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Co Disposal Commingling Paste Rock DEFINITION Mine waste streams - - PowerPoint PPT Presentation
Co Disposal Commingling Paste Rock DEFINITION Mine waste streams - - PowerPoint PPT Presentation
Co Disposal Commingling Paste Rock DEFINITION Mine waste streams are typically separated according to their particle size (due to their origin in the mining process) Conventionally disposed of separately Co-disposal combines waste
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CO-DISPOSAL WITH MINING PRODUCTS
- Tailings: disposed as a slurry
– high porosity – water-filled voids.
- Waste Rock:
– high porosity (>30%) – air-filled voids “hopefully”
Co-disposal - tailings filling at least some of the voids in the coarse waste.
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TYPICAL “RULE OF THUMB” POROSITIES
Conv. Slurried Tailings Compacted/ Filtered Tailings Waste Rock Particle SG 2.65 2.65 2.65 Dry Density (pcf) 65 – 90 90 – 110 90 – 110 Void Ratio 0.8 – 1.5 0.5 – 0.8 0.5 – 0.8 Porosity, pct 50 – 60 35 – 45 35 – 50
Porosity: ratio of volume of voids to total volume (*100%) Void ratio: ratio of volume of voids to volume of solids The intent is to “hide” tailings within the voids of the waste rock
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EXAMPLE EFFECT OF C:F RATIO
0% 20% 40% 60% 80% 100% 120% 1 2 3 4 5 Percent of voids filled with tailings Coarse:Fine Ratio - X:1
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DEGREES OF MIXING
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PERFECTLY BLENDED, HOMOGENEOUS MIXTURES OF TAILINGS AND WASTE ROCK: PASTE ROCK
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BLENDED, RELATIVELY HOMOGENEOUS MIXTURES OF TAILINGS AND WASTE ROCK
- Tailings and mine waste are mixed
relatively homogeneously
- Tailings essentially fill “all” the voids
between waste rock particles
- Waste rock has predominantly rock-to-
rock contact
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Blended Tailings/Waste Rock
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Benefits/Goals:
- Reduced footprint
- Shear strength like waste rock
- Permeability like tailings
- Low oxygen diffusion rates
- Greatly(?) reduced ARD potential
- Improved permitting timeline
- Better public acceptance
- Improved closure opportunities…
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Governing equations for ARD Keep the Fe from going ferric
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Above about 85% Saturation: Oxygen Diffusion Essentially Eliminated
Keeping the air out will keep the Fe from going ferric
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Proxy waste rock
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LA Abrasion Machine
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11 Secret Herbs and Spices
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PROCTOR TEST RESULTS
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Proctor in terms of solids content
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At least in these tests: a lower solids content is better
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Zero Air Voids
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6-inch dia. Triaxial shear testing
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3:1 Blend
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4:1 Blend
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Co-disposed Tailings
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Challenges:
- Maintaining +/- proper mixing ratios
- Defining proper mixing ratios
- Developing design properties (hydraulic,
shear strength, etc.)
- Mixing method
- Placement/spreading method
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Co-disposed Tailings
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Challenges:
- Maintaining +/- proper mixing ratios
- Defining proper mixing ratios
- Developing design properties (hydraulic,
shear strength, etc.)
- Mixing method
- Placement/spreading method
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Material Mixing: Where to from Here?
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No, no, bigger, BIGGER!
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SECRECTS TO MIXING???
Flow-through Ball Mill Agglomerator
- Continuous concrete mixer
- PUG mill
- Agglomerator
They all want very dilute slurry and small sized rock particles
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Material Mixing: The Concept
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Laboratory Mixing: The Concept
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“The water slide from hell”
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Blending: The Next Step?
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