Abstract
Problem Statement: This article describes the results of theoretical and experimental studies that looked at a new gold flotation method and at the corresponding laboratory unit designed by the Department of Mineral Processing of the North Caucasian Institute of Mining and Metallurgy. The unit is designed to change the size of air bubbles in the process simulating the industrial agitation-froth process. Objectives: The authors of this research look at improving the flotation process in the conditions of unsteady heat applied to the gas-liquid interface aimed at enhancing the recovery of gold from ores. Originality: Contribution has been made to the theory of designing floatation installations in which heat is applied to the wetting film. The authors identified the flotation mechanism for the environment in which a mixture of air and hot steam is used as the gas phase. They also established the enabling factors and what makes it a highly efficient process. The analysis shows that when a bubble filled with hot water vapour suddenly comes in contact with cold liquid, the surface of the bubble starts oscillating due to the phase mass transfer, i.e. when the disperse phase condenses and the carrier phase evaporates. The intensity of phase transitions is determined by the heat transmission properties of the components within the interacting phases. When the bubble is compressed, the steam transfers more heat to the liquid than the heat it receives from the liquid during expansion. The factors that change the stability of wetting films when the temperature rises include the surface forces of the structural origin with nanobubbles involved. Findings: The flotation process developed, in which the heat transfer medium, i.e. hot water vapour, is supplied directly to the wetting film, enables to improve both the recovery of the valuable metal and the quality of the concentrate at a high specific throughput rate. Practical Relevance: With the help of the gas-liquid interaction pattern identified with the two phases having different temperatures, one can develop a specific approach to engineering new high-effeciency flotation processes.
Keywords
Steam-air mixture flotation, heat exchange, mass transfer, evaporation, condensation, performance of the bubbles.
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