Surface Morphology of Blended Molding Pellets Made of Desert Caragana and Maize Stover

Abstract

The surface morphology of biomass pellets can provide data for the contact mechanics fractal model between the molding pellet and hole in biomass molding machines and for predicting wear of the molding hole. In this study, desert caragana (Caragana korshinskii) was mixed with residue from maize production, crushed, and compressed into pellets, which were used to collect data on their circumferential surface roughness profile, density, diameter, and hardness. The results showed that frictional wear occurs during contact between the forming hole and the molding particles, increasing the diameter d₀ of the forming hole and the diameter d of the molding particles. The density ρ and hardness HD of the molded pellets decreased as their diameter d increased, and the ρ and HD of caragana were higher in autumn than in summer. The values of the roughness parameters R_a, R_c and R_z of the molded particles increased with their diameter d. The maximum material rate M_r2 value of the roughness's central profile remained at 86% with the increase of diameter d. Molded particles had surface roughness kurtosis R_ku>3 and roughness skew R_sk<0 with the increase of diameter d. The surface of molded particles was spiky and negatively skewed, and with a low number of spikes.