Agglomeration, typically carried out via drum agglomerator, has become a pivotal technology in modern copper extraction, as the Solvent Extraction Electrowinning (SX-EW) process is increasingly employed for low-grade sulfide ores, tailings, and oxide ore bodies.
As demand for copper grows and these low-grade sources become more critical, SX-EW has emerged as the go-to method for meeting copper demand, cementing agglomerationโs role as a key optimization step in maximizing recovery and efficiency.
By utilizing agglomerators, miners can increase copper recovery, throughput, and overall efficiency in the heap leaching step of their SX-EW process flow.
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Benefits of SX-EW
For decades, smelting was the primary method of copper extraction, but itโs only effective for high-grade sulfide ores. As these sources dwindle, miners have had to adapt, developing technologies that can economically recover copper from lower-grade resources.
In this effort, the use of SX-EW has grown exponentially in the past few decades, owing much credit to advancements in extractants (reagents) that have made the process increasingly viable and effective. The benefits of utilizing the SX-EW process for copper extraction are many:
Significantly Less Capital Cost
One of the main attractions to the SX-EW process is that it requires significantly less capital cost than a traditional smelting operation.
Opportunity for New Ore Bodies
Unlike smelting, which is only feasible for large-scale operations, SX-EW is economically viable even at small scales. This makes it possible to process smaller, lower-grade ore bodies that would otherwise be overlooked.
Additionally, while smelting is only economically viable for processing higher grade sulfide ores, SX-EW can be used for oxide ores, as well as low-grade sulfide ores. Until the advent of SX-EW, there were no economically viable options for processing these ores. Yet, these sources represent significant amounts of untapped copper.
According to the International Copper Study Groupโs World Copper Factbook, in 2023, SX-EW facilitated the recovery of an estimated 20% of total copper production. In the 1960โs, that number was less than 1%.[1]
As high-grade copper ores become a thing of the past, with most ore falling in the range of .5% โ 2%,[2] this will likely further increase the importance of the SX-EW process in future copper production.
SX-EW has also become a viable means of processing tailing piles, which were previously considered a waste because the ore in them was either too low grade to justify processing, or because it had since oxidized.
Reduced Environmental Impact
Not only does SX-EW help the environment by making use of what would otherwise have been considered a waste, but the process itself also has a lower impact on the environment when compared to traditional smelting methods.
How Agglomeration Improves SX-EW
Agglomeration is the process of forming fine particles into larger, more uniform particles. In the context of heap leaching, this may refer to โrimโ agglomerates, where fines adhere to larger ore particles, or conglomerates where fines adhere together to create a larger particle.[3]
โRimโ agglomerate (left) vs conglomerate (right)
This binding of fines lends a host of benefits to the leaching process:
Improved Percolation of Leach Liquids
One of the primary challenges in heap leaching is ensuring uniform distribution of the leach solution throughout the ore heap. Fine particles often create blockages in the heap, reducing the percolation rate and slowing down the leaching process. By agglomerating the ore, particles are bound together, creating larger, more uniform agglomerates that allow for better fluid flow through the heap. This helps to avoid โdeadโ spots where leachate cannot penetrate due to fines.
Image: At left, non-agglomerated ore fines clog channels, impeding leachate percolation. At right, agglomerated ore fines allow more even and effective percolation of the leachate through the heap.
Enhanced Intra-Particle Structure
Agglomerated fines offer a porous media that promotes liquid retention and mass transfer, accelerating the leaching reaction.[3]
Increased Heap Leaching Efficiency
The early introduction of the leachate (in the agglomerator) offers the benefit of beginning the leaching process immediately, as well as increasing the contact area between the copper-bearing material and the leaching solution. This leads to more efficient extraction of copper, reducing the overall losses during the leaching process and improving the bottom line of copper extraction operations.
The more uniform particle size distribution of the agglomerated ore also helps efficiency by minimizing segregation of otherwise differently sized ore particles. When the spread in particle sizes is wide, larger particles tend to roll down to the bottom of the heap, with smaller particles staying at the top. This segregation can contribute to increased ponding of the leachate, leading to inefficiencies.[4]
Increased Production
Agglomerated ore creates a more stable heap structure, permitting higher piling of the ore, and subsequently, increased production. [4]
Improved Economics and Environmental Benefits
While the initial investment in an agglomeration system requires capital expenditure, the long-term cost benefits are significant. Enhanced copper recovery means less material is required to produce the same amount of copper, improving the operational efficiency of the SX-EW circuit. Furthermore, by reducing losses, companies can minimize waste and reduce the environmental impact associated with mining operations.
Through these benefits, agglomeration has proven to significantly increase the efficiency of the leaching step, both in terms of recovery and leaching time. In one Arizona silver mine, the incorporation of an agglomeration step increased metal recovery from 37% to 90%, while at the same time dropping the leaching time from 90 days to just seven. Similarly, a gold mine in Nevada saw extraction increase by 60%, with leaching time cut in half.[4]
Agglomerating Ore for Heap Leaching
Agglomeration is typically carried out in an agglomerator (also referred to as an agglomeration drum or ore drum), a large rotating drum through which ore is tumbled and sprayed with the leachate.
The leachate, in this case sulfuric acid, mixes intimately with the fines to produce a homogeneous mixture and begin forming granules. These granules gain density as they tumble and roll through the remainder of the drum, becoming more uniform. Depending on the makeup of the ore, a binding agent may or may not be employed to assist agglomeration.[4]
After agglomeration, the agglomerated ore is piled into heaps, which is typically further irrigated with sulfuric acid.
Through chemical reaction, the copper is dissolved into the sulfuric acid. The solution percolates through the heap, draining as a pregnant leach solution from which the copper can then be extracted via SX-EW.
Agglomeration Equipment: The Key to Efficient SX-EW
When implementing agglomeration for SX-EW copper extraction, the selection of the right equipment is crucial. FEECO offers agglomeration drums designed to meet the specific needs of copper extraction processes. These machines provide:
- Consistency: Ensuring that the agglomerates are uniform in size, which is critical for predictable leaching performance.
- Capacity: With robust designs, agglomeration drums handle large volumes of material, making them suitable for large-scale mining operations.
- Customizability: FEECOโs agglomeration equipment is tailored to suit the characteristics of the material being processed, ensuring optimal results for copper extraction.
- Durability: FEECO agglomerators have a well-earned reputation for reliability and longevity. Their heavy-duty build allows them to provide decades of unwavering service when properly maintained.
Conclusion
Agglomeration is an essential step in optimizing the SX-EW process for copper extraction. By improving heap leaching efficiency, agglomeration leads to higher copper recoveries, shorter leach cycles, and cost savings.
With the growing demand for copper and increasing pressure on mining operations to improve efficiency, adopting agglomeration in the heap leaching stage of the SX-EW process can provide a clear competitive edge. FEECO is the leading provider of heavy-duty agglomerators, with installations around the world. To learn more about our custom ore agglomerators or supporting services, contact us today!
SOURCES:
- International Copper Study Group. Copper Factbook. International Copper Study Group. https://icsg.org/copper-factbook/.
- Sequeira, A., & Liddell, K. (2010). Extractive Metallurgy of Copper. Elsevier. https://www.google.com/books/edition/Extractive_Metallurgy_of_Copper/VdILLpCu9ooC?hl=en&gbpv=1&dq=copper+concentrates+mixer&pg=PP1&printsec=frontcover#v=onepage&q&f=false.
- Ahuja, P. (2022). Agglomeration in Heap Leaching: Practice and Fundamentals. International Institute of Chemical, Biological and Environmental Engineering. https://iicbe.org/upload/4283C1122205%20J%20new%20new%20new%20final%20formatted.pdf.
- Dominguez, J., & Rodriguez, E. (2011). Review of Agglomeration Practice and Fundamentals in Heap Leaching. ResearchGate. https://www.researchgate.net/publication/248933800_Review_of_agglomeration_practice_and_fundamentals_in_heap_leaching.
