Kinetics of Oxygen Refining Process for Ferromanganese Alloys

Abstract

The present analysis of the experimental data by Yamamoto et al. permitted to determine the rate controlling mechanisms for the decarburization and evaporative manganese loss concurrently taking place during the oxygen refining process of ferromanganese melt.When oxygen is supplied by a top lance blowing mode, the decarburization reaction takes place by three different mechanisms in sequence. The chemical reaction at the melt-gas interface controls the rate of decarburization during the first period, the rate of oxygen supply through the boundary layer in gas during the second period, and the mass transfer rate of carbon in melt during the third period when the carbon content is less than 2 mass%.Manganese is lost primarily by evaporative reaction, but its dynamics are affected by the prevailing excess oxygen after accounting for CO formation. The excess oxygen and manganese vapor establish counter-current flux and form MnO mist at some distance away from the metal-gas interface. This creates two diffusion boundary layers, one for the flux of manganese vapor adjacent to the melt-gas interface and the other for the flux of excess oxygen in the gas phase. When the vapor pressure of manganese at the metal-gas interface is low, the rate of manganese vapor loss is controlled by the flux of excess oxygen. Otherwise, it is determined by the flux of manganese vapor.

Modeling and Validation of an Electric Arc Furnace: Part 2, Thermo-chemistry

“…Rate estimations can be obtained from different sources studying thermochemical processes. In this manner, kdC-L can be obtained from, 1) kdC-D and kdSi-1 can be obtained from, 2,4) kdC-1 and kdC-2 can be obtained from, 4,12) kdMn-1 can be obtained from, 13) kdMn-2, kdSi-2, kdCr-1 and kdCr-2 can be obtained from, 4) kdMn can be obtained from 14) and kdP can be obtained from. Table 4 gives the values of enthalpies of formation used in Eqs.…”

The use of fine water sprays to suppress fume emissions when casting ferromanganese

“…The Mn formation is suspected to be controlled by the diffusion of the Mn through the gas-liquid interface, although Lee et al (2005) indicates that no Mn vapour will form if the oxygen partial pressure is below 17kPa.…”

“…Lee et al (2005) suggest that no MnO mist and, therefore, no Mn 3 O 4 forms when the O 2 partial pressure is below 17kPa, which may be the case where decarburisation of HCFeMn occurs during tapping.…”

“…A discussion of the reaction kinetics involved in the Mn 3 O 4 formation will help in the understanding of the unexpected high energy content of the fumes, the fumes' rise velocity and the necessary extraction required to ensure that the fumes are captured. Lee et al (2005) considered various reaction-limiting factors for the fume formation in the casting of the high carbon FeMn produced in the arc furnace. They found that the Mn in the melt is essentially lost through evaporation and oxidation to form MnO mist, which is further oxidised to Mn 3 O 4 particulate.…”

“…Because of the relative abundance of Mn in the melt, it is not likely to be depleted at the metal surface. Therefore the MnO fume formation rate is considered to be controlled by the counter-diffusion of Mn and O 2 in the boundary layer above the metal surface (Dushman et al 1962), which can be expressed mathematically with: Research article: The use of fine water sprays to suppress fume emissions when casting ferromanganese Page 2 of 10 According to Lee et al (2005), the affinity of O 2 with Fe (at high temperatures) is approximately two orders of magnitude less than that of Mn, rendering the formation of FeO negligible.…”