Research On Mechanism And Co-optimization Of Rigid-Flexible Coupling Elastic Screening Under Disequilibrium Excitation

Coal beneficiation is the source technology of clean and efficient utilization of coal,and screening is the key link of coal beneficiation technology.When using traditional equilibrium excitation equal projective intensity vibrating screen with rigid screen surface for 3 mm classification of viscous-moist steam coal,there are some problems such as screen surface plugging,material accumulation and poor screening performance,which seriously affect the large-scale upgrading of coal,and it is the key technology to be improved urgently.Therefore,this paper proposed to combine the disequilibrium excitation method with the rigid-flexible coupled elastic screen surface structure,and to carry out the research on the disequilibrium excitation rigid-flexible coupled elastic screening mechanism and co-optimization by means of theoretical modeling,vibration testing,high-speed camera testing and screening experiment.The mechanism of disequilibrium excitation rigid-flexible coupled elastic screening was revealed,and the disequilibrium excitation rigid-flexible coupled elastic screening environment suitable for viscous-moist steam coal classification was constructed by co-optimization,so as to realize the 3 mm dry screening with high efficiency.A dynamic model of rigid-flexible coupled elastic screen surface with four-sided simple beam was presented.Based on Hamilton principle,the differential equation of elastic screen surface motion was established,and the expressions of natural frequencies and vibration modes of each section of elastic screen surface under free vibration were obtained.The maximum elastic potential energy and maximum kinetic energy of the elastic screen surface were solved based on the functional stationary value condition,and the steady-state response of the elastic screen surface by impact of hitting ball was obtained.The kinematics characteristics of different sections of rigid-flexible coupled elastic screen surface were illustrated by vibration test and analysis system,and spatial trajectories of rigid-flexible coupled elastic screen surface under no-load,impact and steady-state operation were reconstructed.The correlation model between the three-dimensional acceleration of rigid-flexible coupled elastic screen surface and the total excitation force and frequency was established.The former is a linear model,the latter is a quadratic polynomial model,and the Adj.R² of the models was close to 1.Both the linear model and the quadratic polynomial model had high fitting accuracy.The acceleration of the rigid-flexible coupling elastic screen surface was increased more than90%higher than that of the screen body.The vibration intensity of the rigid-flexible coupled elastic screen surface could be achieved by using smaller vibration intensity of the screen body.A force model of plugging particles in rigid-flexible coupled elastic screening process was proposed.The mechanical equations of plugging particles on rigid-flexible coupled elastic screen surface impacted by hitting balls and material on screen surface were established.From the point of energy conversion,the mechanism of rigid-flexible coupled elastic screen overcoming plugging was revealed.When the ball hit the rigid-flexible coupled elastic screen surface,the impact kinetic energy of the ball transformed into the elastic potential energy of the screen surface,and then into the kinetic energy of the elastic screen surface and acted on plugging particles.The penetration capacity of plugging particles on rigid-flexible coupled elastic screen surface was much greater than that of rigid screen.The acceleration of the plugging particles increased rapidly and threw out from the screen mesh.In addition,the elastic screen surface deformed and rubbed the viscous-moist particles which adhered to each other,which led to the rupture of the slime covering film and the loosening of the viscous-moist fine particles,overcoming plugging of the screen surface,thus effectively improving the screening performance of viscous-moist steam coal.The influence of excitation parameters and material characteristics on the rigid-flexible coupled elastic screening performance of viscous-moist steam coal was investigated,and the spatial distribution of the upper material layer and the penetration law of the particles under the screen in the process of equilibrium excitation rigid-flexible coupled elastic screening were clarified.The dynamic model and expressions of the disequilibrium excitation self-synchronous vibration screen were established by using the lumped mass method.The solutions of x,y and?were obtained,and the centroid displacement expressions of the disequilibrium self-synchronous vibration screen in steady state were deduced.The synchronization process of disequilibrium self-synchronous vibration screen was studied by using high-speed camera test and analysis system.Based on the vibration testing,the spatial motion trajectories of rigid-flexible coupled screen surface in different sections of material flow direction were reconstructed.The influence law and mechanism of disequilibrium excitation force coefficients(F_de)and span of excitation shafts(l_vms)on the screening performance of viscous-moist steam coal were stdied.The motion behavior and spatial distribution law of disequilibrium excitation elastic screening material were clarified,and the mechanism of disequilibrium excitation strengthening elastic screening process was revealed.Compared with the equilibrium excitation,the elastic screening efficiency increased by 3.20%and the total mismatch content decreased by 1.37%.The synergistic effects of total excitation force,frequency and disequilibrium excitation force coefficient on the 3 mm disequilibrium excitation rigid-flexible coupled elastic screening process were studied by using multi-factor response surface method.The results showed that the above parameters had significant effects on the elastic screening efficiency and the total mismatch content.The order of significance was:F_t>f>F_de,and there was obvious synergistic effect between factors.A mathematical correlation model between the disequilibrium excitation rigid-flexible coupled elastic screening efficiency,the total mismatch content and the total exciting force,frequency and disequilibrium excitation force coefficients was established.The parameter co-optimization of the disequilibrium excitation rigid-flexible coupled elastic screening process was presented,and the optimum parameters were determined.Under these conditions,the 3 mm screening experiments of Wanli,Li Jiahao,Shi Getai steam coal were carried out.The screening efficiency was above 85%,the total mismatch content was less than 4.90%,and the distribution particle size was close to 3 mm.The accuracy of the prediction results of the quadratic polynomial model was verified,and the 3 mm rigid-flexible coupled elastic high-efficiency screening of viscous-moist steam coal was realized.