Improved CFD Model to Predict Flow and Temperature Distributions in a Blast Furnace Hearth
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furnace (BF) remains the primary process for the production of pig iron. Over the past few decades, there has been a trend in blast furnace technology to (i) reduce fuel consumption, (ii) increase furnace productivity, and (iii) lengthen the campaign life.[1] The latter is an essential aspect of reducing capital expenses and production costs. It is well recognized that one of the main limitations of campaign life is the wear of the hearth refractories.[2–4] Various wear mechanisms have been proposed involving several factors including zinc and alkali attack, thermal stresses, dissolution, and erosion of hearth refractories. Refractory erosion has a particularly strong link with the flow and heat transfer of liquid iron.[5] Therefore, in order to better understand the key mechanisms for hearth refractory wear, it is important to be able to predict the liquid iron flow and temperature distribution in the hearth. The hearth contains two immiscible liquids, slag and iron, as well as a packed bed of coke. The removal of the liquids through a taphole occurs for approximately 2–3 hours. During this process, the liquid iron distributes within the hearth producing a certain flow pattern KEISUKE M. KOMIYAMA, Ph.D. Candidate, BAO-YU GUO, Research Follow (Lecturer), and AI-BING YU, Professor, are with the Laboratory for Simulation and Modeling of Particulate Systems, School of Materials Science and Engineering, University of New South Wales, Sydney, NSW, Australia. Contact e-mail: [email protected] HABIB ZUGHBI, Senior Research Engineer, and PAUL ZULLI, Manager, are with the BlueScope, Port Kembla, NSW 2505, Australia. Manuscript submitted January 28, 2014. Article published online June 25, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
which may impact the erosion of the hearth linings. The coke bed is continuously renewed as coke is dissolved into the liquid iron. The coke size can differ ranging from fines to about 50 mm. The smaller particles as well as other fines such as unburned coal and graphite precipitates may percolate through the bed.[6] For these reasons, the bed is inhomogeneous in coke size and porosity, and hence permeability, which influences liquid flow.[1] The total weight of the burden material is balanced by the upward force of the raceway gases, solids pressure at walls and the buoyancy force of the submerged bed.[7] Therefore depending on the volume of the coke submerged, which is dependent on the porosity and the liquid level, the bed can either be sitting or floating.[6] The states of the bed affect the flow of liquid iron.[2,4,8] In a fully sitting bed, the liquid flows through the coke bed toward the taphole during drainage, whereas in a floating bed, the liquid may pass through the coke free zone at the bottom of the hearth. Finally, the hot face of the refractory, starting initially from the original hearth design, undergoes erosion or forms scaffolds where the hot face profile may change as the furnace ages. The altered hearth volume and wall thickness will in turn change the heat transfer and flow distribution.
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