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Comminution is important in the processing of biological materials, such as cereal
grains, wood biomass, and food waste. The most popular biomaterial grinders are hammer and
roller mills. However, the grinders with great potential in the processing of biomass are mills that
use cutting, e.g., disc mills. When it comes to single-disc and multi-disc grinders, there are not
many studies describing the relationships between energy, motion, material, and processing or
describing the effect of grinding, meaning the size distribution of a product. The relationship be-
tween the energy and size reduction ratio of disc-type grinder designs has also not been sufficient-
ly explored. The purpose of this paper was to develop models for the particle size distribution of
the ground product in multi-disc mills depending on the variable process parameters, i.e., disc
rotational velocity and, consequently, power consumption, and the relationship between the
grinding energy and the shape of graining curves, which would help predict the product size
reduction ratio for these machines. The experiment was performed using a five-disc mill, assum-
ing the angular velocity of the grinder discs was variable. Power consumption, product particle
size, and specific comminution energy were recorded during the tests. The Rosin–Rammler–
Sperling–Bennet (RRSB) distribution curves were established for the ground samples, and the
relationships between distribution coefficients and the average angular velocity of grinder discs,
power consumption, and specific comminution energy were determined. The tests showed that
the specific comminution energy increases as the size reduction ratio increases. It was also demon-
strated that the RRSB distribution coefficients could be represented by the functions of angular
velocities, power consumption, and specific comminution energy. The developed models will be a
source of information for numerical modelling of comminution processes.
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