The chlorination kinetics of zirconium dioxide in the presence of carbon and carbon monoxide

Chlorination of zirconium dioxide, an important step in the commercial production of reactor grade zirconium metal, has been studied using carbon and carbon monoxide as reductants. Zirconium tetrachloride was produced when the oxide was reacted with chlorine alone above 1000°C; by introducing carbon the reaction temperatures could be lowered 200°C, and when carbon monoxide was used the reaction temperatures necessary for similar rates were even lower. With carbon monoxide the chlorination of zirconium dioxide is described by two regions differentiated by temperature and the dependence of reaction rate upon chlorine and carbon monoxide pressures.     

The selective chlorination of iron from llmenite ore by CO-Cl2 mixtures: Part I. intrinsic kinetics

The intrinsic kinetics of the selective chlorination of iron from ilmenite ore using carbon monoxide as the reducing agent were studied in a shallow fluidized bed. Experiments on the effects of chlorination temperature, carbon monoxide and chlorine gas partial pressures, and particle size were conducted in the absence of mass- and heat-transfer influences. Results indicate that the kinetics in the temperature range 923 to 1123 K are represented by the following pore-blocking rate law: λ[ exp (X_Fe/λ) − 1 ] = 33.7 exp (− E/RT)p _co ^0.52 ₂ ^0.32 t where E is 37.2 kJ/mol and p and t are in atm (=101.3 kPa) and minutes, respectively. The partial pressure of carbon monoxide was found to affect the chlorination rate more strongly than that of chlorine. A reaction mechanism in which iron in ilmenite reacts with chlorine before the liberated oxygen is removed by carbon monoxide is proposed. Formerly Graduate Student at the Department of Metallurgical Engineering, University of Utah     

The influence of weathering on the reduction of llmenite with carbon

The reduction of synthetic ilmenite and three ilmenite concentrates (Westralian Sands Limited (WSL), Western Mineral Sands (WMS) and Florida) with coal at 1000 ‡C to 1100 ‡C was stud-ied using thermogravimetry and X-ray diffraction, optical microscopy, and electron probe microanalysis of the products. The rate of reduction and the size of the iron particles decrease with increasing degree of weathering of the concentrate. Stoichiometric ilmenite reduces faster than pseudorutile (Fe₂O₃-3TiO₂), which is a product of weathering. The addition of FeCl₃, which promoted the nucleation of iron, increased the rate of reduction, and significant coars-ening of the iron was obtained at 1000 ‡C. In general, the products of reaction are iron, rutile, reduced rutiles, unreduced ilmenite or a-oxide, and pseudobrookite solid solution. A small amount of manganese (1.2 to 1.6 pct MnO) present in the concentrates stabilizes a pseudobrookite phase which retains a significant amount of iron. The manganese also forms an a-oxide phase, (Fe,Mn)TiO₃, which is mainly a manganese titanate and concentrates toward the center of the reducing particles. Formerly with the Imperial College, London. Formerly with the Imperial College, London.     

The selective chlorination of iron from llmenite ore by CO-Cl2 mixtures: Part II. mathematical modeling of the fluidized-bed process

By modifying a two-phase fluidized-bed model, two mathematical models which describe the behavior of gas and solid movement and reactions in a fluidized bed as well as interpret the experimental results for the selective chlorination of iron were formulated. One model is based on treating the bubble and emulsion phases as separate continuum phases with mass exchange between them, resulting in differential governing equations. The other is based on the compartmentalization of the fluidized bed into a network of perfectly mixed reactors. Predictions from these models produced satisfactory agreement compared with experimental results. The effects of important variables affecting the bed performance—superficial gas velocity, exchange rate between the phases, and reaction rate constant—were tested. Formerly Graduate Student at the Department of Metallurgical Engineering, University of Utah     

On the kinetics of the chlorination of titanium dioxide in the presence of solid carbon

Metallurgical and Materials Transactions B - The influence of solid carbon on the chlorination of TiO2 with Cl2 and CO-CO2-Cl2 gas mixtures was investigated gravimetrically using rutile and...     

High-temperature phase equilibria in the Al-rich corner of the Al-Ti-C system

A thermodynamic analysis of the Al-rich corner in the ternary Al-Ti-C diagram, providing phase relations and regions of phase stability, is presented. An invariant four-phase equilibrium between Al, Al₄C₃, Al₃Ti, and TiC _x takes place at 0.53 at. pct Ti, 7.10⁻⁶ at. pct C, and TiC_0.883 at 966 K. The carbon content of the TiC _x phase, which extends from x=0.48 to 0.98, exerts a significant effect on phase relationships in this ternary system. In particular, it is shown that stoichiometric TiC is not stable in the presence of liquid Al. For example, at 1300 K, a two-phase equilibrium between Al _L and TiC _x exists only in the 0.91<x<0.82 range. Thus, the interaction of Al _L with stoichiometric TiC leads to the formation of the Al₄C₃ aluminum carbide phase, whereas for x<0.82, only the intermetallic compound Al₃Ti can form at this temperature. The results of this analysis were confirmed by X-ray diffraction (XRD) measurements of relevant composites.     

The rate of chlorination of metals and oxides: part III. the rate of chlorination of fe2O3 and NiO in Cl2 and HCL

The rate of chlorination of Fe₂O₃, NiO, and NiFe₂O₄ by Cl₂ (1073 to 1473 K) and by HCl (1073 to 1273 K) diluted with He or Ar has been measured. The rates were measured as a function of particle size, temperature, gas composition and internal surface area. In all cases gas diffusion influences the rate. During the chlorination of the oxides with Cl₂ at low temperatures there was incomplete pore diffusion and the rate is restricted to the pore walls near the external surface. At high temperatures the rate is controlled by the diffusion of Cl₂ through the gas film boundary layer around the oxide particle. During the chlorination by HCl the rate is controlled primarily by the counter current diffusion of HCl to the surface and of the reaction products away from the surface.     

Thermodynamics of the chlorination of manganese oxide in the presence of iron

Conclusions A diagram of the stable state of chloride phases in equilibrium with the [Fe-Mn]_s solid solution has been constructed for the Fe-Mn-Cl-H-O system. It is shown that during chlorination at 1323–1423°C oxides are fully reduced. Chlorination is experienced almost exclusively by manganese, while iron passes into the solid solution. With the aid of the diagram it is possible to determine the composition of gaseous phases ensuring stability of gaseous manganese chlorides for any desired manganese concentration in iron.Translated from Poroshkovaya Metallurgiya, No. 10 (226), pp. 86–90, October, 1981.     

FeS-MnS phase relationships in the presence of excess iron

The FeS-MnS system is reexamined, both with and without excess iron. When excess iron is present, as is true for sulfide inclusions within steel, the pseudobinary reveals a peritectic rather than the previously assumed eutectic invariant. The maximum solubility limits (997 ± 3°C, or 1270 K) in the two solid phases are: a) 7.5 wt pct MnS in FeS, and b) 73.5 wt pct FeS in MnS. The peritectic liquid contains 66 wt pct Fe, ∼34 wt pct S, and ∼0.4 wt pct Mn. The two solid sulfide phases are nearly stoichiometric in the presence of excess iron; the Fe-richer sulfide is metal-deficient in the absence of a metallic iron phase. Based on this study, it is possible to be more specific than heretofore about the Fe-FeS-MnS-Mn region of the Fe-Mn-S ternary. In addition to the presence of a peritectic, it was concluded that the miscibility gap does not cross the univariant line between primary metal and (Mn,Fe)S phases. The peritectic liquid and the Mn-richer solid sulfide equilibrate with a metal containing ≤ 0.36 wt pct Mn. These data help explain the Mn/s ratios required to avoid hot-shortness in regular and resulfurized plain-carbon steels. G. S. MANN, formerly Graduate Student This is a part of the dissertation submitted by G. S. Mann for his Ph.D. at the University of Michigan     

FeSe-MnSe phase relationships in the presence of excess iron

The subsolidus phase relationships of iron selenide and manganese selenide are examined both with and without excess metallic iron. In the presence of excess metal, where the situation is similar to that existing in steels, the FeSe-MnSe pseudobinary has a peritectic at 976 ±3°C (1249 K) with the following phases: Fe (<0.3 wt pctMn) (s), (Fe,Mn)Se(2.5 wt pet MnSe) (s), (Mn,Fe)Se(48.5 wt pct FeSe) (s), and a selenidiliquid (4.3Mn, 37.7Fe, 58 wt pet Se). A minimum is observed in the liquidus surface at ∼920°C and FeSe-9 wt pet MnSe. A qualitative liquidus surface is proposed for the Fe-FeSe-MnSe-Mn section on the basis of these results. This is a part of the Dissertation submitted by G. S. Mann for his Ph.D. at the University of Michigan.     

Fe1.2 Te-MnTe phase relationships in the presence of excess iron

Results are presented for phase-relationships in the iron telluride-manganese telluride system in the presence of excess metallic iron. This portion of the Fe-Mn-Te system has a eutectic at 830 ±6°C (1103 K). The equilibrium phases at this temperature are Fe(<0.1 at. petMn) (s), (Fe,Mn)_1.2Te(<0.1 mole pet MnTe) (s), (Mn,Fe)Te(93.5 mole pet MnTe) (s), and an iron-telluride rich liquid (∼0.5Mn, 55Fe, and 44.5 at. pet Te). A monotectic is at 895 ±3°C (1168 K) where the equilibrium phases are Fe(<0.1 at. petMn) (s), (Mn,Fe)Te (91 mole pct MnTe) (s), an iron-telluride rich liquid (5.9Mn, 47.4Fe, and 46.7 at. pcTTe), and a MnTe-rich liquid (46.2Mn, 9.4Fe, and 44.4 at. pet Te). Additional information is also presented on the Mn-Te system and the iron-rich part of the Fe-Te system. Finally, a qualitative liquidus surface is proposed for the Fe-Fe_1.2 Te-MnTe-Mn part of the Fe-Mn-Te ternary. This is a part of the Dissertation submitted by G. S. Mann for his Ph.D. at the University of Michigan.     

The study of chlorination kinetics of copper(I)sulfide by calcium chloride in the presence of oxygen

The article investigates the influence of temperature, time, quantity of calcium chloride, and oxygen flow on the chlorination degree of copper(I)sulfide by calcium chloride in the presence of oxygen. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis were used to determine morphological changes occurring with the change of temperature and time. The law of additive time and the method of stationary point were used to determine kinetic parameters, i.e., rate constant and activation energy.     

Effect of nickel on sintering processes in the system Ti-Fe. III. High-temperature radiographic investigation of the sintering process

Conclusions During sintering of compacts of mixtures of powdered titanium and iron, and also of powdered titanium, iron, and nickel, the processes of formation of intermetallic compounds at temperatures below the eutectic temperature proceed as a result of solid-phase interaction between the components. The intensity of this interaction increases in dependence on the increase of the degree of dispersity of the powders that are used. Sintering at temperatures higher than the eutectic temperature is accompanied by the active formation of intermetallic compounds. The temperature ranges of intensive formation of intermetallic compounds in the systems titanium-iron and titanium-iron-nickel correspond to the temperatures of abrupt change of direction and speed of the sintering process on the dilatometric curves and to the appearance of exothermal peaks on the DTA curves.Translated from Poroshkovaya Metallurgiya, No. 6(306), pp. 32–39, June, 1988.     

Effect of manganese on sintering processes in the Ti-Fe system. III. High-temperature x-ray diffraction investigation of the sintering process

Conclusions The temperatures of accelerated formation of intermetallic compounds in the Ti-Fe-Mn system correspond to the temperatures of sharp changes in the direction and rate of the sintering process and also of the appearance of heat evolution peaks. The rate of heating of compacts to sintering temperatures affects the mechanism of formation of intermetallic compounds: At lower rates of heating intermetallic compounds are formed by solid-phase reaction, while at higher rates the role of liquid phase grows. A relation has been established between the composition of the intermetallic compounds forming during sintering and the behavior of specimens during this process at various heating rates. At higher rates of heating of Ti-Fe-Mn compacts Ti-Fe intermetallic compounds are formed containing no Mn; the behavior of these specimens during sintering is similar to that of Ti-Fe compacts (the specimens grow). At lower heating rates intermetallic compounds alloyed with Mn are formed, and growth of specimens is followed by their shrinkage.Translated from Poroshkovaya Metallurgiya, No. 4(304), pp. 23–28, April, 1988.