Operations and Process Diagram
“The PV deposit is mined by conventional open-pit mining methods and is being mined in multiple phases. The ore is selectively mined and its allocation within these processes is defined depending on the grade, mineralization, leaching and flotation characteristics:”
Run of mine low-grade ore directly for leach pads
Medium-grade ore to crushing and screening system then moved through the conveyor stacking system to leach pads.
Hydrogen crushed ore form re-handled material to be leached with aeration.
Ore to Concentrate
Hight-grade crushed ore for flotation process sold to Kupari.
Operations and Processes
Copper Cathode Production
We operate 24 hours per day, 365 days per year.
Mining follows a traditional drill, blast, load haul dump sequence of mining. Every day we blast between 170,000 and 220,000 tons of rock. This blasted rock is mined and loaded onto 200-ton haul trucks, and depending of its characteristics is intended within the following processes:
The main crushing system is utilized to crush the ore to a size range that would improve percolation of acid solutions (raffinate) through the heaps and to screen altered ore to reduce high clay content fines to levels that allow good permeability and copper recovery. This crushing system crushes up to 25,000 tons per day and starts with the primary crusher, which reduces rock size to below 6 inches and delivers it to a 75,000-ton buffer. This crushed rock is then delivered by four apron feeders to two secondary crushing and screening systems that reduce rock size to around one inch, in order to maximize copper recovery through leaching. The crushed ore is then moved through a series of conveyors and placed on the leach pads using a TNT grasshopper and stacking system that places it on leach pads. The stacked ore is then leached with a slightly acid solution (raffinate), with a pH similar to lemon juice, which captures most of the copper contained in the ore by chemical and biological processes.
The warm, relatively dry climate at the PV Mine lends itself to a heap leach operation. The process consists of leaching the ROM and crushed ores with acidified solutions (raffinate recycled from the SX/EW plant). As the solution percolates through the heap, it dissolves copper from the oxide and chalcocite ores. Iron containing minerals such as pyrite also oxidize and dissolve to form ferric sulfate solution, which is the active leaching agent for chalcocite ores. The copper-rich solution is termed “pregnant leach solution” (“PLS”).
The process design for the CDM Piedras Verdes Leach SX/EW operation was originally based on a nominal production rate of 32 ktpa of LME Grade A Copper Cathode using conventional sulfuric acid/ferric sulfate heap leaching and ROM ore.
The entire leach pad is lined using a composite liner system consisting of a prepared base material, synthetic liner, and layer of suitably sized material to both protect the liner from damage during ore placement and to promote rapid drainage of the PLS. The PLS collection system is a network of HDPE pipes that collect the PLS and delivers it to the PLS ponds. These collection pipes are placed above the geomembrane liner in shallow collection trenches, which generally follow the natural drainages along original ground contours. The PLS flows by gravity to the PLS collection pond where it is pumped at 3,900 cubic meters per hour to buffer ponds that feed a solvent extraction plant and subsequently flows by gravity to be fed to the electro-winning tank. Here an electrolytic process is used to form copper cathodes. This facility draws 8 megawatts, about enough electricity to power 7,000 homes. The cathodes take a week to be completely formed to meet LME Grade A standard which requires 99.99% purity. These are harvested, separated and stacked for delivery to customers.
The altered ore is processed by the Fines Classification System to enable us to process high clay content and other fines generated by crushing highly altered ore. This system separates the fines into a coarse fraction (leachable ore) that is added to the conveyor system to be sent to leach pads and into a fine fraction (floatable ore or slimes) that is processed into concentrate by floatation by Kupari Metals.
Sale of Ore for Copper Concentrate Production
The higher-grade, refractory and vein type ores are better suited to processing by flotation than by heap leaching. Therefore, these ores are delivered to the high-grade crushing and screening system. This system crushes up to 7,500 tons per day.
The high-grade crushing system starts with a blending area that feeds a primary gyratory crusher, rock moves to secondary and tertiary crushers, and to screening systems that operate in a closed loop to ensure the delivery of rock crushed to below 3/8 of an inch. This finely crushed ore is then sold to Kupari Metals, who operates the adjacent flotation plant that processes about 6,000 tons per day of ore into a copper concentrate by chemical and physical processes.
Marketing & distribution
We sell our copper cathode under agreements with well-known, reliable and creditworthy commodity traders that pay for the copper cathode before it leaves the mine, thereby absorbing all risks and expenses of transporting the copper cathode. We typically conduct a competitive process to select a purchaser for our copper cathode for contracts that have lengths of six to eighteen months.
Cobre del Mayo’s entire copper cathode production for 2015 is currently sold to two renowned international commodity traders at prices slightly above the spot LME Grade A Cash Settlement price (50% of the cathode production to each trader). Both agreements were closed are valid from January 1st, 2015 through and including December 31st, 2015.