The metallurgical technology that could revolutionize copper smelters

Bnamericas Published: Friday, December 16, 2022
The metallurgical technology that could revolutionize copper smelters

Copper production in Chile is declining and smelters face the reality of low competitiveness due to high costs and obsolete technologies, according to state copper commission Cochilco.

To maintain global leadership in copper output, efficient technologies are required to extract and process ore in a sustainable manner.

The closure of the Ventanas smelter of state-owned Codelco due to environmental contamination moved a step closer on Thursday with the approval in principle by the senate of a bill that modifies law No. 19,993. That will allow the concentrates from small and medium miners that are currently treated at Ventanas to be smelted at other Codelco facilities. Ventanas processes some 370,000t/y of copper concentrate.

China is the main player in copper smelting. It imports 56% of the world's internationally traded copper and has a 40% market share in smelting, versus Chile's 9%.

The search for solutions that allow copper to be processed in a sustainable manner, increase productivity, and achieve a better quality product are crucial issues for Chilean mining.

Metallurgical expert Igor Wilkomirsky, a chemical civil engineer and professor at the university of Concepción, is developing a green hydrogen-based technology that could change the course of conventional smelters.

BNamericas: What is the issue regarding technology for copper smelters?

Wilkomirsky: Copper smelters in Chile have a bad name due to environmental problems and the generation of waste, such as slag. They also emit gases with sulfur dioxide and, in some cases, traces of heavy elements such as arsenic. This has been a problem and has led, for example, to the [decision on the] closure of the Ventanas smelter.

Together with a metallurgy group at the university of Concepción, we’re developing an alternative technology to conventional smelting that does not generate emissions or slag.

On the contrary, it allows the recovery of the totality of the contents in the concentrates. Some components are sulfur, copper and iron as sulfides; sterile elements like silica; metals like gold and silver; and impurities like arsenic, antimony and bismuth.

In our process, all sulfur and arsenic are removed. Sulfur is used for the production of sulfuric acid and arsenic is subject to a confinement method with scorodite, whose deposition is allowed by environmental regulations.

The calcine resulting from a first stage is free of sulfur and passes to a second stage where the oxides, which essentially contain copper and iron, are reduced with hydrogen.

Iron is reduced to magnetite, which is a ferrous oxide widely used in blast furnaces in the steel industry. That is, the iron that is currently lost through the slag is recovered.

In addition, copper concentrates contain molybdenum, which has been one of Chile's main mining export products and generally a certain amount is lost. But with this technology it’s all recovered.

The green hydrogen that will be used in the reduction will allow the carbon footprint to be zero and produce green copper that will have a better price in the future.

The last stage is the separation of metallic copper or magnetite [metallic iron], which we’re still exploring. This is, broadly speaking, what we’re developing.

BNamericas: At what stage are you in the project and when would it be put into practice at a mining site?

Wilkomirsky: In metallurgy and mining, developments take time. Large investments and many tests are required to ensure that the technology doesn’t present problems afterwards. Today we have a pilot plant at the University of Concepción, but we’ll expand it in 2023-24. After the pilot phase, we’ll move on to the construction of a demonstration plant that will allow us to validate the economic advantages. The plan is to have the engineering by 2026 so that it enters into operation in 2028, and thus offers the market a new technology that is totally advantageous for smelters.

BNamericas: Have you received interest from copper producers?

Wilkomirsky: Yes, both from Chile and abroad, and they’re willing to contribute capital. Innovation in technology requires very high investments, which often means an additional financial burden for companies. Despite this, it has aroused a lot of interest.

BNamericas: Where will you source your green hydrogen from?

Wilkomirsky: Currently, we’re using gray hydrogen, produced by companies in Chile. But the demonstration plant will require a green hydrogen plant that will use solar energy to power the electrolyzers and advance to the calcine reduction stage.

That way we’ll achieve a zero carbon footprint. It’s important to mention that in the first phase, its own energy will be generated through exothermic reactions. The steam produced at high pressure can be used by turbines to generate electricity, which will feed the electrolyzers and could even be sold to the network.

On the other hand, more than 60% of the water required by the plant will be generated [with steam], meaning that the water footprint is quite low.

BNamericas: What do you think of the technologies used by Chilean smelters?

Wilkomirsky: They have limits. They cannot process low-grade concentrates and, furthermore, they lose a large amount of copper in the slag. They’re not a good business. The investments are very high and the return is very low. Despite the fact that modern technologies are used, such as Mitsubishi's flash smelting and converting, and part of the emissions are controlled, none of them solves the problem of copper loss in the slag and all emissions.

BNamericas: What other challenges does the Chilean copper industry face?

Wilkomirsky: Copper deposits in Chile are seeing lower grades. Fifty years ago the flotation tailings had more copper than what we’re mining now. Therefore, we have to prepare for the next few years with technologies that process more material and are more efficient. Flotation is the most important and difficult stage to predict, we should invest more there and in methods of extraction and recovery of copper as a concentrate, in order to improve yields.

BNamericas: How do you see the current Chilean mining scenario?  

Wilkomirsky: Mining is going through a difficult time. The technology is becoming obsolete. Codelco, for example, is not capable of investing much in itself. An important part of their profits goes to the State. So the technologies that have been implemented have been patchwork and not with a comprehensive vision. Another limitation is the quality of the Chilean deposits, the ore grades are falling and the amount of copper that we will be able to produce and process will progressively fall.

If we want to maintain production, we have to process more material and have concentrator plants with larger capacities. This requires a continuous investment that is not taking place. We’re going to see a sustained decrease in copper production in the coming years.

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