Research On Spatial Distribution Of Materials And Motion Characteristics Of Complex Excitation Elastic Screen Surface

Coal is the ballast stone of China’s energy industry and guarantees the energy security of China.Coal preparation is the basis and premise for realizing clean coal utilization,energy conservation and emission reduction,and sustainable and healthy development,and is the source technology of clean coal technology,while screening operation is the key link to achieve efficient coal sorting.When using a single excitation elastic screen surface for 1mm screening,the vibration intensity of the screen surface is low,it is difficult to loosen,stratify and screen through the material,and the screening effect is poor.In order to solve the above problems,this study proposed a complex excitation elastic screening method,through the elastic screen surface under the additional hitting ball,improved the vibration intensity of the screen surface,strengthened the screening process of the material loose and through the screen,to achieve 1mm dry depth screening of sticky wet materials.The kinematic characteristics of the complex excitation elastic screen surface were analysed in the start-up,stable and shut-down stages using a vibration test system.By comparing the kinematic characteristics of the screen body and the screen surface in the different operating stages,it was found that the screen body took less time to reach the stable stage and the screen surface took slightly longer compared to the screen body.The screen body took longer in the shut-down stage than the start-up stage,and the screen surface took longer from shut-down to rest than start-up to stable stage.In the stable stage,the average absolute value of the acceleration and displacement peaks of the elastic screen surface was greater than that of the screen body under the condition of no additional excitation and additional excitation,and the elastic screen surface produced higher acceleration and displacement after additional excitation.Compared with the addition of 1-ball excitation,the elastic screen surface could produce greater acceleration and displacement when additional 2-ball excitation was applied.According to the acceleration and displacement of the screen body and the screen surface in the stable stage,the acceleration and displacement of the screen body and the screen surface in the stable stage were obtained as shown in the Lissajous figure.The acceleration and displacement Lissajous figure of the screen body were linear,but the acceleration and displacement Lissajous figure of the screen surface were more chaotic under the conditions of no additional excitation and additional excitation due to its own elasticity and additional ball excitation.The kinematic properties of the elastic screen surface under additional 2-ball excitation were analysed for different parameters,as the acceleration and displacement of the screen surface were larger with additional 2-ball excitation.The average absolute values of the acceleration and displacement peaks in the z-axis and x-axis directions of the screen surface during the additional 2-ball excitation increased with the gradual increase of the excitation direction angle,the excitation force and the excitation frequency.The distribution of the material on the screen surface during the complex excitation elastic screening process was studied using a high-speed dynamic system,and the loosening process of the material on the screen under additional excitation conditions was analysed.The small ball in the support frame struck the screen surface,the screen surface was instantaneously deformed,the material on the screen was quickly loosened,the accumulation of the material layer on the screen was solved,and the stratification of the material was accelerated,the material layer on the screen is thinner,which helps the fine grain material to penetrate the screen.The screening effect under different additional excitation conditions was analysed by means of screening test,and it was found that the material movement is faster and the material layer is thinner under the additional 2-ball excitation conditions,and the screening effect was better.The distribution pattern of the material under the screen during the screening process was studied using multi-segment sampling and multi-granular analysis,and it was found that the main permeable area of the material was the second section of the screen surface,and the main influence on the screening efficiency of the complex excitation permeable screen was the permeability of the fine-grained material,with the increase of the screen surface length,the screening effect of the complex excitation elastic screen was better.Screening efficiency and mismatch content as the main screening effect evaluation index,the influence of parameters such as screen surface inclination,excitation direction angle,excitation force,excitation frequency and feed rate on the complex excitation elastic screening was studied,and the optimal parameters corresponding to the effect of complex excitation elastic screening were obtained.The best screening effect was achieved with the following excitation parameters: screen inclination angle of 6°,excitation direction angle of 45.0°,total excitation force of 7.0 k N and excitation frequency of 15.36 Hz,with a screening efficiency of 71.54% and a total mismatch content of 4.76%.On this basis,the feed rate was adjusted and the best screening effect was found at a feed rate of 1.0 kg/s,where the screening efficiency was 79.45% and the total mismatch content was 3.90%.In addition,industrial tests of complex excitation elastic screen and its laboratory experiments were carried out and the results showed that the laboratory test screening efficiency was 79.75% with a total mismatch content of 0.27%;the dry industrial screening test screening efficiency was 76.62% with a total mismatch content of 0.33%;and the wet industrial screening test screening efficiency was 85.30% with a total mismatch content of 0.25%.