Mechanochemical ball milling can degrade high concentrations of persistent organic pollutants (POPs) in contaminated soil and even pure chemicals easily and efficiently. There are many relevant laboratory studies that discuss the selection of reagents and mechanism of pollutant degradation. However, there are few related studies on large-scale treatment and importance of collision energy in the system. The purpose of this study is to optimize the existing collision model and design horizontal ball mill to examine the influence of the internal structure on the collision energy. Studies have shown that not only the collision between balls, but also the collision between the balls and internal structure (balls and blades, balls and cylinder) accounts for a considerable proportion in the system. Besides, we found that the single impact energy determines whether the mechanochemical reaction occurs and the effective collision power determines the mechanochemical reaction rate during ball milling. Finally, we calculated that the effective collision power increases as the number of blades and blade-mill volume ratio, and different operating modes influence collision power significantly when the number of blades and blade-mill volume ratio exceed a certain threshold. (C) 2020 Elsevier B.V. All rights reserved.