Microbial-influenced corrosion (MIC) has been widely recognized as a significant economic and environmental problem in the oil and gas industry. MIC can be classified into two types based on the mechanisms: the extracellular electron transfer MIC (EET-MIC) and the metabolite MIC (M-MIC). The first includes electroactive bacteria that facilitate EET, while the latter includes bacteria that secrete corrosive metabolites. Sulfate-reducing bacteria (SRB) is believed to cause EET-MIC in carbon steel, a widely used metal in the oil and gas industry. In previous electroactive bacteria studies, nanowires have been shown to facilitate EET by acting as electron mediators. This study investigates the use of magnetite nanowires as electron mediators to accelerate EET-MIC of C1020 by Desulfovibrio vulgaris. The addition of 40 ppm (w/w) nanowires to carbon steel incubated with D. vulgaris, corrosive SRB species, for seven days resulted in 45% weight loss and 57% deeper pitting of carbon steel. Furthermore, electrochemical measurements of open circuit potential, linear polarization resistance and potentiodynamic polarization were found to be parallel with weight loss and pitting results. Therefore, these findings highlight the possibility of using magnetic nanowires as an electron mediator with high efficiency and selectivity to EET-MIC for future MIC studies and applications.

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Eleven gas species, including CO, CO2, H2, H2O, H2S, HCl, NOX, O2, SO2, COS and SO3, were measured in a 150 kWth, staged, pulverized coal, down-fired combustor using a Fourier transform infrared (FTIR) spectrometer, gas chromatograph (GC), and a Horiba PG-250 5-gas analyzer. Additional gases such as HCN, NH3, CH4, and other hydrocarbons were also measured. Seven coals of varying rank and composition were investigated. Measurements were obtained in reducing (S.R. = 0.85) and oxidizing (S.R. = 1.15) conditions. In particular, sulfur- and chlorine-containing species including H2S, SO2, COS, SO3, and HCl are discussed. In the reducing zone, all four measured sulfur species were present although SO3 was only 1-3% of the total coal sulfur. A trade-off between SO2, H2S, and COS was clearly identifiable according to S.R. H2S and COS increased and SO2 decreased in highly reducing or high-CO regions. The total amount of sulfur in the measured species in the reducing zone was estimated to be about 65-80% of the total coal sulfur. The total amount of sulfur measured in the four gases increased linearly with coal sulfur in both the oxidizing and reducing zones for the seven coals considered. In the oxidizing zone, SO3 remained low (1-3% of total sulfur) with the only other measurable sulfur bearing species being SO2. Chlorine was found to be released in the reducing zone and form primarily HCl. As the HCl was transported into the oxidizing region, the chlorine remained as HCl. Measurement of HCl was difficult, making some of the data incomplete. The HCl concentration was found to be affected by the flow rate of gases into the sampling line and gas analyzers suggesting HCl is highly reactive and needs to be quenched rapidly or it will react during sampling. Several trends in the data were matched by equilibrium calculations including trends for H2S, COS and SO2 in both reducing and oxidizing conditions. SO3 did not match equilibrium although the amount of SO3 was proportional to the amount of sulfur in the coal. HCl, though consistent with cited literature for several coals, did not agree with equilibrium trends or values.

M. S.

[pt] O presente trabalho consiste de um modelo matemático termoquímico de simulação do processo Tecnored de produção de ferro primário, construído através do estudo e equacionamento da fenomenologia do processo, levando em consideração os aspectos termodinâmicos e operacionais, bem como a geometria do reator. Apesar de ser um modelo estático, considerações cinéticas de laboratório e de planta piloto foram usadas para estimar a extensão das principais reações químicas nas diferentes regiões do forno. Para construção do modelo o reator foi dividido em três zonas, a saber: cuba superior, zona de amolecimento e fusão, e cuba inferior. Para cada uma das zonas foram descritas as fenomenologias e reações químicas envolvidas, condicionadas ao balanço global das espécies químicas presentes no processo. As saídas do programa permitiram uma análise da engenharia de processo global e estagiada. Através do modelo construído é possível prever o comportamento do processo com diferentes tipos de matériasprimas e em diferentes condições operacionais. Adicionalmente, o modelo servirá para a checagem da operação do primeiro forno industrial desta tecnologia, atualmente em construção, comparando com os dados obtidos através da operação da planta piloto. Os resultados obtidos mostraram que a técnica de modelagem utilizada constitui-se em uma poderosa ferramenta de análise global e estagiada, confirmando as vantagens de consumo de combustível, eficiência energética e de geração de gases do processo Tecnored em relação à tecnologia tradicional do alto-forno. / [en] The present work consists of a Tecnored ironmaking process oriented thermo-chemical modeling, built after a thorough assessment of the process phenomena and considering besides the peculiarities of the reactor, a number of applicable thermodynamic and operational aspects. In spite of being a thermochemical model, bench scale and pilot plant based kinetics considerations have been taken in account in order to estimate the extension of the main reactions in different parts of the furnace. The framework involved the division of the furnace in three main zones, namely Solid-state Reduction Zone (SRZ), Softening and Melting Zone (SMZ) and Dripping and Hearth Zone (DHZ). In each of the zones the existing chemical processes and overall process phenomena have been evaluated conditional to the global mass balance ruling the process. The model developed shall be used onwards to predict the behavior of the process under different conditions of raw material usage and operational modes. Moreover, the model shall be applied to compare the results of the industrial plant (under construction) with the available bench and pilot plant data, with the intention of gathering information to be used in the optimization of the model and subsequently the process. The results obtained thus far show that the applied modeling technique is a powerful tool for the global and stage-wise analysis of the process, confirming the advantageous performance of the technology as far as fuel-rate, thermal efficiency and environmental soundness are concerned.

Acid mine drainage (AMD) is an acidic, iron-rich leachate that causes the dissolution of metals. It constitutes a worldwide problem of environmental contamination detrimental to aquatic life and water quality. AMD, however, is naturally attenuated at Davis Mine in Rowe, Massachusetts. We hypothesize that sulfate-reducing bacteria (SRB) are attenuating AMD. To elucidate the mechanisms by which SRB attenuate AMD, three research projects were conducted using a suite of molecular and geochemical techniques. First we established biological influence on the attenuation of AMD by comparing the microbial community and geochemical trends of microcosms of two contrasting areas within the site: AMD attenuating (AZ) and AMD generating (GZ) zones. The differences in geochemical trends between these zones were related to differences in microbial community membership. SRB were only detected in microcosms of the AZ, while iron oxidizers were only detected in the GZ. This study indicates that biological activity contributes to the attenuation of AMD and that SRB may have a role. To further describe the role of SRB, we determined the rates of sulfate reduction, the abundance, and membership of SRB in the second project. The sulfate reduction rate was weakly correlated with the abundance of SRB. This indicates that the SRB population may be utilizing another electron acceptor. One such electron acceptor would be iron, which was investigated in the third project. When SRB are inhibited, neither accumulation of reduced iron nor the formation of reduced iron sulfide precipitates occurred. Higher concentration of sulfide produced an increase in reduced iron and pH. Therefore, iron reduction mediated by reaction with biogenic sulfide contributes to the attenuation of AMD. This is the first report of the biological enhancement of iron reduction by acidotolerant SRB. The interdisciplinary research described in this dissertation provides evidence that SRB attenuate AMD through sulfate and iron reduction and a greater understanding of SRB in acidic environments. It also demonstrates how the biogeochemical cycling of sulfur is coupled to the iron cycle. Overall, the ubiquity and metabolic versatility of SRB offers boundless potential and exciting opportunities of study in the fields of bioremediation, geomicrobiology, and microbial ecology.

Pu (III) is one of the key elements in the safety assessments of Canadian deep geological repository program (DGR). Sorption is a potential mechanism for retarding radionuclide transport from a DGR to the environment. In the current scenario, Pu (III) is considered to be a dominant radioactive element in the deep geological groundwater. Eu, considered to be a chemical analogue of Pu (III), its sorption behavior is now the target of our research. This thesis investigates the sorption properties of Eu on MX-80 under saline reducing conditions, and highly saline reducing conditions. The thermodynamic sorption modelling of Eu is also need to be applied. A surface sorption model is also developed by applying computer program for Eu (III) on MX-80 to investigate the sorption mechanisms of Eu (III) sorption. / Thesis / Master of Applied Science (MASc)

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