Research On Ultrasonic Enhanced Gas-solid Fluidization Preconcentration Of Low-grade Fluorite

Fluorite,as the main source of fluorine element in industry,is widely used in various industrial fields.With the rapid development of China’s economy,the domestic supply of high-quality fluorite resources is challenged.The utilization of low-quality fluorite will consume a lot of energy,reagents and water resources in the grinding and flotation stage.At the same time,compared with the mature dry separation technology of coarse-grained minerals,there is no perfect solution for the separation of fine-grained minerals.Therefore,in this study,ultrasonic technology was introduced into the conventional gas-solid fluidized bed to improve the fluidization characteristics and separation performance of fine-grained minerals,so as to achieve effective preconcentration of low-grade fine-grained fluorite.The dry preconcentration of 1-0.5mm and 0.5-0.25mm fluorite was studied in a gas-solid fluidized bed with ultrasonic wave.Through the analysis of the phase composition of fluorite raw ore,it is known that the main gangue mineral is quartz.After crushing,the grade of 1-0.5mm and 0.5-0.25mm samples are 14.35%and 19.15%respectively.The density composition of the two samples was obtained by the experimental result of float and sink.It is found that the target minerals were mainly concentrated in the products with density greater than 2.7g/cm~3.By analyzing the wave equation of ultrasonic wave propagation in gas-solid fluidized bed,it was found that the secondary wave formed by the non-uniform propagation velocity of ultrasonic wave in gas-solid two-phase will lead to the attenuation of incident wave;through the multi-body multiple scattering theory,the influence of physical properties of gas-solid two-phase medium on the attenuation of ultrasonic wave propagation was analyzed.The application of ultrasonic energy into the gas-solid fluidized bed can effectively reduce the minimum fluidization gas velocity of the particles.With the influence of ultrasonic,the minimum fluidization gas velocity of the two-component simulation material was reduced from 0.201 m/s to 0.174 m/s.The application of ultrasonic energy enhanced the contact between particles and gas,and reduced the apparent gas velocity required for initial fluidization.Therefore,the energy required for fluidization was reduced.Through the force analysis of single particle,the differential equation of particle motion was established.Combined with high-speed dynamic image analysis,it was found that the acoustic radiation force generated by ultrasonic and the shear force between gas and particles conduce to break the force chain between particles and realize the loosening of particles in the bed.With the action of airflow drag and acoustic radiation force,two-component materials can be separated and layered according to density.The preconcentration experiments of 1-0.5mm and 0.5-0.25mm fluorite were carried out respectively.The effects of operation factors such as fluidized gas velocity,static bed height,separation time and die diameter on preconcentration performance were studied.The results showed that the recoveries of 1-0.5mm and 0.5-0.25mm fluorite increased by 10.08%and 12.07%respectively,and the grade of tailings decreased by 3.04%and 6.33%respectively with the condition of ultrasonic.The possible deviation E values of 1-0.5mm and 0.5-0.25mm low-grade fine-grained fluorite were 0.220g/cm~3and 0.175g/cm~3 respectively.