Enhancing Density and Durability of Biomass Pellets through Optimized Pressurized Binder Spraying and Process Parameters

To reduce the energy consumption of biomass densification, this study proposes a method of constructing solid bridges through pressurized binder spraying. The feasibility of this method for producing high-quality biomass molding was studied under ambient temperatures and lower pressures. Four-factor mixed-level orthogonal tests were designed to evaluate the relaxation ratio and durability of density pellets, in which the molasses served as the binder. Pressurized spraying of the binder resulted in a 27.0% increase of relaxation density, 8.21% decrease in relaxation ratio, and significantly enhanced durability compared to stirring method at pressure 40 MPa, which was determined in preliminary testing to conform to at least 95% durability. A multivariate quadratic regression equation through response surface analysis was established by selecting a 2FI model for the 100% importance in binder addition method. The relaxation ratio was normalized to the weights of the influencing factors obtained from model of multi-layer perceptron neural network. The test factors had a significant impact of on the relaxation ratio, and thus, the optimal combination condition for test was determined as 50 (MPa) densification pressure, 14% moisture content, 4% binder ratio, and pressurized spraying at 2 (MPa). These conditions reduced the minimum densification pressure required for biomass densification.