Reactions in the Tuyere Zone of Ironmaking Blast Furnace
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THE blast furnace process is the principal technique used globally for the production of stable-quality molten iron. Efforts are continuously made to achieve progress in terms of energy savings and emission reductions, in particular under the recent pressure of excess production capacity. It is widely recognized that the physico-chemical properties of a series of slags formed in the lower section of the blast furnace play a critical role in the furnace operation including the production rate, fuel consumption, and campaign life. Different types of slags can be formed, namely, primary slag, bosh slag, tuyere slag, and final slag, when the burden materials descend from the cohesive zone to the hearth. Because of the harsh environment and limited access to the blast furnace lower zone, it is impossible to directly observe the actual dynamic phenomena occurring inside the furnace so far. The samples obtained from the tuyere XIAODONG MA, GEOFF WANG, HAE-GEON LEE, and BAOJUN ZHAO are with the School of Chemical Engineering, The University of Queensland, St Lucia, QLD, 4072, Australia. Contact e-mail: [email protected] JINMING ZHU and HAIFA XU are with the Baoshan Iron and Steel (Baosteel) Co. Ltd, Shanghai, China, 201900. Manuscript submitted April 27, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
level of the blast furnace using the tuyere drilling technique can provide useful information on the inner phenomena of the blast furnace. Previous studies about tuyere drilling samples mainly focus on the structural characteristics of coke[1,2] and influence of minerals and alkaline vapors on the coke.[3–5] The evolution of coke properties in a blast furnace was mostly reviewed by Li et al.[6] However, little information has been reported on the evolution and properties of primary slags, bosh slags, and tuyere slags of the blast furnace. Ichida et al. systematically investigated pulverized coal ash and dripping slag in the raceway under high pulverized coal injection operation and suggested the measures should be taken to improve deterioration in the gas and liquid permeabilities at the deadman surface because of the fine unburnt char and pulverized coal ash.[7] Li et al. analyzed the interfaces between coke, slag, and metal by sampling from the tuyere level of the blast furnace using SEM-EDS mapping.[8] The authors investigated the phase equilibria of the CaO-SiO2-Al2O3-MgO system with CaO/SiO2 weight ratios of 1.10 and 1.30 that covered the full compositional range of the blast furnace final slags.[9,10] Since the compositional and phase information of the slags in the tuyere and bosh sections of the blast furnace has not yet been clearly understood due to the above-mentioned reasons, in the present study the samples collected from the tuyere level of the blast
furnace were investigated to obtain meaningful information on the tuyere and bosh levels, with which the systematic phase equilibria study of the blast furnace slag systems was made possible. The information obtained in the present study must be particularly import
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