Segregation mechanism of 0–1 mm fine coal in vibration separation fluidized bed and its influence on the fluidization stability

Abstract

This study investigates the impact of mixing 0–1 mm fine coal with 0.15–0.3 mm magnetite powder to form a binary dense medium. The aim is to examine how the 0–1 mm fine coal influences the stability of vibration separation in a fluidized bed and to achieve steady-state control of vibration fluidization. The vibration segregation behaviour of the binary dense medium under varying fine coal contents is analyzed in this work. The study discovers that the primary contributor to segregation is coal particles smaller than 0.5 mm. As the proportion of fine coal increases, upward movement becomes more pronounced, especially for particles smaller than 0.15 mm, where the upward segregation is most noticeable, with a peak mixing index of 8.06. The study confirms that the larger the particle size of fine coal, the higher the content limit for mixing with magnetite powder. According to studies on the process of fine coal segregation, coal particles larger than 0.5 mm move with the magnetite powder, and the mixing index remains below 3. Coal particles smaller than 0.5 mm fine coal will separate at a uniform speed in a stable environment produced by low vibration energy, with the top-level mixing index remaining constant at 26 after 6 min. Additionally, the study also examines how the fluidization of vibration separation is influenced by the segregation of 0–1 mm fine coal. The evidence shows that longitudinal density segregation within the binary dense medium competes with instantaneous density fluctuation. The longitudinal density distribution of the binary dense medium was found to be nearly uniform when the frequency was set to 25 Hz, amplitude to 2 mm, and upward gas velocity to 1.4 times the minimum fluidization velocity. The density fluctuation was found to be between 0 and 0.1 g/cm³. The best separation effect was achieved with fine coal particles ranging from 6 to 1 mm in size under these conditions.