The depletion of surface copper deposits, which are strongly associated with soluble copper ores in acid media, has increased the search for operational profitability by processing subway copper deposits relevant to primary and secondary sulfides, which are inert to typical chemical dissolution processes. This has boosted the research and development of alternatives to conventional leaching in order to avoid the disuse of hydrometallurgical plants, which have clear environmental and economic advantages over pyrometallurgical plants.
An example of this is the electrochemical dissolution process, which relies on an exchange of electrons through redox reactions to recover the valuable species. The main leaching methods used to obtain the element of interest from copper sulfide ores are leaching in chloride medium and, secondarily, bioleaching, in these processes, the presence of an oxidizing agent such as oxygen is of great importance to achieve the dissolution of the cupric ion, since in the case of chloride leaching, this allows the formation of solid species such as CuCl to be discouraged, thus inhibiting precipitation losses.
However, the oxygen that enters the heap bed does so in the form of dissolved oxygen in the leaching solution flowing through the bed or by molecular diffusion mechanisms, which for the needs of the operation constitutes a poor concentration of oxygen in the process, impairing the subsequent economic benefit by decreasing the efficiency of recovery.
Therefore, if there is not an adequate oxygen concentration in the leaching system, total oxidation of the treated material of interest could easily not be achieved, resulting in a significant decrease in copper extraction from the heap. Therefore, it is essential to ensure the presence of oxygen in the bed to optimize the production process.
Depending on the characteristics and operational needs of the leaching heap being used, the oxygen supply can be carried out by forced convection mechanisms through the implementation of a network of injection pipes located approximately one meter above the base of the pad, although, depending on the drainage system used in the heap, the recommendation will be to locate the aeration system above the basal water table to avoid possible obstructions. The supply network allows the homogeneous distribution of air at low pressure using blowers, then the point emitters of the pipes generate an ascending air flow that contacts the bed. However, if the dimensions of the piles exceed the capacities of the aerators, the air injection is done by natural convection mechanisms through the pipes.
For a correct design of the aeration system, it is necessary to know parameters such as the hydraulic and pneumatic conductivity of the pile, which allows understanding the behavior of the microstructure, pore connectivity and tortuosity of the bed. This information, in addition to the irrigation rate, makes it possible to estimate the liquid saturation of the pile when it comes into contact with the bed, which in turn allows obtaining a conductivity ratio with respect to the air that finally translates into the determination of the air pressure in the emitter necessary to obtain the flow of oxygen required in the process.
Having said this, having an appropriate aeration system in the leaching heap ensures the concentration of oxygen in the bed, which leads to the presence of an oxidizing environment that inhibits the loss of valuable material due to the resistance to acid dissolution inherent in copper sulfide minerals. This favors the dissolution kinetics during the first months of recovery, allowing higher copper recoveries to be obtained, guaranteeing the technical-operational performance of the process and, therefore, generating better quality product in the subsequent stages of the plant.
