An automated tungstic acid technique (TAT) has been successfully used to measure gaseous HNO₃ in the presence of water vapor. The TAT is based on the diffusion of gaseous HNO₃ to the interior walls of a tube coated with tungsten VI oxide (WO₃), where it is selectively chemisorbed. The collected HNO₃ sample is thermally desorbed from the WO₃ surface, as NO, and measured by a chemiluminescent oxides of nitrogen analyzer. The integrated analyzer response is directly proportional to the nitric acid collected. Based on nitric acid hydration characteristics, a decrease in the diffusion coefficient and thus collection efficiency for denuder type measurement techniques may result with increased atmospheric water vapor (i.e., relative humidity). This study emphasizes the effect of water vapor (i.e., relative humidity) as a potential interferent for HNO₃ collection with the TAT system. The effect of water vapor (< 78% RH) on the collection efficiency for HNO₃ with the tungstic acid technique is negligible at 25°C, but is significant only at elevated sampling temperatures. This threshold effect is further substantiated and eliminated when a modified sampling collection system was designed with coolant capabilities. The new design has been tested to sub-part-per-billion (NO_x analyzer detection limit) levels with minimal loss of gaseous HNO₃ signal, thereby increasing sensitivity to atmospheric HNO₃ concentrations and maintaining the gas/aerosol sample integrity. / Ph. D.

O enriquecimento isotópico de nitrogênio-15 por troca química no sistema NO/HNO3 foi estudado através de duas teorias distintas. Os fatores de fracionamento isotópicos, obtidos pela teoria de contracorrente e os estimados pela teoria da eqüipartição isotópica, foram confrontados através de um modelo. Construiu-se uma coluna de contracorrente, em escala de laboratório, e parâmetros tais como: número de placas teóricas, altura equivalente de uma placa teórica, tipo de enchimento, altura total da coluna, produção de H15NO3/semana, obtidos em condições de equilíbrio dinâmico isotópico, foram estudados comparativamente aos da literatura / Nitrogen-15 isotope enrichment by chemical exchange in NO/HNO3 system was studied using two different theories. The isotope fractionation factors obtained by the countercurrent theory was compared to those estimated by the isotope equipartition theory were confronted through a model. It was built a column in countercurrent at laboratory scale and parameters such as: number of theoretical plates, height equivalent to a H15NO3week, obtained under isotope dynamic equilibrium conditions, were studied in comparison to those in the literature

The potential human health issues resulting from the continuous consumption of drinking water containing low concentration levels of persistent emerging pollutants has raised some concerns. The presence of emerging pollutants in surface water bodies and ground-water in Canada together with absence of proper drinking water treatment processes in remote places has created the need for an effective and simple process for removal of emerging pollutants from drinking water. Low seasonal temperatures in regions such as Saskatchewan demand a removal process that is effective at temperatures lower than room temperature. Adsorption with granular activated carbon is a well-established and effective method for removal of organic compounds from drinking water. There are a large number of reports on removal of organic compounds by activated carbon in literature however, the effectiveness of adsorption of emerging pollutants with granular activated carbon is not clear. Effectiveness of ozone treatment for oxidation of emerging pollutants is reported in literature however, effectiveness of regeneration of adsorbents saturated with emerging pollutants with ozone has not been investigated extensively. In the present work, effectiveness of adsorption with granular activated carbon for removal of emerging pollutants is investigated. Three model compounds of Ibuprofen, 2,4-dichlorophenoxyacetic acid, and Bisphenol A reported at considerable concentration levels in Saskatchewan water bodies were selected as model compounds. Bituminous coal based and coconut shell based granular activated carbons with basic point of zero charge were selected as adsorbents. Isotherm adsorption of model compounds on adsorbents was conducted at 280, 288, and 296 K. The Gibbs free energy, enthalpy, and entropy of adsorption were calculated using isotherm model parameters. Nitric acid pre-treatment was applied to reduce the point of zero charge of adsorbents. Adsorption isotherms were conducted with the acid treated adsorbents. Adsorption removal of model compounds in tap water was studied. Effectiveness of regeneration of saturated adsorbents with ozone was investigated. In terms of quality of fit to the isotherm adsorption data, Langmuir model was better than Freundlich model indicating monolayer adsorption of model compounds in all experiments. Higher Langmuir monolayer adsorption capacity (Qmax) of bituminous coal based adsorbent than coconut shell adsorbent for adsorption of model compounds was attributed to the higher porosity of bituminous coal based adsorbent. Adsorption of model compounds (i.e. IBP and BPA) present in molecular form in the pH condition of the experiments were more dependent on adsorbent surface functional groups e.g. carboxyl and carbonyl groups. The Qmax of adsorption of 2,4-D present in anionic form was proportional with the specific surface area of adsorbent. Adsorption at temperatures lower than room temperature was effective. Adsorbent with acidic point of zero charge was more effective in removal of model compounds than adsorbent with basic point of zero charge. Adsorption of BPA was higher in tap water in comparison to Millipore water due to the more neutral surface of adsorbent in tap water. Higher pH of tap water than Millipore water and the ionic interaction between the adsorbent and dissolved solids present in tap water caused the more neutral surface of adsorbent. Regeneration of adsorbents with ozone failed in restoration of adsorption capacity of adsorbents and excessive ozonation destroyed the pore structure of adsorbents.

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O enriquecimento isotópico de nitrogênio-15 por troca química no sistema NO/HNO3 foi estudado através de duas teorias distintas. Os fatores de fracionamento isotópicos, obtidos pela teoria de contracorrente e os estimados pela teoria da eqüipartição isotópica, foram confrontados através de um modelo. Construiu-se uma coluna de contracorrente, em escala de laboratório, e parâmetros tais como: número de placas teóricas, altura equivalente de uma placa teórica, tipo de enchimento, altura total da coluna, produção de H15NO3/semana, obtidos em condições de equilíbrio dinâmico isotópico, foram estudados comparativamente aos da literatura / Nitrogen-15 isotope enrichment by chemical exchange in NO/HNO3 system was studied using two different theories. The isotope fractionation factors obtained by the countercurrent theory was compared to those estimated by the isotope equipartition theory were confronted through a model. It was built a column in countercurrent at laboratory scale and parameters such as: number of theoretical plates, height equivalent to a H15NO3week, obtained under isotope dynamic equilibrium conditions, were studied in comparison to those in the literature

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Orientadores: Roger Josef Zemp, Valdir Apolinário de Freitas / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-21T11:39:16Z (GMT). No. of bitstreams: 1 Assis_CamillaAbbatide_M.pdf: 6993835 bytes, checksum: 7d87e3705f4d5bf8e95ea91406ca5a5b (MD5) Previous issue date: 2012 / Resumo: Um projeto de engenharia e realizado em cinco etapas consecutivas: planejamento do negocio, desenvolvimento do escopo, definição do projeto, execução (engenharia de detalhamento e construção) e, finalmente, partida e operacao. Muitas vezes percebe-se, na conclusão das etapas de desenvolvimento do escopo e de definição do projeto, apos intenso uso de tempo e de recursos, que o projeto não e mais viável economicamente, sendo abandonado ou reestudado. Decisões de projeto tomadas no inicio da concepção determinam configurações que afetarão permanentemente investimentos e custos operacionais. A engenharia de processos pode aliar conhecimentos técnicos a conceitos econômicos nas etapas iniciais, a fim de avaliar o impacto das decisões de configuração na viabilidade do projeto. Apesar de parecer natural, essa não e uma pratica comum na industria. Nesse contexto, o presente trabalho tem por objetivo realizar uma analise técnico-econômica de alternativas de configuração em estágios preliminares de um projeto. Para tal, será utilizado como estudo de caso o processo produtivo de acido nítrico a partir da combustão de amônia, em duas situações distintas: projeto de uma planta nova (síntese) e projeto de modificação de uma planta existente (revamp). A partir de analises simples, utilizando ferramentas que facilitam a avaliação da influencia de parâmetros no projeto, serão analisados os impactos das variações desses parâmetros em diferentes propostas de configurações / Abstract: An Engineering Project happens in 5 consecutive steps: business assessment, scope development, project definition, execution (detailed engineering and construction) and, finally, startup and operations. Many times, in the conclusion of the scope development and project definition steps, after intense use of time and resources, one realizes that the project is not economic feasible anymore, being abandoned or restudied. Project decisions taken in the early stages of design determine configurations that will affect permanently the investments and operational costs. The process engineering can combine technical knowledge to economic concepts at the early stages, to evaluate the impact of configurations decisions in the feasibility of the project. Although this may seem natural, it's not a common practice in the industry. In this context, this work aims to make a techno-economic analysis of configuration alternatives at the preliminary stages of a project. For this purpose, it will be used as a case study the production process of the nitric acid through the ammonia combustion, in two different situations: project of a new plant (synthesis) and project of modification in an existing plant (revamp). Through simple analysis, using tools that facilitate the evaluation of the parameters influence in the project, the impacts of the variations of these parameters in different alternatives of configuration will be evaluated / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestra em Engenharia Química

Dans le procédé de traitement du combustible nucléaire usé, de l’acide nitrique concentré est utilisé pour dissoudre le combustible. Pour résister à ces milieux de dissolution très acides et oxydants, des matériaux passifs comme le zirconium ou les aciers inoxydables ont été choisis pour construire les équipements industriels. Pour ces matériaux, la présence d’une couche passive a pour effet de ralentir les réactions d’oxydo-réduction à l’interface métal / acide nitrique. L’objectif de ce travail est de déterminer et quantifier les étapes élémentaires du mécanisme de réduction de l’acide nitrique concentré et d’étudier spécifiquement le rôle de la couche passive sur la cinétique de réduction de l’acide nitrique.Une première étape a été d’étudier un transfert monoélectronique sur des couches passives modèles (Zr/ZrO2) de différentes épaisseurs et ensuite sur acier passivé. Cette étude a mis en évidence une cinétique de transfert de charge pilotée par les propriétés semi-conductrices des couches passives.Ensuite, une étude expérimentale électrochimique, couplée à des techniques analytiques (UV-visible) a permis d’émettre des hypothèses sur les réactions mises en jeu lors de la réduction de l’acide nitrique 4M à 40°C et 8M à 100°C sur électrode d’acier passivé. Dans les conditions 4M à 40°C, il apparaît un processus unique sur toute la plage de potentiel. En revanche, il est mis en évidence que dans les conditions pour 8 mol.L-1 à 100°C, deux processus de réduction différents ont été identifiés en fonction de la surtension cathodique. Une modélisation cinétique de ces processus a été effectuée. / In France, the spent nuclear fuel reprocessing involves the use of nitric acid at various concentrations and temperatures. The corrosiveness of these nitric mixtures leads to the use of corrosion resistant materials such as austenitic stainless steels (SS), which naturally forms a protective oxide layer under those conditions. The goal of this work is to study the influence of the passive layer on the mechanism and kinetics of concentrated nitric acid reduction reaction (NRR).We firstly focused on a single step in the reduction reaction of Fe(III) on passivated zirconium with different oxide layer thicknesses. The electrochemical impedance spectroscopy can lead to estimate the semiconducting properties of the film.Then, an electrochemical experimental study, coupled with analytical techniques (UV-visible) allowed to propose hypotheses on the reactions involved in the reduction of the nitric acid 4M in 40°C and 8M in 100°C on electrode of stainless steel. In the conditions 4M in 40°C, it appears an only process on all the range of potential. On the other hand, it is highlighted that in the conditions for 8M in 100°C, two different processes of reduction were identified according to the cathodic overvoltage. A kinetic modelling of these processes was proposed.

Ce travail de thèse s’inscrit dans le cadre des recherches sur le cycle du combustible nucléaire et notamment sur le développement du procédé de cogestion du plutonium et de l’uranium pour les usines de retraitement futur. Son but est l’étude de la faisabilité de la réduction cathodique de solutions concentrées mixtes d’uranium (+VI) et de plutonium (+IV), en milieu acide nitrique et en présence d’un agent anti-nitreux, sur électrode de platine. Cette étape de réduction est nécessaire à la préparation de la charge mixte U(IV)/Pu(III), destinée à la coconversion par précipitation oxalique (et calcination du précipité en précurseur oxyde du combustible MOX). Dans un premier temps, les paramètres thermodynamiques et cinétiques des réactions mises en jeu à l’électrode, ainsi que le transport de matière dans la couche de diffusion ont été caractérisés pour les couples redox d’actinides Pu4+/Pu3+ et UO22+/UO2+. La détermination des coefficients de diffusion, des potentiels standards conditionnels, ou encore des constantes cinétiques de transfert électronique a été obtenue par analyses voltampérométriques. Dans un second temps, un électrolyseur plaque à membrane miniaturisé (électrode de titane platiné de surface utile A = 12 cm²) a été conçu afin de réaliser des électrolyses de solutions d’U(VI) et/ou de Pu(IV). La faisabilité scientifique et technique d’une réduction électrochimique concomitante des actinides U et Pu, en solution aqueuse acide nitrique en présence de nitrate d’hydrazinium, a été démontrée. Cette réduction a été réalisée sur une solution mixte U(VI)/Pu(IV) de concentrations respectives 10 et 40 g/L, en présence du nitrate d’hydrazinium, et en mode de fonctionnement galvanostatique, pour une densité de courant de 12 mA cm-2, à une température de 25°C. Elle a permis de convertir de manière quantitative le Pu(IV) en Pu(III) et jusqu’à un taux de 60 % l’U(VI) en U(IV). Enfin, sur la base de ces résultats expérimentaux d’électrolyse de solutions simples ou mixtes, en présence ou non de nitrate d’hydrazinium, deux modèles numériques ont été développés. Un premier modèle de type « 0D » a permis de représenter l’évolution des concentrations dans le catholyte considéré comme un volume homogène, en prenant en compte l’ensemble des réactions électrochimiques et chimiques mises en jeu ; et en adoptant une description simplifiée de la couche de diffusion à partir de l’hypothèse de l’établissement d’un courant limite de diffusion pour les réductions de U(VI) et Pu(IV), en négligeant la réactivité chimique des espèces dans le volume de cette interface. Un second modèle, plus complet, de type « 0D-1D » a servi à décrire les évolutions de concentrations dans la couche réactionnelle située à l’interface électrode – solution, et les échanges entre cette couche et le volume du catholyte. Ces deux modèles ont permis de réaliser des ajustements paramétriques afin de déterminer l’épaisseur de la couche réactionnelle et les différentes constantes cinétiques mettant en jeu les espèces Pu(IV), Pu(III), U(VI), U(IV), HNO2 et NH, et qui sont propres au système d’étude ; à savoir la réduction de solutions simples ou mixtes d’U(VI)/Pu(IV) (gamme de concentration de 1 à 40 g/L), en milieu HNO3 2 M, sur électrode de platine à T = 25°C, avec un débit de recirculation de 240 mL/min dans l’électrolyseur miniaturisé EM-CEA 16 / This study concerns the nuclear Fuel cycle and notably the co-management of plutonium and uranium for future reprocessing plants. It deals with the study of the scientific feasibility of the cathodic reduction of mixed and concentrated solutions of uranium (+VI) and plutonium (+IV), in nitric acid medium and in presence of an anti-nitrous agent, on a platinum electrode. This reduction step is necessary for the preparation of the mixed load of U(IV)/Pu(III), dedicated to coconversion by oxalic precipitation and production of oxide precursor for MOx fuel fabrication. At first, the thermodynamics and kinetics parameters of the reactions involved at the electrode, as well as the mass transport parameters were characterized for Pu4+/Pu3+ and UO22+/ UO2+ redox couples by voltamperometric analysis. Secondly, a miniaturized plate electrolyzer (electrode of platinized titanium, area A = 12 cm²) was designed in order to perform electrolysis of U(VI) and/or Pu(IV) solutions. The scientific and technical feasibility of a concomitant electrochemical reduction of U and Pu, in nitric acid aqueous solution in presence of hydrazinium nitrate, was demonstrated. This reduction was realized on a mixed U(VI)/Pu(IV) solution at the concentration of 10 and 40 g/L respectively, in presence of hydrazinium nitrate, and in a galvanostatic mode, for a current density of 12 mA cm-2, at a temperature of 25°C. It allowed to convert Pu(IV) to Pu(III) quantitatively and U(VI) to U(IV) at a yield of 60 %. Finally, on the basis of these experimental results of electrolysis on simple or mixed solutions, in presence or not of hydrazinium nitrate, two numerical models were developed. A first one, named "0D", allowed to represent the evolution of concentrations in the volume of the catholyte, taking into account the reactivity of reactants at the electrode, and also all chemical reactions involved in the bulk (considered as a homogeneous volume); with a simplified description of the diffusion layer, by considering the establishment of a limiting diffusive current for the reductions of Pu(IV), Pu(III), U(VI), U(IV), HNO2, and NH species, and by neglecting the chemical reactivity of these species in this layer. A second one, named "0D – 1D", allowed to describe more finely the reactive layer at the electrode – bulk interface, and the exchanges between this layer and the volume of the catholyte compartment. These two models allowed to run parametric fitting in order to determine the kinetic constants of the different reactions taking place at the electrode, in the diffusion layer and in the bulk, for the reduction of simple or mixed U(VI)/Pu(IV) solutions (concentration range from 0 to 40 g/L), in HNO3 2 M medium, on a platinum electrode and at T = 25°C, with a recirculation flow rate of 240 mL/min, in the EM-CEA 16 electrolyzer

L'acide nitrique est largement utilisé dans le procédé de retraitement du combustible nucléaire usé, le procédé PUREX (Plutonium and Uranium Refining by EXtration). Ce procédé est fondé sur l'extraction liquide-liquide de l'uranium et du plutonium aux degrés d'oxydation (+VI) et (+IV) respectivement. Le plutonium est ensuite désextrait, et ainsi séparé de l'uranium par ajout d'uranium (+IV) stabilisé en milieu acide nitrique par des ions hydrazinium (N2H5+). Or, la radiolyse de l'acide nitrique, inhérente à la présence d'émetteurs α dans ces solutions, génère des espèces radicalaires et moléculaires susceptible de modifier, d'une part, le comportement redox des actinides et, d'autre part, de réagir avec les ions hydrazinium. Le but de ce travail est de mieux maîtriser les paramètres chimiques et physico-chimiques susceptibles de modifier les degrés d'oxydation de l'uranium et du plutonium dans les solutions d'acide nitrique. Parmi ces paramètres, le rôle de l'acide nitreux et du peroxyde d'hydrogène, générés par radiolyse de l'acide nitrique, est primordial. L'objectif est de repréciser les cinétiques de formation du peroxyde d'hydrogène et de l'acide nitreux par radiolyse alpha des milieux acide nitrique / nitrate de sodium en fonction des paramètres : acidité, concentration des ions nitrate et transfert d'énergie linéique du rayonnement ionisant.Il a été montré que la formation de peroxyde d'hydrogène diminue avec l'augmentation de la concentration des ions nitrate et augmente fortement avec l'acidité de la solution, jusqu'à atteindre une valeur stationnaire pour une acidité proche de 0,2 mol L-1. Pour sa part, la formation de l'acide nitreux est favorisée par l'augmentation de la concentration des ions nitrate. Il a été observé que G(HNO2) évolue selon deux tendance distincte, la première dans les solutions diluées d'ions nitrate et la seconde dans les solutions concentrées d‘ions nitrate. Ces deux variations traduisent des phénomènes radiolytiques directs et indirects modifiant les mécanismes de formation de HNO2. L'étude de l'acidité des solutions irradié a montré que la formation de H2O2 et de HNO2 est favorisé avec l'augmentation de la concentration des ions hydronium, jusqu'à atteindre une valeur stationnaire pour une acidité proche de 0,2 - 0,5 mol L-1.Par ailleurs, les effets induits par la nature du rayonnement ionisants (,,,…), sur les rendements de formation de H2O2 et HNO2, ont été étudiés. Il a été montré que le transfert d'énergie linéique (TEL), compris entre 0,2 keV µm-1 (caractéristique d'un rayonnement gamma) et 130 keV µm-1 (caractéristique d'un rayonnement alpha émis par la décroissance radioactive d'un actinide), a une influence significative sur les rendements de formation de H2O2 et de HNO2. Il a été observé que l'impact des ions nitrate sur le rendement de formation de H2O2 devient plus marqué, lorsque le TEL augmente. A contrario, l'impact des ions nitrate favorisant le rendement de formation de HNO2, diminue lorsque le TEL augmente. Sur la base des résultats acquis durant cette étude et des données présentes dans la littérature, deux équations paramétriques ont été développées. L'intérêt de cette paramétrisation des effets est de prédire les rendements radiolytiques de formation de H2O2 et de HNO2 selon les conditions chimique du milieu ([NO3-] ≤ 4 mol L-1 et 10-5 mol L-1 ≤ [H+] ≤ 4 mol L-1) et selon la nature du faisceau (TEL compris entre 0,2 – 130 keV µm-1).La finalité de cette étude serait de prédire les quantités de H2O2 et de HNO2 formés par radiolyse de HNO3/NaNO3 dans les étapes du procédé de retraitement des combustibles nucléaires. / Nitric acid is widely used in spent nuclear fuel reprocessing, especially in PUREX process (Plutonium and Uranium Refining by Extraction). This process is based on liquid-liquid extraction of Uranium (+VI) and Plutonium (+IV). Plutonium is separated from Uranium by addition of Uranium (+IV) in nitric acid, stabilized by hydrazinium ion (N2H5+). However, the radiolysis of nitric acid, result of the presence of alpha emitting radionuclides, generates in solutions free radicals and molecular species. These species are capable of modifying the redox state of actinides and reacting with hydrazinium ions.The aim of this work is to reveal the chemical and physical-chemical parameters that may modify the oxidation states of Uranium and Plutonium in nitric acid solutions. Among these parameters, the role of nitrous acid and hydrogen peroxide, generated by radiolysis of the nitric acid, is very important. The objective is to redefine the kinetics of formation of hydrogen peroxide and nitrous acid during alpha radiolysis of nitric acid / sodium nitrate, as a function of three parameters: acidity, nitrate concentration and the linear energy transfer of ionizing radiation.It was shown that the formation of hydrogen peroxide decreases with increasing nitrate ions concentration and increases greatly with the acidity of the solution (until it reaches a stationary value for an acidity of 0.2 mol L-1). The formation of nitrous acid is promoted by the increase the nitrate ions concentration. It was observed that G(HNO2) varies according to two trends. The first one in dilute nitrate solutions and the second in concentrated nitrate solutions. These two trends reflect the direct and indirect radiolytic phenomena, modifying the mechanisms of formation of HNO2. The study of acidity has showed that the formation of H2O2 and HNO2 is promoted by increasing the concentration of hydronium ions, until it reaches a steady state value for an acidity close to 0.2-0.5 mol L-1.Furthermore, the effects induced by ionizing radiation (,,,…) on formation yields of H2O2 and HNO2 were studied. It has been shown that the linear energy transfer (LET), between 0.2 keV µm-1 (characteristic of a gamma radiation) and 130 keV µm-1 (characteristic of the alpha radiation emitted by radioactive decay of actinides), has a significant influence on formation yield of H2O2 and HNO2. It was observed that the impact of nitrate ions on the formation yield of H2O2 becomes more pronounced when the LET increases. Conversely, the impact of nitrate ions which promote the formation of HNO2, decreases when the LET increases.Based on these results, two parametric equations were developed. The advantage of this parameterization is to predict the radiolytic yields formation of H2O2 and HNO2 according to chemical conditions ([NO3-] ≤ 4 mol L-1 and 10-5 mol L-1 ≤ [H+] ≤ 4 mol L-1) and the nature of the beam (LET between 0.2 to 130 keV µm-1).The purpose of this study is to predict the quantity of H2O2 and HNO2 formed by radiolysis of HNO3/NaNO3, during the different steps of the nuclear fuel reprocessing.