The main advantage with a pyrometallurgical route is that one utilizes the iron present in the limonite ores to make the nickel containing pig iron. In hydrometallurgical routes, the limonite is the major consumer of acid and after getting it into a soluble phase, it is selectively precipitated out in order to make a nickel-cobalt product.

After precipitating out the alumina, one could co-precipitate the iron, nickel and cobalt as metal hydroxides, but then dewatering (q major task) and reduction would be required to make a nickel containing pig iron. Of course, electrowinning could be considered to recover the metals after the impurities were removed.

Nickel pig iron (NPI) is usually made with lower grade limonite ores while ferronickel (typically 8 to 12% Ni) is made with higher grade nickel laterite ores, often saprolites (lower iron content) or in the case of limonites by lowering the iron recovery.

The only pyrometallurgical route that would be economic at a suitable scale is the RKEF process or variations on it.

How about blast furnace smelting, any commentary? Some Plant in China and Indoferro Indonesia (erected in 2008, relative new) used it to produce NPI. Eventhough its process consume a lot of energy and produces great carbon emission. What's the main advantage of using BF smelting process?

Blast furnaces were used as a stop gap measure in China when iron ore supplies either became too expensive or dwindled, however proved to be uneconomic - hence you do not see any BFs being built in China for treating nickel laterite ores. New plants are based on the RKEF technology.

BFs have been muted in Indonesia for a few projects however you need size and coking coal - which Indonesia effectively does not have.

Nonetheless, I have seen plans for a few hybrid plants employing a RKEF front-end and treating the magnetic product in a Mini Blast Furnace (MBF) - which has apparently proven itself in Brazil.

Is there any possibilities to improve BFs or make BFs run economically? Like, we purpose to develop palm kernel shell biochar for reduce coke consumtion or Integrated BFs with calcium carbonate plant or something else with heat integration?

I would say so based on the Brazilian experiences. The plans I was examining were also looking at non-coking coal sources...which is very reasonable approach.

I would suggest that you do some research on Brazilian MBFs, find out who built them, the design features and how they are operating as well as the associated operating costs.

The projects were all integrated to produce power and recycle some of the heat for pre-heating.

My memory is that the application of treating limonitic laterite in blast furnaces was triggered in china when the government imposed a ban on operating small (<300CM) blast furnaces, unless they could produce a product of higher value than straight out pig iron. Pig nickel was deemed higher value and therefore these small blast furnaces were allowed to keep operating. Of course it is inefficient to feed 40% iron into a blast furnace containing high levels of magnesium to boot, but as long as the nickel price stays above a break-even threshold then the process is profitable (they do get the iron units for nothing and only pay about 10% the value of the contained nickel!!).

This is why production of pig-nickel varies directly with nickel price, once the price of nickel drops below approx$7/lb pig-nickel production becomes very marginal (this threshold varies according to price of fuel (coal) and iron as well as nickel).

I think it is one of the reasons why BHPB decided to essentially get out of the nickel business because production of pig-nickel has put a ceiling price on nickel due to the vast laterite nickel resources around the world, if nickel price goes up production goes up and nickel price comes down! in relatively quick cycle.

The Indonesian ban on exporting laterite hasn't had much of an effect because of the vast laterite resources that are available, I note the nickel stockpiles are the highest they have been for a long time!

Getting back to your question the pig nickel that is produced in BF is around 2-3%nickel, it can be upgraded to ferro-nickel (around 8%) in an electric arc furnace by mixing stainless scrap with the pignickel.

Direct reduction is a method that may have merit, however slag chemistry can be problematic. With low iron ore prices and low nickel prices, there would be little incentive to build new plants with new technology. 62% Fe ore is now trading at less than $70/tonne, which is below break even costs for a lot of producers.

The main attraction to producing Pignickel is that the economics are favored because the BF feedstock is very cheap (no payment for iron units and only 10%payment for contained nickel). This is why the highly prized feedstock is a high iron/high nickel laterirte, something around +45Fe/2%Ni ideally, but nature has not produced much of this stuff!

Low prices are now reducing the value of pignickel so it would be difficult to produce BF PNI at a profit, even though lower energy prices will help.

There are all sorts of efforts going into coming up with improved nickel production from lateritic ore, both pyro and hydro metallurgical, but they all face the same problem low grade and low nickel extraction selectivity which combine to increase costs.

Thanks in advance to you all. I learn a lot from you all. But i'm still wondering about when you said no payment for iron units, what the specific means for iron unit? A casting unit? Only 10% payment for contained nickel, 10% payment from what? So, the main problems of using BFs are big coking coal consumption which is mean the energy issue related, either Nickel/Iron prices cause.

Let we say if there is new plants that integrated with new technology to produce side product that has higher value than NPI as main product, there is a chance to make BFs process more economical, right?

Then, how about RKEF process? is it same reduction process like BF? How could RKEF has more advantages than BF?

I presume you will be purchasing the limonite to feed the BF to produce Nickel-Pig-Iron? typically you will be purchasing a limonite containing +/-40%Fe, and +/- 1%Ni plus MgO etc. If so, the purchase price is calculated on 10%of the value of the contained nickel only, if nickel price is at $15,000/t your one tonne of 1%Ni limonite contains 10kg Ni which is worth $150, but you only pay 10% of this which is equal to $15/t, this is very cheap because in most cases there is no payment included for the contained 40%Fe in the limonite.

Of course most sales deals are open to negotiation to determine the final payment terms.

I also presume you already have a BF in operation? this is the only reason you would contemplate producing NPI because the capital cost of building a brand new BF with associated infrastructure would certainly kill the economics of the NPI project.

Anyone know why China does not import laterite ore from New Caledonia, even if it is the biggest producers in the world ? China would rather choose Indonesian and Philippine ores than New Caledonia already has.

No-one effectively pays for the iron contained in limonitic ores and depending upon the nickel grade and nickel price, may receive USD25 to 45/ dry tonne FOB. As for New Caledonia, probably arises since the Chinese are not that active and that suitable limonitic ores are not that abundant. The Philippines is certainly taking up the slack.

RKEF offers as more cost effective pathway employing a slightly different and less intensive reduction pathway compared to the BF, which is historically has been driven by throughput to control costs.

Perhaps the Brazilian have overcome some of these scale of operation issues. As I noted earlier, I like the approach of recovering your product with appropriate technology that the RKEF for the easier to recover NPI and more intensive technologies (EAF/BF) for the more difficult materials.

I don't believe producing NPI or other Ni products is related to what is the most suitable technology. In my opinion the production of NPI in china was an opportunistic development when small blast furnaces were threatened with closure. Producing NPI in a redundant blast furnace (zero capital) will always beat building new process plants because of the capital requirement, especially when in most cases the government subsidizes operating costs, add to this the very low cost of feedstock and there is an opportunity to make money regardless of technological effectiveness.

Why doesn't china buy New Caledonia-costs more and:

• Caledonian laterites are pretty well tied up by other companies, ---philippines/Indonesia has many small producers who will sell without long term contracts, and they are closer to china which means very flexible shipping ( some just barge it over )

BTW, RKEF is more suited to saprolite ore (low iron/high magnesium) than limonite (higher iron/low magnesium)

As noted, the Chinese have little action in New Caledonia (many of the ores are smelted using EAF) while RKEF does work reasonably well with limonitic ores (does depends on silica/MgO contents) - often used to treat both ore types as a process compromise.

I agree that the BF period was an anomaly driven by other factors however the Brazilians have apparently had some wins with small BFs but unsure of the cost data.

Could well be Andrew, but I think it is still tied to opportunistic small players and good luck to them, I can't see VALE or BAOSTEEL building BF plants specifically for producing NPI.

I had made mention of a proposed flowsheet employing RK at the front end followed by a choice between EAF or BF at the backend.

However BFs are problematic on the smaller scales.