On the Kinetics of Carbon-and Oxygen-Transfer between CO-CO<SUB>2</SUB>, Mixture and Molten Iron

Abstract

Synopsis:Measurements have been done on the rates of carbon and oxygen transfer between CO-CO2 mixtures and levitated iron droplet. Supposing that the mass transfers between two phases determine the total reaction rate, the kinetics of this reaction has been considered. Results obtained here are as follows: Type of reaction at the initial period is different from that at the later period. At the initial, a simple absorption of gas takes place independently of the composition of gas mixture. The rate is controlled by the mass transfer at the melt side. At the later period, decarburization or carburization proceeds and the countercurrent flow of CO and CO2 in gas phase controls the total rate. It is concluded that whether iron is melted by the levitation technique or in usual crucibles, there is no essential differences in the mechanism of reaction, and that one or both of the mass transfers at gas and melt determines the total rate of reaction according to the experimental conditions such as the flow rate and composition of gas, mass and violency of stirring of melt. Re-examinations have been done for the previous investigations which proposed the interfacial chemical reaction mechanism as the rate determining step.

Carburization of Iron by Ar-CO-H2 at 1523 K.

“…Unfortunately, most of these results [15][16][17] were found to be under the effect of mass transfer process. In the previous work, 6) based on the established chemical reaction rate constant of CO 2 dissociation on the liquid iron, it was confirmed that the rate of the carburization reaction after the formation of the liquid Fe-C phase was controlled by the reaction of: As already mentioned, no work of the carburization of molten iron with CO-H 2 has been reported.…”

“…Also the rate of CO dissociation on the liquid iron has not yet been established. Itoh et al 15) investigated the reaction of levitated molten iron droplet with CO at more than 2 073 K. They found that the reaction (2) dominantly occurred initially until the concentration of C and O reached to the line of C-O concentration relation that was determined by the equilibrium gas composition with the condition of CO 2 ϩ COϭ1 (atm). After that, the carburization was proceeded by the reaction (1) with the reaction (2) being at virtual equilibrium.…”

“…Several works 6,[15][16][17] for the carburization of molten iron with CO have been carried out. Unfortunately, most of these results [15][16][17] were found to be under the effect of mass transfer process.…”

The Least Number of Chemical Reactions to Describe the Oxidation and the Carburization of Liquid Iron in Irreversible Processes.

“…5,6) However, in several previous studies, the observed concentration changesof carbon and oxygen in the liquid iron were found lower3 '4) or higher5) than those on the equilibrium line. It has been polnted out by Suzuki et al 7) that the supply of oxygen from the crucible in the range of low oxygen concentration cannot be neglected in the crucible method.…”

Dynamic Surface Tension Behavior of Liquid Iron during Carburization and Decarburization Processes

“…Many researchers [1][2][3][4][5][6][7][8] have measured the reaction rates of carburization and decarburization, and investigated the rate-determining step under various conditions. Ito et al 2) measured the reaction rate of carburization using an electromagnetic levitation technique with CO-CO2 gas mixtures. They reported that the concentrations of carbon and oxygen in liquid iron rapidly increased when the CO partial pressure in the gas phase was increased during carburization.…”