In this study the effect of a flotation device as well as non-conventional collectors and diesel oil on flotation response of low rank coal was investigated at different conditioning times. Additionally, Fourier transform infrared spectrometer, specific surface area analyzer, scanning electron microscopy, and contact angle measurements were used to determine the properties of coal and flotation of coal slime after conditioning with the collector. The results obtained from this study showed that the reagents containing oxygen-functional groups significantly improved the flotation of low rank coal. However, these oxygenated chemicals showed complex interactions with the surfaces of coal and gangue minerals. The combustible matter recovery at a low collector dosage was lower than that obtained at a higher consumption of collector while the ash content of concentrate could be higher. Therefore, it is important to create a suitable environment to separate low rank coals using oxygenated chemicals as collectors. A suitable conditioning time was crucial for the flotation performance. There was a marked decline in the concentrate recovery when the conditioning time was longer. This clearly indicated that flotation machines may not be the suitable equipment to separate the low rank coals. The better performance can be obtained by flotation column. The characters of flotation column which works under semi-static separation environment in column flotation zone and density separation in cyclone separation zone just met the requirements of low rank coal separation.