Dynamic evolution of bubble and separation characteristics of fine coal in vibrating fluidized bed

The vibrating fluidized bed can effectively strengthen the separation and quality improvement process of fine coal. By using the pressure sensor to measure the pressure signal,combining with the high-speed dynamic camera to synchronously capture the evolution behavior of bubbles in the two-dimensional vibrating separation fluidized bed with the mixture of pulverized coal and magnetite powder as the binary composite weight,the dynamic evolution of bubbles and the influence of bubble behavior on the separation effect of fine coal were explored. In addition,the expansion height of the bed and the volume proportion of bubbles under different operating conditions were studied, and the suppression effect of vibration airflow synergy on the dynamic evolution of bubbles was revealed. The results indicate that the introduction of vibration energy can promote the uniform fluidization of the particle bed. Under the conditions of v=16 cm/s,f=20 Hz and A=2 mm,the pressure drop fluctuation of the bed is stable. With the increase of vibration frequency,the fully fluidized expansion height H_e increases first and then decreases, but the change of the bubble phase volume fraction Y is opposite to that of the fully fluidized expansion height. With the increase of amplitude,the fully fluidized expansion height H_e increases first and then decreases,as well as the bubble phase volume fraction Y gradually increases. The results show that the synergistic effect of vibration and gas flow has an obvious inhibitory effect on the bubble behavior in the bed. Meanwhile,under the optimal operating conditions,the average bubble size is 1.12-2.45 cm. The disturbance of bubble on the separation effect of fine coal is weak,and the separation effect of fine coal is the best. The ash content and yield of bed clean coal products are 8.2% and 56.1% respectively,and the ash content and yield of discharged gangue are 44.5% and 43.9% respectively.