Formation And Prevention Of Scarring In The Alumina Production Process

Scale is a solid substance attached on the surface of the equipment in the alumina production process. Scaling is a difficulty problem that gradually obsessed alumina production. It seriously impacts every production stage and results in many problems such as pipeline jam, strong decrease of diathermanous coefficient of heat exchanger. So it reduces the production ability, increases the energy consumption and raises the cost.At present, there is not a potent method to arrest scaling in pipeline and other equipments. Therefore, Many researches have been focused on how to tardily release scaling or clean scaling.Advanced instrument and experimental means are used to systemically investigate scaling during the different parts of alumina production system in this paper, especially scaling of pipeline. After analyzing the chemical composition and physical phase constitution, the form course and mechanism of different kinds of scaling were subsequently analyzed; Effects of technical condition and material composition on scale formation were researched according to the technology properties of alumina production flow. The orderliness of scale formation and important physical and chemical properties of scale created in every part were in control through studying the influences of temperature, ore content, lime addition, slurry flow-rate on scaling; Especially the mechanism and characters of scaling in digestion and circling water system were studied in this paper.Some feasible and effective approaches of clearing out scale were obtained via researching all sorts of methods about scale elimination in detail. The research's key was focused on the study of scaling in the evaporation, digestion, Bayer-raw-slurry and circling water pipeline, in which the research on elimination approaches of scale appeared in the evaporation and digestion pipeline indicates that acid washing method with adding the Great Wall delay corrosive is suitable. Comparison with others delay corrosives nowadays, it can greatly decrease the corrosive rate of equipments and prolong the life of evaporators more than 40%.Practicable and effective measures were founded on the basis of systemically studied mechanism of scaling, operation running, technology modification andultrasonic anti-scale. All work aims at giving some guides for alumina production process.