Mining Tailings Dewatering

Client Overview

An open-pit copper mine in South America processing 75,000 tonnes of ore per day. The concentrator plant generated approximately 1,200 m³/h of tailings slurry at 18-22% solids, requiring continuous dewatering to reclaim process water and reduce tailings storage facility (TSF) deposition rates.

The Challenge

The site's existing thickener + vacuum belt filter circuit was underperforming in multiple dimensions:

• Low cake solids: Belt filters achieved only 14-16% solids, requiring larger TSF footprint
• High water loss: Only 62% of tailings water was being recovered for reuse
• Frequent cloth blinding: Fine clay particles in ore caused rapid filter media degradation (replacement every 6 weeks)
• High Operating expenditure: Vacuum pumps, cloth inventory, and wash water consumed annually
• Climate vulnerability: Belt filters struggled during rainy season with elevated humidity

The Solution

Reynolds & Bauhm conducted a 4-week pilot trial with a containerised multi-disc screw press (MDSP) unit operating in parallel with the existing belt filters.

Phase 1: Pilot Validation

The pilot unit processed 15 m³/h of thickened underflow (18% solids) continuously. Key findings:

• Cake solids consistently 20-24% without polymer preconditioning
• Filtrate suspended solids < 200 mg/L — suitable for direct recycle
• Specific energy consumption 2.1 kWh/tonne (vs. 4.8 kWh/tonne for belt filters)
• No filter media replacement required during 4-week run

Phase 2: Full-Scale Design

Based on pilot data, Reynolds & Bauhm was involved in designing and commissioning a 6-unit MDSP installation:

• 6 x MDSP-1200 units (200 m³/h each, 1,200 m³/h total)
• Integrated polymer dosing: Automated 2-stage polymer preparation station
• Cake conveying: 180m covered screw conveyor to TSF deposition point
• SCADA integration: Full remote monitoring with torque, speed, and filtrate turbidity feedback

Results

Water Balance Impact

Financial Impact

• Fresh water reductions: (reduced pumping and treatment)
• Filter media elimination: belt cloth inventory saved
• Energy reduction: lower electricity consumption
• TSF deferral: capital deferral (extended facility life by 8 years)

Compliance & Environmental

The project supported the mine's ICMM Water Stewardship commitments. Independent water auditing confirmed zero discharge to surrounding watershed and full containment within the closed-circuit water balance. The operation now holds sufficient water rights buffer to support a planned 20% concentrator expansion without additional freshwater abstraction.

Key Learning

Multi-disc screw presses outperform conventional belt filters in mining tailings applications where fine particles, high throughput, and climate extremes challenge filter media. The self-cleaning disc mechanism eliminates cloth replacement, while the slow screw rotation (2-5 rpm) handles abrasive slurries with minimal wear.