Char morphology characterization from pulverized coal: a review

Abstract

Char is the solid remainder from coal when subjected to volatile matter extraction at high temperatures in inert atmosphere and at short residence time (devolatilisation process). Generally, this process is carried out in fluidized bed reactors, in drop tube furnace and electrical meshes. The operation conditions, such as atmosphere type, heating rate, temperature and pressure, and coal characteristics, such as rank, petrographic composition and microlitotypes, produce morphologic changes in the char structure and different solid remainder types is obtained. These morphologic differences directly affect the combustion process characteristics. In this paper, the historical development of the char morphologies classification is summarized. Initially, the classification was carried out by manual analysis, and actually automatic image analysis is used. However, different classifications were reported in the literature, which led to the need for a unified system of classification. Recently, ICCP (International for Committee Coal and Organic Petrology) introduced a morphology char classification system.