Suppressing the volatilization of alkali metals during pyrolysis is crucial for advancing biomass gasification. In this study, the release of potassium (K) during corn stover (CS) pyrolysis was effectively inhibited by in situ modifying the char structure with addition of polyethylene (PE), and the mechanism was also explored. At 700 ℃, the K retention in the mixed char containing 30% PE reached 91.36%, significantly higher than the 69.73% observed without PE addition. The positive role of PE on the improvement of C-O content in mixed char was an important reason for the higher K retention. Compared to pure CS char, both organic and inorganic K (KCl) contents increased after PE was added, with organic K consist of C-K and C-O-K showing a more pronounced rise, especially the significant increase of C-O-K. PE also facilitated the conversion of some inorganic K into organic forms. Additionally, PE moderately enhanced the defects of chars, conducive to K retention. This study provides theoretical support for restricting K release during biomass pyrolysis and gasification.

pyrolysis, potassium retention, biomass, polyethylene