Effect of different pyrolysis temperature on alkali metal K and Na emission and existence in semi-char

The modes of occurrence and emission of alkali metal of corn straw were studied at different pyrolysis temperature and all experiments were conducted on a horizontal tubular reactor. Experiment analysis included pyrolysis gases release measured with FTIR, alkali metal concentration analyzed with ICP-AES, existence form of AAEM with chemical fractionation analysis (CFA), microscopic structure of semi-char with SEM/ EDX, and type of alkali metal tested with XRD. The results showed that most of K in corn straw was inorganic K (91%). The major organic K was released during 300-600℃ with the main releasing compounds of inorganic K of KCl and K₂SO₄, etc. K migrated from inner to the surface of particle, leading to enrich K at the surface (700℃), and the content of K decreased with further increasing temperature. The release characteristics of K and Na were similar, however, the main transformation element was K. Due to the thermal stability of Ca and Mg, they were difficult to release during pyrolysis.