Screw Feeder for Metering Oil-Dri at Freeport McMoRan in Safford, AZ

General Description

Freeport McMoRan (FMI) is one of the world’s leading international mining companies. FMI operates one of the world’s largest copper and gold deposits and has significant mining operations in America. Located in Safford, Arizona, FMI owns and operates a copper mine that is a zero-discharge facility and one of the most environmentally advanced copper mines ever built since becoming fully operational in 2008. The Safford mine includes two copper deposits that have oxide mineralization overlaying primary copper sulfide mineralization. The predominant oxide copper minerals are chrysocolla and copper-bearing iron oxides with the predominant copper sulfide material being chalcopyrite.

FMI was in search of a way to reduce manual labor associated with loading Oil-Dri into two “Gunk” tanks at the site. Oil-Dri, made from all-natural bentonite clay, has highly porous clay granules that are used to absorb most types of oils, soluble oils, acids, inks, paints, and water. Bentonite clay is unloaded from bulk bags into a hopper and is conveyed into their Gunk Tanks to adjust the pH and get the solids to fall out of solution. The solids then go to filter presses so it can be disposed of properly. FMI batched the Oil-Dri to track how much they need per batch and developed a fully automated system.

Design Parameters

1. Product Type: Oil-Dri (Bentonite Clay)
2. Material Density: 33 Lbs. per Cubic Foot
3. Capacity: 110 Cubic Feet per Hour
4. Designed Duty: Intermittent Duty

KWS Advantages

KWS provided FMI with a very cost-effective, robust screw feeder. Engineers at KWS determined important design features based on application requirements. Oil-Dri is a mildly abrasive bulk material and required heavy duty carbon steel construction for the screw feeder. KWS selected the heaviest-duty CEMA standard components and provided a long-lasting screw feeder within the project budget.

KWS Special Features

The new KWS screw feeder was designed with variable pitch under the inlet to meter Oil-Dri from bulk bags and transfer it over 40-feet to the Gunk Tanks. Heavy-duty helicoid screws and formed-flange U-troughs were selected. The drive unit was located on the discharge end, so the the bulk material was “pulled” to the discharge. A screw conveyor adapter was provided with the drive unit to eliminate any potential material contamination. Locating the drive unit on the discharge end of the screw feeder kept the screws in tension and prevented misalignment under load.

A custom-designed inlet was fabricated to fit a round, flexible sleeve and allowed the connection between the new KWS screw feeder and the bulk bag discharger to be adjustable while maintaining a totally enclosed, dust-tight connection.