SIMULAÇÃO FISICA DO ESCOAMENTO DO AÇO NO INTERIOR DO DISTRIBUIDOR DE LINGOTAMENTO CONTINUO COM OU SEM MODIFICADORES DE FLUXO

O distribuidor de lingotamento contínuo tem como função básica a distribuição contínua de aço líquido para os moldes atuando como “pulmão” durante a troca de panela. A busca na melhoria da qualidade dos aços, principalmente no caso de aços “limpos” (clean steels), faz com que este equipamento também seja empregado como um reator metalúrgico capaz de atuar na limpeza inclusionária do aço. Esta função é importante por que as inclusões não metálicas normalmente prejudicam as propriedades mecânicas dos aços. O estudo do escoamento interno do distribuidor é essencial para que se consiga favorecer a flotação das inclusões não metálicas e, consequentemente, evitar tanto problemas de qualidade de produto como problemas operacionais do processo (clogging). Acrescentar o objetivo e algum resultad

EAF dust: An overview on the influences of physical, chemical and mineral features in its recycling and waste incorporation routes

Electric-arc furnace dust (EAFD) is one of the several process residues generated in mini mills during steel production. The presence of valuable zinc in EAF dust and the rising costs for waste disposal are the motivating factors for EAFD recycling or its incorporation into other materials. Features such as small particle size, high zinc content and the existence of the decomposition-resistant mineral franklinite have long influenced both positively and negatively EAF dust processing. More recently, the growing presence of deleterious chlorine, lead and chromium is affecting equally the traditional as well as the new recycling routes or waste incorporation processes in a decisive way. In this study, a critical overview on the fundamentals of pyrometallurgical and hydrometallurgical EAF dust recycling or incorporation processes is presented, as a starting point for the understanding of how the EAF dust processing routes are influenced by all cited factors. Especially important is the discussion on the influences of the dust composition – including the effects of the deleterious elements – which can point out some relevant issues that ought to be considered for a successful ending to old and new dust processing proposals

Fluidized bed modeling applied to the analysis of processes: review and state of the art

The fluidized bed is a technology that involves multiple phases, allowing for efficient contact between them, therefore it is widely used in the chemical industry, metallurgy, oil and thermal power generation. In fluidized bed processes, the gas–solid interactions and chemical reactions generate a large number of variables to be handled, making the process very complex. Therefore, fluidized bed modeling and simulation is widely used to predict and analyze different processes, but it is possible to find in the literature many mathematical correlations that describe this type of flow. Based on this, the present work presents a review of the main mathematical models that describe the behavior of a fluidized bed reactor, and the state of the art regarding the use of modeling and simulation of the bed to predict and analyze different processes. As a result of this review, we can observe the importance of further development of the hydrodynamic modeling of fluidized beds, where understanding the interactions between the phases and the influence of this interaction is crucial for a better understanding and control of the processes. Generating experimental data of gas–solid and solid–solid interactions is also required for the validation of the numerical models

Absorption of non-metallic inclusions by steelmaking slags—a review

The formation of non-metallic inclusions during steelmaking is inevitable and, when not properly controlled, can cause performance and production problems. Slag is one of the resources available to carry out this control. In steelmaking, it is generally understood that inclusions are naturally absorbed by slag when flotation is sufficient. However, separation and dissolution may define the inclusion absorption capacity of slag. The discussion in this review explains the relationship between separation and the contact angle at the steel/inclusion interface, which differentiates the mechanism from liquid and solid inclusions. Whereas liquid particles show more predictable behavior in experimental observations, thermodynamic analysis is necessary in order to describe the removal of solid particles. Among other findings, it is evident that slag viscosity and the formation of compounds at the inclusion/slag interface strongly influence inclusion dissolution capacity. Following a detailed description of findings in the literature, this review considers the most influential factors to aid in optimizing slags for inclusion absorption

Influência do agente fluidizante na desfosforação aço inox

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Carbothermic reduction of Electric Arc Furnace Dust via thermogravimetry

Abstract Electric Arc Furnace Dust (EAFD) is a solid waste originated from electric steelmaking furnaces. Currently, according to some authors, there is an estimated generation of 15 to 25 kg of dust per ton of steel produced. The formation of the dust is related to the following steps of the process: furnace charge, metal volatilization, iron vaporization under the arc, drag of solid particles and, mainly by the collapse of CO bubbles from metallic bath decarburation. The dust has metals that are harmful to the environment. Otherwise, it is mostly composed of the elements iron, zinc and oxygen. Due to increasing costs for disposal and because it is considered a hazardous waste, industry is looking at the possibility of returning the dust to the steelmaking process. One of the alternatives is by reintroducing the waste in an electric melting shop using self-reducing agglomerates as part of the furnace burden. In this study, self-reducing mixtures are prepared with EAFD and petroleum coke (PET), presenting chemical and physical characterizations. An evaluation about the behavior of the mixtures is carried out in thermobalance, regarding the possibility of use in measuring accurate PET content in self-reducing pellets. As results it could be stated that the elements of economic interest, Zn and Fe, represent, respectively, 34.23 and 22.80%, in weight. These elements are present in chemical species frankilinite, zincite and magnetite and the reducible oxygen was estimated as 17.90%. Also, it was concluded the optimal content of petroleum coke in the mixtures varies from 10 to 15%, in weight. Therefore, the utilization potential of the thermogravimetric technique in the industrial field for adjustment of carbon content in batches of self-reducing pellets is satisfactory

Evaluation of zinc removal and compressive strength of self-reducing pellets composed of Electric Arc Furnace Dust

Abstract The amount of Electric Arc Furnace Dust (EAFD) is continuously increasing in mini-mill steel plants. This dust is considered a hazardous waste because of the presence of elements like lead, cadmium and chromium. Among many different treatment processes for this issue, there is the possibility of returning the EAFD back to the Electric Arc Furnace. This article presents a study of the compressive strength of self-reducing cold bonded pellets as well as their zinc removal, in an agglomerate containing EAFD, petroleum coke (PET) and Portland cement. The effects of the reductant and binder employed were discussed. Moreover, an apparatus was built to prevent zinc gas reoxidation inside an electric vertical laboratory furnace. Thus, the fraction of weight loss complemented the result of a previous study indicating the optimal content of PET source usage between 10 to 15%, in mass. Zinc removal and additional X Ray Diffraction outcomes are shown and discussed, concluding that 80% of zinc removal for this system could indicate the possibility of the EAFD reuse

Assessment of inclusion analysis via manual and automated SEM and total oxygen content of steel

The search for increasingly cleaner steels has heightened the demand for additional analysis techniques, especially for the evaluation of inclusions in steel where greater cleanliness is required. A range of factors should be taken into account when selecting a particular method, in accordance with analysis objectives and in order to maximize the reliability of results. Although statistical techniques make it possible to correlate data from smaller samples with entire heats of steel, some methods are more suited to evaluating different inclusion profiles. The objective of this study was to evaluate the main characteristics of certain techniques used to study inclusions. Two of the primary methods for direct inclusion analysis of solid steel are metallographic techniques and chemical analysis, with total oxygen content used as an indirect inclusion measurement. A search of the literature identified the main advantages and disadvantages of each method, as well as the primary limitations for their use. This makes it easier to determine the most suitable methods for carrying out the desired analysis