Let's talk DSO, page-208

Refer to a previous post on

Nanisivik Mine - Operations and Innovations in an Arctic Environment
(Old Technical Paper extract, operated by Cominco Ltd. from 1976 to2002, Mine now closed)
By W H McNeil, K R Rawling and R A Sutherland

07/07/23

12:30

Post #: 68674866

In Arctic mining operations like Nanisivik, preventing processing equipment and process water from freezing relies on efficient heat recovery and careful temperature control, especially given the extreme environment. Here’s how it’s done:

1. Waste Heat Recovery: Diesel power generators produce significant heat, which would otherwise be wasted. This heat is captured from the glycol cooling system via heat exchangers, then circulated throughout the facility. Radiators on this cooling system transfer warmth to the building complex, providing a reliable indoor temperature even in harsh weather.

2. Heated Process Water: Water for the concentrator processes, often reclaimed from the tailings pond, is pre-heated as it enters the concentrator. This helps maintain suitable temperatures within the grinding and flotation circuits and prevents the water from freezing when it contacts frozen ore. The target temperature for this water is around 20°C, which is crucial for the effective operation of the grinding and flotation circuits.

3. Building and Process Equipment Heating: The concentrator building temperature is maintained between 10-20°C year-round, using heat not only from the radiators but also from other sources like the power input to equipment, radiation, and steam introduced during the flotation process. This ensures that all equipment remains functional without risk of freezing.

4. Drying Concentrate: Final concentrate moisture is reduced with a co-current rotary kiln. The kiln uses the hot exhaust gases from the diesel engines to dry the concentrate, eliminating the need for auxiliary burners. While the gas temperature (370°C) might contribute to some caking and corrosion in the kiln, the system effectively keeps moisture levels low enough (around 5-6% by weight) to prevent freezing issues during winter storage.

5. Fuel Choice: The site uses Arctic-grade diesel fuel, with a pour point as low as -50°C, ensuring it remains pumpable and functional for power generation and mining equipment even in extreme temperatures. The fuel is delivered annually and pumped from a storage facility 5 km away to the site, demonstrating the importance of an appropriately selected fuel type in maintaining consistent energy supply.

This comprehensive heat management strategy leverages waste heat recovery to not only keep the facility warm but also reduce fuel consumption and costs, showcasing a cost-effective approach in Arctic conditions.