Red Mud기반 산업 부산물을 활용한 고효율-저원가 용선 탈황 Flux 개발

Abstract

In Kanbara Reactor (KR) process, Hot Metal (HM) is vigorously stirred by an impeller to remove S from molten iron alloy. For the desulfurization (DeS) flux of KR, the liquid fraction in the flux influences not only the volume of the S-absorbing part of the flux but also the interfacial reaction area by detachment and aggregation. Therefore, the optimum solid fraction in flux is also essential to enlarging the interfacial area of the flux by detachment. The effect of the additives on desulfurization was investigated in terms of kinetics and reaction mechanism in a well-controlled atmosphere with a lab-scale high-temperature furnace. Here, the solid fraction of flux was varied by adding red mud (RM), MgO, and graphite in addition to CaO. The influence of MgO and graphite addition on the desulfurization rate was confirmed by thermodynamic calculations for the phase fraction in the flux, electron probe micro-analysis (EMPA), and a series of reaction rate calculations considering flux detachment/aggregation in stirring conditions. It showed that graphite-mixed flux improved the desulfurization rate by rapidly reducing RM and increasing the flux's solid flux dispersion and interfacial area. MgO mixed flux decreased the desulfurization rate, partly due to unreduced RM. In MgO-C mixed flux, RM was reduced by C, and the remaining MgO was also helpful in the solid flux dispersion. The effect of interfacial area increments of MgO, C was confirmed by the aggregate model introduced. The calculated particle size was qualitatively in agreement with the measured one (flux size after the experiment). The calculated interfacial area and [S] trend was well matched with the measured results. These results could explain the proportional relationship between the increase in the interfacial area of flux and the desulfurization rate when MgO and graphite were added. To compare the desulfurization performance more quantitatively, the desulfurization index was introduced. The MgO-C mixed flux showed similar desulfurization to commercial desulfurization fluxes used in Gwangyang, Pohang steelworks, POSCO with lower CaO consumption. To develop low-cost desulfurization fluxes, excess CaO and fluorite must be replaced with other residues of the process. In this study, an economic flux composition with the same level of desulfurization efficiency was found by replacing excess CaO with MgO-C, and replacing fluorite with red mud, a by-product of alumina smelting. It is expected that developed MgO-C mixed flux can be used in practical operations with additional research considering the particle size, impurities (Binder-CaO, Al2O3), and melting characteristics.