Degradation of a Steam Dryer for Copper Concentrate before Smelting

Sammanfattning

Steam dryers used for copper concentrate drying at Boliden Rönnskär are exposed to harsh operating conditions, resulting in material degradation and limited component lifetime. The aim of this study was to investigate the degradation mechanisms affecting different components of the steam dryer and to evaluate possible improvements regarding material selection and design. Visual inspection, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyze samples collected from different regions of the dryer. The results showed that both corrosion and erosion contribute to the degradation, although their influence varies depending on the location within the dryer. In the earlier stages of the drying process, galvanic corrosion and dealloying were observed, whereas in the later stages erosion was identified as the dominant degradation mechanism on stainless steel 2205, resulting in significant material losses. Based on the identified degradation mechanisms, alternative material choices including 654 SMO and 2507 were evaluated together with possible design modifications, intended to reduce wear and improve the components’ lifetime. The results from this study contribute to an improved understanding of the degradation mechanisms in the steam dryers used for copper concentrate drying, and may support future improvements regarding material selection, maintenance and operational efficiency as well as lower the material consumption relevant from both an economical and a sustainability perspective.