Kinetics and Mechanism of the Simultaneous Carbothermic Reduction of FeO and MnO from High-Carbon Ferromanganese Slag

Abstract

The carbothermic reduction of 38.7 pct MnO-12.1 pct pct MgO-9.3 pct Al 2 O 3 -24.1 pct SiO 2 -10.4 pct FeO slag in Ar at 1600°C was studied using the sessile drop wettability technique. Pure graphite, coke, and charcoal were used as the carbon material substrates. The reduction rates were evaluated by sampling at different reduction times and by analyzing the chemical compositions of the reduced slag and the produced metal. The carbothermic FeO reduction from slag is initially fast followed by a much slower reduction rate. However, the rate of the MnO reduction is slow in the fast FeO reduction stage, and it starts to increase significantly during the slow FeO reduction stage. The kinetics of FeO and MnO reduction are affected by the type of carbonaceous materials. Moreover, the rate of the carbon dissolution/transfer into the produced metal phase and the amount of the transferred manganese to the metal phase depend on the type of carbon. Based on the experimental observations and the thermodynamic calculations, a mechanism for MnO reduction was proposed. According to this mechanism, MnO is mainly reduced through a metallothermic reduction by Fe and the rate of MnO reduction is controlled by the rate of the consumption of FeO from the slag, which takes place simultaneously. In contrast, the rate of FeO reduction in the fast initial reduction stage is controlled by the rate of the carbon dissolution/transfer into the metal phase. However, at the second slow FeO reduction stage, it is reduced mainly by the solid carbon.

Interfacial Reactions between Coke/HDPE Blends and High Carbon Ferromanganese Slag

“…The increase in porosity has the chance to impact on wettability with increased surface roughness, inducing improved wetting and thus improving reaction rates and extents. This noted, similar work by Safarian et al 17) found that more than the surface roughness or CO2 reactivity of a carbonaceous substrate, the 'type' of carbon had a larger effect, suggesting that the porosity increase may only partially impact on wetting and/or reduction of high MnO containing slags.…”

“…[16][17][18][19] The study involved the use of a laboratory scale horizontal alumina tube furnace (schematics shown in Fig. 2).…”

“…Safarian et al [16][17][18] used this method to show that MnO activity had little impact on MnO-graphite reactions, the rate instead being influenced by activation energy and the extent of slagsubstrate surface area contact for temperatures between 1 450, 1 500 and 1 600°C in Ar(g). Safarian et al 16) also found large wetting angles of slags with coke substrates (>150° for high MnO% slags), the wettability had an impact on the degree of surface area contact between the slag and the solid carbonaceous material impacting on solid-liquid reactions such as that presented in Eqs.…”

Microscopic Study of Carbon Surfaces Interacting with High Carbon Ferromanganese Slag

“…If there is FeO in the slag, this is reduced initially and then a FeMn alloy is produced through further MnO reduction. 4 If the initial slag does not contain FeO, the produced Mn through the carbothermic reduction is rapidly evaporated due to the high vapor pressure of Mn at elevated temperatures as described in our previous work 1) .…”

Characteristics of Calcium-Aluminate Slags and Pig Iron Produced from Smelting-Reduction of Low-Grade Bauxites

“…FeO and even Fe can be also formed in solid state; however, we here assume that Fe is mainly produced from FeO in the slag. Reactions [6] through [10] show the reduction mechanism of FeO and SiO 2 at slag/gas, gas/metal, and slag/metal interfaces as observed by Pomfret and Grieveson, [26] Teasdale and Hayes, [27] and Safarian et al [28] A simple illustration can be given as in Table VII. WDS Analysis of Phases Observed in B-, G-, and I-Slag Structures Shown in Fig.…”