with BDD electrodes showed that even if other advanced oxidation process (AOPs), such as processes such as ozonation or UV/H2O2, demonstrate the same efficiency as electrochemical oxidation in the future, electrochemical oxydation using BDD electrode remains strongly competitive economically.

2012

Chargement

Assessment of ammonia as energy carrier in the use with reversible solid oxide cells

Jan Van Herle, Michele Zendrini

Ammonia represents one of the most promising potential solutions as energy vector and hydrogen carrier, having a higher potential to transport energy than hydrogen itself in a pressurized form. Furthermore, solid oxide fuel cells (SOFCs) can directly be fed with ammonia, thus allowing for immediate electrical power and heat generation. This paper deals with the analysis of the dynamic behavior of commercial SOFCs when fueled with ammonia. Several measurements at different temperatures have been performed and performances are compared with hydrogen and a stoichiometrically equivalent mixture of H2 and N2 (3:1 M ratio). Higher temperature led to smaller drops in voltage for both fuels, thus providing higher efficiencies. Ammonia resulted slightly more performant (48% at 760 °C) than hydrogen (45% at 760 °C), in short stack tests. Moreover, different ammonia-to-air ratios have been investigated and the stack area-specific resistance has been studied in detail by comparing numerical modeling predictions and experimental values.

2021

Chargement

Investigation of the Electrochemical Destruction of X-ray Contrast Media using Boron-‐Doped Diamond Electrodes (BDD)

Guillaume Tissot

2012

Ammoniac

Investigation of the Electrochemical Destruction of X-­ray Contrast Media using Boron-­‐Doped Diamond Electrodes (BDD)

Assessment of ammonia as energy carrier in the use with reversible solid oxide cells

Assessment of ammonia as energy carrier in the use with reversible solid oxide cells

Investigation of the Electrochemical Destruction of X-­ray Contrast Media using Boron-­‐Doped Diamond Electrodes (BDD)

Investigation of the Electrochemical Destruction of X-ray Contrast Media using Boron-‐Doped Diamond Electrodes (BDD)

Investigation of the Electrochemical Destruction of X-ray Contrast Media using Boron-‐Doped Diamond Electrodes (BDD)