The Surface Characteristics and Reactivity of Residual Carbon in Coal Gasification Slag^†

Abstract

In a slagging entrained-flow coal gasifier, a large portion of the inorganic matter will form liquid slag that may have strong physical and chemical interactions with char. Understanding the char−slag interaction is important for improving the modeling and design of gasifiers. This paper reports the characteristics of residual carbon in both coarse and fine slag from a typical entrained-flow coal water slurry gasifier. The surface characteristics of slag and residual carbon in slag were evaluated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The reactivity of the residual carbon in slag was compared through thermal gravimetric analysis. It was observed that fine inorganic matters in the slag tend to exist in spherical shape whereas residual carbons tend to stay as loose floccule. A melting test on fine carbon−slag mixture validated that inorganic matters have a tendency to agglomerate into large carbon-free spheres when melting in a carbon powder matrix due to surface tension change. It was also found that the reactivity of the carbon in fine slag was lower than carbon in coarse slag, which implies the formations of the carbon in fine and coarse slag are different.