Investigation on microwave torrefaction: Parametric influence, TG-MS-FTIR analysis, and gasification performance

Microwave torrefaction (MT) was proposed for pre-treating herb residue (HR), which is a typical high moisture biomass waste. A series of comparative experiments between MT and conventional torrefaction (CT) on HR were conducted. The effects of temperature, time, moisture content of HR, and microwave power on torrefaction performance and microwave energy consumptions were comprehensively investigated. With the response surface methodology (RSM), the combined effects between each two parameters were analyzed, and the moisture content was evaluated as the most influential factor for torrefaction and energy consumption. The effects of microwave on torrefaction were comparatively evaluated by TG-MS-FTIR. MT could remove bound water efficiently. With the rupture of HR structure and the high-degree decomposition of hemicellulose and lignin, MT positively influenced the yields of the permanent gases and organic volatiles. Moreover, the gasification performance of different HR samples were evaluated in a fixed bed gasifer. MT-HR showed the highest gas yield (0.86 Nm(3)/kg) and heating value of gaseous products (13.70 MJ/Nm(3)), with the lowest tar generation (12.72 wt %). This study provides an in-depth understanding of MT process, and the MT integrated with steam gasification can be regarded as a feasible approach for high-moisture biomass waste treatment. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study compared the effectiveness of microwave torrefaction (MT) and conventional torrefaction (CT) on herb residue (HR), showing that MT is more efficient in removing bound water and generating gases. Moisture content was identified as the key factor affecting torrefaction and energy consumption, while MT-HR exhibited superior gasification performance.