Selective comminution and grinding mechanisms of spent carbon anode from aluminum electrolysis using ball and rod mills

Abstract

The recovery of spent carbon anode (SCA) materials plays important roles in environment protection and resources recycling, while this cannot be efficiently achieved without liberation. In this study, grinding characteristics of spent carbon anode from aluminum electrolysis in both ball mill and rod mill were analyzed, and compared based on the utilization of the selective Fuerstenau upgrading curves. In addition, the different grinding mechanisms of ball and rod milling were evaluated by analyzing the shape factor and surface roughness of the ground samples. Results of mineralogical characterizations indicated that carbon particles (d50 = 46.86 μm) presented in the SCA were closely associated with cryolite particles. At 5 min grinding time, the maximum selective comminution factor (β) values of ball milling and rod milling were 2.00 and 1.63, respectively, indicating a higher degree of selective comminution of SCA was achieved from ball milling. Comparisons of the valuable component content (cv, cum) of -125 μm ground particles and the shape characterizations of 74-125 μm ground particles generated from ball and rod milling manifest that a direct relationship exists between the degree of selective comminution and the grinding mechanism.

Recovery of carbon and cryolite from spent carbon anode slag of electrolytic aluminum by flotation based on the evaluation of selectivity index

“…The operational speed of the ball mill was set at 115 rpm (62.16% of critical rotational speed). The calculation of critical rotational speed for ball mill refers to the published literature ( Ni et al, 2022 ). A mass of 200 g carbon anode slag with the size of −1 mm was fed into the ball mill.…”

“…Comparing Figures 6A,B, it is found that there were significantly more black carbon particles in the product after grinding treatment than in the raw carbon anode slag, indicating that cryolite Frontiers in Chemistry frontiersin.org particels were enriched in the fine-grainded carbon particles were enriched in the coarse-grainded fraction. This was because there was a difference in hardness between cryolite and carbon particles, which led to the selective crushing of carbon anode slag in the grinding process (Ni et al, 2022).…”

“…Flotation is a physical separation method used to separate particles by using the difference in surface property of particles ( Chen et al, 2022 ; Ni et al, 2022 ). However, the flotation method is generally considered to be difficult to improve carbon purity and recovery efficiency, because cryolite are embedded during the process of carbon anode slag formation.…”

Study on Impact Crushing Characteristics of Minerals Based on Drop Weight Tests

“…In addition, the difference in the crushing resistance of different mineral components is essentially a comprehensive manifestation of the difference in impact resistance and grinding resistance [22][23][24][25], and the macroscopic result is the selective crushing of minerals. Although relevant scientific researchers discovered the selective crushing phenomenon a long time ago and have since carried out corresponding theoretical research work [26][27][28], no one has yet studied the selective crushing phenomenon from the perspective of mineral impact crushing.…”