Steel scrap melting model for a dephosphorisation basic oxygen furnace
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ORIGINAL PAPER
Steel scrap melting model for a dephosphorisation basic oxygen furnace Shuai Deng1 • An-jun Xu1 Received: 18 May 2019 / Revised: 14 October 2019 / Accepted: 17 October 2019 / Published online: 12 August 2020 Ó China Iron and Steel Research Institute Group 2020
Abstract Dephosphorisation basic oxygen furnaces (deP-BOFs) greatly differ from conventional BOFs in the melting process, especially its many limits on adding scrap. A mathematical model of the steel scrap melting process was established in MATLAB to investigate the mechanism of scrap melting in deP-BOF in terms of coupling effects of the carbon content of the molten steel, temperature, scrap preheating and converter blowing time on the melting rate and size of the steel scraps. The scrap melting rate was influenced by both the heat and mass transfer during the melting process: at 1350 °C, when the carbon content was increased from 4.5 to 5.0 mass%, the scrap melting rate increased by 43%; for the carbon content of 4.5 mass%, when the temperature was increased from 1350 to 1400 °C, the scrap melting rate increased by 60%. The carbonisation was found to be the restrictive step of the scrap melting process in deP-BOFs with respect to conventional ones. The scrap heating from room temperature to 800 °C reduced the crusting thickness on the scrap surface but there was no obvious influence on the melting rate. The scrap melting size in the deP-BOF was rather limited by its low melting rate and short melting time. Keywords Scrap Melting Dephosphorisation basic oxygen furnace Mathematical model Heat transfer Mass transfer
1 Introduction Steel scrap has been widely used in steel production as a green and renewable resource. Extensive studies have been conducted on the melting of steel scrap. Some of the relevant papers [1–5] are theoretical and probe into the mechanisms of the different stages of scrap melting as well as the impact of cold materials on the melting of steel scrap. Asai and Muchi [1] studied the effects of different temperatures and carbon contents on the melting of steel scrap, whereas Oeters [2] provided a thorough analysis on the dynamics of steel scrap melting in his book, Steel Metallurgy, and Szekely et al. [3] studied the heat transfer and mass transfer phenomena in the boundaries of steel scrap melting. On the other hand, some of the existing & An-jun Xu [email protected] 1
School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
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papers [6–9] are also experimental in nature, mostly presenting the studies on the melting time of steel scraps with varying sizes, shapes, temperatures and oxidation levels. Pehlke et al. [6] studied the melting rate of steel scrap rods at the temperature from 1300 to 1650 °C; Li et al. [7] investigated the melting of steel scrap rods of different sizes, shapes and preheating temperatures in 1650 °C molten baths. Other than the above theoretical and experimental studies [10–12], n
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