Concentrator Request: Cornerstone:
Kennecott Utah Copper LLC

Addition of an Ore Grinding Line and an Ore Sorting Plant

Public comment is being sought through August 18, 2011 on Kennecott’s request to install and operate a fifth ore grinding line and an ore sorting plant at the Copperton Concentrator.

The new equipment will consist of an ore sorting plant with a baghouse, a small natural gas fired heater, a cold solvent degreaser, a fuel oil tank, a conveyor belt with transfer points, a pebble crusher, two lime bins with bin vents and a cooling tower to support the fifth ore grinding line.

The Concentrator Plant emissions, in tons per year will change as follows:

• PM10 will increase by 12.77 tpy to 34.62 tpy
• PM2.5 will increase by 3.61 tpy to 25.46 tpy
• VOC will increase by 1.68 tpy to 4.04 tpy
• NOX will decrease by 0.37 tpy to 10.55 tpy
• CO will decrease by 0.31 tpy to 9.87 tpy
• SO2 will decrease by 0.002 tpy to 0.10 tpy
• Cyanide will decrease by 2.24 tpy to 0 tpy

The draft permit is available for review online.
Existing operations at the Concentrator Plant are permitted under Approval Order (AO) DAQE-AN010571029-10.

Comments may be submitted to:

For questions, contact: Tad Anderson ([email protected]@utah.gov): (385) 306-6515

Process Overview

Ore from the Bingham Canyon Mine (BCM) is stockpiled in a storage pile in an A-frame enclosure. The process works like this:

• From the storage pile, the ore is fed to the grinding lines through the coarse ore reclaim tunnels and a series of conveyors directly into the semiautogenous grinding (SAG) mills.
• The SAG mill is equipped with a trommel screen allowing minus 5/8-inch material in slurry to pass through for further processing while discharging the larger pebbles at the trommel exit, where they are conveyed to the enclosed pebble crushing building and further reduced.
• The slurry is sent to the cyclone clusters, where the overflow (30 percent solids) is sent to the flotation circuit for concentrating and the underflow (70 percent solids) is sent to the ball mills for further size reduction before being sent back to the cyclones and on to the flotation circuit. Inherent moisture content of the material in the SAG mill, ball mill, and cyclone processes eliminate emissions.
• A cooling tower is used to cool the motors used in the grinding circuit. Drift eliminators installed on the cooling tower will eliminate drift to 0.005 percent of the process water flow.
• Cyclone overflow is fed into the flotation circuits, mixed with reagents, and aerated to float copper and other valuable by-products from the ore. Concentrate overflow is pumped to the existing regrinding circuit, while tailings underflow gravity flows to a collection trench. Because the rougher scavenger flotation process is aqueous based, no emissions are emitted from the flotation circuit.
• Tailings underflow from the flotation circuits feeds from the collection trenches to the tailings thickener feed distributor. Tailings are transported by gravity flow to the tailings impoundment for final deposition via pipelines. Thickener overflow is pumped back to the process water reservoir. No air emissions are emitted from the tailings thickening operations.

For more information see our Contacts page.