Sequential evolution of structures resulting from anthracites graphitization: Petrographic approach Evolução sequencial de estruturas resultantes da grafitização de antracites: Abordagem petrográfica

This paper aims to highlight the significance of petrography in the study of structures resulting from the graphitization of anthracites. Three anthracite from Peñarroya- Belmes-Espiel (PBE), Spain, Alto Chicama (AC), Peru and Douro (D), Portugal basins, with different composition and rank (Rr 2.62%, 5.23% and 6.25%, respectively), were carbonized at 1000℃ (carbonization), and then heat treated at temperatures of 1500℃, 2000℃ and 2500℃, in a graphite furnace (graphitization). All samples resulting from heat treatment are predominantly composed of dense particles whose optical behavior varies with temperature, showing similar characteristics to those of graphite in the D sample at 2500℃. With increasing temperature, other graphitic structures develop, such as crystalline aggregates, flakes, and microspheres, which seem to grow mainly at the expense of dense particles. Although occurring in small percentage, these particles reach a significant proportion in the D sample at 2500℃. All these aspects may be observed in a routine microscopic analysis, facilitating the selection of material for further studies