However, the energy associated with the double impeller impact crusher is much higher and energy intensification, rather than energy efficiency, is the main gain of the double impeller design. ... −19.0 + 16.7 mm, −13.2 + 11.20 mm, and −7.92 + 5.60 mm. For each size class, three impeller speeds were used: 510 rpm, 1040 rpm, and 2080 rpm ...