The blast furnace is still the dominant form of iron production, but over the years, direct reduction methods have increased due to a number of reasons. Overall, iron production methods have optimal requirements with respect to the feed materials especially iron ore. In this study, tests were carried out on Muko iron ore from Uganda to analyse its suitability to meet the feed requirements of today's dominant iron production methods. More specifically, the Tumbler, Abrasion, and Shatter Indices of the ore were determined. In addition, porosity, thermoanalysis, and reducibility tests were performed. Overall, the Muko ore was found to have good mechanical properties exemplified with tumble and shatter index data &gt;89.0 wt% and &lt;2.5 wt%, respectively. Furthermore, its reducibility at 0.87%/min is within the acceptable range as a natural material feed for blast furnace and direct reduction furnaces. Also, the energy requirement for heating the ore to 1100°C was found to be higher in the samples containing a wider size range of irregular grains and the largest contaminations. In summary, it is concluded that the Muko iron ore has good physical and metallurgical properties to serve as a natural material for the blast furnace and direct reduction furnaces. / <p>QC 20130531</p> / Sustainable Technology Development in the Lake Victoria Region

Thesis (Ph. D.)--University of New South Wales, 2005. / Also available online.

This project examined the reduction and formation of cementite from hematite and titanomagnetite ores and cementite stability. The aim of the project was to develop further understanding of cementite stability under conditions relevant to direct ironmaking and the mechanism of cementite decomposition. The reduction of hematite and ironsand by hydrogen-methane-argon gas mixtures was investigated from 600??C to 1100??C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The hematite ore was reduced more quickly than the ironsand. Preoxidation of the ironsand accelerated its reduction. Hematite was converted to cementite faster than preoxidised ironsand. The decomposition of cementite formed from hematite was investigated from 500??C to 900??C. This cementite was most stable at temperatures 750-770??C. The decomposition rate increased with decreasing temperature between 750??C and 600??C and with increasing temperature above 770??C. The stability of cementite formed from pre-oxidised titanomagnetite was studied from 300??C to 1100??C. This cementite was most stable in the temperature range 700-900??C. The rate of decomposition of cementite increased with decreasing temperature between 700??C and 400??C and with increasing temperature above 900??C. Cementite formed from ironsand was more stable than cementite formed from hematite

This project examined the reduction and formation of cementite from hematite and titanomagnetite ores and cementite stability. The aim of the project was to develop further understanding of cementite stability under conditions relevant to direct ironmaking and the mechanism of cementite decomposition. The reduction of hematite and ironsand by hydrogen-methane-argon gas mixtures was investigated from 600??C to 1100??C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The hematite ore was reduced more quickly than the ironsand. Preoxidation of the ironsand accelerated its reduction. Hematite was converted to cementite faster than preoxidised ironsand. The decomposition of cementite formed from hematite was investigated from 500??C to 900??C. This cementite was most stable at temperatures 750-770??C. The decomposition rate increased with decreasing temperature between 750??C and 600??C and with increasing temperature above 770??C. The stability of cementite formed from pre-oxidised titanomagnetite was studied from 300??C to 1100??C. This cementite was most stable in the temperature range 700-900??C. The rate of decomposition of cementite increased with decreasing temperature between 700??C and 400??C and with increasing temperature above 900??C. Cementite formed from ironsand was more stable than cementite formed from hematite

[pt] As pelotas de minério de ferro têm suas propriedades fortemente dependentes da natureza das fases escorificadas que se formam durante o processo de queima. Neste trabalho são apresentados os resultados de uma das pesquisas que compõem o projeto cooperativo entre a Samarco e o Grupo de Siderurgia do DEMa / PUC-Rio, envolvendo a possibilidade de utilização de minérios de ferro portadores de fósforo (pellet feed), na produção de pelotas para redução direta. Com este objetivo foram geradas amostras de escórias sintéticas de mesma composição que as das pelotas RD comerciais, as quais foram submetidas a condições experimentais análogas as do processo industrial. Inicialmente a ciclos térmicos em forno tipo pot-grate e, posteriormente, em escala laboratorial, usando forno de mufla, seguido de etapas de resfriamento em velocidades distintas. Foi possível então constatar que velocidades mais altas de resfriamento, aplicadas na etapa final dos ciclos térmicos, produziam escórias sintéticas sensivelmente amorfas, o que levou a conclusão que as fases escorificadas das pelotas RD também se apresentariam como estruturas não cristalinas. Finalmente, por meio de teste especificamente desenvolvido para a análise seletiva de fósforo em fases oxídicas, conseguiu-se obter uma maior eficiencia na mensuração deste elemento quando dissolvido em escórias amorfas, o que viabilizou a medida das quantidades de fósforo que efetivamente migraram para as mesmas, quando se submetiam as amostras de pellet feed a diferentes temperaturas, variados tempos de residencia e distintas basicidades. Por fim, foi possivel concluir ser o incremento de basicidade do pellet feed um fator de significativa melhoria para o transporte e a dissolução do fósforo pelas escórias, em particular quando submetidos a temperaturas superiores a 900 graus Celsius. / [en] Iron ore pellets have their properties strongly dependent on the nature of the phases present in the slags formed during pelletization. In this work are presented the first results of a research program involving the utilization of phosphorous bearing iron ores in the production of DR pellets (Direct Reduction pellets). Aiming at this, synthetic slags, produced with same composition of the gangue of a commercial DR pellet, were submitted to operational conditions similar to those of the industrial pelletizing process, but performed in a pot-grate reactor and in a laboratory furnace. The obtained slags samples were cooled at different rates, permitting to observe that at high cooling rates the slags obtained were amorphous, suggesting the occurrence of a similar amorphous structure for the slags present in the DR pellets. Finally, tests developed for a selective analysis of phosphorous in oxide phases, showed better efficiency when applied to amorphous slags than in crystalline ones. Further, the behavior of the phosphor dissolution in the obtained slags during the heating of pellet feed samples was evaluated. In this phase different temperatures, resident times and basicities were tested using a laboratory furnace. The results indicated improvements in the phosphor dissolution with the basicity increase when temperatures above 900 Celsius degrees were applied.

[pt] O presente trabalho apresenta uma análise da influência da temperatura, composição gasosa, vazão e pressão sobre a cinética da redução de dois tipos de pelotas de minério de ferro para redução direta, de baixo conteúdo de sílica, na faixa de temperatura de 500 a 900°C. Os valores adotados para cada parâmetro operacional procuraram reproduzir as condições reais da zona de redução de um processo industrial de redução direta, utilizando o forno de cuba, onde existe um perfil térmico longitudinal, além de gradientes de pressão e potencial redutor. A metodologia experimental envolveu um modelo estatístico fatorial de múltiplos níveis, ou seja, 3 níveis para a temperatura e 2 níveis para o poder redutor, a pressão e a vazão, com o intuito de avaliar os efeitos destas variáveis no processo de redução. A partir dos dados experimentais foi proposto um modelo semiempírico baseado no princípio da superposição e reação exponencial, que mostrou uma correlação de 99,2% para a pelota A e 98,5% para a pelota B. O coeficiente de saturação da redução (B), o parâmetro da escala temporal (t) e o tempo correspondente ao grau de reação global máximo (tG.R.máx), obtidos pelo modelo, foram plotados em função da temperatura, todos apresentando um erro global inferior a 10%. Mediante este formalismo se pode também prever que, na faixa de 500°C até 900°C, o coeficiente B e t se mostraram dependentes da temperatura e do potencial redutor da mistura gasosa. Verificou-se ainda a dependência de tG.R.máx com a pressão total. O estudo em questão é parte de um programa de doutorado em andamento e que envolve a PUC-RJ e a Samarco Mineração S/A. / [en] An analysis of the influence of the temperature, flow, pressure and gas composition on the kinetic of reduction for two types of lo w silica hematite pellets for direct reduction, over the temperature range 500°C to 900°C is presented. The values adopted for each variable tried to reproduce the real parameters of the reduction zone of the shaft furnaces where exists gradients of reducing potential, gradients of pressure and longitudinal thermal profile. The experimental methodology involved a factorial statistical model of multiple level, i.e. 3 levels for the temperature and 2 levels for the reducing potential, pressure and flow, with the aim to evaluate the effects of the variables on the reduction process. One semi-empiric model was developed from the experimental data. It was based on the superposition principle and exponential reaction. The model showed a correlation of 99.2% for the pellet A and 98.5% for the pellet B. The reduction saturation coefficient (B), time scale factor (t) and the time of the maximum reaction grade (tG.R.máx), all obtained through the model, were plotted versus temperature and they had presented an inferior global error to 10%. The coefficient B and t had depended of the temperature and reducing potential and allowed the prediction of its behavior over the temperature range 500°C to 900°C. Also, the analysis showed the tG.R.máx is dependent of total pressure. The investigation in question is part of a doctorate in progress at Catholic University in Rio de Janeiro/Brazil, counting on professionals from the academic area and experts from the iron ore agglomeration industry.

This study aims to find how density affects the reduction extent and reduction rate. H2-CO gas mixture is used as reducing agent. Five groups of different density pellets were reduced at four different temperatures. Light optical microscope (LOM) and scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDS) used to detect completely and partially reduced pellets to investigate how density affects the reduction mechanisms. Results illustrate that density affects reduction extent and reduction rate a lot. However, when reaction temperature is 1123 K, density has less influenc on reduction extent. The carbon deposition occurred for high density pellets at 973 K and 1023 K. The reduction process cannot be described by a single rate controlling step. Reduced layer is denser compared with unreduced layer. Reaction at initial stages goes much faster than later stages.

Around 50 million tones hematite iron ores with high iron content at a grade of 68% were found in Muko area of Uganda. Currently, the iron and steel making industry in the country has not yet developed to meet the demand to process the natural ores. Based on the analysis of its composition and mechanical properties, I infer that the natural iron lump ores can charge directly into reduction furnace without any prior treatment, so that the cost of whole process without additional enrichment and sintering will be reduced quite much. Also direct reduction iron (DRI) process use natural gases instead of coals which can greatly reduce the environmental pollution and lower the processes cost. If the raw materials that fit for requirements of majority plants, the seller´s market can get greater control over prices, terms due to the easy and cheap processing. All lump ores were from Butare area which is one occurrence of Muko and named sample A in this work. This research aims to use the lowest cost method to reduce Butare area iron ores and find out the optimum parameters on reduction reactions of Butare iron lump ores, such as flow rate, temperature, size of samples. Base on experiments with different designed parameters, Butare iron lump ores successfully reduced by DR furnace and microstructure was found to be an important parameter that strongly influent reduction degree of Butare iron lump ores.

Aluminium recycling requires 95% less energy than primary production with no loss of quality. The Black Dross (BD) produced during secondary aluminium production contains high amounts of water-soluble compounds, therefore it is considered as a toxic waste. In the present work, salt removal from BD by thermal treatment has been investigated in laboratory scale. The optimum conditions for treatment were established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature. Even Pretreated Black Dross (PBD) was evaluated as a possible raw material for the production of a calcium aluminate-based ladle-fluxing agent to be used in the steel industry. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e. CaO/Al2O3 ratio, temperature, holding time, and cooling media. The utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results. The iron/steel industry is responsible for 9% of anthropogenic energy and process CO2 emissions. It is believed that the only way to a long-term reduction of the CO2 emissions from the iron/steel industry is commercialization of alternative processes such as Direct Reduction (DR) of iron oxide. Detailed knowledge of the kinetics of the reduction reactions is, however, a prerequisite for the design and optimization of the DR process. To obtain a better understanding of the reduction kinetics, a model was developed step-by-step, from a single pellet to a fixed bed with many pellets. The equations were solved using the commercial software COMSOL Multiphysics®. The final model considers the reaction rate and mass transfer inside the pellet, as well as the mass transfers and heat transfer in the fixed bed. All the models were verified against experimental results, and where found to describe the results in a satisfying way. / <p>QC 20161128</p>

O ferro-esponja ou DRI (Direct Reduced Iron) é obtido pelo processo de redução direta onde o minério de ferro é transformado em ferro metálico através de reações químicas envolvendo o estado sólido (minério) e o gasoso (gases redutores). Neste processo o minério de ferro não passa pelo estado líquido como ocorre com o ferro-gusa. Isto confere ao ferro-esponja algumas desvantagens que prejudicam o seu desempenho nas aciarias. Pode-se citar a redução no rendimento metálico e o maior consumo de energia elétrica como principais impactos de sua utilização intensiva. O ferro-esponja apresenta menor quantidade de ferro total (maior quantidade de impurezas) do que o ferro-gusa e também apresenta óxidos de ferro remanescentes em sua estrutura (menor metalização). Para torná-lo mais competitivo, inúmeras melhorias no processo têm sido promovidas para aumento da metalização. No entanto, o limite superior alcançado na prática tem ficado ao redor de 95%. Visando contribuir para melhorar a qualidade do ferro-esponja este trabalho apresenta uma proposta inovadora a partir da técnica de auto-redução. O objetivo é aumentar o grau de metalização do ferro-esponja através de seu aquecimento. Para isso, foram realizadas análises termogravimetrias e aquecimentos em forno mufla; análises químicas por via úmida, difração de raios-x, espectroscopia mössbauer e análise de microssonda de raios-x. As análises estruturais foram realizadas utilizando microscópio eletrônico de varredura para confirmar a efetividade da técnica apresentada. Nesta dissertação pode-se comprovar que, através da técnica de auto-redução, o ferro-esponja alcança metalizações acima de 98% em detrimento da queda do teor de carbono total. Um aumento de 4% na metalização traz um ganho estimado de 5 a 10% no consumo de energia elétrica nos fornos de fusão e um acréscimo proporcional na produção horária das aciarias. / The direct reduced iron is obtained by direct reduction process, where iron ore is transformed in metallic iron via chemical reactions involving solid (ore) and gaseous (reductant gases) states. In this process the iron ore does not pass by liquid state like pig iron. This become to direct reduced iron some disadvantages, which decrease its performance in the steelmaking process. It can be mentioned the reduction of metallic yield and the higher consumption of electric energy as the main impacts of its intensive use. The direct reduced iron presents lower amount of total iron (higher amount of impurities) than pig iron and presents iron oxides remained in its structure (lower metallization). To become more competitive, several improvements in the reduction process have been carried out to increase its metallization. However, the highest level of metallization, which has been reached, is 95%. To improve the direct reduced iron quality, the present work evaluates, in an innovative way, using the technique of self reduction. The objective is increase of metallization of the direct reduced iron through its heating. Thermal, chemical and structural characterization was carried out to check the effectiveness of the investigated technique. The research confirms that the direct reduced iron can reach a metallization higher than 98% with a decrease of total carbon amount using the technique presented in this work. An improvement of 4% in the metallization brings savings of 5 to 10% in the electric energy consumption of the electric arc furnaces and a proportional increase of the production in the steelmaking plants.