Study on surface cleaning of coarse/fine coal particles in high-intensity conditioning: hydrodynamic mechanism and surface physicochemical changes

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This study conducted a theoretical analysis on the hydrodynamic factors of surface cleaning and then carried out detection on the surface physicochemical properties of coarse/fine coal particles after surface cleaning. Results show that the desorption degree of fine slimes does not increase monotonically with the impeller speed. Within the range of conventional high-intensity conditioning rotation speeds, a medium impeller speed of 1600–1900 rpm was the appropriate speed for surface cleaning. The cleaning effect depended on the impeller speed rather than the cleaning time. Surface cleaning increased the contact angle, single-bubble loading capacity, and induction time by 18.67%, 65.96%, and 28.99%, respectively. XPS analysis results indicated that when the cleaning impeller speed was 1600 rpm, the content of C-C/C-H on the surface of +75 μm coal samples increased by 4.10%, while the content of hydrophilic groups such as C-O-C/C-OH decreased by 15.23%. SEM-EDS analysis results showed that, after surface cleaning, the content of C element on the surface of coarse coal and fine coal increased by 34.48% and 25.51%, respectively; the contents of O, Al, and Si elements in coarse coal decreased by 57.16%, 88.79%, and 83.85%, respectively, while those in fine coal decreased by 32.22%, 62.79%, and 55.42%, respectively.

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