CO2 gasification reactivity and syngas production of Greek lignite coal and ex-situ produced chars under non-isothermal and isothermal conditions: structure-performance relationshipsCO2 gasification reactivity and syngas production of Greek lignite coal and ex-situ produced chars under non-isothermal and isothermal conditions: structure-performance relationships Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2023-10-102022enThis research was co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH-CREATE-INNOVATE (project code: T1EDK-01894).The presented work explores the structural properties, gasification reactivity, and syngas production of Greek lignite fuel (LG) and ex-situ produced chars during CO2 gasification. Three different slow pyrolysis protocols were employed for char production involving torrefaction at 300 °C (LG300), mild-carbonization at 500 °C (LG500), and carbonization at 800 °C (LG800). Physicochemical characterization studies, including proximate and ultimate analysis, X-ray Diffraction (XRD), and Raman spectroscopy, revealed that the thermal treatment under inert atmospheres leads to chars with increased fixed carbon content and less ordered surface structures. The CO2 gasification reactivity of pristine LG and as-produced chars was examined by thermogravimetric (TG) analysis and in batch mode gasification tests under both isothermal and non-isothermal conditions. The key parameters affecting the devolatilization and gasification steps in the overall process toward CO-rich gas mixtures were thoroughly explored. The gasification performance of the examined fuels in terms of carbon conversion, instant CO production rate, and syngas generation revealed an opposite reactivity order during each stage. TG analysis demonstrated that raw lignite (LG) was more reactive during the thermal devolatilization phase at low and intermediate temperatures (da/dtmax,devol. = 0.022 min−1). By contrast, LG800 exhibited superior gasification reactivity at high temperatures (da/dtmax,gas. = 0.1 min−1). The latter is additionally corroborated by the enhanced CO formation of LG800 samples under both non-isothermal (5.2 mmol) and isothermal (28 mmol) conditions, compared to 4.1 mmol and 13.8 mmol over the LG sample, respectively. The pronounced CO2 gasification performance of LG800 was attributed to its higher fixed carbon content and disordered surface structure compared to LG, LG300, and LG500 samples.http://creativecommons.org/licenses/by/4.0/Energies153Lampropoulos_et_al_Energies_15(3)_2022.pdfChania [Greece]Library of TUC2023-10-10application/pdf6.8 MBfree Lampropoulos Athanasios Binas Vassilios Zouridi Leila Athanasiou Costas Montes-Morán Miguel A. Menéndez J. Angel Konsolakis Michail Κονσολακης Μιχαηλ Marnellos, Georges E MDPI Greek lignite coal Lignite chars CO2 gasification Raman analysis Gasification reactivity Syngas production