Principles of operation and control of oxidizer in countercurrent leaching configurations

An apparatus for recovering a target metal from a feed material, comprising;

• a leaching circuit having a plurality of leaching vessels V1, V2, Vn in series;
• and
• a control module including:
• a metering system adapted for delivering the feed material feed stream to the leaching vessel V1 and moving the feed material feed stream through the leaching circuit in a first direction toward leaching vessel Vn and delivering a liquid phase, including an ammonia-based lixiviant and a Cu(II) reagent, to the leaching vessel Vn and moving the liquid phase through the leaching circuit in a second direction toward leaching vessel V1;
• at least one Cu(II) concentration monitor adapted for monitoring the concentration of Cu(II) in at least one of the leaching vessels V1, V2, Vn in the leaching circuit and collecting data respecting the concentration of Cu(II) in each of the leaching vessels V1, V2, Vn in the leaching circuit;
• and
• a controller adapted to receive the data from at least one Cu(II) concentration monitor and maintain the concentration of the copper II (Cu(II)) in the ammonia-based lixiviant in the leaching vessels V1, V2, Vn by changing the flow rate of the liquid phase, and/or the flow rate of the feed material feed stream to achieve metal removal from the feed material feed stream of between 1 and 50% in each vessel.