Trevali Provides Caribou Zinc Mine Commissioning Update - Seite 2

CARIBOU MILL COMMISSIONING

As expected a multitude of minor troubleshooting challenges have been identified and corrected during the initial June commissioning period by the experienced mill team. These positive changes have resulted in an approximately 94% mill availability factor by month end at a 1,500-tonne-per-day capacity, or 50% of nameplate design. Based on progress to date it is expected that mill throughput will continue to ramp-up throughout the summer months as the plant team increases its familiarity with the mineralized mill feed and reagent characteristics.

The commissioning status of the various major mill components is as follows:

Instrumentation - Various software patches have been installed and all circuits are now communicating as designed. The On-Stream Analyzer is functioning and Outotec is completing final training in July.

Crushing - The radial surface crushing circuit is fully operational and feeding into the dual Mill Feed Bins. From here feed is conveyed into the SAG Mill, which is the first stage of the grinding circuit (Figure 1). Ongoing optimization during the remainder of the year will seek to upgrade the conveyor feed system in order to optimize winter operations.

Grinding - The newly installed SAG Mill, the two Ball Mills and the three IsaMills are integrated, charged and operational (Figure 1). The SAG Mill has successfully achieved a primary grind of approximately 30 microns at current feed rates. Future optimization, once sufficient data is collected, will seek to optimize charge rates, grind characteristics and media composition.

To view Figure 1: Crushed UG feed being conveyed into the SAG Mill for finer grinding (left). Ball Mills in foreground with flotation circuits in background at Caribou Mill (right), please visit the following link: http://media3.marketwire.com/docs/trev1.jpg

Reagents - The full complement of reagents are all on site and available. The commissioning team initially focused on zinc reagents, with lead reagents gradually being introduced towards the end of June.

Flotation - Both Zn and Pb flotation including the rougher and cleaner cells are fully functional (Figure 2). Piping and pumping optimization and replacement occurred during June (modification of the sprays & blowers), which is expected to result in improved circuit stability.