Advanced Furnace Modeling

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The transformation of iron oxide/reductant pellets into metallic iron nuggets is highly time- and temperature-sensitive, and so it is crucial that the furnaces be designed and controlled so that all pellets are transformed completely and uniformly. The furnace environment is a complex system with temperature profiles that can vary considerably over short distances depending on how the furnace is operated. A fundamental knowledge of the gas and heat flows in the furnace, as well as heat exchange between the pellets and the heat source, is needed to ensure that the process zone of the furnace can be adequately controlled to produce uniformly high-quality pellets. Current furnace technology performs poorly in this respect, with large variations in iron nugget quality due to inhomogeneities in the furnace heating (Anameric and Kawatra, 2007). The industry will need to be able to maintain higher levels of reproducibility in order to produce nuggets as a viable product.

Project Objectives: The objectives of the project are to develop computational fluid dynamics (CFD) models of the furnaces used to produce iron nuggets, and to use these models to relate the thermal profiles within the furnace with the metallographic characteristics of the nuggets produced. These models will need to take into account the heat transfer to and from the nuggets, heat transfer within the furnace volume, exothermic and endothermic reactions that occur within the nuggets, and reaction rates of the individual metallic iron grains with slag and with carbonaceous or hydrogen-rich reductants.

Proposed Deliverables: A CFD model of the furnace type that will be used in the production of iron nuggets, and a thorough understanding of the exact time and temperature conditions needed to produce high-quality iron nuggets that completely separate from slag impurities.

Proposed Methodology: The CFD modeling will be carried out using the FEMLAB multiphysics software. Model results will be validated against performance of actual furnaces to the maximum extent possible, and the predicted transformations will be validated against the observed behavior of the pellets as they transform into metallic iron nuggets.

Milestones and Time to Completion: The overall project is expected to require 3 years to complete.p> The primary milestones will be: (a) Modeling of the thermal profiles of the interior of a rotary hearth furnace, of the type used for large-scale iron nugget production – 9 months; (b) Modeling of the heat flow from the surface of the individual pellets to the interior, incorporating the exothermic and endothermic reactions that occur as the temperature increases – 15 months; (c) Overall thermal behavior of the pellet bed as the pellets transform, as a function of position within the thermal profile of the furnace – 12 months.