Relationship between coal ash composition and ash fusion temperatures

► This study is based on a five-component SiO2-Al2O3-CaO-Fe2O3-K2O system. ► This study uses a combination of XRD and SEM techniques. ► The effects of CaO, Fe2O3, K2O and silica-to-alumina ratio on AFTs are studied. ► Conclusions found from synthetic ashes are applicable to real coal ashes.