Influência do manuseio e caracterização mineralógica do minério de ferro na confiabilidade operacional das plantas de beneficiamento

Abstract

Operational reliability studies developed for mineral processing plants have identified several contributors to production losses over the past years. Generally, the main factors are correlated with mineralogical characteristics, flow properties, beneficiation type, equipment design, and operational conditions. It is important to note that ore bodies vary across different regions of Brazil, as well as globally, in terms of particle size, moisture, chemical composition, and crystal structure, making the definition of operational criteria and standards highly complex. Likewise, beneficiation plants are customized according to the characteristics of the existing mineral deposit. The plants observed for the operational reliability study consist of comminution, classification, filtration, storage, and dispatch stages, with production loss-related issues present in all stages, although with varying intensities throughout the year and as mining progresses. In order to assess the contributors impacting the beneficiation process, various tests were conducted, including mineralogical characterization, chemical analysis, particle size analysis, flow property tests, among others, focusing on ore samples from Plants B (MFUN) and A (MFB7030) to understand the causes of operational losses due to material flow difficulty. The analyses reveal that samples from Plant B are predominantly composed of iron oxides and gibbsite, while those from Plant A mainly contain iron oxides. Differences in mineralogical composition are reflected in distinct fluid dynamic behaviors, with MFUN demonstrating greater cohesion and the need for higher chute angles for flow compared to MFB7030. These differences are explained by the processing route, where Plant B natural moisture processes, resulting in a higher presence of fine fractions of clay minerals, while Plant A employs wet processes, removing these fractions. This affects material flow, influencing screening classification and crusher performance. Additionally, the presence of cohesive materials can lead to obstructions at various stages of the production chain. Therefore, adequate mineralogical characterization is essential to define process routes and operational conditions. Considering the results, it was identified that approximately 10% of transition points between plants are critical and require further studies to minimize operational bottlenecks. Through the results, it is possible to obtain technical inputs to determine important information regarding beneficiation processes and asset performance, such as silo and chute outlet openings, volumetric occupancy (belts, chutes, silos, screens, and crushers), lining for material flow optimization, resting and discharge chute angles (chutes, silos, and yards), dead space sizing, belt occupancy, equipment capacity sizing, etc. In summary, this study highlights the importance of the interaction between flow properties and mineralogical characterization to optimize the operation of beneficiation plants.