Model Study of Blast Furnace Operation with Central Coke Charging
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making blast furnace (BF) is one of the most important but complex industrial reactors. In this process, coke, as the main fuel and reducing agent in BF ironmaking, together with iron ore are charged in alternate layers through a rotating charging chute from furnace top, resulting in a layer-structured coke and ore burden distribution. The burden will then descend slowly and affect furnace performance predominantly, including gas flow pattern, temperature distribution and species distribution of various phases. However, ironmaking BF is facing many new challenges, including decreased quality of raw materials, leading to lowered permeability, increased pressure drop and worse BF stability, and increased social pressure of environmental protection. Many innovative operations have been adopted in modern ironmaking BFs for improving BF stability and efficiency, for example, oxygen-enriched blast,[1,2] pulverized coal injection,[3–6] and central coke
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 6, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
charging (CCC) operations.[7–10] In the process, modeling has played an important role in the investigation and optimization of BF internal states.[11–17] CCC operation is an efficient and flexible way to maintain stable operation. This is particularly true when the resources and supply of high-quality raw materials of coke become limited. For example, CCC operation can better tolerate the side-effects of quality fluctuations in raw materials on BF smelting process in practice.[7,18–20] A schematic diagram of burden layers of the CCC operation is shown in Figure 1. In the design of CCC operation, a high percentage of coke is charged at the BF central region, forming a central coke column. As a result, BF reducing gas generated inside the raceway tends to flow towards the furnace center rather than cutting across the periphery regions, leading to a relatively robust central gas stream. There are many benefits to have a robust central gas flow in the BF smelting practice by simple reasoning, which can be summarized as follows. First, the amount of heat and chemical reactants needed at the furnace center can be transferred via gas flow much easily, and thus iron oxides accumulation in the hearth center can be avoided; second, it is beneficial for BF shaft wall protection and campaign prolongation because of the decreased hot gas flush and chemical corrosion on the refractory; thirdly, zinc and other alkali elements which deteriorate BF
Fig. 1—Schematic of sectional views of BF under the CCC operation: (a) top view and (b) front view near the further top.
smelting performance and BF wall refractory can be discharged much easily with a relatively strong central gas flow; fourthly, coke abrasion at the furnace center can be suppressed, which promote the hot metal and slag penetration through the stagnant region (deadman), and help to reduce the ci
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