Effective regulation reagents are essential in low-rank coal flotation for improving the floatability of ultrafine particles. Polymer regulators have great potential in the surface modification of ultrafine coal particles. A novel nonionic polymer, polyvinylpyrrolidone (PVP), is evaluated in this study to determine its effectiveness as a regulator in floating ultrafine low-rank coal. Laser particle size analysis is used to discern both the size distribution of coal particles and the change in size distribution. Contact angle tests are carried out to evaluate the wettability of low-rank coal. Surface functional groups of low-rank coal are analyzed by Fourier transform infrared spectroscopy, and the surface interaction energy is tested by X-ray photoelectron spectroscopy. The results show effective adsorption of PVP and demonstrate the effects of PVP at the coal surface. The adsorption of PVP changes the proportion of exposed carbon and oxygen-containing functional groups on the surface of low-rank coal, regulating the size distribution of low-rank coal particles in suspension. The success of polyvinylpyrrolidone as a regulator in low-rank coal flotation is demonstrated, and the mechanisms by which PVP can affect ultrafine low-rank coal flotation are elucidated.

Uniform and stable bed density is the basis of efficient coal separation by a gas–solid dense medium fluidized bed. The traditional air dense medium fluidized bed (ADMFB) is a kind of bubbling bed. By introducing vibration energy, a vibrated dense medium fluidized bed (VDMFB) with uniform and stable bed density can be formed, where the bubble merger is suppressed, the gas–solid contact can is strengthened, and the fluidization quality is also improved. In this paper, the transfer process of vibration energy in a fluidized bed is studied in detail. By calculating the coherence of pressure signals induced by vibration energy and bubbles at different bed heights, the suppression effect of vibration energy on bubble merger is analyzed. The coefficient R_imp to quantitatively evaluate the improvement effect of vibration energy on the fluidization quality is proposed. The differences and incentives of density uniformity and stability in different height bed areas have been clarified under different vibration parameters and gas flow parameters. It is proposed that the optimal separation bed height area of VDMFB is about H = 40–150 mm. The separation effect of the ADMFB and the VDMFB on 1–6 mm fine coal was compared. The results show that, compared with the ADMFB, the VDMFB reduces the separation probable error, E, from 0.134 to 0.083 g/cm³, and the ash content of the clean coal is reduced from 18.83 to 14.97%. The vibration energy significantly improves the fluidization quality of the ADMFB and the separation effect of fine coal.