This dissertation investigates the level of acid‐resistance of concrete degradation. Concrete specimens obtained from four mixtures (M1, M2, M3 and M4) were prepared with calcareous, siliceous and a blend of calcareous and silica sand; and then, tested in low (30 g/l) and highly (200 g/l) concentrated sulphuric acid solutions. To this end, an architecture of artificial neural networks (ANNs) was implemented to predict the performance of concrete specimens due to sulphuric acid solutions. Neural networks were composed with one hidden layer for one input and output layer. Nine input parameters were: cement composition, proportions of coarse and fine aggregates, water content, and compressive strength, weight loss of concrete, time impacting corrosion, acid concentration and sulphur concentration. Thickness expansion and concrete conductivity are used as output targets to evaluate the degree of deterioration. In this study, the learning through ANNs from training data sets have been proved to be better than measured data. Excellent results were found with a coefficient of determination (R2 ) of 0.9989, 0.9999, 0.9989 and 0.9998, respectively for the four mixtures M1, M2, M3 and M4 using siliceous aggregate. Also, the results show that two ANN models performed with both the thickness (expansion) and the electrical conductivity can successfully learn the prediction of concrete corrosion. In both low and highly concentrated sulphuric acid condition, the model thickness was more accurate in predicting concrete corrosion compared to the model conductivity. The lowest error in neural networks was provided by the mixture (M2) for the concrete using siliceous aggregate. For this purpose, the root mean squared error (RMSE) and the average absolute error (AAE) were of 0.0049 and 0.0048 % respectively. / College of Engineering, Science and Technology / M. Tech. (Chemical Engineering)

<p>Anodic protection has shown to be a viable method for reducing corrosion rates of stainless steels over a wide range of temperatures and is used to protect equipment in H₂SO₄ manufacturing. While effective at controlling corrosion in H2SO4 manufacturing, Impressed Current Anodic Protection (ICAP) systems have shown to have a number of issues. They require a constant source of current to ensure reliable corrosion protection; are relatively complex systems and expensive to install; improper potential control can lead to loss of corrosion protection; and some issues with cathode fouling and erosion have been reported. Galvanic Coupled Anodic Protection (GCAP) systems have not been widely utilized in industry, but offer some solutions to these issues. GCAP systems have been developed using Pt and Au as the cathode materials for use in H2SO4. Previous work on the oscillatory behaviour of austenitic stainless steels indicates that nickel sulphide (NiS) could be used as cathode material in a GCAP system in concentrated H₂SO₄ to protect stainless steel. The objective of this study was to develop a better understanding of the behaviour of NiS when galvanically coupled to Type 430 stainless steel to determine whether it can be used in a GCAP system. NiS and NiS(Ni) electrodes are able to provide the Icrit needed to passivate Type 430 at anode/cathode ratios of 10:1, while NiS(Ni) electrodes were able to provide the Icrit needed to passivate the Type 430 stainless steel at a ratio of 20:1. In addition it was shown that the NiS(Ni) electrode was able to maintain passivity of the Type 430 stainless steel array using an anode/cathode surface area ratio of 100:1. NiS was shown not to be inert in concentrated H₂SO4 and corrosion rate calculated via Tafel extrapolation and shown to be 0.014 mm/yr at room temperature and 0.128 mm/yr at 60 ºC.</p> / Master of Applied Science (MASc)

1 ABSTRACT: This study is dedicated to the study of nucleation of sulphuric acid and water, which presents the key process associated with secondary aerosol formation via gas to particle conversion. We investigated the nucleation rates, new aerosol particles formation and growth dynamics of newly nucleated particles. These processes were explored in both laboratory and field experiments. In the laboratory measurements, we explored the H2SO4 - H2O nucleation rates and growth rates of newly formed particles under well-defined conditions and we also investigated the effect of experimental conditions on particle growth dynamics. Furthermore, we proposed a model, which predicts the particle growth and accounts for condensation of H2SO4, H2O and NH3. The comparison of experimental growth rates with atmospheric ones was made and resulting implications of the chemical nature of compounds involved in the early growth of nucleated particles is also presented. To investigate the atmospheric H2SO4 - H2O nucleation and new particle formation, we analysed a two-year long dataset of particle number size distributions, obtained from a urban background station in Prague Suchdol. A special attention was given to a recently reported special feature of particle growth dynamics - a particle shrinkage following previous new...

L'activité volcanique peut représenter une source naturelle de pollution atmosphérique. Cette pollution peut engendrer une dégradation de la qualité de l'air, affecter la santé humaine et perturber la sécurité aérienne. Le Piton de la Fournaise à La Réunion est l'un des volcans basaltique les plus actifs au monde. Ses éruptions sporadiques génèrent des panaches volcaniques essentiellement constitués de gaz et de nanoparticules qui se propagent dans l'atmosphère. En journée, la formation d'oxydants (photolyse) permet d'oxyder une partie du dioxyde de soufre en acide sulfurique. Les molécules d'H2SO4 peuvent réagir avec les molécules d'eau atmosphérique pour former des embryons via la nucléation binaire homogène. Puis, ces embryons grossissent grâce aux processus de condensation et/ou coagulation conduisant alors à la formation d'un aérosol volcanique submicronique. Cette thèse vise à observer, comprendre et modéliser les processus de Formation de Nouvelles Particules (FNP) au sein des panaches volcaniques. De ce fait, elle s'organise en deux parties. La première se base sur les données recueillies lors de la campagne multidisciplinaire STRAP menée à l’observatoire du Maïdo et au Piton de la Fournaise en 2015. Elle expose les résultats issus d’une double analyse de la fréquence et de l’intensité des événements de FNP à l’observatoire. Tandis que la première analyse s’intéresse aux processus en l’absence du panache volcanique, la seconde met en exergue les spécificités de la FNP liées à sa présence au Maïdo. La seconde partie s'axe autour de la modélisation d'abord 0D puis 3D des processus de FNP au sein des panaches volcaniques via le modèle atmosphérique Méso-NH. / Volcanic activity can be a natural source of air pollution. This pollution can lead to a deterioration in air quality, affect human health and disrupt aviation safety. The Piton de la Fournaise in Reunion Island is one of the most active basaltic volcanoes in the world. Its sporadic eruptions generate volcanic plumes consisting mainly of gases and nanoparticles that spread in the atmosphere. During the day, a part of the sulphur dioxide can be oxidized to sulphuric acid thanks to oxidants production (photolysis). H2SO4molecules tend to react with atmospheric water molecules and form clusters via homogeneous binary nucleation. Then, these clusters grow by condensation and/or coagulation processes leading to the formation of a submicronic volcanic aerosol. This thesis aims to observe, understand and model the New Particle Formation (NPF) processes within volcanic plumes. Consequently, it is organized in two parts. The first is based on the data gathered during the multidisciplinary STRAP campaign conducted at both the Maïdo Observatory and Piton de la Fournaise volcano in 2015. It presents the results from a dual analysis of the NPF events frequency and intensity at the observatory. While the first analysis focuses on processes in the absence of the volcanic plume, the second highlights the specificities of the NPF related to the presence of the plume at Maïdo. The second part focuses on 0D then 3D NPF processes modelling within volcanic plumes via the Meso-NH atmospheric model.

The escalating pollution of the environment has been one of the greatest concerns of science in recent years. Industrial advances in agriculture, expansion of chemical industries and a general change in lifestyle all over the world has lead to release of a variety of pollutants into the environment, thus contaminating the atmosphere, water bodies and many soil environments. In general, other than some natural processes, soils are increasingly being contaminated by anthropogenic sources such as leakages from waste containment facilities, accidental spills and industrial operations. Apart from affecting biotic components of the ecosystem, these pollutants greatly affect the performance, behavior and stability of the soil ecosystem, these pollutants greatly affect the performance, behavior and stability of the soil systems, thus causing severe damage to structures founded on them. The hydraulic and/or chemical alterations which allow these polluting substances to move within soil pores lead to physico-chemical decomposition processes, chemical alterations, leaching and ion exchange reactions. Such reactions could also result from natural processes such as weathering; but the effects caused by pollutants occur at faster rates. Soils are composed of clays, silts and sands. Due to charged nature of the particles and their large specific surface, engineering properties of clays are greatly affected by pollutants. The magnitude of these effects can vary significantly depending on the type of soil, the type and concentration of contaminant, duration of interaction and the environmental conditions. Hence, an understanding of contaminant-clay interactions is important for prevention of geotechnical features, if possible, or at least for planning of remedial measures. Understanding these effects and planning remedial measures requires measurement of the affected properties of polluted soils. This may involve the modification of standard test procedures or the development of new test procedures. The main types of contaminants include inorganic acids, alkalis, sulphates, organic contaminants, toxic or phytotoxic metals and combustible substances. All of these are widely used in industries. While the adverse effects of presence of sulphate in alkaline conditions is well known, little information is available on the effect of sulphate in natural soils under acidic environments. Sulphuric acid is widely employed in the production of fertilizers, pharmaceuticals, pigments, rayon, film, iron, steel, explosives, paper and paper industry. It is also used in cleaning, etching, petroleum refining, electroplating, metallurgy, and in lead-acid batteries. Due to its widespread but often improper usage and the difficulty in safe storage, sulphuric acid is often found as a contaminant in natural soils. Sulphuric acid is also generated in natural soils by oxidation by pyrites in the presence of atmospheric oxygen. Hence, an attempt has been made in this thesis to study the behavior of soils containing different clay minerals during acid-sulphate interaction. The effect of sulphate on soils containing calcite, whose presence is quite common, has also been studied. A review of literature suggests that most common geotechnical failures due to contamination occur due to significant changes on the volume change behavior. Also, it is known that severe changes that occur in soil properties can essentially be attributed to mineralogical changes that occur during interaction with pollutants. Therefore, volume change behavior of soil and detailed mineralogical changes and the consequent morphological changes that occur in soils with acid sulphate are studied.

Abstract New methods are being sought for the production of chemicals, fuels and energy from renewable biomass. Lignocellulosic biomass consists mainly of cellulose, hemicellulose and lignin. Cellulose and hemicellulose can be converted to their building blocks, i.e. sugars, via hydrolysis. This thesis is focused on glucose production from cellulose by dilute acid hydrolysis. Acid hydrolysis has the drawback of limited glucose yields, but it has the potential to become a short-term solution for biochemical production. During acid hydrolysis, the cellulose chain is split into glucose, which undergoes further decomposition reactions to hydroxymethylfurfural, levulinic acid, formic acid and by-products like insoluble humins. The present thesis aims to increase our knowledge on complicated acid-catalysed hydrolysis of cellulose. Glucose decomposition and cellulose hydrolysis were studied independently in laboratory experiments. Kinetic modelling was used as a tool to evaluate the results. The effect of the hydrogen ion on the reactions was evaluated using formic or sulphuric acid as a catalyst. This thesis provides new knowledge of cellulose hydrolysis and glucose decomposition in formic acid, a novel catalyst for high-temperature dilute acid hydrolysis. Glucose yields from cellulose hydrolysed in formic or in sulphuric acid were comparable, indicating that a weak organic acid could function as a cellulose hydrolysis catalyst. Biomass fibres in the form of wheat straw pulp were hydrolysed more selectively to glucose than a model component, microcrystalline cellulose, using formic acid. Glucose decomposition took place similarly in formic and sulphuric acid when the temperature dependence of the hydrogen ion concentration was taken into account, but a significant difference was found between the reaction rates of cellulose hydrolysis in formic acid and in sulphuric acid. The observations can be explained by changes in the cellulose hydrolysis mechanism. Thus, it is proposed in this thesis that side-reactions from cellulose to non-glucose compounds have a more significant role in the system than has earlier been understood. / Tiivistelmä Uusia menetelmiä etsitään kemikaalien, polttoaineiden ja energian valmistamiseen uusiutuvasta biomassasta. Eräs biomassa, ns. lignoselluloosa, koostuu pääasiassa selluloosasta, hemiselluloosasta ja ligniinistä. Selluloosa ja hemiselluloosa voidaan muuttaa hydrolyysin avulla niiden rakennuspalikoikseen eli sokereiksi. Tämä väitöskirja keskittyy glukoosin tuottamiseen selluloosasta laimean happohydrolyysin menetelmällä. Happohydrolyysi kärsii rajoittuneesta glukoosin saannosta, mutta sillä on potentiaalia tulla lyhyen aikavälin ratkaisuksi biokemikaalien tuotannossa. Happohydrolyysin aikana selluloosaketju pilkkoutuu glukoosiksi, joka reagoi edelleen hajoamisreaktioiden kautta hydroksimetyylifurfuraaliksi, levuliini- ja muurahaishapoiksi ja kiinteäksi sivutuotteeksi. Tämän tutkimuksen tavoitteena on kasvattaa ymmärrystämme monimutkaisesta happokatalysoidusta selluloosan hydrolyysistä. Glukoosin hajoamista ja selluloosan hydrolyysiä tutkittiin erikseen laboratoriokokein. Kineettistä mallinnusta käytettiin työkaluna arvioimaan tuloksia. Vety-ionien vaikutus reaktioihin arvioitiin käyttämällä muurahais- ja rikkihappoja katalyytteinä. Tämä väitöskirja antaa uutta tietoa selluloosan hydrolyysistä ja glukoosin hajoamisreaktioista muurahaishapossa, joka on uusi katalyytti korkean lämpötilan laimean hapon hydrolyysissä. Glukoosisaannot muurahaishappo-hydrolysoidusta selluloosasta olivat vertailukelpoisia vastaaviin rikkihappo-hydrolyysi saantoihin. Tämä viittaa siihen, että heikko orgaaninen happo voisi toimia selluloosahydrolyysin katalyyttinä. Kun katalyyttinä käytettiin muurahaishappoa, vehnän oljesta tehdyt kuidut hydrolysoituivat selektiivisemmin glukoosiksi kuin mallikomponenttina toimineen mikrokiteisen selluloosan. Kun vetyionikonsentraation lämpötilariippuvuus otettiin huomioon, glukoosi hajosi samalla tavalla sekä muurahais- että rikkihappokatalyytissä, mutta merkittävä ero havaittiin selluloosahydrolyysin reaktionopeudessa. Havainnot voidaan selittää selluloosahydrolyysin mekanismissa tapahtuvilla muutoksilla. Väitöskirjassa esitetään, että sivureaktioilla selluloosasta ei-glukoosi-tuotteiksi on merkittävä vaikutus systeemiin.

This work examines an electrochemical determination of mixed nitric and sulphuric acid solution that is formed during calorimetric determination of gross calorific value of coal carried out under the ISO 1928:1995 standard. Knowing the amount of these acids is necessary for calculating net calorific value. The named standard only allows use of volumetric methods which are time-consuming. Conductivity and ion-selective measurements were used here which significantly shortened analysis time. Overall conductivity measurement was taken with a 4-electrode meter while nitric acid was measured with a nitrate ISE by known addition method. Sulphuric acid was then calculated according to actual temperature. This research has defined the calibration relations and temperature effect. Several simulated and real-world samples were analysed and the method was evaluated for a possible use in a future automated analyser.

This diploma thesis is concerned with the design of the machinery with an extraction steam condensing turbine in Precheza corp. The theoretical part of this thesis describes the energetical situation in the company and the primary consideration about recovery of the heat, released at sulphuric acid production, for electrical power production. There is also presented brief description of the sulphuric acid production and the fundamental principles of the steam production at this process. In the practical part of this thesis there is performed the calculation of the heat-flow diagram of the steam turbine and the calculation of heat and producted electrical power at the basic operational states. There is presented the source code for the calculation of the heat-flow diagram using Matlab software. In the end there is mentioned the economical evaluation of the whole project, using the fundamental economical methods, such as net present value method, or profitability index, including the calculation of the pay-back period.

Résumé Les rejets des Usines à Zinc de Kolwezi contiennent majoritairement du zinc sous forme réfractaire (ferrite) au traitement hydrométallurgique conventionnel. Ils contiennent d’autres métaux « lourds » qui les rendent dangereux vis-à-vis de l’environnement dans lequel ils sont actuellement entreposés. Ces métaux, dont la plupart peuvent être valorisés, font de ces rejets un véritable gisement secondaire. Il est donc impératif de mettre au point un procédé adéquat de valorisation ; d’où le thème de la présente thèse : « Etude de valorisation des rejets des Usines à Zinc de Kolwezi, RDC ». A l’aide des techniques modernes de caractérisation (physico–chimique, minéralogique et morphologique), nous sommes arrivés à cibler, à adapter et à justifier l’utilisation d’une technique de valorisation des matières minérales existantes. Les minéraux utiles contenus dans les rejets UZK ont été sulfatés par digestion et sélectivement mis en solution après un grillage. La sulfatation s’est avérée l’étape déterminante du procédé et un intérêt particulier a été focalisé sur cette étape en réalisant une étude cinétique approfondie. Les données et informations récoltées tout le long de cette recherche nous ont permis de réaliser une simulation du procédé par le logiciel ASPEN PLUS. Ce qui a permis de faire une ébauche d’un schéma de traitement industriel. Ce dernier s’est avéré souple vis-à-vis de l’utilisation d’autres matières comme les calcines des concentrés sulfurés cuivre-zinc. Residues from the Kolwezi Zinc Plant (Usines à Zinc de Kolwezi UZK) essentially contain zinc in a refractory (ferrite) form, which is difficult to recover by conventional hydrometallurgical methods. « Heavy» metals are also present that make them hazardous towards the environment in which they are currently stored. Most of these metals are valuable; thus, the UZK residues are a real secondary deposit. It is therefore imperative to develop an appropriate method of treatment, hence the theme of the present thesis: « Recovery study of values metals from Kolwezi Zinc Plant residues, DRC ». Using modern techniques of characterization (physical and chemical, mineralogical and morphological), we focused, adapted and justified the use of a technique for efficient recovery of the existing valuable minerals. The minerals contained in UZK residues have been sulphated by digestion and thereafter selectively dissolved after roasting. Sulphatation proved to be the decisive step of the process and a particular attention has been given to this step by performing a detailed kinetic study. The data and information collected throughout this research allowed a simulation of the developed method by using the « Aspen Plus » software. This allowed us to propose a draft scheme of industrial processing. The latter proved flexible towards the use of other materials such as calcines of copper-zinc sulphide concentrates.

Les rejets des Usines à Zinc de Kolwezi contiennent majoritairement du zinc sous forme réfractaire (ferrite) au traitement hydrométallurgique conventionnel. Ils contiennent d’autres métaux « lourds » qui les rendent dangereux vis-à-vis de l’environnement dans lequel ils sont actuellement entreposés. Ces métaux, dont la plupart peuvent être valorisés, font de ces rejets un véritable gisement secondaire. Il est donc impératif de mettre au point un procédé adéquat de valorisation ;d’où le thème de la présente thèse :« Etude de valorisation des rejets des Usines à Zinc de Kolwezi, RDC ». <p>A l’aide des techniques modernes de caractérisation (physico–chimique, minéralogique et morphologique), nous sommes arrivés à cibler, à adapter et à justifier l’utilisation d’une technique de valorisation des matières minérales existantes. Les minéraux utiles contenus dans les rejets UZK ont été sulfatés par digestion et sélectivement mis en solution après un grillage. La sulfatation s’est avérée l’étape déterminante du procédé et un intérêt particulier a été focalisé sur cette étape en réalisant une étude cinétique approfondie.<p>Les données et informations récoltées tout le long de cette recherche nous ont permis de réaliser une simulation du procédé par le logiciel ASPEN PLUS. Ce qui a permis de faire une ébauche d’un schéma de traitement industriel. Ce dernier s’est avéré souple vis-à-vis de l’utilisation d’autres matières comme les calcines des concentrés sulfurés cuivre-zinc.<p><p>Residues from the Kolwezi Zinc Plant (Usines à Zinc de Kolwezi UZK) essentially contain zinc in a refractory (ferrite) form, which is difficult to recover by conventional hydrometallurgical methods. « Heavy» metals are also present that make them hazardous towards the environment in which they are currently stored. Most of these metals are valuable; thus, the UZK residues are a real secondary deposit. It is therefore imperative to develop an appropriate method of treatment, hence the theme of the present thesis: « Recovery study of values metals from Kolwezi Zinc Plant residues, DRC ».<p>Using modern techniques of characterization (physical and chemical, mineralogical and morphological), we focused, adapted and justified the use of a technique for efficient recovery of the existing valuable minerals. The minerals contained in UZK residues have been sulphated by digestion and thereafter selectively dissolved after roasting. Sulphatation proved to be the decisive step of the process and a particular attention has been given to this step by performing a detailed kinetic study. <p>The data and information collected throughout this research allowed a simulation of the developed method by using the « Aspen Plus » software. This allowed us to propose a draft scheme of industrial processing. The latter proved flexible towards the use of other materials such as calcines of copper-zinc sulphide concentrates.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished