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ABSTRACT
To investigate the selectivity of different size fractions in the flotation process, the Fuerstenau upgrading equation was used to fit the results of flotation kinetics of various size fractions and to evaluate the flotation selectivity. The hydrophobic and hydrophilic functional groups on the surface of coal of different size fractions were analyzed quantitatively by Fourier Transform Infrared (FTIR) Spectroscopy, and a hydrophilicity index (HI) was defined. The difference in the values of HI was also applied to assess the flotation selectivity. The results show that the fitting constant k from the Fuerstenau upgrading equation is positively correlated to the flotation selectivity. The constant k values of the three size fractions are as follows: 3.16 for 0.25–0.125 mm, 2.86 for 0.125–0.074 mm, and 2.03 for –0.074 mm. It reflected that the selectivity of the coarse size fraction was the best, followed by the medium size fraction, and the selectivity of fine size fraction was the worst. The required clean ash content of 12% was achieved at a separation density of about 1.6 g/cm3. The difference in the HI values between 1.4–1.6 g/cm3 and > 1.6 g/cm3 determine the selectivity. The greater the difference in the HI values is, the better the selectivity is. The difference in the HI values were 1.2195 for 0.25–0.125 mm, 0.8327 for 0.125–0.074 mm, and 0.5873 for –0.074 mm, which is consistent with the results obtained using the Fuerstenau upgrading equation to characterize the selectivity of coal slime.
Funding
This research was supported by the National Nature Science Foundation of China (51574236) and the Fundamental Research Funds for Central Universities (2015XKMS095) for which the authors express their appreciation.