Bo Zhang

Dry mineral separation methods are based on the pseudo-fluid properties of two-phase gas-solid fluidization during the air dense medium fluidized bed separation. In this paper, the air dense medium fluidized bed separation method was introduced for coal deashing. In order to better understand the impact of separation performance of air dense medium fluidized bed, the uniform stability of fluidized bed on separation performance the factors (fluidization number (N), height-to-diameter ratio (λ) and feeding volume fraction (γ)) were varied. The process optimization of these three factors was investigated. The results showed that the fluidization number was the main factor reflect on fluidized characteristics. The separation efficiency achieved the optimal value when the feeding volume fraction reached 13%. The segregation stabilized at 0.90–0.95, with the possible deviation ranged from 0.10 to 0.15. Further, the yield of cleaned coal is 78.5–80%, and ash content reduced by 75–78%. The dense medium fluidized bed can achieve efficient deashing of coal.

Due to the serious environmental problem, dry coal separation has become the hot research topic in the world. In the study, an air dense fluidized bed was used for reduction of ash content and mercury rejection with shallow bed heights. The results showed that pressure drop fluctuation was smallest when bed height was 100 mm. When fluidized gas velocity was 1.50 U_mf, the ash content decreased to 9.65, 10.33, and 11.74% for −6 + 3, −3 + 2, and −2 + 1 mm samples; the yield of clean coal were 77.45, 81.52, and 83.65% for −6 + 3, −3 + 2, and −2 + 1 mm samples; the mercury content decreased to 0.47, 0.48, and 0.48 ppm for −6 + 3, −3 + 2, and −2 + 1 mm samples. The results indicated that an air gas-solid fluidized bed has satisfied separation performance on fine coal beneficiation with shallow bed height.

The production of pyrite extraction by the conventional magnetic separation method was effectively improved by increasing the magnetic susceptibility of pyrite. The electromagnetic characteristics and the absorption response of fine high-sulfur coal were studied for their improving effect on the magnetic susceptibility of pyrite. In this study, the complex dielectric constant and the loss tangents of fine coal samples obtained from Weinan Co. were investigated in the frequency of 0.5 ∼ 6.5 GHz. The complex dielectric constant of raw coal was small, indicating comparatively less loss of microwave energy during the magnetization process, essentially acting against the microwave energy absorption. The microwave energy absorption and electromagnetic parameters of coal samples depend on the thickness of the coal sample. When the microwave treatment time of the fine coal was 240 s, the sulfur content of the clean coal reached as low as 2.92%, and the optimum desulfurization degree and yield were 32.01% and 91.97%, respectively.