Effect of struvite addition on relieving the slagging tendency during Zhundong coal combustion

Zhundong coal is a kind of high-quality power coal, but serious fouling and slagging may occur due to the rich content of alkali and alkali earth metals (AAEMs). Combustion experiments were carried out on an electrically-heated tube furnace at different temperatures air atmosphere. The raw coal and its mixtures with struvite additive (2~8 wt% of coal mass) were respectively burned in air atmosphere. Combustion-generated ashes were collected and analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffractometry (XRD), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). Results show that the mixed coal ash at high temperatures has a looser and brittle structure than the raw coal ash, and is easier to be removed. With the introducing of struvite, whitlockite, and chladniite appear, which improves the melting temperature of the mixed coal ash while gehlenite (Ca2Al2SiO7) and akermanite (Ca2MgSiO7) disappear. The high content of calcium in Zhundong coal ...