The degradation mechanism analysis of alkali metal adsorption-induced coke

Coke, as the core skeletal material, plays an irreplaceable role in blast furnace ironmaking; however, the structural degradation mechanisms under alkali metal (K/Na) adsorption conditions remain controversial. This study systematically reveals the deterioration mechanism of alkali-induced coke through adsorption experiments conducted in simulated blast furnace conditions, combined with multi-scale characterization techniques (ICP, XRD, CT, Raman, FTIR, SEM, and DFT). Results demonstrate that K induces more significant lattice distortion as its larger ionic radius, resulting in a 14.6 % reduction in crystallite size. Alkali metals adsorption increases porosity by 15 %, and K dominates the formation of medium/large pores through fragmentation of high-density matrices, whereas Na primarily enhances surface roughness. The catalytic effects accelerate sp 3 → sp 2 transformation, promoting aromatization and hydroxyl network formation while inhibiting small carbon molecule restructuring. K shifts the p-band center upward by 2.24 eV through a strong charge transfer, reducing the energy barrier of CO₂ gasification by 34 %. This behavior of K exhibits significantly higher catalytic activity than Na. K and Na demonstrate a competitive pattern between K-priority adsorption and Na-dominated destruction without synergistic effects. These findings provide atomic-scale theoretical support for coke quality control and alkali hazard mitigation in modern high-coal-ratio blast furnaces. • Elucidates the competitive K/Na adsorption mode in blast furnace coke. • Reveals the atomic-scale mechanism of alkali-induced microcrystallite deterioration. • Establishes quantitative electronic structure-catalytic activity linkage. • Proposes alkali-catalyzed graphitization and functional group reorganization. • Provide a catalytic mechanism diagram for the gasification reaction of alkaline metals on coke.