Caracterização da cinética de reação e comportamento das cinzas dos carvões minerais injetados através das ventaneiras dos altos-fornosda CST

Abstract

Pulverized coal injection (PCI) into blast furnaces became a very important technology in the last twenty years. One of the most relevant aspects for the success of this technology is the appropriate choice of the coals to be injected. At Companhia Siderúrgica de Tubarão (CST), coals are selected based mainly on their chemical analysis and price. It has been shown that these criteria are not enough to guarantee adequate performance of the blast furnaces where the coals are injected into. In the present work, two different coals that presented completely different performances when injected into blast furnaces have been characterized in terms of chemical and petrographic analysis, reactivity in CO2 and O2 atmospheres and reactivity of the char in air. The behaviour of the ash at high temperatures has been analyzed using X-ray diffraction and scanning electronic microscopy. The fusibility and the viscosity of the ash have also been determined. The results of these tests have been correlated to the performance of CST blast furnaces during the injection of these coals. It was demonstrated that the results of the reactivity tests, conventionally used in the selection of coals for injection into blast furnaces, could not explain the differences in the performances of the blast furnaces when those coals were injected. The results of the analysis indicated that the behavior of the ash at high temperatures,particularly in terms of fusibility and viscosity, plays a significant role in determining the performance of the coals in the blast furnace.The evaluation procedure proposed in the present work are now being incorporated into CST routine for coal selection.