Effects of Na and Na/CO2 Synergism on Gas/Tar Production During Rapid Coal Pyrolysis

Coal pyrolysis and gasification are among the key technologies for the clean and efficient utilization of coal. This work examined the individual and synergistic effects of Na and CO2 on gas/tar generation during rapid coal pyrolysis using a fixed-bed reactor integrated with gas chromatography–mass spectrometry (GC-MS) and a flue gas analyzer. Key findings reveal that Na, CO2, and Na/CO2 synergism increased total gas volume by 671 vol.%, 772 vol.%, and 667 vol.%, respectively, while reducing tar yields by 4.14%, 3.12%, and 7.15%. Light oil yields reached 27.18%, 27.93%, and 40.35% under corresponding conditions. Crucially, Na significantly enhanced CO and CH4 release (dose-dependent), with low-concentration Na (1–3%) promoting light-component condensation versus high-concentration Na (5%) facilitating heavy-component cracking. Na/CO2 synergism intensified heavy-component fragmentation (efficacy increasing with Na loading), while low-concentration Na (1–3%) substantially boosted CO yield, highlighting its potential for selective syngas modulation. This work plays a pivotal role in advancing the low-emission, high-efficiency utilization of coal energy, aligning with global carbon reduction strategies.