| Coal is one of the most important primary energy in China. Clear utilization and nearly zero release is the only way for the development of energy and coal in our country. At present, wet beneficiation technology is very important in coal preparation yield. However, in recent years, with the shortage of water resource and the problem of environmental pollution, the application of wet beneficiation technology is limited. Therefore, research on dry beneficiation technology is more and more important. With the industrial application of the air dense medium fluidization bed, coal with +6 mm size fraction can be separated efficiently. However, with the increasing content of fine coal in raw coal increases as the day goes on, dry beneficiation technology for fine coal is extremely urgent. In this study, pulsing air flow is introduced into the air dense medium fluidized bed. Due to the action of the vibration energy of pulsing air flow, the quality of fluidization can be modified, the homogeneity and stability of the separating fluidized bed can be enhanced, and fine coal can be separated efficiently in the pulsed fluidized bed.By the stability and ergodic test, the pressure and density time series of the pulsed fluidized bed can be regard as a stationary random process. Based on the method of stationary random process, the density of pulsed fluidized bed at different conditions was tested. Furthermore, the contour of density’s distribution of the fluidized bed was plotted. With the increase of gas pulsation frequency, the density at the top, central section, and bottom of the fluidized bed is quite different. Due to the effect of gas pulsation frequency on the bed density, three regions were proposed, named lowfrequency region, middle-frequency region, and high-frequency region. In the middlefrequency region, the density increases linearly from top to bottom of the bed. Furthermore, the density distributes uniformly, and is suitable for fine coal beneficiation.The characteristics of pressure fluctuations can reflect the hydrodynamics and bubble behaviors of a gas-solid fluidized bed. In the pulsed fluidized bed, acting by the pulsing air flow, a additional gas motion is generated. By the method of frequency domain analysis, it can be seen that the dissipation rate of pressure energy increases with bed height. Different types of pressure signals can be divided from the primary signal by the coherence analysis, reflecting the different bubble behavior. Based on the analysis of pressure fluctuations, the vibration system between bubbles and particles was proposed. Bubbles were regarded as springs, and the kinetic equation was established.Using the method of computational particle fluid dynamics(CPFD), the simulation experiments were conducted for the pulsed fluidized bed. Results show that the bubble’s motion in the gas-solid fluidized bed can affect the motions of heavy-medium particles seriously. Acting by the pulsing air flow, the intensity of bubble’s motion was decreased. The gas and particle velocity in the horizontal direction can be decreased, and the motion of particles in the vertical and horizontal direction became ordering. The circulating current and backmixing of heavy-medium particles were restrained.Finally, the separation experiments were conducted in the pulsed fluidized bed using fine coal with-6+1 mm size fraction. The ash segregation standard deviation was proposed for evaluate the characteristic of ash segregation in the separating fluidized bed at different gas velocity and gas pulsation frequency. Results show that the best probable error, E value, for-6+3 mm and-3+1 mm fine coal was 0.19 g/cm3 and 0.10 g/cm3. For the anthracite with-6+1 mm size fraction, the E value can be achieved as 0.09 g/cm3. Separated by the pulsed fluidized bed, inorganic sulfur can be removed efficiently. |
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