Numerical Study of the Influence of Burden Batch Weight on Blast Furnace Performance
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AN ironmaking blast furnace (BF) is a critical chemical reactor in ironmaking industries. It still dominates iron production because of its high efficiency in terms of energy utilization and iron oxide reduction. In the BF ironmaking process, the solid phase including coke and iron ore is charged alternatingly at the furnace top. The burden distribution was proved to be capable of improving gas distribution and utilization efficiency in commercial BF practice.[1] Meanwhile, the hot blast provided by the blower system is injected at the tuyere level to generate the reducing gas. Inside a BF, the counter-current flow of gas–solid–liquid takes place with mass-, momentum- and heat-transfer among them.[2] From BF dissection results, the burden layer structure was observed to exist until reaching a cohesive zone (CZ).[3–8] The distributions of solid phase such as burden layer thickness and burden profiles are thus quite vital as they inevitably affect gas flow patterns and the in-furnace thermal-chemical behaviors. Therefore,
XIAOBING YU and YANSONG SHEN are with the School of Chemical Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Contact e-mail: [email protected] Manuscript submitted March 7, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
solid-phase charging parameters, including batch weight, are recognized as one vitally important approach to tune BF performance not only to ensure the smooth operation but also to obtain a decreased fuel rate and higher efficiency. Burden batch weight (a quantity of iron-bearing ore charged at one time) is a critical operating parameter in the BF solid-charging system. In practice, it is predominately determined by the charging capability, including the coke and ore bin volume and bucket volume, and affected by many other factors, such as BF inner volume, raw material quality and in-furnace thermal conditions.[9] In general, for a BF with a larger volume, a more considerable burden batch weight is chosen compared to a small-scale BF. When the raw materials’ quality deteriorates and gas permeability at the furnace center decreases, the burden batch weight can be adjusted to improve the in-furnace conditions. Some qualitative analyses of burden batch weight on BF performance were proposed in the past: when a lower burden batch weight is adopted, the thickness of the coke layer in both the shaft and cohesive zone (CZ) decreases; thus, the resistance for gas flow in coke windows (the coke layers in CZ) increases and more gas flows out through the BF central areas. On the contrary, with an increased burden batch weight, the number of burden layers inside a BF decreases, and the gas flow field can be more uniform because of the increased
burden layer thickness[10]; it is reckoned that the change of gas flow pattern brought by batch weight adjustment will lead to different in-furnace phenomena because the gas phase is a carrier of the reducing gas and thermal energy. Specifically, the reduction process of iron ore is driven by many factors, including phase temperature, ga
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