Investigation of sintering and fusibility of iron-rich coal ashes derived from varied coal mines under air condition

Coal is the largest single source of electricity in China. Feeding low-quality coal in combustion boilers, such as high-iron bearing coal, is an effective way to raise the competitiveness of boilers. However, the ash-related issues need carefully demonstrated to ensure the safe running of boilers. In this work, the sintering and melting behaviors of three representative iron-rich coal ashes being derived from largely varied coal mines are comparatively investigated. The results indicate that the occurrence mode of iron differed largely in various high iron-bearing coal, nonetheless, iron contents present a finite ability to decrease onset sintering and fusion characteristic temperatures. Further exploration demonstrates that iron-bearing matters are excluded in the formation of initial slag. Besides, the swelling during the melting process was observed for all iron-rich coal ashes and the swelling extent positively relates to the gas content, and the swelling temperature range negatively relates to the gas emissions speed. The melting events following the swelling finished in a short temperature range for iron-rich coal ashes and present more like the mechanism of “melting-dissolution”. The study can provide guidence for utilization of high-iron-bearing coal in combustion boilers.