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What kinetic and thermodynamic characteristics are established in a melt of hydrogen-reduced iron ore pellets? The pellets contain self-fluxing slag components which upon melting form an initial slag. Refining capabilities of this slag, such as dephosphorization power, are investigated in a lab-scale vertical furnace. Understanding the initial slag and the reactions taking place when hydrogen-reduced iron ore pellets melt is important for future optimization of ingoing raw materials as well as industry scale process design. A sample of either crushed hydrogen-reduced iron ore pellets or a powder mixture representative of iron ore pellets in terms of composition was melted in a lab-scale vertical furnace. The sample was lowered into the argon atmosphere furnace which had a temperature of 1600°. The sample was kept inside a magnesia crucible with a molybdenum loosely-fitted lid. The purpose of the lid was to fix the oxygen partial pressure. The reduction degree of the pellets or corresponding powder mixture as well as the total melting times were varied. XRF and OES analysis were employed to find the composition of the slag and metal phases, respectively. SEM analysis was employed to investigate phases present in the slag. Comparison of melted iron ore pellets and corresponding powder mixture show that powder can be employed to represent reduced iron ore pellets accurately. It was found that reduction degree strongly impacts both phosphorus and vanadium distributions as well as the types of phases formed in the slag fraction. During melting, almost all of the Vanadium and most of the Phosphorus content goes to the slag fraction. At lower reduction degrees, dephosphorization is greater; however, the Phosphorus content in the steel is still quite high at 130 ppm or higher. Modification to the amount and/or composition of the self-fluxing slag is suggested to reach lower levels of phosphorus in the steel. / Vilka kinetiska och termodynamiska egenskaper skapas i en smälta av vätgasreducerade järnmalmspellets? Pellets innehåller självflussande slaggkomponenter som vid smältning bildar en initial slagg. Slaggens raffineringsförmåga, till exempel fosforreningsförmåga, undersöks i laboratorieskala. För framtida optimering av ingående råvaror såväl som industriellskalig processdesign är det viktigt att förstå den initiala slaggen samt de reaktioner som äger rum vid nedsmältning av vätgasreducerade järnmalmspellets. Ett prov av antingen krossade vätgasreducerade järnmalmspellets eller en pulverblandning som är representativ för järnmalmspellets med avseende på sammansättning smältes ned i en laboratorieskalig vertikal ugn. Ugnen hade en argonatmosfär och temperatur på 1600°C då provet sänktes ner i ugnen för smältning. En magnesiumoxiddegel med ett löst inpassat molybdenlock användes som behållare för provet under nedsmältningen. Syftet med locket var att kontrollera syrgaspartialtrycket. Reduktionsgraden av pellets eller motsvarande pulverblandning såväl som de totala smältningstiderna varierades. XRF och OES mätverktyg användes för att undersöka sammansättning av slagg- och metallfraktionerna. SEM analys användes för att identifiera närvarande faser i slaggfraktionen. Jämförelse av nedsmälta vätgasreducerade järnmalmspellets med motsvarande pulverblandning visar att de två är representativa av varandra till stor grad. Resultaten visar på att reduktionsgraden påverkar starkt både fosfor- och vanadinfördelningarna samt faserna som bildas i slaggfraktionen. Vid smältning går nästan all mängd vanadin och majoriteten av fosfor till slaggfraktionen. Vid lägre reduktionsgrader är fosforreningen bättre. Fosforhalten i stålet är relativt hög och har ett värde på 130 ppm eller högre för samtliga prover. Ändring av mängden och/eller sammansättning av den självflussande slaggen rekommenderas för att nå lägre nivåer av fosfor i stålet.

Much attention has been recently devoted to sensorially active substances affecting beer quality in the Czech Republic and worldwide. Among them, the heterocyclic and sulphur containing compounds play an important role, some of them with high sensorial activity even in extremely low concentrations. Trace amounts of these compounds, which can be frequently found in foods, participate in formation of their aroma and this effect can be generally evaluated as favorable However, in malt or beer it is true only to a limited extent and the presence of heterocyclic and sulphur containing compounds are in this respect assessed rather unfavorably. The aim of the present study was to provide a survey about of problems in the field of sulphur containing compounds in barley, malt and beer, to describe metabolic paths leading to their formation and to verify experimentally possibilities of their determination using modern analytical methods. Sulphur-containing amino acids are a natural part of barley, malt and beer and are precursors of the origin of volatile sulphur substances. The most frequently occurring sulphur amino acids, metionine, cysteine and homocysteine, were selected for analytical monitoring. The method of gas chromatography was used to determine sulphur-containing amino acids in barley, malt and beer. Prior to the analysis, sulphur-containing amino acids were derived and volatile N(O,S)-ethoxycarbonyl propyl esters were formed; they were subsequently analyzed using the gas chromatography with mass detector (GC/ MSD) and the gas chromatography with flame photo detector (GC/ FPD). Direct analysis of sulphur volatile substances is possible only rarely as they are found in the analyzed matrices (malt, beer) only in very low concentrations ( g/kg,l - ng/kg,l). Before the analysis, the analytes must be extracted from the matrix and concentrated. The modern analytical methods SPME (Solid Phase Micro Extraction), SPDE (Solid Phase Dynamic Extraction) and TDAS (Thermal Desorption Autosampler) were experimentally compared for the extraction and subsequent concentration of sulphur volatile substances. The method of gas chromatography with flame photo detector was used to determine sulphur volatile substances. Following volatile sulphur substances were monitored: dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, carbon disulphide, ethyl sulphide, diethyl disulphide, methionol, 3-methylthiophen, ethyl thioacetate, 2-methyl-1-buthanthiol. Only metionine was detected in significant amounts in the barley samples analyzed. Not only content but also dependence on a variety and locality were studied. Further, changes in methionine, cysteine and PDMS content during malting were followed. Results proved a significant decline in these substances content depending on the kilning temperature. Three types of fibers were tested for the analyses of the selected volatile sulphur substances in beer in the SPME method. PEG - a fiber with stationary phase Carbowax, PDMS - a fiber with stationary phase polydimethylsiloxan and a combined fiber CAR/PDMS - Carboxen and polydimethylsiloxan. Carbon disulphide, methionol, dimethyl sulphide, 3-methylthiophen and diethyl disulphide were detected with this method. Content of the other analyzed volatile sulphur substances was below the limit of detection. Further was tested usage the SPDE and TDAS methods. Both methods appear to be the suitable for the determination of volatile sulphur substances in beer.

<p> The sulphur dioxide converter of the contact sulphuric acid plant ~f the Hamilton Works of Canadian Industries Ltd., is optimized using the so2 conversion as the objective function to be maximized. The simulation model used is fitted to the plant data. The number of beds, the inlet temperatures, the catalyst bed depths and the air addition are the variables considered in this work. The effect due to the imposition of a constraint on the system is also examined. </p> <p> Four integration techniques are studied to solve the set of nonlinear ordinary differential equations that simulates the transformation in a bed. The Runge-Kutta third-order is found to be the most efficient. </p> <p> Four optimization techniques, namely, dynamic programming, gradient search, direct search of Hooke and Jeeves and discrete maximum principle, are used. Their applicability and efficiency are compared. </p> <p> A very flat response (conversion) surface is found in the neighbourhood of the optimum. </p> <p> The optimal operating conditions are compared with the simulation of the C.I.L. operation. The reachability of these optimal conditions in the plant is also considered. </p> / Thesis / Master of Engineering (ME)

The kinetics for sulphidation on a Ni-20 wt. % Cr alloy at 700ºC and sulphur potentials below 10⁻⁹ atmospheres have been studied using a thermogravimetric technique. The morphology of the reaction product was studied using optical microscopy, electron probe microanalysis and X-ray techniques. The kinetics were observed to be parabolic at sulphur potentials below 5 x 10⁻¹⁰ atmospheres with rates much slower than those reported for pure chromium under similar conditions. The parabolic kinetic reaction rate constant was found to vary as a semilogarithmic function of sulphur potential. The reaction product consisted of an external scale, identified as mainly Cr₃S₄, with dissolved nickel up to 5% and a subscale with morphological break-down of the alloy/external scale interface. Approximate determinations of the diffusivity of chromium in the alloy and the scale as well as sulphur diffusivity in the alloy have been made. Tentative mechanisms have been proposed to explain the diffusion control of the reaction and the stabilization of the external scale by dissolved nickel. / Thesis / Master of Engineering (ME)

<p> The dominant slag-metal reaction site in AC electro-slag remelting (ESR) has been directly determined by estimating the rate of sulphur transfer at the electrode tip/slag and metal pool/slag interfaces. In this investigation, negligible sulphur transfer has been assumed at the droplet/slag interface, and the basis for such assumption is discussed. Using a 5.825" diameter mould and CaF2-CaO slags, it has been established that the electrode tip/slag interface is the dominant reaction site. Calculations indicate that the pool sulphur is close to equilibrium with the slag. The importance of all six reaction sites in AC ESR are discussed. The results indicate the importance of the slag/atmosphere interface, especially when using slags of low lime content. Conventonal overall sulphur balances have been carried out and the results are in agreement with the rates obtained at the different interfaces, thus indicating internal consistency of the results. </p> / Thesis / Master of Engineering (MEngr)

In the presented work, the compatibility of photoelectric readout of the spin state of nitrogen vacancy centers with the recently discovered strong creation yield en- hancement for these centers by sulfur doping of the host material was successfully demonstrated. For this purpose, first a measurement setup was built, where photoelectric detection of magnetic resonance is possible in the continuous wave as well as in the pulsed mode. Using this setup and a diamond sample that was prepared with ion implan- tation, it could be proven by a suitable separation of the measurement spots as well as the selected sequence of implantation and measurement steps that photoelectric spin readout is not only possible despite strong sulfur doping, but in fact also results in a moderate improvement of the signal-to-noise ratio. However, the investigations also reveal the occurrence of an additional photocurrent associated with the sulfur doping, which could be observed delocalized from the implantation site on the entire sample. This additional photocurrent represents a significant interfering signal at least for the continuous wave mode, which is, however, the less relevant operation mode for spin readout. In the last part of this work, efforts have been made to understand the interfering signal and its origin in more detail. Investigations of the electrical conductivity of the sample as a function of the wavelength of the excitation light revealed impor- tant properties that clearly narrow down the field of potential sources, although no definite identification was possible.

No description available.

The variation in the carbon isotope composition of the cap rock of Texas and Louisiana sulphur wells was investigated by means of a simultaneous collection mass spectrometer. These rocks showed anomalously large depletions in C-13. The isotope depletion in the decarboxylation of pyruvic acid, both by chemical means and by bacteria, was measured and the isotope composition of the carbon dioxide released was found to be similar to that of the cap rock. The hypothesis is advanced that the carbonate of the cap rock may have originated by the precipitation of carbon dioxide released in the bacterial decarboxylation of an organic substrate. / Thesis / Master of Science (MSc)

No description available.