NICKEL
What new laterite technologies might change the game?
November 2017
Nickel laterites accounted for around 60% of nickel production in 2016. Laterite processing is more complex than sulphide processing and, given laterites are expected to grow to around 74% of nickel supply by 2030, it prompts the question: what are the advantages and limitations of existing laterite technologies, and what new technologies might change the game in the future?

Nickel laterite processing is dominated by three main processes: rotary kiln-electric furnace (RKEF), blast furnace production of nickel pig iron (NPI), both pyrometallurgical processes, and the hydrometallurgical high-pressure acid leach (HPAL) process. A fourth process—Caron—is still in operation but no new projects are likely due to the high-cost and energy-intensive nature of the process. 

RKEF involves the calcination of ore in a rotary kiln, followed by smelting in an electric furnace at over 1,600°C in the presence of carbon. RKEF was responsible for around 40% of world finished nickel production in 2016, having grown from around 380kt in 2010 to 773kt in 2016. Production increases were largely driven by Chinese domestic processing of imported laterite ore. AME forecasts RKEF to make up around 91% of the 727kt of new project production by 2030, with 545kt added in Indonesia alone. 

The key strengths of RKEF are high nickel recoveries of around 93%, and 100% nickel payability. RKEF can produce a ferronickel product with over 10% nickel content for use in 300-series stainless steel. There are a number of limitations—RKEF generally requires high-grade saprolite feed (>1.8% Ni, <20%Fe). It is not well suited to process lower-grade limonite feed economically.

Electricity availability is a key limitation of RKEF. RKEF furnaces constructed in China took power from the grid, while new RKEF capacity planned in Indonesia and elsewhere is often remote and requires construction of its own power plant, increasing capital costs. The cost of power plant construction for new RKEF facilities in Indonesia is generally around 40% of total capital cost.

RKEFs have moderate to high operating costs averaging US$5.33/lb, and significant capital intensity. Large RKEF projects such as Koniambo have capital intensities up to US$40/lb of annual capacity.

 

 

AME estimates the blast furnace route contributed 70kt of finished nickel, or 3.6% of world production, in 2014. Since 2010 lower cost RKEF capacity has replaced blast furnace output in China. We forecast blast furnace nickel production to rebound to 120kt by 2030. In the blast furnace, carbon as coal or coke is charged with the ore to act as both a reductant and an energy source. 

Blast furnaces are able to process low-grade limonite (down to 0.7% Ni, >40% Fe) into a NPI product suitable for 200 series stainless steel, with significant value attributed to the iron content input into the steel via the limonite feed.

Electricity is not a constraint and blast furnaces do not require the construction of large power plants, as coal and coke is used to generate heat, as well as reduce the ore. This allows blast furnaces to be built easily in remote areas.

There are, however, a number of drawbacks—blast furnaces are a significantly greater emitter of airborne pollution than RKEF, due to the use of coal/coke in ore reduction. 

They also produce a product unsuitable for 300-series stainless steel without additional nickel units sourced from nickel metal or higher-grade ferronickel. 

Small blast furnaces operations can have operating costs up to US$7.00/lb, and low capital costs of under US$5/lb of annual capacity making blast furnaces the marginal swing producer.

AME forecasts increased integration of RKEF and blast furnace plants within integrated stainless steel mills to take advantage of the hot melt generated by these processes, and minimise the loss of valuable heat along the supply chain stages. 

HPAL involves leaching laterite ore in sulphuric acid within titanium lined autoclaves at up to 270°C and pressures of up to 45 atmospheres. Solvent extraction is used to separate nickel (and cobalt) from solution as metal, or the nickel is precipitated as an intermediate product (oxide, hydroxide or sulphide concentrate). HPAL contributed over 10% of world finished nickel production in 2016, after growing at a CAGR of 11% from 2010. Finished nickel production growth from HPAL is forecast to be flat to 2030, growing at 0.3%pa to 211kt. 

HPAL projects have some distinct advantages, such as electricity being generated as a by-product of sulphuric acid generation. Revenue is increased through the production of cobalt and, in some cases, ammonium sulphate by-products.

HPAL is largely limited to processing low-magnesium limonite ore. The higher magnesium levels found in saprolite ores increase acid consumption to uneconomic levels. Some saprolite may be incorporated into the process by using saprolite to neutralise residual acid from the HPAL step, but the volumes of this are limited.

Also, the extreme operating intensity—high pressures, temperatures and the highly acidic nature of the process—has seen many HPAL operations, such as Murrin Murrin and VNC, take years longer than planned to near nameplate capacity.

HPAL plants have moderate to high operating costs of around US$4.50/lb, and high capital intensities around US$30/lb of annual capacity. At the upper end of capital costs, the Ambatovy plant has a capital intensity of almost US$50/lb of annual nickel capacity. High capex is a barrier to entry, only making very large projects economic.

For any new technology to succeed, it must overcome the limitations of current processes. Touted technologies, such as heap leaching, did not live up to expectations, due to low nickel recoveries and high acid consumption. Several alternative processes have been promoted in recent years.  

One process currently in development, which may have potential to enter commercialisation, is the Direct Nickel Process. This atmospheric pressure process can process both limonite and saprolite horizons equally well, and Direct Nickel claims that the process has nickel and cobalt recoveries of over 90%, produces MgO and Fe by-products, and has low plant operating costs of US$1.84/lb (before Co and other by-product credits) and a reported capital cost of US$12/lb of annual capacity.

Another alternative is the CleanTeq process, which uses a continuous ion exchange process to extract nickel, cobalt, and other base metals, as well scandium, efficiently from solution. However, a limitation of the process is it still requires the metals to be put into solution, necessitating a HPAL front end to the plant, as will be the case at CleanTeq’s proposed Syerston project.