Example Parameters I am leaching 5000 tons per day of sulfide based Cu ore –The ore has been crushed and placed on pads Size is about 1.5 inch topsize Grade is 0.27% Cu on average My weight is 3000 lbs per cubic yard (loose partly packed volume) My leach cycle is about 200 days I will get about 50% recovery In practice recovery, leach time, are dependent on crush size and mineralogy –Sulfide leaching is usually not carried out with a continuous 200 day run There is a leaching cycle – as solution grade falls it is put into rest Then leaching is resumed after a rest cycle
My Design Conditions Ore is in piles with a 6560 square foot cross sectional area –See example presentation on pad design for dimensions My Solution Application rate is gallons per minute per square yard –This is about the highest application rate not likely to produce ponding or flooding.
Derived Parameters 200 days of ore at 5000 tons per day is 1 million tons At 0.27% copper and 50% recovery I will recover 2.7 million pounds of copper. 1million tons is 18 million cubic feet at 3000 lbs/cubic yard A pile with 6560 square feet of cross section will be 2743 feet in length –With base parameters from last presentation area under leach will be 23,171 square yards –This suggests a flow rate of 579 gallons per minute (2200 liters per minute) –Over 200 days that is million gallons –With 2.7 million lbs of copper the leachate will average 1.93 grams/liter
We Can Estimate Our Costs for this System with the Bureau of Mines Cost Estimating System The 1982 dollar cost is –103, *(X) for labor (including burden) –442, *(X) for equipment X is the flow rate is liters per minute (2200) in my case The cost provides for the distribution system, the pond, pumping to an SX/EW plant, and pumping the solutions back for circulation By Plug and Chug my cost is $1.44 million dollars
Operating The System Labor for moving and handling the piping and doing maintenance is –4.21*(X) Operating the Pumps, buying replacement parts and reagents is –0.07*(X) The results are daily operating costs –Operating $ –Labor $64 (USBM base labor rate is $18.55/hour including the benefits – obviously this is useful for upgrading to 2009 dollars)
What Information Is Needed for the Leach Economics Make sure the cost of blasting, mining, and delivering the material to the leach is counted – but only once The cost of crushing operations was supposedly developed separately The cost of trucking the material to the piles and then dozing to shape the piles is assumed to have been developed using FPC by Caterpillar The Capital Cost for Building the Pads was illustrated in the previous slide presentation This presentation provides capital and operating costs for the ponds and the leachate distribution and collection system (obviously the dollars need to be updated) Costs for running SX/EW are presumed to come from other sources