Micromechanical characteristics of compression densification of spent mushroom residue biomass based on DEM

To fill the research gap regarding the influence of particle breakage on biomass densification, waste mushroom substrate (SMS) was used as the raw material. A Tavares breakage model was established, and EDEM simulations together with experimental analyses were carried out. The results show that particle breakage exhibits a staged evolution during compression. The relative breakage rate increases slowly, then rapidly, then slowly again before stopping. The voidage decreases nonlinearly with compression. After compression, the voidage along the compression direction shows spatial inhomogeneity, increasing from top to bottom, which is consistent with the BET pore volume measurements. Force response analysis reveals that a pronounced arching effect is observed, which is one of the reasons for the decrease of force chains along the compression direction. A quantitative analysis of force chain evolution was also performed, and the results are in good agreement with the trend of experimental particle microhardness changes. SEM analysis further indicates that fine particles generated by breakage fill the pores and, together with lignin softening, form a bonding structure, which corroborates the simulation results. This study provides a basis for understanding particle breakage during biomass densification and its impact on fuel quality.