| Coal-series kaolin is one of the important non-metallic mineral resources,which is abundant in our country.Due to its high carbon content,it can not be directly processed and utilized.The traditional wet process is costly and complicated.Compared with the mature fluidized bed technology of dry separation of coarse-grained minerals,the rotary triboelectric separation can achieve higher degree of separation of fine-grained minerals.However,the existing electrostatic field structure can not meet the requirements of efficient and accurate particle separation.In this thesis,a cascade distributed electrostatic field structure was designed,which was suitable for high efficiency separation of materials with large charge-to-mass ratio range.The influence of plate distance,plate angle and plate voltage on the offset behavior of coal-series kaolin particles in the cascade electrostatic field was studied by numerical simulation.The offset and the range of charge-to-mass ratio in each collection trough were used as evaluation indexes,the offset effects of two cascade distributed electrostatic field structures were compared.The cascade distributed electrostatic field separation system was established,and the separation tests of coal-series kaolin with different particle sizes were carried out.The effects of different operating parameters（feed speed,rotation speed,plate voltage,etc.）on the decarbonization performance of coal-series kaolin in the cascade electric field were investigated,and the pre-concentration of coal-series kaolin was realized.The numerical simulation results of distributed electrostatic field showed that typeⅠstructure of the electric field intensity distribution of cascade was relatively narrow,A,B,C section of the electric field intensity only reached 0.7?105～1.7?105、1.7?105～2.5?105、2.5?105～3.0?105 V/m.The gradient distribution of field strength of typeⅡstructure was more obvious than that of typeⅠstructure.When the distance between plates was 347 mm,the angle of plate was 15°,the voltage gradient of A,B and C section were set to 20 k V and the voltage were-20,-40 and-60 k V,the electrostatic field of typeⅡreached 0～2.0?105、2.5～4.5?105、4.5～7.0?105V/m,respectively.The analysis results of the offset behavior of coal-series kaolin particles in the cascade electrostatic field of type II structure showed that the higher the charge-to-mass ratio made the bigger the offset displacement.The charge-to-mass ratio ranged from 18～14,12～6,4～2,1～-1,-2～-4,-6～-12,-14～-18 n C/g in the 1#～7#collection troughs,respectively.The offset of charged particles ranged from 5 mm to90 mm,which was conducive to the effective separation of different charged particles.In addition,the fitting equation x=-cln（（y-y0）/b）of particle charge-to-mass ratio and offset was established to predict the range of particle charge mass ratio in different collection troughs,which was consistent with the results of high-speed dynamic system analysis.The experimental results by cascade triboelectric separation of coal-series kaolin showed that the optimal plate voltages of A,B and C section for coal-series kaolin with different particle sizes were-20 k V,-40 k V and-60 k V,respectively.Under the conditions of feed speed of 12.49 g/min and friction medium speed of 315 rpm,the decarbonization efficiency of 0.5-0.25 mm coal-series kaolin was 47.09%.Under the conditions of feed speed of 8.83 g/min and friction medium speed of 225 rpm,the decarbonization efficiency of 0.25-0.125 mm coal-series kaolin was 53.47%.Under the conditions of feed speed of 8.83 g/min and friction medium speed of 135 rpm,the decarbonization efficiency of 0.125-0.074 mm coal-series kaolin was 44.63%.In conclusion,the high-efficient decarbonization pre-concentration of coal-series kaolin was realized by cascade triboelectric separation.The thesis contains 82 figures,16 tables and 105 references. |
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