Haishen Jiang

The double-layer forced synchronous circular vibrating screen (DLFSCVS) is one of the most effective solutions for material screening. In this paper, a dynamic model was established to control the vibration of the screen, and the vibration characteristics of DLFSCVS are obtained by vibration experiment and parameter analysis. The classification performance of DLFSCVS was studied by EDEM, and the screening mechanism of DLFSCVS was revealed. The results show that the established dynamic model can describe the vibration of DLFSCVS well, and the maximum deviation between the experimental results and the theoretical results was within 4.78 %. The trajectory of the screen box is approximately circular. When the vibration frequency is 14 Hz, the acceleration amplitude of the screen box in the X and Y axis directions is 34.7 and 35.2 m/s ² , respectively. With the increase of vibration frequency, the displacement amplitude of the screen box is basically unchanged, and the velocity and acceleration amplitude increase gradually. The results showed that when f =   14 Hz, the screening efficiency of the upper and lower screen plates up to 0.87 and 0.93, respectively.

Banana-shaped Vibrating-Dewatering Screen (BVDS) is effective for dehydrate and demud sand aggregate, fine coal slime, ore and other materials. In this paper, the mechanical structure of the BVDS was revealed by means of theoretical modeling, simulation research and experimental test, and its dynamic and vibration characteristics were studied. The mathematical model was established, and the dynamic curve and spatial trajectory of the BVDS were obtained by MATLAB/Simulink software. Lissajous displacement diagram shows that the spatial motion trajectory of the shaker is an oblique line. The vibration test was carried out by using dynamic characteristic test system, and the dynamic characteristics of displacement, velocity and acceleration of the BVDS were revealed. Finally, through theoretical analysis, the changing trend of vibration characteristics of the BVDS with the increase of rotating velocity was obtained. The results show that the experimental data is basically consistent with the theoretical data, and the deviation is less than 6.58 %, which verifies the accuracy of the theoretical model. This paper provides a reference for the design and efficient operation of the BVDS.

Dry coal separation is the key technology for coal separation in arid and water-scarce areas. The content of −6 + 1 mm coal gradually increases, and the weak gravity affect of this part of coal restricts the separation effect, causing serious resource waste and environmental pollution. In this paper, a process intensification method for compound dry separation based on high-frequency vibration was proposed to improve the separation effect of fine coal. The kinematic characteristics of the bed surface with high-frequency vibration was captured by the three-channels acceleration sensor, and the motion trajectories of different regions on bed surface were reconstructed. The separation area was located at the front end of the vibrating bed, and the elliptical trajectory promoted the material to roll. However, the tail of the bed showed a linear trajectory, the main team to the transport of the material. And then the force characteristics of various density particles were studied by using spherical inertial sensors. Compared with low-density particle swarm, the collision between high-density particles was more obvious, causing serious loss of kinetic energy, which increased the motion difference of particles with different densities. Furthermore, the significance of the effects of vibration frequency, bed inclination and air velocity on the separation effect of −6 + 1 mm coal and the interaction between the factors were investigated. Furthermore, the influence of vibration frequency, inclination, and air velocity on the separation effect and the interaction among various factors were explored. The influence of frequency and inclination was more obvious than that of gas velocity. And then a mathematical model was established to predict the calorific value of clean coal. The results illustrated that at a vibration frequency of 37.52 Hz, a bed inclination angle of 13.69°, and an air velocity of 2.26 m/s, the calorific of product was increased from 4306 kcal/kg to 5868 kcal/kg, and the heat efficiency reached 90.18%. The results provide a referable way to realize the large-scale and high-efficiency dry separation of fine coal.

Equal-thickness screens are widely used in coal processing due to their advantages in overcoming the problems of material accumulation, low utilization of the screen surface, and poor screening accuracy. In this paper, the variable amplitude equal-thickness method was introduced into the combined screen, a novel variable trajectory combined equal-thickness screen was proposed and the combined excitation coefficient was introduced. The motion of the variable trajectory combined equal-thickness screen under different combined excitation coefficients was investigated using vibration test analysis system and the particle motion characteristics and the spatial distributions of materials in the screening process were analyzed using a high-speed camera system. The distribution law of the material was studied by screening experiment. The results show that when the combined excitation coefficient D is increased, the first section screen amplitude increases, the material transport speed of the first section increases, the material accumulation situation of the first section is resolved. When the unbalanced excitation coefficient k is increased, the material layer at the feeding end of each screen becomes thinner, the material transport speed of the first section screen is accelerated, the screen body does variable amplitude elliptical motion, the material is equal-thickness. When D = 1.2, k = 1.2, an optimum screening efficiency of 96.12% was obtained, with a total misplaced material content of only 1.82%.

China is the world’s largest producer and consumer of coal. The method of dry coal beneficiation is a key method of separation technology in the field of coal mining. In this paper, the structure of a novel compound dry separator (NCDS) was revealed. The dynamic characteristics and vibration behavior of the NCDS were studied through theoretical modeling, simulation research, and experimental test methods. The mathematical model and simulation model based on ADAMS of the NCDS were established. The experiment for the NCDS was carried out using the dynamics characteristic testing system. The dynamic curve and spatial trajectory of the NCDS were obtained. The Lissajous figure of displacement indicated that the space motion trajectory of the NCDS was an oblique line. The dynamic characteristics of the NCDS with different rotational speeds were revealed. The effect of eccentricity on the dynamic characteristics of the NCDS was discussed, and the vibration amplitudes increased with the increase of eccentricity. The results showed that the deviation of the simulation data and theoretical data was within 3.75%, and the result of the experiment data and theoretical data was within 6.98%. Through comparison and verification, the theoretical model with high accuracy can accurately calculate the dynamic characteristics of the NCDS before processing and manufacturing. This paper provides a reference for the design and efficient operation of the new compound dry separation machine.

Screening is an important technological challenge to alleviate environmental contamination and resource waste and enhance the large-scale synthesis of coal gangue solid waste resources. Single inclination vibrating screen for coal gangue grading process can easily cause concentrated accumulation of materials at the infeed end, loosening and stratification difficulties, and deterioration of grading effect. This study replaces a single inclination screen surface with a variable inclination (banana-type) for coal gangues classification and separation. After studying the spatio-temporal permeability distribution characteristics of the screen surface with variable and single inclination, it is found that the integrated optical density (IOD) of gangue on the screen surface with variable inclination is 1.5 times of single inclination, and the gangue under the screen with variable inclination is 2.5 times that of a single inclination. The particle penetration position on the variable inclination’s screen surface is in the middle, while the penetration is significant. Moreover, the screening performance and the whole mismatch content are increased by 2.24 and 1.74% points compared with the single inclination, respectively. At the same time, the distribution size is closer to 6 mm. In addition, the range and screen inclination angle adaptation characteristics are studied. When >6 mm, gangue accounts for 55%, a smaller screen inclination gradient should be selected, such as 3° and 4°, matching the productivity of 18t/h, achieving the best screening performance and processing capacity.

To effectively separate 3–13 mm steam coal, new separation equipment which was a heavy-medium separation column was designed and tested in this study. Particles were measured to analyze the changes in the axial medium force of particles in the medium by employing the force measuring system. The influence of the medium flow rate (q), medium density (ρ), separation column height (h), and feed volume (g) on the separation effect was investigated by using the control variable method to establish the optimum separation condition. Under the optimum separation condition, the yield and the ash content of the clean coal were 74.05% and 16.18%, respectively. Based on the single factor study, the Box-Behnken response surface methodology (BBRSM) was used to investigate the influence of each interaction factor on the separation effect. The significance of each factor on the quantitative efficiency was in the order of ρ > q > h. Through the regression analysis, the mathematical model for the relationship between the quantitative efficiency and the separation parameters was established. The predicted quantitative efficiency and experimental quantitative efficiency were 87.88% and 89.32%, respectively. The difference between them was small, verifying the high accuracy and reliability of the prediction results of the regression equation model.

Equal-thickness screening is a critical part of mineral processing; recently, the multistage variable-inclination equal-thickness screen (MSVIETS) has been utilized in the mining industry across the world. In this work, a model of the collision mechanics between particles and the multistage variable-inclination screen surface was established. The maximum collision force (F _max) was found to be closely related to amplitude, frequency, screen surface inclination, and number of stages. The time-frequency response characteristics of multistage (3-, 4-, and 5-STAGE) screen surfaces were studied by the vibration test analysis system. The permeation screen distribution law of grain groups on the screen surface was revealed. The obtained results show the best screening performance can be obtained from the 5-STAGE scheme with a screening efficiency of higher than 95% and total mismatch content of less than 2%. The synergistic mechanism between two of the parameters was revealed by Box-Behnken response surface methodology (BBRSM). Then, the correlation between the screening evaluation index and the multiple parameters was obtained, and the significant order of the parameters influencing the screening evaluation index was F _t > f > n.

Banana-type vibrating screen has been widely used in classification operations in coal cleaning and mining fields due to good screening performance and large processing capacity. In this work, a new analytical method was introduced to clarify the mechanism of equal-thickness formation of banana-type vibrating screens. The vibration characteristics of the collision between the screen surface and the particles were analyzed using the wavelet packet frequency and the energy spectra. The main frequency band of the collision at the infeed and outfeed ends was the 2nd frequency band (low-frequency band). The corresponding amplitude and energy percentage value of the screen surface at the infeed end were 0.12 mm and 4.3%, respectively, which were higher than those at the outfeed end. The spectral amplitude and the energy percentage value had “high-in and low-out” characteristics which verified the mechanisms of thin-layer penetration and equal-thickness formation of banana-type vibrating screens. This work contributes to the theory of equal-thickness screenings and provides new research ideas and technical support for designing vibrating screens.