Signal Peak Tests Hybrid Element Wet Drum Magnetic Separator

Eriez recently collaborated with Signal Peak Energy, a Montana-based coal operator, on a field evaluation study of the Hybrid Element Wet Drum Magnetic Separator, focusing on improving magnetite recovery efficiency in a heavy medium coal processing circuit.  In these applications, small losses of magnetite into reject streams can create substantial ongoing operating costs over time.  The results were presented at the Society of Mining, Metallurgy and Exploration (SME) annual meeting in Salt Lake City earlier this year.

For heavy medium coal preparation plants, magnetite is a critical consumable material used to maintain separation efficiency. Because magnetite continuously recirculates throughout the process, any losses to coal product or reject streams directly impact operating economics. Although conventional wet drum separators already provide high recovery performance, even minor inefficiencies can become financially significant due to the cumulative effect of recirculation.  Eriez and Signal Peak Energy sought to evaluate whether a redesigned magnetic circuit could reduce these losses while improving overall separator performance.

To validate the technology under real production conditions, two adjacent 36-in. diameter by 117-in. width wet drum magnetic separators were installed side-by-side in the plant. One separator used the standard 950 Interpole magnetic element, while the second employed the’ hybrid magnetic circuit configuration. Both separators operated from the same feed distributor to ensure identical feed conditions and allow direct performance comparison.

The field trial program involved hourly sampling over an 8-hour operating period. Composite samples were prepared and analyzed using a Davis Tube tester on feed, concentrate, and tailings streams. This methodology accurately evaluated recovery efficiency, magnetite losses and performance differences between the two magnetic circuit designs.

Results from the field trial demonstrated a clear performance advantage for the hybrid magnetic circuit. The Hybrid Wet Drum Separator achieved a recovery rate of 99.78% vs 99.4% while significantly reducing magnetite carryover into reject streams. Measured magnetite loss rates fell from 1.293 g/gallon with the standard 950 Interpole drum to 0.553 g/gallon. The hybrid design shows a reduction of more than 50%.

Although the single-pass recovery gain appeared relatively small, it is important to recognize that heavy medium circuits continuously recycle magnetite. As a result, incremental improvements accumulate rapidly into meaningful operational savings over time. Lower magnetite consumption reduces replacement costs, minimizes waste generation and improves long-term plant efficiency. This study demonstrated how advanced magnetic circuit engineering can create both economic and sustainability benefits simultaneously.

The success of this study also highlighted the value of OEM and end-user collaboration through practical side-by-side testing in mining process optimization. By evaluating both systems under identical operating conditions, the test clearly quantified the advantages of the hybrid technology and verified its effectiveness under actual plant conditions.

This study also delivered an important takeaway: relatively small recovery improvements can produce significant financial and operational impacts in high-throughput recirculating systems. As mining operations continue to pursue lower operating costs, improved sustainability performance, and greater process efficiency, technologies such as the Hybrid Wet Drum Magnetic Separator provide a practical pathway toward achieving those objectives.

Nee San Yap is global product manager – mining magnetics for Eriez.