In the extraction of non-ferrous metals, composites in the shape of polymer are viewed as a practical option in the design of new containment cell structures and retrofitting of older cells.
Polymer reinforced concrete is commonly viewed as an alternative material to steel reinforced concrete in the fabrication of containment cells or acid tanks used in the extraction of non-ferrous metals such as copper, zinc, nickel, cobalt and manganese. Surely, for mining companies that go for polymer, there must be compelling reasons which have a strong bearing on their businesses.
Specifically, what are they?
By examining the merits and demerits of reinforced concrete and polymer cells, one would establish why some mining companies opt for the latter. Author, Ginger Gardner delves on the subject, in an article published on Composites World: Composites and Polymer Concrete Refine Mining Processes for Nonferrous Metal – composites world.
She underlines the benefits using polymer reinforced concrete cells in containment cells. At the outset, truth be told, in terms of upfront costs, steel-reinforced concrete provides an affordable tank solution.
Nonetheless, the structure of a concrete containment cell gives in to pressure with time during usage. The first problem lies with the chemical-resistant but unbounded inner liner of either lead, polyethyleneor polypropylene protect are used to protect the reinforced concrete containment cells.
The litmus test occurs during the process of extraction of non-ferrous metals, through electrowinning and electrowining processes. When electrical current is passed through large quantities of heated acidic solution, purified metals are deposited onto the cathodes. The deposited metal adds more weight to the cathodes.
The concrete electrolyte cells have to support both the weight of acidic solution and the electrodes sagging with deposits. All the more, cells must bear the temperatures of the reaction, in addition to the extremely corrosive electrolyte solution.
With these conditions, at some point something has to give. And it always does. Eventually, the unbounded inner liners suffer damage from falling electrodes and impacts from misaligned cranes (used toinstall and remove the electrodes). Then, the damaged liners permit corrosive electrolytes to directly contact the cell’s concrete walls and floors, resulting in the erosion of rebars, causing cell deterioration that eventually requires widespread repair.
Damage to reinforced concrete structures also frequently affects the tank support structures, including columns and beams.
In the long run, a mining company bears these effects through high cell maintenance costs, not only in terms of material and labour but cell downtime as well. This can be a big liability to a mining business. Polymer as an alternative Polymer reinforced concrete cells addresses shortcomings of steel-reinforced concrete cells.
The electrolytic cells made from polymer concrete with bonded surface linings are commonly used. This renders polymer reinforced cells to be more robust than reinforced concrete. As cost-effective alternatives to steel-reinforced concrete, they offer corrosion-resistant acid tanks to electrolytic refinery operations.
In polymer concrete, a thermosetting polymer resin- epoxy, vinyl ester, polyester, furan or methyl methacrylate- replaces cement as the binder, with compositions typically ranging from 8 to 12 percent polymer by weight. Certainly, it should be surprising why find composites in the shape of polymer are viewed as a practical option in the design of new containment cell structures and retrofitting of older cells.