Smelting

What it is

Smelting is the pyrometallurgical process that converts mineral concentrate into metal by applying high heat and chemical oxidation. In copper, the chain runs: ore grading 0.5-2% copper is mined, concentrated by flotation to 25-35% copper, smelted into blister copper or anodes at 98-99% purity, then electrolytically refined to cathode-grade 99.99%. Zinc, lead, and nickel follow the same sequence adapted to their feed chemistry.

Two commercial technologies dominate primary copper smelting. Outotec flash smelting, first commercialised in Finland in 1949, oxidises finely ground concentrate suspended in a hot gas stream, achieving high energy efficiency and sulphur capture. Isasmelt, an Australian development, uses a submerged lance to inject air and fuel into a molten slag bath. Both technologies capture sulphur dioxide and convert it to sulphuric acid, a commercially valuable by-product.

The financial relationship between miners and smelters is expressed through the treatment charge (TC) and refining charge (RC), together TC/RCs. Miners pay smelters a TC denominated in US dollars per dry metric tonne of concentrate and an RC in US cents per pound of payable copper. TC/RCs are set in annual bilateral benchmark negotiations between major miners and smelters; they compress when miners are short of smelter capacity, and expand when smelters are short of concentrate feed.

History

Copper smelting dates to at least 4000 BCE in the Middle East and Balkans. Industrial-scale operations expanded through South American colonial mining from the 16th century onward. The Outotec flash furnace, commercialised in Finland in 1949, became the global standard for primary copper by the 1980s. Chinese smelter capacity then grew faster than any other region from 2000 to 2020, fed by concentrate exports from Chile, Peru, and the Democratic Republic of Congo. By 2024, ICSG data showed China producing 12 million tonnes of smelted and refined copper, 51% of the global total of 23.3 million tonnes.

Current state

As of mid-2026, the TC/RC mechanism is under structural stress. Smelter capacity has grown faster than mine output globally, compressing the concentrate available per facility. The 2026 annual benchmark settled at US$0 per tonne TC and zero US cents per pound RC, the first zero benchmark on record; spot TC/RCs fell to around negative US$70 per tonne, meaning smelters were paying miners to receive concentrate. China's top smelters cut output by roughly 10% in early 2026 in response.

New capacity is opening in producer countries. The Kamoa-Kakula Direct-to-Blister smelter in the DRC, Africa's largest at 500,000 tpa nameplate, produced 71,417 tonnes of copper anodes in Q1 2026 after its December 2025 first fire, running on DRC hydroelectric power. Freeport-McMoRan's US$2 billion PTFI smelter in Indonesia is advancing toward commissioning, fulfilling Indonesia's domestic-processing requirement; the Grasberg underground mine intended to feed it operated at roughly 65% of normal capacity in 2026 after a September 2025 mud rush.

Relationships

For most of the 2000s and 2010s, miners in Chile, the DRC, and Indonesia exported concentrate to Chinese smelters, ceding the processing margin to China. The IEA's 2025 Global Critical Minerals Outlook found the average share of the top three refined-material suppliers rose from 82% in 2020 to 86% in 2024, with China dominant across copper, cobalt, and rare earths. Producer countries are contesting this structure: Indonesia has required domestic copper smelting since 2023; the DRC holds a 20% stake in Kamoa-Kakula, giving it a direct share of smelting economics. Chile's Codelco and Glencore signed a Memorandum of Understanding in May 2026 to study a joint 1.5 million tpa concentrate smelter in Chile, targeting 2032-2033 commissioning, in response to Chile's ageing smelter fleet.

What to watch

Whether the zero-or-negative TC/RC benchmark persists into the 2027 annual negotiations, forcing deeper Chinese output cuts or a structural rationalisation of Chinese smelter capacity. The Kamoa-Kakula ramp to full 500,000 tpa and whether the DRC's domestic-smelting ownership model becomes a template applied to other DRC copper producers. The PTFI Indonesia commissioning date and whether reduced Grasberg feed affects the facility's economics. The Codelco-Glencore Chilean smelter feasibility timeline. Decarbonisation of smelting: flash smelting is energy-intensive, and Kamoa-Kakula's hydroelectric-powered 98.5% sulphur capture rate is being positioned as the benchmark for lower-carbon anode production.