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Highlights

The rice husk and straw biochar particles were statistically analyzed, and two representative particles were obtained.

Abstract. The discrete element method (DEM) is widely used in modelling particulate materials and related applications. DEM modelling requires the calibration of a large number of microparameters that are difficult to experimentally measure. This study aims to obtain the contact parameters of different types of biochar accurately and quickly and proposed a parameter calibration method for biochar particles to verify, which uses particle density, moisture content, inter-particle friction coefficient, particle and steel plates. A mathematical model was established for predicting parameter of friction coefficient, Johnson-Kendall-Roberts (JKR) surface energy, and contact behavior. The parameters were verified using the engineering design measurement method and a simulation analysis using a commercial software called Rocky. The results showed that: (a) the data obtained using the cylinder lifting method and the stacking and angle of repose tests of the drawing plate method were stable, the angle of repose of the biochar pellet pile was measured to be 36.55°; (b) the steepest climbing test results indicated that with the increased of Biochar-biochar rolling coefficient, Biochar-steel restitution coefficient, and JKR value, the angle of repose gradually increases; (c) a quadratic regression model was established through a Box-Behnken experiment, and it was found that the interaction term had an extremely significant effect on the angle of repose of biochar particles; (d) a preliminary design of a biochar return machine was created based on the calibration, simulation and actual test results.