Post by
ganndolph1 on Oct 23, 2020 6:51pm
Taguas SART Plant would reduce costs by $120 USD/oz Au
all,
To follow up on my previous post, I looked at the Lindero heap leaching model and its applicability to Taguas, and asked the following questions:
What is the heap leaching plan? What is the irrigation rate? Did the consultant writing the 43-101 report do numerical heap leach modeling?
In the case of Lindero, yes there is a heap leaching plan which calls for 12 liters per hour of primary leach for 30 days followed by 60 days of secondary leach at 6 liters per hour. And the 43-101 report provides the following summary of the heap leach numerical modeling presented in Section 13.3 of the Lindero 43-101 report:
"The heap leach and associated processes were modeled using METSIM simulation software (version 2015.08) to develop a dynamic mass balance for the life of the operation. The primary objectives were to estimate monthly metal productions for gold, silver and copper and to evaluate the buildup of copper that will occur in leach solution. For the model, the heap leach was divided into about 1,700 3-D blocks to represent the geometric shape of the heap as it is stacked with ore. The heap blocks were sequentially filled with ore according to the mine plan, and leach extractions for gold, silver and copper were performed according to extraction curves established for each ore type.
Solution transport through the heap lifts was calculated according to the primary and secondary applications of leach solution to ore. The dynamic model tracked inventories in heap pore solution for water, cyanide and metals (Au, Ag, and Cu). Solution exiting the heap was managed for preg-building by routing the highest gold tenors to the pregnant leach solution (PLS) tank, while lower tenor solution was recycled and applied to the heap as intermediate leach solution (ILS).
A daily mass balance was calculated for the heap leach, solution ponds/tanks, the ADR plant and the SART plant. The size of the SART plant was varied in early modeling trials and it was determined the SART plant will be designed to treat 400 m3/hr of pregnant solution. The model was developed according to the configuration of systems shown on the overall process flow diagram as detailed in Figure 17.2 in Section 17."
For Taguas the assumed irrigation rate is 12 liters per hour per square meter with a total design irrigation rate of 419 cubic meters per hour which is almost identical to the Lindero primary leach flow rate. The design cyanide concentration is 500 ppm at Taguas, and the projected cyanide use is 0.59 kg/t of throughput. The ADR plant production capacity is 50000 oz per year gold.
So at Taguas, the copper values in the ore are between 18 and 27 percent of the copper values at Lindero, so the question is whether Taguas would benefit from a SART plant added to the design of the Taguas production facility.
Let's assume that the Taguas SART plant is identical to Lindero and sized to handle 400 cubic meters of throughput per hour. Capex for the SART plant is $20 million USD.
The SART plant at Lindero is projected to produce 330 tons of copper per quarter. So with the identical leach strategy as Lindero, Taguas could produce between 59.4 tons per quarter to 79 tons per quarter of copper. With copper at $3 USD per pound, the additional revenue from copper sales would be between $389,400 USD and $521,400 USD per calendar quarter.
The SART plant also recovers any zinc and silver that are present in the throughput. If we assume that silver recovery increases by 10 percent with the addition of a SART plant that is 50,350 additional ounces of silver production. At $23 USD silver, that adds $1.158 million USD in additional silver revenue per quarter.
The SART plant also enables the recovery of between 2 to 4 tons of cyanide for each ton of copper produced, so between 118 and 237 metric tons of cyanide would be recycled to the heap leach per quarter. The estimated quarterly cyanide requirement is 637 metric tons, so the quarterly cyanide use could be reduced by between 18 and 38 percent with the addition of a SART plant in the Taguas design.
That is a savings of between $260,000 to $520,000 USD per quarter in material cost.
The estimated cost of operating the Lindero SART plant is $1.5 million USD per quarter, The same size SART plant at Taguas would cost $1.0 million USD to operate and generate additional revenue of between $800,000 USD and $1,200,000 USD per quarter. The key factor at Taguas would be how much extra silver could be recovered by the SART plant? If the silver recovery was increased from 52 percent to 72 percent, then that would add another $1 million USD per quarter in revenue at the current silver price.
With respect to the cost per ounce of gold production, a SART plant at Taguas would decrease the cost of gold production by between $78 USD/oz to $120 USD per ounce based on the assumption of a 10 percent increase in the silver recovery as a result of having a SART plant.