Reduction Equilibria of Iron Oxides. I : Measurement of the Equilibrium of Reaction, Fe_3O_4 (in Wuestit) +CO=3FeO (in Wuestit) +CO_2

The author measured the equilibrium of the following reaction at the temperature range from 700℃ to 1.200℃, Fe_3O_4 (in wuestit)+CO=3FeO (in wuestit) +CO_2 According to experimental results, wuestit can not be recognized as an ideal solution. Consequently considering the activities of FeO and Fe_3O_4 in wuestit, the author obtained the equilibrium constant of the reaction (5) at given temperatures and temperature function of log K. Then, from the equilibrium constant of the reaction (5) and the equilibrium constant of water gas reaction or the dissociation constant of CO_2, the author calculated the equilibrium between wuestit and H_2O-H_2 mixed gas and dissociation pressure of wuestit. Furthermore the author calculated activities of a_ and a_ in wuestits with several O_2 concentrations at given temperatures from experimental data, and performed some thermodynamical calculations

On the Equilibrium among Silicon in Molten Iron, Blast Furnace Slag and H_2-H_2O Mixed Gas. III : Investigation of the Equilibrium of the Reaction (SiO_2)CaO-Al_2O_3(Sat.)+2H_2=Si+2H_2O

Using a pure Al_2O_3 crucible, author measured the following reaction under the conditions of 3Al_2O_3-2Al_2O_3, Al_2O_3 Or 3CaO-5Al_2O_3 saturation at the temperatures of 1, 550 and 1, 600℃, (SiO_2)CaO-Al_2O_3 (sat.) + 2H_2 =Si+2H_2O Further, the activities of SiO_2 in the molten slags of SiO_2-CaO-Al_2O_3 ternary system were calculated from the equilibrium values of Si in molten iron at a given temperature and gas ratio pH_2/pH_2O, where the pure β-Cristobalite was taken as the standard state. The author illustrated the relation of the equilibrium among Si in molten iron, activity of SiO_2 of the SiO_2 -CaO-Al_2O_3 molten slag saturated with Al_2O_3 and H_2-H_2O mixed gas. Finally author determined the liquidus lines in the presence of molten iron at temperatures of 1, 500°and 1, 600℃on the Al_2O_3 side of SiO_2 -CaO-Al_2O_3 ternary diagram from the equilibrium compositions of slags

Reduction Equilibria of Iron Oxides. III : Measurement of the Equilibrium of the Reaction, FeO(1)+CO=Fe(1)+CO_2

The author measured the equilibrium of the reaction, FeO(1)+CO=Fe(1)+CO_2, at the range from 1, 530℃ to 1, 670℃, and the following equation was obtained as the temperature function of the equilibrium constant : numerical formula (a) Then, the author calculated the equilibrium constant of the reaction, FeO(1)+H_2=Fe(1)+H_2O, from the equation (a) and the equilibrium constant of the water gas reaction, and the following equation was obtained as the temperature function of log K : numerical formula (b) Finally, the author, calculated the dissociation pressure of molten FeO and the following equation was obtained as the temperature function of PO_2 : numerical formula (c

Research on the Activity of Components in Fundamental System in Iron Blast Furnace Slag. III : Measurement of the Activity of Silica and Alumina in CaO-MgO-SiO_2-Al_2O_3 System

Our previous reports described the determination of activity of SiO_2 and Al_2O_3 in the slag of CaO-SiO_2-Al_2O_3 system by using the e. m. f. method of double cell. The present study investigated the effect of MgO on the activity of SiO_2 and Al_2O_3. From the experimental results it was found that at a constant concentration of Al_2O_3, activity coefficient of SiO_2, γ SiO_2 increased as substitution of MgO for CaO increased. With the addition of MgO, the activity of silica approached Raoult\u27s law. At a constant MgO concentration, the amphoteric nature of Al_2O_3 was clarified as in CaO-SiO_2Al_2O_3 system. Concerning the effect of MgO on the activity of Al_2O_3, an intimate relation exists between αAl_2O_5 and basicity, that is, by chosing the basicity as N_/N_, a relationship could be found between log αAl_2O_3 and basicity which corresponded to the results obtained in the slag of CaO-SiO_2-Al_2O_3 System. The above facts show the behaviour of MgO which acts as a base

On the Equilibrium among Silicon in Molten Iron, Blast Furnace Slag and H_2-H_2O Mixed Gas. I : Measurement of the Equilibrium among Silicon in Molten Iron, SiO_2-CaO Binary Slag and H_2-H_2O Mixed Gas

1. Measurement of Equilibrium of the Reaction, (SiO_2)^_+2H_2=Si^+2H_2O The reduction of silica from molten slag to molten iron by H_2 gas is one of the important reactions in iron and steel making process which may be expressed in the equation as follows : (SiO_2)+2H_2=Si+2H_2O……(1) When the slag is saturated with SiO_2, equation (1) becomes (SiO_2)_sat.+2H_2=Si+2H_2O……(2) As the direct measurement of the equilibrium of equation (1) was difficult, the equilibrium of equation (2) was measured, using a pure silica crucibe in the temperature range from 1, 500°to 1, 600℃. From the experimental results, it was found (a) that the relation between p^2H_2/p^2H_2O and Si% at a given temperature could be expressed by a straight line and (b) that the temperature function of the equilibrium constant could be expressed as follows : Chemical formula. 2. Measurement of the Equilibrium of the Reaction, (SiO_2)_+2H_2=Si+2H_2O The equilibrium of this reaction was measured in the temperature range from 1, 550° to 1, 650℃, using a pure CaO crucible^ and a SiO_2-CaO binary slag in which SiO_2 content was about 60% From the results of measurement, the values of the activity of SiO_2 on the liquidus line at 1, 550°, 1, 600° and 1, 650℃ were calculated as follows : a_ N_ Temperature, ℃ 0.22, 0.41, 1, 550, 0.18, 0.40, 1, 600, 0.16, 0.39, 1, 650 where pure β-cristobalite was taken as the standard of the activity of SiO_2 at each temperature. Combining these results with the data of activities of SiO_2 in SiO_2-CaO binary slags reported by Chang and Derge^, the authors performed the thermodynamic calculation on the molten SiO_2-CaO binary slag and established the relation of equilibrium among silicon in molten iron, molten SiO_2-CaO slag and H_2-H_2O mixed gas

On the Reduction Equilibrium Diagram of Iron Oxide

The author has previously made some investigations on the reduction equilibrium of iron oxides and proposed a reduction equilibrium diagram of Fe-C-O system. But the equilibrium constants applicable to Fe_3O_4-liquid oxide-CO/CO_2 gas mixture and wustite-liquid oxide-CO/CO_2 gas mixture systems, and the relation between oxygen percentage and CO/CO_2 gas mixture has not been measured. These relations were inferred from known facts and tentatively plotted in the diagram. Recently, these equilibrium values were measured by Darken and Gurry, (2) and the relation between the oxygen percentage in wustite and CO/CO_2 gas mixture was calculated by Takeuchi and lgaki (1) from the view point of statistical thermodynamics. With reference to these results, the author has corrected his previous reduction equilibrium diagram for Fe-C-O system and drawn up that for the Fe-H-O system by calculation

Reduction Equilibria of Iron Oxides. II : Measurement of the Equilibrium of the Reaction, FeO(1)+CO=Fe(s)+CO_2

The author measured the equilibrium of the reaction, FeO(1)+CO=Fe(s)+CO_2, at the range from 1, 370℃ to 1, 490℃, and the following equation was obtained as the temperature function of the equilibrium constant : Chemical formula. (a) Then, the author calculated the equilibrium constant of the reaction, FeO(1)+H_2=Fe(s)+H_2O, from equation (a) and the equilibrium constant of the water gas reaction and the following equation was obtained as the temperature function of log K : Chemical formula. (b) Finally the author calculated the dissociation pressure of molten FeO and the following equation was obtained as the temperature function of PO_2 : Chemical formula. (c

On Activities of Coexisting Elements in Molten Iron. I : The Activity of Carbon in Molten Iron

It is indispensable to know values of activities of coexisting elements, C, Si, Mn, etc., in molten iron, in order to obtain the exact equilibrium relation of the fundamental reaction in iron and steelmaking. Recently some researchs have been performed on this field but the detailed researchs are remained in future. So that, in order to know the behaviour of carbon in molten iron, authors have constructed the following concentration cell and measured electromotive force E corresponding to the change of carbon content by potentiometer. The theoretical relation between, E and the activity of carbon, a_c, is as follows. Fe-C (I) |Carbide Slag|Fe-C(sat.) (II) E= RT/nFlna^i_c/a_c-RT/nFlna^i_c/a\u27_c…… (1) where a_c and a\u27_c are respectively the activities of carbon in Fe-C melt (I), (II). a\u27_c is the activity of carbon ion in the molten slag. Because the carbon saturated system is taken as a standard state, a\u27_c equals to unity and the following equation is obtained from Eq. (1) : E≒-0.0002 T/n loga_c……(2) n is approximately determined as n≒2 by the calculation from authors\u27 data. The activities of carbon at about 1, 450℃, 1, 500℃ and 1, 550℃ have been obtained from Eq. (2). Judging from this result, mole fraction of carbon, N_c, is considered to be approximately equal to a_c up to about 0.04 N_c, that is, about 1%C but a_c increases rapidly as the carbon content increases above 1%C. Using the values of a_c thus obtained, authors have examined the equilibrium relation of Fe-C-O system and performed some calculation from the view point of the statistical thermodynamics

On Activities of Coexisting Elements in Molten Iron. II : The Activity of Silicon in Molten Fe-Si System

Constructing the following electrode concentration cell, the authors measured electromotive force corresponding to the change of silicon content in iron by potentiometer. Fe-Si/silicate slag/pure Si The temperature range of the experiment was 1,520～1,540℃ and for the measurement of temperature Pt-Pt-Ph thermocouple was used. As preliminary experiments, the reversibility and thermoelectromotive force were investigated. The theoretical relation between electromotive force E and the activity of silicon a_ is as follows : E=RT/nF×lna^i_/a_-RT/nF×ln a^i_/a\u27_……(1) where a^i_ : the activity of silicon ion in the molten slag. a\u27_ : the activity of pure silicon. n : the number of Faradays required for the cell reaction. Because pure silicon is selected as a standard state, then the following equation is obtained from eqn. (1) : E≒- 0.0002T/n×log a_ ……(2) n is approximately determined as n=4 by the calculation from authors\u27 data. The activity of silicon has been obtained by substituting the values E, n and T in eqn. (2) Judging from this result, Fe-Si binary solution is recognized to be semi-regular solution and obeys Henry\u27s law up to about N_=0.08, where N_ represents the mole fraction of silicon in Fe-Si binary solution. Furthermore, the free energy change ΔG^0_ of the following reaction at 1,530℃ has been calculated from authors\u27 data, Si (liquid)=Si (in Fe)……(3) ΔG^0_ represents the free energy of solution of silicon at unit activity on a scale in which the activity is equal to percentage at infinite dilution. To convert this to activity on a mole fraction scale which the activity of pure liquid silicon is unity requires the following eqn. (4) : ΔG^0_=μ^0_ (dil. soln.)-μ^0_ (pure)=RTlna_ (dil. soln.)/a_ (pure)……(4) From the relation between loga_/N_=γ_ and square of the mole fraction of iron N^2Fe, activity coefficient γ^0_ which represents r_ at N_=0 is obtained as 0.013 and the mole fraction of silicon in dilute solutions is 0.0199 times its weight percentage. From these two values, the ratio of the activities of silicon on the two scales is obtained as 0.00026. Substituting this value to eqn. (4), authors have been obtained the following value : ΔG^0_=-29,700 cal

Research on the Activity of Components in Fundamental System of Iron Blast Furnace Slag. II : Measurement of the Activity of Alumina in the System CaO-SiO_2-Al_2O_3

The e. m. f. of the following cell Fe-Al-C_ | CaO-SiO_2-Al_2O_3 (I) | C or MgO | CaO-SiO_2-Al_2O_3 (II) | Fe-Al-C_. was measured at 1630℃ with the reference slags CaO 45.2, SiO_2 2.2 and Al_2O_3 53.7 wt % respectively. It was found that the e. m. f. sharply increased with increasing concentration of lime, and then decreased gradually. On the other hand, with constant alumina series, a marked increase of the e. m. f. was observed in the range near the liquidus of 2CaO-SiO_2. Now choosing the standard state as the solid alumina at 1630℃, the activity of alumina. in a given slag was calculated from the e. m. f. by the following equation : E=RT/6Flna_ From the authors\u27 data, the isoactivity lines were drawn on the ternary coordinates of CaO-SiO_2-Al_2O_3. And symmetrical isoactivity lines were obtained about the straight line connecting between 2CaO-SiO_2 at CaO-SiO_2 system and Al_2O_3 coordinate, which may be explained by the change of existing anion species of aluminum in the slag. Finally the most probable anion species and their stabilities were discussed