Inovação Tecnológica no Processo de Cominuição da Pelotização: Substituição da Moagem a Úmido Por Multiprensagem a Umidade Natural

Abstract

The pelletizing process of Vale S.A.'s pelletizing plants is composed of different unit operations, among them, the comminution, or fragmentation, of iron ore particles, traditionally carried out by wet ball mills, known to have low energy efficiency, and highpressure grinding roll (HPGR), commonly associated with higher fragmentation efficiency equipment. Due to the operation of a wet grinding, dewatering operations such as thickening and filtration are necessary to adjust the moisture of the particles for the agglomeration process. The development of dry or natural moisture grinding routes can simplify the pelletizing process, promoting opportunities for gains such as reduction of operating expenses, environmental gains and reduction of risks associated with pumping and transport of pulps. The present work analyzed on a pilot scale the replacement of the traditional route by the route performed by multiple pressings, analyzing its application potential in Vale S.A.'s Plants 1 and 2. The results of the new route demonstrated a 53% reduction in operating expenses, environmental benefits with the reduction of 457,250 l of water, which represents the elimination of new water consumption in the comminution process, 89,292 l of lubricating oil, 6,480 kg of mineral grease and 29,760 MWh of electricity per year, equivalent to 98,4, 66,7 and 18,3% reduction, respectively. The fired pellets of the new route showed good compressive strength and a minor abrasion increase, demonstrating viability regarding their physical quality. On the other hand, there was a slight loss of metallurgical quality (lower metallization and reducibility) that may be associated with a lower moisture of the green pellets (necessary for the formation of the pellets of the new route), and greater degradation after reduction, which can be addressed in a greater degree of deepening in future studies, to increase the reliability and attractiveness of this new route of comminution.