Nickeliferous laterite ores are currently processed using complex energy intensive flowsheets. Limited mineral upgrading can be achieved by low-cost mineral processing as the nickel is not found as a separable mineral phase but finely disseminated throughout the host goethite mineral. Whole ore extraction processes are required which result in intrinsically higher capital and operating costs. Market pressure has provided incentives to develop alternative upgrading techniques that can produce a nickel concentrate and reduce the material input to downstream processing facilities. Thermal upgrading through a selective reduction mechanism to produce a ferronickel concentrate has been studied extensively and has shown promising potential. In this research, a two stage selective reduction of nickeliferous laterite ore was investigated at 600oC and 1000 – 1100oC with varying coal and sulphur additions. Experiments showed that the limonite ore could be selectively reduced using a coal additive to a ferronickel and wustite phase. A combination of XRD and bromine/methanol diagnostic leach tests confirmed the presence of metallic nickel and iron in the calcine. Higher degrees of metallization corresponded with higher sulphur additions and growth zone temperatures. Sulphur was added to improve particle growth through the establishment of a Fe-O-S liquid phase, which was found to improve Ni recovery from 13.8% to 75.8% over the range of 0 – 4 wt% S. Ferronickel particles ranging in size from 20 – 60 microns were shown to be present but highly dispersed throughout the upgraded ore. Particle growth improved with higher growth zone temperatures and longer retention times. Magnetic separation of the calcine showed maximum upgrading of grades to 3 – 4 wt% nickel with recoveries ranging from 83.7 – 93.2%. Partial oxidation of wustite particles to magnetite caused the particles to be magnetic and resulted in recovery of unwanted iron oxides. The presence of iron oxide fines was believed to allow for rapid oxidation of wustite phase and also produce slimes that hindered physical separation of the upgraded ore. / Thesis (Master, Mining Engineering) -- Queen's University, 2013-12-29 22:34:20.417

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21122号 / 工博第4486号 / 新制||工||1697(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 陰山 洋, 教授 佐藤 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

[pt] Os materiais nanoestruturados têm sido estudados ao longo das últimas décadas, por apresentarem propriedades particulares, promissoras propriedades térmicas, mecânicas e catalíticas, que muitas vezes não estão presentes no material não manométrico. Alguns avanços recentes têm mostrado que estas propriedades podem ser reforçadas pela inclusão de materiais com propriedades diferentes na sua estrutura, formando assim nanocompósitos. Por exemplo, as ligas de CuNi são muito dúcteis, mas a presença de nanopartículas de Al2O3 depositadas na matriz pode melhorar consideravelmente a dureza do material. Tal nanocompósito pode ser obtido, por exemplo, através de decomposição térmica nitratos, seguido por redução seletiva com hidrogênio. Nesse contexto, o presente trabalho tem como foco a síntese de ligas de CuNi e CuNi com adição de nanoparticulas de Al2O3, baseados na redução seletiva de CuO e de NiO com H2, e óxidos coformados com o óxido de alumínio por meio da decomposição térmica de seus nitratos metálicos. Cálculos termodinâmicos mostraram que a redução de Cu e Ni pode ser realizada a temperaturas relativamente baixas (400 mais ou menos 5 Graus C), e também que o processo se desenvolve seletivamente (apenas os óxidos de Ni e de Cu reagem nas condições impostas), resultando em compósitos de CuNi/Al2O3, que consiste na formação de uma liga CuNi contendo 1 por cento de Al2O3 como finas nanopartículas distribuídas homogeneamente. Precursores e amostras reduzidas foram caracterizados por difração de raios x (DRX) para determinar a natureza das fases individuais presentes (óxidos e ligas), microscopia electrónica de varredura (MEV) como uma primeira aproximação da morfologia das partículas e microscopia eletrônica de transmissão (MET). Os resultados obtidos indicam que a via química proposta resultou satisfatória para a elaboração das ligas CuNi contendo nanopartículas de Al2O3 homogeneamente distribuídas. Os resultados obtidos também indicam que, para as condições experimentais impostas tanto a decomposição dos nitratos como as reações de redução alcançaram conversões de 100 por cento. / [en] Materials containing nanostructured particles have been studied over the last decades in order to take advantage of their promising thermal, mechanical and catalytic properties. Some recent progress has shown that these properties can be further enhanced by the inclusion of materials with different properties in their structure, thereby forming nanocomposites. For instance, Ni-Cu alloys are highly ductile, but the presence of Al2O3 nanoparticles deposited inside the alloy matrix can considerably improve the material s hardness. Such a nanocomposite can be obtained, for example, through nitrate solutions thermal decomposition followed by selective reduction with hydrogen. In this context, the present work focuses on the synthesis of CuNi alloys and CuNi/Al2O3 composites based on the selective reduction of copper and nickel oxides with pure H2, co-formed with aluminum oxide through thermal decomposition of aqueous solutions of their metal nitrates. Thermodynamic computations showed that the Cu and Ni reduction can be accomplished at relatively low temperatures (400 plus or minus 5 C degrees), and also that the process develops selectively (only the oxides of Ni and Cu react at the imposed conditions), resulting in Cu-Ni-Al2O3 composites, consisting in a Cu-Ni alloy crystals containing 1 percent of Al2O3 as fine homogeneously distributed nanoparticles. Both the original (co-formed) and reduced oxide samples were characterized using x ray diffraction (XRD) for determining the nature of the individual phases present (oxides and alloys) and scanning electron microscopy (SEM) as a first approach to the investigation of the morphology of the particles. The results indicate that the proposed chemical route resulted in composite materials containing CuNi alloy and Al2O3 particles of controllable composition and homogeneously distributed among the samples. The achieved results also suggest that for the imposed experimental conditions both the nitrate decomposition as well as the reduction reactions could be conducted to 100 percent conversion.

No description available.

The subject of this study is the effect of in-cylinder selective non-catalytic reduction (SNCR) of NOx emissions in diesel exhaust gas by means of direct injection of aqueous urea ((NH2)2CO) into the combustion chamber. A single cylinder diesel test engine was modified to accept an electronically controlled secondary common rail injection system to deliver the aqueous urea directly into the cylinder during engine operation. Direct in-cylinder injection was chosen in order to ensure precise delivery of the reducing agent without the risk of any premature reactions taking place. Unlike direct in-cylinder injection of neat water, aqueous urea also works as a reducing agent by breaking down into ammonia (NH3) and Cyanuric Acid ((HOCN)3). These compounds serve as the primary reducing agents in the NOx reduction mechanism explored here. The main reducing agent, aqueous urea, was admixed with glycerol (C3H8O3) in an 80-20 ratio, by weight, to function as a lubricant for the secondary injector. The aqueous urea injection timing and duration is critical to the reduction of NOx emissions due to the dependence of SNCR NOx reduction on critical factors such as temperature, pressure, reducing agent to NOx ratio, Oxygen and radical content, residence time and NH3 slip. From scoping engine tests at loads of 40 percent and 80 percent at 1500 rpm, an aqueous urea injection strategy was developed. The final injection strategy chosen was four molar ratios, 4.0, 2.0, 1.0 and 0.5 with five varying injection timings of 60, 20, 10, 0, and -30 degrees after top dead center (ATDC). In addition to the base line and aqueous urea tests, water injection and an 80-20 water-glycerol solution reduction agent tests were also conducted to compare the effects of said additives as well. The comparison of baseline and SNCR operation was expected to show that the urea acted as a reducing agent, lowering NOx emissions up to 100% (based on exhaust stream studies) in the diesel exhaust gas without the aid of a catalyst. The data collected from the engine tests showed that the aqueous urea-glycerol solution secondary had no effect on the reduction of NOx and even resulted in an increase of up to 5% in some tests. This was due to the low average in-cylinder temperature as well as a short residence time, prohibiting the reduction reaction from taking place. The neat water and water-glycerol solution secondary injection was found to have a reduction effect of up to 59% on NOx production in the emissions due to the evaporative cooling effect and increased heat capacity of the water.