NAP battles as crusher sleeps

Mill throughput and palladium production dipped slightly at North American Palladium‘s (PDL-T) Lac des les palladium-platinum mine in northwestern Ontario, during the third quarter.

During the three months ended Sept. 30, the mill processed just more than 1.2 million tonnes of ore, or 13,161 tonnes per day, averaging 1.83 grams palladium per tonne to produce 51,168 oz, of palladium. That’s a recovery rate of about 71.9%, which is down from 76% in the previous quarter when the mine churned out 62,168 oz.

The recent quarter’s production also included 4,753 oz. of platinum, 4,137 oz. of gold, 655 tonnes of copper and 298 tonnes of nickel.

The drop in production is thanks mostly to the temporary shutdown of the primary crusher at the mine in early September, after the company discovered two vertical fractures in the bottom shell.

The shutdown forced the operation’s secondary crusher, which typically provides finer crushed ore, to switch to producing a coarse mill feed reducing throughput during Sept. Also, with mining operations suspended, milling targeted existing ore stockpile which run a lower grade than the run-of-mine material.

Plagued by operational problems over the past year, the company has: replaced the pebble crusher with a larger one; contracted out fine-ore crushing; and installed a new liner in the semi-autogenous grinding mill. Modifications were also made to the grinding and flotation circuits.

Those improvements were starting to show. Prior to the shutdown, the mill had been running through ore at the design capacity of 15,000 tonnes per day during August.

Since early October, mining has resumed, crushing capacity has been supplemented via the reactivation of the old primary crusher and an existing portable contract crusher. Throughput has recovered to around 14,000 tonnes per day.

Ongoing repairs to the primary crusher are expected to wrap up by mid-November.

In an attempt to boost throughput, Lakefield Research has commissioned a pilot plant at the Lac des les mill. Beginning in November, NAP plans a large-scale, in-plant test on finer grinding utilizing the existing tower mills to confirm the recovery improvements seen in the pilot plant.

At last count, reserves at Lac des les stood at 93.5 million tonnes grading 1.53 grams palladium, plus platinum, gold, copper and nickel credits. The estimate is based on a cutoff grade of 0.7 gram palladium and a palladium price of US$400 per oz.