Efeito da temperatura na velocidade de redução do MnO pelo carbono dissolvido em ligas líqüidas Fe-C-Mn

Abstract

Esse trabalho estuda a redução do MnO por banhos de ferro saturado em carbono, nas temperaturas de 1500&deg;C, 1550&deg;C e 1600&deg;C. São determinados os valores da energia de ativação aparente para essa reação, através do método das velocidades iniciais, para teores de manganês iniciais no banho de 0%, 10% e 40%. Os valores encontrados foram, respectivamente, 64,8 kcal/mol, 63,13 kcal/mol e 63,25 kcal/mol .<br>The objective of this work was to investigate the effect of temperature on the velocity of MnO reduction by a carbon saturated liquid iron bath. The tests were performed in a laboratory apparatus specially designed to simulate smelting reduction reactions. The reactions were carried out respectively at 1500&deg;C, 1550&deg;C and 1600&deg;C, and also the initial manganese concentration in the bath were 0%, 10% e 40%. The apparent activation energies were graphically determined for the overall reduction process through the initial velocity method. The overall reaction rate increases as the temperature increases, and the apparent activation energies were 64,8, 63,13 and 63,25 kcal/mol, respectively for 0%, 10% and 40% of initial manganese content in the carbon saturated iron bath

A Review of Ore Smelting in High Carbon Ferromanganese Production

“…Apparent rate constant values from these studies as displayed in Table 5 and Figure 3 illustrate this point as well. The highest values are those for graphite dissolution in manganese containing alloys (de Oliveira et al, 1999).…”

“…From the rate values of de Oliveira et al (1999) as illustrated in Table 3 it is seen that the carbon dissolution rate is two orders of magnitude larger than the reduction rate from carbon dissolved in the alloy. Therefore, given similar reaction interface area values for these two reactions, the alloy bath should stay saturated even if MnO reduction from dissolved alloy carbon takes place.…”

“…de Oliveira et al (1999) measured the rate of graphite carbon dissolution into iron containing 5%Mn and 15%Mn, respectively and 0%C initially, at 1600°C in an induction furnace and under argon gas atmosphere. The authors assumed mass transfer control for the carbon dissolution reaction and found that the mass transfer equation described their alloy bath carbon content measurements well.…”

“…The authors concluded that the rate of carbon dissolution into Fe-Mn alloys is faster than the rate of reduction of MnO by carbon saturated Fe-Mn alloy. The initial rates of carbon dissolution and MnO reduction from de Oliveira et al (1999) were reworked to comparable units as illustrated in Table 3 by using the stated alloy volume (38.22cm 3 ) and alloy-graphite crucible contact area (25.64cm 2 ) in the carbon dissolution experiments with Fe-Mn alloy density data from Lee et al (2011). Skjervheim and Olsen (1995) showed that mechanical stirring of the slag and alloy (carbon saturated manganese) did not affect the MnO reduction rate, and therefore diffusion is not the rate controlling step in this reaction system.…”

“…The relative importance of reactions at the bath-heap interface was investigated by calculating the expected carbon dissolution rate from equation ( 6), using rate constant values from literature. Rate constant values for graphite dissolution were taken from the work of de Oliveira et al (1999) for dissolution into 5%Mn-Fe alloy at 1600°C and from the work of Jang et al (2012) for dissolution into pure iron at 1550°C. The rate constant for the slowest coal carbon dissolution rate into Fe-2%C-0.02%S alloy was taken from the study by Wu and Sahajwalla (2000).…”