Heavy Duty Screw Conveyors for Stillwater Mining Columbus, MT

General Description

One of Stillwater Mining Company’s largest mining operations is in Columbus, MT where palladium and platinum is mined. As the only producers of palladium and platinum in the US, Stillwater Mining Company is actively involved in all aspects of mining and marketing of platinum group metals or PGMs from a geological formation in the Stillwater igneous complex in south central Montana and from the recycling of spent catalytic converters. Spent catalyst material is smelted and refined to recover PGMs using the same process as the mined PGMs. The recycling process can be very abrasive and cause significant wear to conveying and processing equipment.

Both dense-phase pneumatic conveyors and screw conveyors are used in a large portion of the refining and smelting process. Due to the abrasive characteristics of the bulk materials, Stillwater Mining was experiencing excessive maintenance and downtime. Working together, Stillwater Mining, Motion Industries and KWS replaced the pneumatic conveyors with screw conveyors and solved many of the conveying problems at the plant. The cost savings was significant and continues to pay off for Stillwater Mining.

Design Parameters

1. Product Type – Platinum, Palladium and Spent Catalyst
2. Material Density – 40 Lbs. per Cubic Foot
3. Conveyor Capacity – 12,000 Lbs. per Hour
4. Duty – 24 Hours per Day, 7 Days per Week

KWS Advantages

After visiting the plant to fully understand operating conditions and examining worn or failed dense-phase pneumatic conveyor and screw conveyor components, Motion Industries and KWS offered long term solutions for the problems at the plant. Screw conveyor components made from standard A-36 carbon steel only lasted a few weeks before wearing out. KWS recommended upgrading to abrasion resistant (AR) plate for the screw flights and increasing the thickness of all materials for the screw conveyors. Also, KWS recommended continuously welding the flights to the center pipe of each screw for additional strength. Trough thickness was also increased and weld-in removable AR liners added for further abrasion resistance. The screw conveyors were now “bullet-proof” and constructed for mine-duty applications.

Special Features

The smelting and recycling process is extremely dusty and even with an enclosed conveyor, the dust will escape. Breathing any form of metal dust is unhealthy and therefore, controlling the emission of dust was a vital part of the KWS solution. The screw conveyor covers were made from heavy-gauge material and bolted on very close centers to be completely dust tight. KWS utilized air purged shaft seals on both the tail and drive shafts to prevent dust leakage at the shafts. Each shaft seal was provided with an air regulator and purged with approximately 2-psig air pressure. On the drive end KWS provided a bulkhead trough end to keep the drive unit away from the abrasive bulk materials and eliminate a possible failure point.