(DMMP)
- Support the Philippine's Environmental Management Bureau (EMB) in addressing environmental concerns related to overflowing mine tailings caused by the rapid rise in artisanal small-scale gold mining due to higher gold prices. By buying the mine tailings artisanal miners and reprocessing them to recover residual precious and base metals and repurposing the remaining tailings for environmentally friendly uses, DMMP will help prevent an environmental crisis.
- DMMP's mining and processing technology package will enable DMMP to assist artisanal small-scale miners in the region to extract gold without relying on mercury and cyanide.
- StackCell® technology for ultra-fine particles (<150 µm)
- HydroFloat® CPF for coarse particles (>150 µm)
- Hydrocyclone classification at 150 µm to optimize each technology's performance range
- Gold Recovery: Material uplift through improved capture across the full particle-size spectrum
- Throughput: +10–35% via coarser economic grind and reduced circulating loads
- Energy: 10–20% net plant-level reduction (30–50% on secondary grinding)
- Water Efficiency: Up to 85% recovery from readily dewatered coarse tailings
- Tailings Volume: 30–40% reduction through coarse-gangue rejection
- Reagent Use: Lower consumption via targeted size-specific chemistries
- Conduct size-by-size liberation studies (QEMSCAN/MLA) and Au deportment analysis
- Complete bench-scale StackCell and HydroFloat testing to confirm cut-size and reagent suite
- Pilot confirmation of operating parameters and integrated circuit performance
- Design process control and instrumentation framework for stable operation
- Ultrafine gold (<20 μm): Poor recovery due to low particle mass, minimal bubble-particle collision probability, and detachment after collision
- Coarse liberated gold (>150 μm): Poor recovery due to excessive particle weight exceeding bubble carrying capacity
- Middlings in optimal range (20-150 μm): Reasonable conventional flotation performance
Strategic Advantages of DMMP's Circuit Configuration
A. Size-Dependent Technology Matching DMMP's circuit applies the "right technology to the right size fraction" principle: B. Liberation Enhancement The ball mill regrind serves multiple critical functions: Further liberation of locked gold particles from gangue Surface cleaning of oxidized/tarnished gold surfaces in old tailings Particle shape modification improving flotation kinetics Fresh surface exposure enhancing collector adsorption C. Prevention of Technology Overload By separating fines from coarse particles: StackCell isn't burdened with heavy particles that would short-circuit through its compact design HydroFloat isn't overwhelmed by ultrafines that would consume excessive fluidization energy and create muddy conditions Each technology operates within its design envelope for maximum efficiency
Overflow Fraction to StackCell (Target: 80-90% <38 μm)
Particle Size Range Conventional Flotation Recovery StackCell Potential Recovery Improvement <10 μm 10-25% 45-65% +35-40% 10-20 μm 30-50% 65-80% +30-35% 20-38 μm 55-75% 75-88% +15-20% Underflow Fraction to HydroFloat (Target: 80-90% >38 μm) Particle Size Range Conventional Flotation Recovery HydroFloat Potential Recovery Improvement 38-75 μm 60-75% 75-88% +10-15% 75-150 μm 40-60% 70-85% +25-30% 150-300 μm 15-35% 55-75% +35-45% Hydrocyclone Operating Parameters Critical Variables: Feed pressure: 60-100 kPa (8-15 psi) for sharp classification Vortex finder diameter: Determine via pilot testing, typically 0.3-0.4 × cyclone diameter Spigot diameter: 0.15-0.25 × cyclone diameter, adjusted to achieve desired underflow density Feed solids concentration: 25-35% by weight for optimal separation efficiency Apex angle: 10-20° for sharp cut-point with minimal bypass Expected Performance: Separation efficiency (Ep): 0.45-0.55 (tighter separation than conventional applications) Partition curve sharpness: Critical for minimizing ultrafines in underflow and coarse particles in overflow Bypass percentage: <15% ultrafines reporting to underflow
A. StackCell for Fine Fraction (<45 μm)
Core Technology Principles The StackCell employs intensified flotation through: High bubble surface area flux: 150-200 s⁻¹ (vs. 40-80 s⁻¹ in conventional cells) Stacked cell architecture: Vertical integration maximizing footprint efficiency Short residence time: 1-3 minutes per stage vs. 8-15 minutes conventional Plug flow hydrodynamics: Minimizing short-circuiting of fine particles Why StackCell Excels with Fines Enhanced Collision Probability High bubble generation rate (1-2 mm diameter bubbles) creates exponentially more collision opportunities For a 10 μm particle: Collision probability increases 3-5× versus conventional flotation Reduced Detachment Quiescent froth zone with minimal turbulence reduces particle detachment Particularly critical for low-mass particles with weak bubble adhesion force Optimal Carrying Capacity Fine particles have low mass-to-surface area ratio StackCell's fine bubble swarm easily carries ultrafine gold without overload Kinetic Advantages Fast-floating liberated fine gold recovered in early stages (minutes 1-2) Slower-floating partially locked particles recovered in later stages (minutes 3-6) Staged addition capability: Progressive reagent addition optimizes recovery Addressing Conventional Flotation Limitations Limitation StackCell Solution Low bubble-particle collision 3-5× higher bubble surface area flux Particle entrainment vs. true flotation Rapid kinetics separate true floaters from entrained material Large footprint requirements Vertical stacking reduces footprint by 60-75% Poor selectivity with fines Staged operation enables selective rejection of fine gangue
B. HydroFloat for Coarse Fraction (>45 μm)
Core Technology Principles The HydroFloat combines flotation with fluidized-bed classification: Upward fluidization flow: Creates teeter-bed preventing coarse particle settling Bubble injection into teeter-bed: Maximizes bubble-particle contact time Enhanced carrying capacity: Fluidization assists bubble transport of heavy particles Density separation component: Exploits density differences between gold and gangue Why HydroFloat Excels with Coarse Particles Overcoming Weight Limitations Conventional flotation: Bubble carrying capacity ∝ bubble diameter² For 200 μm gold particle (SG 15-19): Requires 3-4 mm bubbles minimum HydroFloat: Fluidization provides 40-60% of lifting force, bubbles provide remainder Net result: Effective flotation of particles up to 600-800 μm Extended Contact Time Particles suspended in teeter-bed for 20-60 seconds (vs. 2-5 seconds in conventional cells) Increased collision probability: ~10× improvement for >150 μm particles Multiple bubble attachment opportunities for partially hydrophobic surfaces Hydrodynamic Efficiency Reduced turbulent detachment: Teeter-bed provides stable environment Hindered settling regime: Particle-particle interactions reduce settling velocity by 50-70% Optimal bubble distribution: Uniform bubble dispersion throughout fluidized bed Density Separation Synergy Gold (SG 15-19) vs. quartz/silicate gangue (SG 2.6-2.8) Fluidization velocity can be tuned to preferentially suspend gangue while gold particles require bubble attachment to float Provides additional selectivity beyond hydrophobicity alone Addressing Conventional Flotation Limitations Limitation HydroFloat Solution Insufficient bubble carrying capacity Fluidization provides 40-60% of lifting force Rapid particle settling Teeter-bed suspends particles 20-60 seconds Low collision efficiency Extended contact time increases probability 10× Poor selectivity coarse particles Density separation adds orthogonal selectivity mechanism High turbulence → detachment Stable fluidized bed minimizes turbulence xxx
A. Elimination of Conflicting Operating Requirements
Problem in Single-Stage Conventional Flotation: Fines require: High aeration, low turbulence, extended residence time Coarse require: Moderate aeration, moderate turbulence, sufficient carrying capacity Compromise conditions suboptimize both size fractions Solution via Your Circuit: Each technology operates at independent optimal conditions No compromise necessary Maximum efficiency for entire size distribution
B. Minimized Overgrinding Energy
Strategic Regrinding: Ball mill targets optimal liberation without excessive overgrinding Target grind: P80 = 150-180 μm (coarser than conventional flotation requirements) Energy savings: 15-25% versus grinding to conventional flotation optimal size (P80 ~75-100 μm) Rationale: HydroFloat handles coarse liberated particles effectively Only partially liberated particles require finer grinding Avoids producing excessive problematic slimes
C. Water Circuit Efficiency
Reduced Water Consumption: StackCell: Higher pulp density operation (35-45% solids vs. 25-35% conventional) Reduced water requirement: ~20-30% per tonne HydroFloat: Fluidization requires water, but overall circuit water balance improves Efficient dewatering of teeter-bed reject (underflow) Net water savings: 10-15% versus conventional circuit
D. Reagent Efficiency Optimization
Size-Specific Reagent Optimization: Overflow to StackCell: Higher collector dosage for fines (surface area effect) Fine gold requires 2-3× collector dosage per unit mass Frother optimized for small bubble generation Underflow to HydroFloat: Moderate collector dosage for coarse particles Lower specific surface area Depressant addition may enhance selectivity Staged Reagent Addition: Regrind mill: Flotation reagents added during grinding (enhanced conditioning) Hydrocyclone: No reagent addition (classification only) StackCell stages: Progressive collector addition optimizes kinetics HydroFloat: Tailored reagent suite for coarse particle flotation Net Reagent Efficiency: 20-30% reduction in overall collector consumption per unit gold recovered
A. Gold Recovery Rates by Size Fraction
Baseline: Conventional Flotation of Tailings Size Fraction Weight % Grade (g/t Au) Conventional Recovery Gold Recovery Distribution <20 μm 35% 1.8 25% 26% 20-45 μm 25% 2.2 65% 27% 45-150 μm 30% 1.5 70% 33% >150 μm 10% 2.5 30% 14% Overall 100% 1.9 49% 100% Proposed Circuit: Size-by-Size Treatment Size Fraction Technology Projected Recovery Gold Recovery Distribution Recovery Gain <20 μm StackCell 55% 32% +30% absolute 20-45 μm StackCell 82% 34% +17% absolute 45-150 μm HydroFloat 83% 31% +13% absolute >150 μm HydroFloat 68% 28% +38% absolute Overall Combined 71% 100% +22% absolute
B. Overall Circuit Recovery Performance
Expected Performance Metrics: Overall gold recovery: 68-74% (versus 45-52% conventional flotation) Absolute improvement: +20-25 percentage points Incremental gold production: For 1,000 tpd tailings @ 1.9 g/t: Additional ~400-500 oz Au/month Payback implications: Significant additional revenue from previously unrecovered gold
C. Throughput Capacity
Volumetric Efficiency: StackCell: Footprint: 60-75% smaller than equivalent conventional flotation Throughput per unit volume: 2.5-3.5× higher Modular design enables easy capacity expansion HydroFloat: Single unit capacity: 50-200 tph depending on model Compact design: ~50% smaller footprint than conventional flotation Higher throughput per unit area: 2-2.5× conventional Circuit Throughput: Design capacity: 500-2,000 tpd depending on equipment selection Turndown ratio: 40-100% (excellent operational flexibility) Surge capacity: Can handle ±20% variations without performance degradation
D. Energy Consumption Analysis
Component Energy Requirements: Unit Operation Specific Energy (kWh/tonne) Notes Ball mill regrind 8-12 Target P80 150-180 μm from P80 200 μm feed Hydrocyclone pump 0.3-0.5 Low pressure classification StackCell 1.5-2.5 Efficient air compression, low agitation HydroFloat 2.5-4.0 Fluidization water + aeration Total Circuit 12.3-19.0 Average ~15.5 kWh/t Comparison to Conventional Circuit: Conventional flotation to equivalent recovery (if possible): 18-25 kWh/t Energy savings: 15-25% overall Primary savings from: Less aggressive grinding required Efficient StackCell design (minimal mechanical agitation) Elimination of oversized conventional flotation banks
E. Water Consumption
Circuit Water Balance: Stream Water Flow (m³/tonne) Notes Ball mill 0.4-0.6 Regrind circuit Hydrocyclone 0.2-0.3 Classification StackCell 0.3-0.5 Higher solids density operation HydroFloat 0.6-0.9 Fluidization requirement Total Fresh Water 1.5-2.3 Average ~1.9 m³/t Conventional Circuit Comparison: Conventional flotation: 2.2-2.8 m³/t Water savings: 10-20% Water recycle potential: 70-85% (with appropriate thickening/filtration)
F. Reagent Efficiency
Collector Consumption: Overall dosage: 80-150 g/t (typical for gold flotation) StackCell feed: 120-180 g/t (fines require higher dosage) HydroFloat feed: 60-100 g/t (coarse particles, lower specific surface area) Comparative Analysis: Conventional circuit for equivalent recovery (theoretical): 150-220 g/t Your circuit savings: 25-35% collector per unit gold recovered Improved efficiency from: Size-specific reagent optimization Enhanced conditioning in regrind mill Reduced overgrinding (less surface area inflation) Staged reagent addition in StackCell Frother Consumption: Overall: 20-40 g/t (lower than conventional due to optimized bubble size) StackCell emphasis on fine bubbles requires careful frother selection HydroFloat utilizes larger bubbles, less frother-sensitive
A. Ball Mill Regrind Circuit
Primary Control Variables: Grind Size (P80): 150-180 μm target Monitor: Online particle size analyzer or regular sampling Control: Mill speed, ball charge, feed rate Impact: Liberation degree directly affects flotation recovery Critical: Avoid overgrinding below 120 μm (generates problematic ultrafines) Circulating Load: 150-250% Monitor: Cyclone feed, overflow, and underflow flow rates Control: Pump speed, cyclone geometry Impact: Determines grinding efficiency and mill throughput Mill Discharge Density: 65-75% solids Monitor: Density gauge or nuclear densometer Control: Mill feed water addition Impact: Grinding efficiency, downstream pumping requirements Power Draw: 70-85% of rated capacity Monitor: Ammeter on mill motor Control: Feed rate, mill speed Impact: Grinding energy efficiency, product size consistency Reagent Conditioning in Regrind: Collector addition: 30-50% of total dosage in mill Conditioning time: 5-8 minutes (inherent in grinding residence time) pH control: Maintain 8.5-10.5 (lime addition as needed)
Hydrocyclone Classification
Primary Control Variables: Cut-Point (d50c): 40-50 μm target Monitor: Particle size analysis of overflow and underflow Control: Feed pressure, vortex finder diameter, spigot diameter Impact: Directly determines size split to StackCell vs. HydroFloat Critical: Sharp partition curve (Ep <0.50) for minimal size overlap Feed Pressure: 60-100 kPa (8-15 psi) Monitor: Pressure gauge on feed line Control: Pump speed (VFD) Impact: Cut-point, separation sharpness, capacity Rule: Higher pressure → finer cut-point Feed Density: 25-35% solids Monitor: Density gauge on feed line Control: Water addition to regrind mill discharge Impact: Separation efficiency, capacity Optimal: ~30% solids for gold applications Underflow Density: 55-70% solids Monitor: Density gauge or manual sampling Control: Spigot diameter Impact: HydroFloat feed density (critical for fluidization) Critical: Maintain roping discharge (not spraying or umbrellaing) Volumetric Split: Target 40-50% to overflow Monitor: Flow measurement both streams Control: Vortex finder/spigot ratio Impact: Mass balance, size separation efficiency Troubleshooting Parameters: Air core diameter: 10-30% of cyclone diameter (indicates stable operation) Underflow spray angle: 25-35° (roping discharge) Overflow discharge pattern: Uniform, no pulsation Explanation of d50c (Hydrocyclone Cut-Point) Definition d50c is the cut size or separation size of a hydrocyclone classifier. Specifically: d50c = the particle size at which there is a 50% probability of reporting to the overflow (fines) and a 50% probability of reporting to the underflow (coarse) It represents the median point of separation in the classification process. Conceptual Understanding Think of the hydrocyclone as making a "decision" for each particle based on its size: Particles smaller than d50c: Higher probability of exiting via overflow (to StackCell in your circuit) Particles larger than d50c: Higher probability of exiting via underflow (to HydroFloat in your circuit) Particles exactly at d50c: Equal chance (50/50) of going either direction Example with d50c = 45 μm: Particle Size Probability to Overflow Probability to Underflow 10 μm ~95-98% ~2-5% 25 μm ~80-85% ~15-20% 45 μm ~50% ~50% 75 μm ~15-20% ~80-85% 150 μm ~2-5% ~95-98% The Partition Curve The relationship between particle size and separation probability is visualized using a partition curve (also called a Tromp curve): Probability to Underflow (%) 100% | ___--- | _--- | _-- 50% | _-| ← d50c (cut-point) | _-- | _-- 0% |---- +------------------------ Particle Size (μm) ↑ d50c Key features: S-shaped curve showing probability distribution Crosses 50% line at d50c (by definition) Steepness indicates separation sharpness (discussed below) Why d50c Matters for Your Circuit 1. Technology Matching to Particle Size Your recommended d50c = 40-50 μm strategically divides the feed into two optimized streams: Overflow (to StackCell): Bulk of particles: <45 μm Dominated by ultrafines where StackCell excels Example distribution: 60-70% <20 μm, 25-30% 20-45 μm, 5-10% >45 μm Underflow (to HydroFloat): Bulk of particles: >45 μm Dominated by coarse particles where HydroFloat excels Example distribution: 5-10% <45 μm, 30-40% 45-150 μm, 50-60% >150 μm 2. Optimizing Overall Recovery The d50c selection maximizes recovery by ensuring: Fine gold (<45 μm) predominantly routes to StackCell where fine particle recovery is 2-3× better than conventional flotation Coarse gold (>45 μm) predominantly routes to HydroFloat where coarse particle recovery is 2-3× better than conventional flotation Minimal misrouting of particles to suboptimal technologies 3. Why 40-50 μm Specifically? This range is chosen because: Lower Boundary (40 μm): Below this, too many coarse particles would report to overflow StackCell would be burdened with particles it's not optimized for Fine particle advantage would be diluted Upper Boundary (50 μm): Above this, too many fine particles would report to underflow HydroFloat would be overwhelmed with ultrafines These fines would consume excessive fluidization water and create poor separation conditions Sweet Spot (45 μm): Empirically, this represents the transition zone between "fine" and "coarse" behavior in flotation Below ~45 μm: Surface forces dominate, particle mass relatively unimportant → StackCell optimal Above ~45 μm: Particle mass becomes significant, bubble carrying capacity critical → HydroFloat optimal Controlling the d50c Primary Control Variables: 1. Feed Pressure (Most Important) Higher pressure → finer d50c (more particles to overflow) Lower pressure → coarser d50c (more particles to underflow) Typical relationship: doubling pressure reduces d50c by ~25-30% Example: At 50 kPa: d50c ≈ 55 μm At 80 kPa: d50c ≈ 42 μm At 120 kPa: d50c ≈ 35 μm 2. Vortex Finder Diameter Larger vortex finder → coarser d50c (more coarse particles escape to overflow) Smaller vortex finder → finer d50c (restricts coarse particle overflow) Fixed during design/installation, changed only during maintenance 3. Spigot (Apex) Diameter Larger spigot → slightly coarser d50c (reduced back-pressure) Smaller spigot → slightly finer d50c (increased back-pressure) More impact on underflow density than d50c Subject to wear → requires periodic replacement 4. Feed Solids Concentration Higher density → slightly coarser d50c (increased viscosity, hindered settling) Lower density → slightly finer d50c (reduced particle interference) Effect is secondary compared to pressure Separation Efficiency: Beyond d50c While d50c tells you the median separation size, it doesn't tell you how sharp or efficient the separation is. This is where Ep (Ecart probable) comes in: Ecart Probable (Ep) Ep = (d75 - d25) / 2 Where: d75 = particle size with 75% probability to underflow d25 = particle size with 25% probability to underflow Lower Ep = Sharper separation (better performance) Example Comparison: Sharp Separation (Ep = 0.40): d25 = 30 μm (25% to underflow) d50c = 45 μm (50% to underflow) d75 = 62 μm (75% to underflow) Ep = (62-30)/2 = 0.36 Interpretation: Very clean size split, minimal overlap Poor Separation (Ep = 0.70): d25 = 20 μm (25% to underflow) d50c = 45 μm (50% to underflow) d75 = 83 μm (75% to underflow) Ep = (83-20)/2 = 0.70 Interpretation: Broad overlap, significant misrouting For Your Circuit: Target: Ep = 0.40-0.50 This ensures: Minimal ultrafines (<20 μm) in HydroFloat feed (would consume fluidization water) Minimal coarse particles (>75 μm) in StackCell feed (would short-circuit through compact cells) Clean feedstock for each technology to operate in optimal range Practical Determination of d50c Methods: 1. Particle Size Analysis (Most Accurate) Sample overflow and underflow simultaneously Measure particle size distribution of each stream (laser diffraction, sieve analysis) Calculate mass balance and construct partition curve Read d50c where curve crosses 50% line 2. Online Monitoring Install particle size analyzers on overflow and underflow streams Continuous measurement allows real-time d50c tracking Enables automated control of feed pressure to maintain target d50c 3. Empirical Correlation (Preliminary Estimate) Plitt Model (simplified): d50c ≈ K × D^0.46 × D_i^0.6 × D_o^0.21 × D_u^0.5 / (ΔP^0.5 × Q^0.15) Where: D = cyclone diameter D_i = inlet diameter D_o = vortex finder diameter D_u = spigot diameter ΔP = feed pressure drop Q = volumetric flow rate K = constant depending on feed characteristics Practical takeaway: For your application, commissioning tests will establish the actual operating conditions (pressure, flow rate) needed to achieve d50c = 40-50 μm with your specific cyclone geometry and feed characteristics. Optimization Strategy for Your Circuit Phase 1: Establish Baseline Commission at d50c ≈ 45 μm (middle of recommended range) Measure actual StackCell and HydroFloat performance Determine baseline recovery by size fraction Phase 2: Systematic Testing Test d50c range 35-55 μm in 5 μm increments: d50c Setting Expected Impact Monitoring Focus 35 μm More fines to StackCell StackCell overload? HydroFloat starved of fines? 40 μm Balanced, more fines to StackCell Optimal StackCell recovery? 45 μm Balanced, design condition Baseline performance 50 μm Balanced, more coarse to HydroFloat Optimal HydroFloat recovery? 55 μm More coarse to HydroFloat HydroFloat overload? StackCell starved of coarse? Phase 3: Lock in Optimum Analyze gold recovery, concentrate grade, and overall efficiency Select d50c that maximizes: Overall Gold Recovery × Concentrate Grade Establish operating window: Optimum ±5 μm Set control system to maintain target d50c via pressure adjustment Summary d50c is the fundamental parameter defining how your hydrocyclone splits the feed between StackCell (fines) and HydroFloat (coarse). The recommended range of 40-50 μm represents the strategic balance point where: ✓ Ultrafines are predominantly sent to StackCell for superior fine particle recovery ✓ Coarse particles are predominantly sent to HydroFloat for superior coarse particle recovery ✓ Each technology receives a feed distribution within its optimal operating range ✓ Overall circuit gold recovery is maximized Proper control of d50c through feed pressure adjustment, combined with sharp separation (low Ep), is critical to realizing the synergistic benefits of your size-by-size treatment circuit.
StackCell Flotation
Primary Control Variables: Air Rate: 0.8-1.5 cm/s superficial gas velocity Monitor: Air flow meter Control: Blower speed, valve position Impact: Bubble surface area flux, carrying capacity Target: 150-200 s⁻¹ bubble surface area flux Critical: Maintain small bubble size (1-2 mm) for fines flotation Residence Time: 4-8 minutes total (across all stages) Monitor: Calculated from feed rate and cell volumes Control: Feed rate Impact: Recovery, especially for slower-floating particles Staged design: Fast floaters recovered in first 2-3 minutes, remainder in later stages Pulp Density: 35-45% solids Monitor: Density measurement at feed Control: Water addition (minimal in StackCell - density set by upstream) Impact: Bubble-particle collision, apparent viscosity Higher density: Generally favorable for fines flotation (reduced drainage) Froth Depth: 30-60 cm Monitor: Visual observation or level sensor Control: Dart valve position on concentrate launder Impact: Concentrate grade, froth stability Optimization: Deeper froth = higher grade, potentially lower recovery Collector Dosage: 120-180 g/t (distributed across stages) Monitor: Reagent flow meters Control: Pump speed for each stage Impact: Fine gold hydrophobicity, flotation kinetics Staged addition: Stage 1: 40-50% of total Stage 2: 30-35% of total Stage 3: 20-25% of total Frother Dosage: 25-45 g/t Monitor: Reagent flow meter Control: Pump speed Impact: Bubble size, froth stability Critical: Select frother that produces 1-2 mm bubbles at operating conditions pH: 8.5-10.5 optimum Monitor: pH probe in feed sump Control: Lime addition Impact: Collector adsorption, surface chemistry Gold flotation: Generally favors mildly alkaline conditions Performance Monitoring: Recovery by stage: Measure concentrate mass and grade from each stage Target: 60-70% recovery in first stage, 20-25% in second, 10-15% in third Concentrate grade: 20-60 g/t Au typical (depends on feed grade and selectivity) Froth appearance: Stable, mineralized froth with minimal water drainage Tailings grade: <0.3-0.5 g/t Au target Advanced Control: Wash water addition: 0-20% of concentrate volume (grade improvement) Mechanical agitation (if equipped): Minimal, just sufficient to prevent settling Temperature control: Ambient acceptable, 18-25°C optimal
HydroFloat Flotation
Primary Control Variables: Fluidization Water Rate: Critical parameter - unit specific Monitor: Flow meter on fluidization water Control: Valve position or pump speed Impact: Teeter-bed height, particle suspension, bubble dispersion Target: Achieve 40-80 cm teeter-bed height Empirical determination: Too low → bed collapses, coarse particles settle Too high → excessive water, poor bubble-particle contact, gangue entrainment Teeter-Bed Height: 40-80 cm Monitor: Nuclear or pressure-based level detector Control: Fluidization water rate Impact: Particle residence time, carrying capacity Optimal: Bed height where coarse gold particles are fully suspended Air Rate: 0.5-1.0 cm/s superficial gas velocity Monitor: Air flow meter Control: Blower or compressor Impact: Bubble availability, carrying assistance Target: Lower than conventional cells (fluidization provides lift) Feed Rate: Match design capacity Monitor: Mass flow meter or volumetric measurement Control: Pump speed from hydrocyclone underflow Impact: Bed loading, residence time distribution Critical: Maintain steady feed rate (avoid surging) Feed Density: 55-70% solids Monitor: Density gauge Control: Upstream (hydrocyclone spigot diameter) Impact: Bed stability, fluidization requirements Sweet spot: 60-65% solids for gold applications Underflow (Reject) Removal Rate: Balance feed solids Monitor: Visual observation of underflow discharge Control: Underflow valve position Impact: Bed density, particle retention Target: Remove only true rejects (dense gangue, unrecoverable particles) Collector Dosage: 60-100 g/t Monitor: Reagent flow meter Control: Pump speed Impact: Coarse gold hydrophobicity Note: Lower than StackCell due to reduced surface area Bubble Size: 2-4 mm preferred Control: Air sparger design (fixed), frother type/dosage (variable) Impact: Carrying capacity for coarse particles Larger bubbles: Better for heavy, coarse gold (higher carrying capacity) Performance Monitoring: Concentrate grade: 15-45 g/t Au typical Recovery: Target 70-85% for >45 μm fraction Bed density profile: Should show gradual increase from top to bottom Underflow grade: <0.2-0.4 g/t Au target Froth appearance: Coarser, more mineralized than conventional cells Advanced Control: Fluidization water quality: Clean water preferred (minimize fine particle interference) Teeter-bed monitoring: Real-time density profile measurement Depressant addition (optional): 50-150 g/t for gangue rejection (e.g., CMC for silicates) Bubble coalescence prevention: Maintain optimal frother concentration
Integrated Circuit Control Strategy
Mass Balance Control: Feed rate stability: ±5% variation maximum Maintain steady ball mill feed rate Buffer capacity with surge tank if needed Water balance: Total circuit water addition = evaporation + concentrate water + tailings water Minimize fresh water by maximizing recycle Solids inventory: Monitor and control circulating load in regrind circuit Prevent accumulation or depletion in any section Quality Control Metrics: Hourly: Froth appearance, density measurements, pH Every 2-4 hours: Particle size (regrind product, cyclone O/F and U/F) Every shift: Assays (StackCell concentrate, HydroFloat concentrate, final tailings) Daily: Mass balance reconciliation, metallurgical performance calculation Optimization Approach: Phase 1 (Commissioning): Establish baseline at conservative operating conditions Phase 2 (Optimization): Systematic variation of key parameters Grind size: Test P80 140-200 μm range Cyclone cut-point: Test d50c 35-55 μm range Flotation reagents: Dosage and type optimization Phase 3 (Fine-tuning): Lock in optimal conditions, establish control limits Phase 4 (Advanced control): Implement automated control loops for critical variables
- Adequate Liberation: Regrind must sufficiently liberate gold without excessive overgrinding
- Sharp Size Classification: Hydrocyclone must achieve clean separation (minimal overlap between StackCell and HydroFloat feeds)
- Reagent Optimization: Size-specific collector and frother selection is critical
- Operator Training: Technologies require understanding of principles, not just conventional flotation experience
- Metallurgical Testing: Pilot-scale testing strongly recommended to validate design assumptions and optimize parameters
- Instrumentation: Adequate online monitoring for proactive control (particle size analyzers, density gauges, pH meters, flow meters)
- Strategic regrinding for liberation
- Precision classification for size-by-size treatment
- StackCell technology maximizing fine gold recovery
- HydroFloat technology capturing coarse liberated gold
- Detailed metallurgical test work (locked-cycle tests, pilot-scale trials)
- Equipment vendor engagement for detailed design specifications
- Economic modeling incorporating capital and operating cost estimates
- Permitting and environmental impact assessment for the facility