Experimental and DFT investigation on the impact of red mud waste on syngas and char from lignite partial gasification

In this study, partial gasification experiments of Shaerhu coal (SC) were conducted under varying temperatures and RM addition ratios, combined with DFT calculations and characterization techniques, to investigate their effects on the properties of products. The results showed that elevated temperatures promoted CO and H2 generation, whereas RM primarily enhanced H2 production. Consequently, CGC yields increased by 416.49 mL/g and 47.93 mL/g under temperature rise and RM addition, respectively. Temperature elevation facilitated char graphitization and lateral growth, with oxygen-containing groups initially decreasing and then increasing. RM addition caused an initial increase in oxygenated groups due to enhanced surface reactivity, followed by their consumption and later regeneration. DFT calculations revealed that α-Fe2O3, the active component in RM, formed Fe-O-C coordination bonds with SC and acted as a bridge to adsorb O2, reducing the adsorption energy from −0.32 eV to −0.54 eV and lowering the activation energy. This promoted the cleavage of aromatic structures and regeneration of oxygen-containing groups, explaining their N-shaped variation with RM. The pore structure of char showed a rise-then-fall trend with both temperature and RM, while reactivity declined with temperature but also exhibited an N-type trend with RM, indicating reactivity was primarily governed by chemical structure rather than physical porosity.