José Miguel Ortiz
April 12, 2022
In recent years, there has been a proliferation of copper mining projects in Chile using chloride leaching technology. Indeed, Antofagasta Minerals, CODELCO, BHP and Collahuasi, among other companies, have in their portfolios projects for the transformation of their hydrometallurgical operations to this technology.
So, the question is what is driving mining companies to consider migrating their projects to leaching. This shift is explained by the high impact it has on fine copper production; the possibility of applying it to existing hydrometallurgical facilities; mining operations with depleted oxidised copper resources, but have abundant resources of secondary and transitional sulphide ores; the transformation of a plant is more profitable due to lower CAPEX and OPEX, compared to the milling-flotation concentration process; it has limited environmental and community externalities; they are brownfield projects, with a reduced level of operational interference; and the low costs of sodium chloride (salt), which has a developed supply and is close to large mining deposits.
While Chloride Leach technology has been industrially validated for the treatment of secondary sulphides to date, these same companies are developing intensive research programmes to enable the Chloride Temperature Leach Process. This variation of the technology is being studied at the laboratory column level, and presents very interesting copper extraction levels for primary sulphides at temperatures in the region of 40°C, emerging as a competitive technological alternative for primary copper sulphides with low by-product grades (molybdenum and gold).
However, this raises the need to evaluate at industrial scale several relevant aspects of this process, such as temperature management and thermal dissipation for large heaps, heat sources, heap stability, aeration, materiality in the heap environment and solution transport, among other key aspects when defining an industrial process.
Although the capital and operating costs of this type of project have clear advantages over conventional concentration processes, there are already challenges in reducing these costs in future projects.
Some aspects that should be addressed by equipment suppliers and engineering consultants in these new projects are: environmentally friendly environmental solutions; reasonable costs for temperature management and control within the pile and in the solution handling system; corrosion control with the development of equipment based on anti-corrosion materials that are more competitive in comparison with costs and long manufacturing times, such as titanium or hastelloy; incorporation of materials with adequate structural resistance to these temperatures, as an alternative to traditional high-density polyethylene, in the design of binders and drainage systems; efficient systems for the control and reduction of more particulate matter in leach solutions; non-traditional solutions for the control of chloride carry-over from the solvent extraction vessel to the electrowinning vessel, as an alternative to the costly increase in washing stages and/or coalescers and decanters; and design and materiality of reliable, available and efficient heap aeration systems.
The development of this temperature chloride leaching technology is generating expectations in the mining market and, if it progresses along the lines envisaged, will lead to the extension of the useful life of existing hydrometallurgical facilities and the emergence of new projects. This will progressively increase the demand for low-cost technological solutions suitable for handling solutions with high chloride content.