Direct Leaching Alternatives for Zinc Concentrates

As zinc consumption is gradually increasing worldwide, many zinc plants are exploring potential expansions. However, the saturation of the sulphuric acid and fertilizer markets poses challenges, particularly with the costs associated with the roasting-acid plant section impacting feasibility calculations for these expansions. To address these challenges, two proven direct leaching technologies for zinc concentrates are available, while a third method lacks industrial application. This paper discusses the economic considerations scrutinized by zinc plants regarding cost efficiency, total recovery of zinc, and the accessibility of consumer markets for zinc and sulphuric acid. Profitability analyses often indicate that expanding the roasting/acid plant-leaching-solution purification-electrowinning-casting route may not be economically viable due to low market prices for sulphuric acid. The paper also examines three alternative direct leaching methods, emphasizing pressure leaching and atmospheric leaching processes that have established applications in the zinc industry, alongside challenges in iron removal during direct leaching of zinc concentrates. This comprehensive evaluation aims to highlight feasible alternatives for zinc plant expansions amid market constraints.