Migration behavior of potassium under condition of steam gasification of Yulin coal

A fixed bed reactor and atomic absorption spectroscopy were used to investigate potassium recovery efficiency of Yulin coal loaded with potassium carbonate (ZA-K), Yulin demineralized coal loaded with potassium carbonate (ZA-THK) and synthetic ash (Configurations of four oxides: SiO₂, Al₂O₃, CaO, Fe₂O₃) loaded with potassium carbonate after reaction. Fourier infrared spectroscopy and Raman spectroscopy were used to study influence of structural evolution of ZA-K and ZA-THK on migration of potassium during pyrolysis. The results show that the yield of water-soluble potassium decreases with increasing temperature. Three times water washing could recover 94.06%−98.80% of the total water-soluble potassium. Formation of insoluble potassium is due to the phase of potassium aluminosilicate formed by potassium, silicon and aluminum in the coal ash. Potassium is easier to volatilize from ZA-THK than that from ZA-K. At 700−850 ℃ potassium in ZA-THK is volatilized 10.28%−44.92% higher than that of ZA-K, resulting from that the ash in ZA-K would fix the loaded potassium in coal ash. Another reason may be caused by decrease in the degree of aromatic polymerization of ZA-THK through demineralization process, leading to more small-ring aromatic structures (2−8 rings) appearing in the coal.