The effect of microwave pretreatment on the moisture content window and particle properties during the densification of bamboo biomass

This study addresses common issues associated with bamboo biomass pellet fuel, such as low energy density, poor compaction strength, and unstable combustion, particularly focusing on the critical challenge of precisely controlling moisture content during the manufacturing process. To tackle these issues, the study employs microwave pretreatment technology in conjunction with the response surface method to simplify moisture control and enhance pellet performance. Scanning electron microscopy (SEM) observations of the formed pellets revealed that the lignocellulosic structure of bamboo fibers became looser after microwave pretreatment, while the internal structure became denser following compression molding. Moisture content experiments demonstrated that microwave pretreatment markedly dampened moisture-content fluctuations in bamboo powder, improving its homogeneity, fundamentally broadening the operational process window and reducing control difficulties. Grouped experiments indicated that molding pressure and microwave pretreatment are the primary influencing factors, while moisture content has a negligible effect. Response surface analysis indicates that molding pressure and microwave pretreatment significantly impact the physical properties of the particles, whereas the effect of moisture content is relatively weak. By constructing a quadratic polynomial equation to establish the relationship between density, compressive strength, and molding factors, the optimal process parameters were established as follows: microwave treatment at 300 W for a duration of 3 min, molding pressure set at 66 MPa, and moisture content maintained at either 8.71% or 9.29%.TG-DTG curves indicate that microwave pretreatment improved the combustion performance index (S) of the bamboo pellets, lowering the combustion completion temperature while maintaining the ignition temperature, thus enhancing the efficiency of the combustion process. This study provides new technical solutions, process routes, and theoretical foundations for the high-value utilization of bamboo pellet fuel.