The increasing use of nickel in many important technological applications has resulted in sustained growth in its demand over many decades. With a historic growth rate of around 4 % per year, the annual demand for nickel in recent years has doubled over the working life of a typical mine (20 years), meaning there would need to be two new mines opened for every one that closes.
Not surprisingly, this has sparked a drive to increase recycling rates to complement primary production. For example in the USA, nickel from recycling now amounts to 45 % of primary supply, up from 35 % in 1994. With primary supply growing, reclaiming nickel through recycling must also grow, just to keep up.
Need for more “urban mining”
Clearly, new secondary sources are required to meet society’s increasing need for nickel.
In some cases, society’s wastes contain higher valuable metal content than naturally-occurring ores.
Petrochemical industry promising
The petrochemical industry has some of the most promising secondary sources of nickel.
Crude oil naturally contains low levels of nickel, which becomes concentrated in the ash fraction and comprises typically around 10 wt % in fully combusted ash from heavy fuel oil combustion systems. Catalysts used in refineries and the petrochemical industry contain very high amounts of nickel. Previously they were often sent to landfills, but more and more are being recycled.
Steel production has high potential
Since over two-thirds of all nickel is used in the production of stainless steel, the ferro-alloy output of most smelting-based recovery methods makes them an obvious source of secondary nickel.
Tetronics’ DC plasma arc smelting is one typical example, with two commercial plants operating for decades to recover nickel, chromium, molybdenum and other metals from stainless steel production wastes.
“Coke or anthracite reductant is added to the feed material. The plasma arc provides the input energy to produce a ferroalloy for re-use in stainless steel production at a scale ideally suited to the current availability of spent petrochemical catalysts and related secondary materials,” explains Dr. Tim Johnson, Tetronics’ Technical Director.