antónio fiúza (feup - cerena) · open pit mine waste rock waste rock stripping ratio 7.2:1 114...
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Resíduos mineiros: Contribuições para a Economia Circular
António Fiúza (FEUP - Cerena)
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Open PitMine
Waste Rock
Waste RockStripping Ratio 7.2:1114 Mm3
Processing
Ore15,9 Mm3
Mean Grade: 66 kg/ton
Tailings
Metallic Copper
1.05 Mm3
14.5 Mm3
Total Extracted Material – 129.9 Mm3
Total Wastes – 128.m3 Mm3
Percentage of Wastes – 98.53%
Resíduos mineiros: Contribuições para a Economia Circular
The Project ERA- MIN/0007/2014 has the financial support of FCT/MCTES through national funds (PIDDAC)
Improve Resource Efficiency and Minimize Environmental Footprint - REMinE
Metal
Ore Mined
Million Tons
Share of ore that becomes waste,
not including overburden (%)
Iron 25503 60
Copper 11026 99
Gold 7235 99.99
Lead 1077 97.5
Aluminium 856 70
Source: Gardner & Sampat (1998)
Resíduos mineiros: Contribuições para a Economia Circular
Principle 1: Preserve and enhance natural capital… by
controlling finite stocks and balancing renewable resource flows.
Principle 2: Optimize resource yields… by circulating products,
components, and materials at the highest utility at all times in
both technical and biological cycles.
Principle 3: Foster system effectiveness…
by revealing and designing out
negative externalities
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
TYPES OF MINE WASTES
1. OVERBURDEN2. WASTE ROCK3. LOW GRADE ORE4. TAILINGS5. HEAP LEACH SPENT ORES
What to do with the wastes?Conventional Solutions…
• Usage as construction material• Usage as backfill• Storage
New imaginative usages are required!
Resíduos mineiros: Contribuições para a Economia Circular
Next challenge will be the production with an almost null level of solid waste generation as it was possible in the recent
past to have mining facilities almost without industrial effluents.
Resíduos mineiros: Contribuições para a Economia Circular
SOLID PRODUCTS IN MINING
MAIN PRODUCT MAIN CONCENTRATE
SUB-PRODUCT OTHER MINOR CONCENTRATES
CO-PRODUCT Extracted Bedrock (Sand, Gravel,…)
OVERBURDEN Enveloping rock; normally easily
commercialized.
WASTE ROCK Huge quantities
RECYCLABLE TAILINGS Ex: Non sulfide and non-toxic
tailings
STORABLE, NON RECYCLABLE TAILINGS Ex: Pyritic tailings
NON-STORABLE, NON-RECYCLABLE
TAILINGS
Ex: Radioactives, High grades in As,
Hg,…
Resíduos mineiros: Contribuições para a Economia Circular
Largest dams ever built – seen from space
Unlike water dams, have to last “for ever”
Normally built progressively over a long period
– up to 50 years
Often built with non-engineering materials
Should be considered as a living entity
Żelazny Most (Poland)
1. Tailings with sulfides2. Radioactive tailings3. Tailings with high grades in toxic
elements (Ex: As)4. Tailings from Coal mines5. Highly Alkaline tailings
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
• Highly caustic nature of the red mud slurry • Extreme pH (13.1) and alkalinity (up to
6600 mg L−1 as Na2CO3), • Elements soluble at high pH, such as Al, As, Cr,
Mo, and V• Fine particle size, which once desiccated, can
generate fugitive dust
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
ALTERNATIVES
•Re-mining •Additive for cement industry•Civil construction – Roads, Pavements •Geo-cementation•Geo-polymerization
Resíduos mineiros: Contribuições para a Economia Circular
Example: Penouta Mine (Spain)Exploitable Reserves
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Project of final shape tailings re-deposition
Mineral reserve model for the open pit re-extraction
Tailings re-extraction Project Final shape model of the pit
Different percentages of copper tailings as additive for cement were tried (2.5; 5 and 10%)
Copper tailings have a slight negative impact on the slump, setting time and porosity of mixtures. However, improved mechanical strengths and abrasion resistance, and reduced chloride penetration compared to the control specimens were observed in mixtures incorporating copper tailings.
Toxicity characteristic leaching test results revealed that the release of heavy metals from mixtures containing copper tailings is considerably lower than the Regulations.
Resíduos mineiros: Contribuições para a Economia Circular
The major goal is to develop an environmentally friendly and cost effective method for recycling and utilizing mine tailings as construction materials:
• Bricks• Concrete for pavement• Concrete for structures, e.g. bridges• Highway base material• Highway embankment material
Resíduos mineiros: Contribuições para a Economia Circular
Cement Hydration Reaction (Thomas, 2004):
xCaSiO + yH2O → xCaO.ySiO.zH2O + wCa(OH)2 + Heat Calcium Silicates + Water → Calcium Silicate Hydrate (C-S-H) + Lime + Heat
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Geopolymerization consists of 2 basic steps:
(1) Dissolution of aluminosilicates by alkali to produce reactive silica and alumina.
(2) Polycondensation process leading to formation of amorphous to semicrystalline polymers
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Advantages of geopolymer over PC
Abundant raw materials resourcesEnergy saving and environment protectionGood volume stabilityReasonable strength gain in short timeUltra-excellent durabilityHigh fire resistance and low thermal
conductivityAbility to immobilize toxic and hazardous
wastesSuperior resistance to chemical attack
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
New tailings deposition techniques such as PASTE OR CO-DEPOSITION allow for:
Simultaneous Remediation and production; Absence of environmental passives at the end
of life. Safe storage of wastes, and even toxic wastes,
from other industries in a more safe way than allowed by the landfills for toxic products.
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
FOR THOSE TAILINGS THAT CANNOT BE RECYCLED:
• In-Situ Immobilization• In-situ Solidification• In-situ Immobilization technologies using
various types of grouting, especially clays with iron micro or nanoparticles. Other types of nanoparticles.
• Geo-polymerization• Geochemical immobilization
Resíduos mineiros: Contribuições para a Economia Circular
In-situ immobilization
• Injection of grouting with Clays and nanoparticles in the tailings; this technology aims to inertize a solid contaminated source.
•The nanoparticles will oxidize and/or sorb the contaminant that will be incorporated into a solid matrix with very low permeability.
•The groundwater will be diverted and will not flow through the grouted contamination source.
Resíduos mineiros: Contribuições para a Economia Circular
In-situ immobilization
Possible options are: ① Physical encapsulation by creating solidified
monolith (In-situ grouting); ② Chemical inclusion in CSH and CAH by
isomorphic substitution and ③ Sorption on clay and pozzolanic reaction product
or cation/anion exchange④ Geochemical immobilization
Resíduos mineiros: Contribuições para a Economia Circular
ZVI Clay/Soil Mixing Process
ZVI Clay/Soil Mixing
In-situ geochemical stabilization –sequential injection of solutions that react in the aquifer to form a sparingly soluble solid with high adsorption capacity for the element of concern.
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
Cement Hydration Reaction (Thomas, 2004):
xCaSiO + yH2O → xCaO.ySiO.zH2O + wCa(OH)2 + Heat Calcium Silicates +Water → Calcium Silicate Hydrate (C-S-H) + Lime
–Reduces mobility of chemicals of concern
–Increases strength
–Reduces permeability
–Minimizes free liquid.
Geo-Solidification
Process forms a granular or monolithic solid that incorporates the
waste material
A solid matrix, calcium-silicate-hydrate (C-S-H) is formed in presence
of water
Resíduos mineiros: Contribuições para a Economia Circular
Resíduos mineiros: Contribuições para a Economia Circular
In-situ geochemical stabilization – sequential injection of solutions that react with the tailings forming insoluble compounds that include or sorb the toxic elements.
AND STILL
VITRIFICATION and IN-SITU VITRIFICATION…
Resíduos mineiros: Contribuições para a Economia Circular
① A new typology for mining wastes considering its recyclability potential is required. Specifications for each category must be defined.
② Recyclable tailings may be remined or used as additive for cement industry, utilized in civil construction, as for instance in roads, pavements or produce new elements of construction such as bricks by geo-cementation and geo-polymerization. Usage as backfill has also been a current practice during the last 60 years.
③ Storable, non recyclable tailings may be deposed in a safe way as paste. Tailings disposed as paste may be used commercially as a very safe confined system to store wastes from other industries. It is more safe than the landfills for toxic products currently used;
④ Non storable, non recyclable toxic tailings may be submitted to in-situ immobilization, in-situ solidification or immobilized by special grouting, with clays and nanoparticles; they also may be submitted to geo-polymerization or in-situ geochemical immobilization.
⑤ CIRCULAR ECONOMY IN MINING IS POSSIBLE (ENHANCING NATURAL CAPITAL, MAXIMIZING YIELD AND FOSTERING EFECTIVENESS)
⑥ FINALLY, many other applications are possible. USE YOUR IMMAGINATION .