Comparison of structural models for high-ash char gasification

Abstract

Structural models for the gasification of high-ash char are developed from different approaches to the depiction of the char pore structure. The description of the pore structure of a high-ash char particle is based on the structural characteristics of high-ash containing coal reject char. A finite overlapping grain model (FOG), modified random pore model (MRP) and a model based on the percolation theory on Bethe lattice (PBL) are formulated. These models take into account the effect of ash content by considering it as an inactive inclusion. Comparisons of these models are presented based on the parametric simulation results. It has been shown that both the MRP and PBL models can predict similar behavior of high-ash char gasification. The effect of ash content on the surface area and reaction rate evolution is shown to be significant. The percolation model has an advantage in that it can describe the closed pore evolution and predict particle fragmentation.