Effect of the rotor blade geometry on particle size and energy demand for knife-milled beech chips: Experimental identification and mathematical modelling.

Rotor blade geometry (linear and screw) was experimentally identified for particle size characteristics and specific energy demand for knife-milled beech chips (7.8 wt % moisture content). The operational conditions of peripheral speed (6.8–20.4 m s−1) and screen sieve openings (0.75–6 mm) were considered for the knife milling of beech chips. The Rossin-Rammler-Sperling-Bennet model precisely described particle size distribution of comminuted beech chips with its parameters depending on screen sieve, rotor speed and blade geometry in a linear relationship. This relationship allowed the development and calibration of a unique empirical linear model. The model predicted particle size under the conditions considered for each blade geometry with accuracy. Energy demand values between 6.97 and 101.6 kW h t−1 were identified for D 50 particle sizes between 0.29 and 2.60 mm. Energy demand was independent of the rotor blade geometry, and it was mainly affected by particle size characteristics, even though speed was also impactful. The linear model obtained allowed the prediction of energy requirements using speed and final particle size with an R2 value of 0.97. [Display omitted] • Particle size is affected by screen sieve, rotor blade geometry and its revolutions. • The lower the blade peripheral speed the greater the difference in particle size. • Larger screen sieve sizes and lower rotor speeds produce bigger particle size. • Size reduction factor dominates the energy requirement for biomass comminution. [ABSTRACT FROM AUTHOR]