Wettability and Reduction of MnO in Slag by Carbonaceous Materials (original) (raw)
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INTERFACIAL PHENOMENA AND REACTION KINETICS BETWEEN CARBON AND SLAG CONTAINING MnO
Wettability of graphite by synthetic SiO 2 -Al 2 O 3 -CaO-MnO slags with varied MnO content and by industrial slags was studied at 1350-1600 °C using sessile drop method under argon atmosphere. Initial contact angle was the lowest (110-115 o ) for the MnO-free slag. For slags with 10-40 wt% MnO, the initial contact angle was in the range 125-135 o . The contact angle decreased with the contact time. The change in the contact an- gle with slag mass was found insignificant. The surface tension of slags obtained from the drop shape analy- ses was 500-800 mN/m and varied in a narrow range with temperature and MnO concentration. The reduction rate increased with increasing MnO content in the synthetic slag from 20 wt% to 40wt% and tem- perature. Increasing temperature also increased the rate of reduction. No correlation was observed between the reduction rate and MnO content in the synthetic slags in the range 0-20 wt% and in the industrial slags. The rate of SiO 2 reduction from the mol...
Kinetic of Carbothermic Reduction of MnO from High-carbon Ferromanganese Slag by Graphite Materials
ISIJ International, 2008
The kinetics of MnO reduction from a synthetic ferromanganese slag by different graphite materials was investigated using sessile drop wettability technique. It was found that the graphite substrates are not wetted by the slag drop at 1 450°C, 1 500°C and 1 600°C. On the other hand, processing the photos taken during the reduction revealed that the contact angle between the graphite substrates and the slag drop is not changing appreciably during slag reduction, while the changes in the slag drop volume are more significant. A new method was developed and applied to convert the changes in the slag drop volume to the MnO concentration and therefore the MnO reduction curves for different graphite substrates were extracted. The relationship between the density of slag and its MnO content was also studied. A new kinetic interpretation method was developed and a main differential equation for carbothermic MnO reduction from a slag drop in sessile drop method was obtained. This method was used to calculate the MnO reduction rate constants for different graphite materials considering the changes in the slag/carbon contact area. Multivariate analysis was also used to determine the possible relationships between the graphite properties and the MnO reduction rate.
Metallurgical and Materials Transactions B, 2008
The kinetics of MnO reduction from synthetic and industrial high-carbon ferromanganese slags were investigated using a sessile drop technique at 1600°C. The effects of the reductant type, ambient atmosphere, and slag composition on the MnO reduction were illuminated. Six different types of carbonaceous reductants were used as substrates for small slag droplets, which were reacted in a CO or Ar atmosphere, with the reaction studied in situ. The cross sections of the reacted slag-carbon samples were subsequently studied by electron-probe microanalysis (EPMA), to find the extent of the MnO reduction as a function of the reaction time. It was found that the rate of the MnO reduction is affected by both the type of reductant and the ambient atmosphere. It was observed that the MnO reduction rate from synthetic slag by cokes produced from single coals is lower than that from industrial cokes. Reduction rates obtained when charcoal was used as the reductant were higher than when coke was used, while the CO atmosphere yielded a faster initial MnO reduction than did the Ar atmosphere. It was found that the faster reduction rates in the CO atmosphere are related to the MnO reduction by CO gas. A newly developed kinetic method was applied, to calculate the rate constants for the MnO reduction by carbon and CO that considered the reaction interfaces. It was indicated that the rate of the MnO reduction by CO is less than that by carbon; however, the contribution of these reductants to slag reduction is very dependent on their contact with the slag.
Interfacial Phenomena and Reaction Kinetics between the Carbon and Slag in the Ironmaking Process †
Energy & Fuels, 2007
slags was studied at 1350-1600 °C using sessile drop method under argon atmosphere. Initial contact angle was the lowest (110-115 o ) for the MnO-free slag. For slags with 10-40 wt% MnO, the initial contact angle was in the range 125-135 o . The contact angle decreased with the contact time. The change in the contact angle with slag mass was found insignificant. The surface tension of slags obtained from the drop shape analyses was 500-800 mN/m and varied in a narrow range with temperature and MnO concentration. The reduction rate increased with increasing MnO content in the synthetic slag from 20 wt% to 40wt% and temperature. Increasing temperature also increased the rate of reduction. No correlation was observed between the reduction rate and MnO content in the synthetic slags in the range 0-20 wt% and in the industrial slags. The rate of SiO 2 reduction from the molten slag was close to the rate of MnO reduction. The MnO-free slag had the largest contact area with graphite substrate.
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2004
Silica reduction reactions taking place in the slag/carbon interfacial region were investigated for synthetic/natural graphite in the temperature range 1500 °C to 1700 °C. Two silica-rich blast furnace slags, with low levels of iron oxide, were used in this study. Silica concentration in these slags, labeled as 1 and 2, was 30.80 pct and 36.80 pct with a respective basicity of 1.67 and 1.22. Reaction rate investigations were supplemented with wettability measurements on these systems with an aim to probe a possible interdependence between wetting characteristics and reaction rates of silica reduction. Wettability and slag/carbon reactions were studied in a horizontal tube resistance furnace in argon atmosphere, using the sessile drop approach. While the contact angles were measured by recording live images of the assembly with a charge-coupled device camera, the volumes of CO and CO2 evolved were obtained from an analysis of off-gases with the help of a mass spectrometer. Reaction rates for silica reduction showed a wide variation for different systems. Synthetic graphite showed nonwetting behavior with both slags. Natural graphite, however, showed dynamic wetting with slag 2, resulting in low contact angles. This is attributed to the difference in the deposition of Si-based reaction products in the interfacial region, which in turn influences wettability. Temperature had a significant effect on both the wettability and silica reduction rate of the graphite/slag system. Activation energies for silica reduction in slags 1 and 2 with natural graphite were estimated to be 253 and 241 kJ/mol, respectively. Chemical composition of carbonaceous materials and slags were found to play a very important role in dictating overall reaction rates and wetting characteristics.
Effect of Waste Plastics addition on the Reduction of Mn (II) Oxide from Silicomanganese Slag
2017
The effect of waste plastics addition on the reduction of Manganese (II) Oxide (MnO) from Silicomanganese (SiMn) slag by metallurgical coke (Coke) has been investigated through experiments conducted in a laboratory scale horizontal tube furnace coupled with off-gas analysis through an infrared (IR) gas analyser. Composite pellets of SiMn slag with Coke, HDPE and blends of Coke with HDPE (in three different proportions) were rapidly heated at 1500°C under pure argon gas and the off gas was analysed continuously for CO, CO 2 and CH 4 . The extent of reduction of MnO from the slag after 20 min was then calculated by mass balance for removable oxygen. The results showed improvements in the extent of reduction of MnO from the slag when coke is blended with HDPE. The time for complete reduction was found to decrease with an increase in the amount of HDPE that was blended with coke. Generally, a decrease in CO 2 emissions was observed with HDPE addition; the extent of lowering, however, de...
REDUCTION KINETICS OF MANGANESE OXIDE FROM HC FeMn SLAGS
2000
The kinetics of MnO reduction from high carbon ferromanganese slag was investigated using a sessile drop technique at 1600 ºC. The effects of reductant type, ambient atmosphere and slag composition on the MnO reduction were illuminated. Two different types of industrial reductants (ground to a particle size of 44 to 106 micron and pressed to pellets) were used as substrates
Reduction and Dissolution Behaviour of Manganese Slag in the Ferromanganese Process
Minerals
The reduction and liquidus behaviour of manganese slag with different basicities were studied in non-isothermal experiments in the temperature range of 1400–1500 °C. Certain amounts of quartz were added to Assmang ore (South Africa), and lime was added to Comilog ore (Gabon), to adjust the charge basicity to 0.5, 0.8 and 1.2. The extent of manganese ore reduction as a function temperature were determined by thermo-gravimetric (TG) balance. Morphology of ores and its change in the course of reduction was examined by scanning electron microscopy (SEM). The results show that the reduction rate of Assmang slag decreases with decreasing basicity, as the liquidus temperature of slag decreases. When spherical MnO phase is present, the activity of MnO is high, and the reduction rate is rapid. Comilog slags show a much higher reduction rate than Assmang slags. The activation energies of MnO reduction between 1400 to 1500 °C are estimated in this study and found to be 230 kJ/mol for Assmang c...
Activity of MnO in MnO-CaO-MgO-SiO2 -Al2 O3 Slags at 1500 °C
steel research international, 2006
A thermodynamic study was made on the MnO-CaO-MgO-Si0 2-AI203 slags that are typical of the production of ferromanganese in submerged arc furnaces. The AI 203 content of the slags was kept constant at 5 per cent by mass. The activity-eomposition relationship in Pt-Mn binary alloys were re-determined for calibration purposes at 1300, 1400 and 1500 0C and p~values between 5.40x1Q-6 and 4.54x1Q-13 atm. A linear regression equation was derived to predict the activity coefficients of manganese, in Pt-Mn alloys at 1500°C_ The effect of concentration, basicity ratio and CaO-to-MgO ratio on MnO activities in above mentioned complex slags was investigated at 1500°C and at two different p~values of 4.76x1Q-7 and 5.80x10-s atm. It was found that aMnO values increase with increasing MnO, and tend to increase with an increasing CaO-to-MgO ratio. The aMnovalues also increase with increasing basicity ratio. The activity coefficient of MnO increases with an increase in its mole fraction in the slag. Quadratic multivariable regression model equations which represent the activity data successfully and which can be used to predict the MnO activities in the compositional range of this study were developed. The MnO activity data was interpreted in terms of a slag model which describes the thermodynamic properties of the slag successfully.