Separation of super clean coal with two-stage cyclones and related characteristics

To recover super clean coal from raw coal slime of 28.53% ash, in this study, single factor experiment and response surface optimization experiment was used to design and optimize the design parameters of the two-stage cyclones for the separation and recovery of super clean coal. A quadratic mathematical model between the ash of super clean coal and the design parameters of the cyclones was established. Considering the minimum ash content as the optimization index, the following optimal experimental conditions were obtained: minimum ash content could reach 2.55%, which represented 5.35% recovery of the whole sample. The migration law of particles of different sizes, densities in classification and separation process, and the principle of preparation of super clean coal were explored under optimal conditions. Through the separation effect of the second-stage, overflow with particle size ≥ 0.125 mm could effectively recover super clean coal. However, the separation density was increased, and the separation effect was weakened when the particle was small. Therefore, to effectively recover super clean coal, sieving and desliming are necessary.