Modeling of Internal State and Performance of an Ironmaking Blast Furnace: Slot vs Sector Geometries
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BLAST furnace (BF) plays a dominant role in iron production worldwide, in which iron is efficiently reduced from iron-bearing materials.[1–3] In this process, the lump solids, i.e., iron ore in various forms and coke, are charged from the top of the furnace. Hot air (blast) enters the furnace through the tuyeres into the lower part of BF and combusts coke to form reducing gas. As the solid descends and gas ascends, the gas reduces and melts the iron ore to form liquid iron and slag in the cohesive zone, typically ranging from 1473 K to 1673 K (1200 °C to 1400 °C). The liquid then percolates through the coke bed to the hearth, as illustrated in Figure 1. If pulverized coal injection is practised at high injection rates, unburnt coal will leave the raceway region and enter the furnace as a separate phase-fine.[4–8] Hence, physically the BF is a moving bed reactor, and involves counter-, co-, and cross-current fluid flows of gas, liquid, and solid phases, coupled with their heat exchange and chemical reactions, where these phases affect each other via inter-phase forces and heat
YANSONG SHEN and BAOYU GUO, Research Fellows, and AIBING YU, Professor, are with the Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia. Contact e-mail: [email protected] SHENG CHEW and PETER AUSTIN, Principal Research Engineers, are with Steelmaking Technology and Planning, BlueScope, PO Box 202, Port Kembla, NSW 2505 Australia. Manuscript submitted April 10, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
transfers.[9,10] All these practical and physical features demonstrate the complexity of BF operation and hence the difficulties in understanding and optimizing BF operation. It is important to understand the complex phenomena in a BF, including both internal state and measurable performance indicators, for process control and optimization. In the past decades, various techniques have been used to understand and characterize the flow and thermo-chemical behaviors of a BF, mainly focusing on two aspects, i.e., describing the internal state of the furnace; and also predicting performance indicators at the furnace outlets, for example, gas properties (e.g., concentration/temperature) at furnace top and liquid properties (e.g., output rate/composition/temperature) collected from tapholes. The first technique is referred to as industry-scale investigation by, for example, dissection studies[11] and in situ measurements[12], which was practised in the past to provide direct information. This technique is limited and difficult due to the harsh in-furnace conditions and the need for a stoppage of furnace running. To date, in practice, the performance of a BF is mainly judged from the indicators collected from the furnace outlets, top or bottom. The second technique used for understanding and optimizing the BF operation is based on pilot- or laboratory-scale physical experiments. While useful, this technique is difficult to reproduce the in-furnace phenomena or predict the performance indicators of a real BF. The third technique
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