Physicochemical properties and carbon dioxide gasification reactivity analysis of lignin and lignite co-pyrolysis char

Co-gasification of biomass with coal enables more efficient utilization of carbon resources and reduces greenhouse gas emissions. In this study, the isothermal CO₂ gasification behavior of lignin/Manglai lignite co-pyrolysis char was investigated at 900–1100 °C using a thermogravimetric analyzer and a fixed-bed reactor. The structural characteristics of co-pyrolysis char were analyzed by N₂ adsorption-desorption, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray fluorescence spectroscopy. The results show that the degree of graphitization of co-pyrolysis char is higher than that of lignin and lignite char. Additionally, the morphology of the internal minerals in the char changes during the gasification process, resulting in a significant reduction in gasification reactivity. The gasification reactivity of lignin/Manglai lignite (LLC) co-pyrolysis char is lower than that of single lignin char, and its maximum CO formation rate and gas accumulation are the lowest at 1100 °C pyrolysis temperature. These findings highlight the influence of pyrolysis temperature on char structure and gasification performance, and provide valuable insights for optimizing the co-gasification process and improving CO₂ utilization efficiency. This study provides new insights into the gasification behavior of lignin–lignite mixtures and offers practical implications for sustainable energy utilization.