Purpose: to determine the effect of temperature and duration of firing on the dissociation-reduction reaction of mineral components of manganese ores. Recovery of manganese ore is carried out in four stages, which are determined by temperatures: <150°C, 150°C - 300°C, 300°C - 480°C, above 480°C. Topicality. Ores and concentrates undergo a number of complex transformations during heat treatment (agglomeration, firing of pellets and briquettes, preheating). The nature of such transformations is largely determined by chemical, mineralogical and particle size distribution, as well as other properties of the source ore. In addition to external conditions (temperature, pressure, nature of recovery, gas flow rate), the reaction rate is influenced by the physicochemical properties of the renewable substance, its mineralogical composition, structure, surface condition. The kinetic features of the reduction of pure manganese oxides are difficult to apply to manganese ores and concentrates with a rather complex structure and chemical composition. Understanding the basic chemical processes occurring in the smelting of manganese alloys is important for finding and justifying technological solutions to increase the efficiency of smelting of alloys. Method. Kinetic studies at different temperatures and fractional composition of the components under study. Results. The available literature data clearly indicate the dependence of the kinetic parameters of the processes occurring when heating manganese oxides in reducing conditions, from their physicochemical nature. To a lesser extent, process performance differs for natural minerals, although the composition of minerals may vary depending on the place of extraction. In this paper, it seems more appropriate to study the transformations that occur with manganese ores when heated, to use as an object of study the natural minerals that are part of these ores. Experimental data obtained in the study of physicochemical characteristics of the reducing processes of natural minerals can be used in the analysis of ore reduction and improvement of ferroalloy production processes. Scientific novelty. Kinetic studies of the process of interaction of minerals with reducing gas were performed at a constant heating rate of 14 degrees in the temperature range of 25-1000°C. Oxide concentrate and natural minerals lose moisture in the first 5-6 minutes. Their recovery proceeded at high speeds at temperatures of 300-4000C. A significant increase in speed was observed during the transition from a temperature of 4000C to a temperature of 6000C. Subsequent heating at 2000C led to a small increase in the total process speed. The total weight loss of the samples during heat treatment consisted of weight loss due to dissociation of manganese dioxide, weight loss due to dehydration and dissociation of carbonates that are part of the concentrate, as well as oxygen loss due to reduction. Calculations showed that the temperature of the beginning of the dissociation of MnO2 in a helium atmosphere is 460K. Dissociation of pure MnO2 is thermodynamically possible in the studied temperature range. The final decomposition product can only be manganese oxide. Practical significance. The obtained experimental data allowed to draw a conclusion about the inefficiency of grinding of oxidative manganese materials smaller than to the fraction -2.0 +1.5 mm before their heat or reduction-heat treatment in the processes of preparation of the charge for melting manganese ferroalloys.
Key words: manganese ore, minerals, dissociation, kinetics, ore fractions
Contributions of Experimental Data Obtained in Concentrated Mixtures to Kinetic Studies: Application to Monomethylhydrazine Pyrolysis
