On the 1st of February 2021, MIRU’s interview team from IRUNIVERSE had the opportunity to conduct an exclusive interview with Australian Cobalt producer, Cobalt Blue Holdings’ (ASX: COB) CEO Mr. Joe Kaderavek.
Cobalt Blue Holdings are currently working on an innovative project in which they will extract cobalt from pyrite. For this unique cobalt project, they are receiving substantial attention from numerous companies.
During our 1 hour interview session, we were fortunate enough to be able to obtain a deeper understanding on their project and metallurgy through Mr. Kaderavek’s deep knowledge and invaluable insights.
This article, Vol.1 primarily covers rather technical aspects whilst Vol.2 will include more general information, such as their current partnerships, contract status and advice for Japanese companies etc.
Q1.
MIRU Team: We are very much interested in this special source of cobalt, that is included in pyrite ore. In our poor knowledge, there is not such a mineral in the world. We didn’t know that pyrite includes cobalt. So, if your project will perform successfully, it will be very big source of cobalt in pyrite ore, in Australia or other countries such as Brazil. You project will make a very big impact on cobalt producers. If cobalt can be successfully extracted from the ore, what are your thoughts about this point?
Joe Kaderavek: Pyrite is a common mineral globally. Cobalt Blue has devoted time and research to understanding various ways of extracting the host metals. And part of our success has been able to use extraction of copper from pyrite, which is currently being used overseas, and help shape our test work. So, if you’re dealing with pyrites, you need a sledgehammer. And, we’ve developed what we think is a very elegant sledgehammer but a sledgehammer nevertheless. So, typically, in pyrite globally, it’s roasted. That’s an easy reaction, it’s exothermic, but you’re left with SO2. And SO2 means you’re making acid. That was never going to be feasible for Broken Hill. Most acid plants need to be co-locate with customers, you simply can’t freight or transport acid long distances typically, for economic purposes.
The other two ways globally had been pox, effectively a pressure oxidation or acid leach if you like, and the last way is a heap leach, a natural atmospheric leach.
The problem with all of those processes is that the recoveries are very poor. So, we’ve used pyrolysis, in other words thermal decomposition. The only difference between pyrolysis and roasting is that we do not add oxygen. So, we use a furnace in a bath of nitrogen, and the pyrite, the FeS2, simply breaks apart, it decomposes. And in doing so, we created a calcine, which is pyrrhotite, and the pyrrhotite is very leachable. So, that simple step solves a lot of problems for us.
You asked about where pyrite is prevalent. Pyrite is prevalent in a lot of places but pyrite with cobalt and pyrite with copper cobalt is an Australian feature. I’m sure there is more of it in the world, certainly with copper, but in our district of Broken Hill, we have this unique ore, this cobalt in pyrite.
In South Australia, we’ve just completed some test work, with another copper mine, Carrapateena. And Carrapateena is one of the OZ Minerals’ mines, OZL is the ticker. And we’ve done some test work in processing their waste pyrite stream, in other words, they are streaming their pyrite to tails, and it contains copper, cobalt and gold.
We’ve also done test work in QLD, around the Cloncurry Mt Isa district, and there is more cobalt in tailings dams in QLD than we have in resource. In other words, it’s a major opportunity for us, and it’s a good opportunity because we can effectively process a waste product, which is already mined and already crushed, and effectively extract the metal from it.
Beyond SA, NSW and QLD, we are aware of opportunities globally, I’m not aware of Brazil in particular, but we have conducted an audit globally, and we are yet to stretch out globally. So, our view at the moment is we build our core project, we look to take the intellectual property into other mines, if they are existing mines, then it’s a small addition, and if it’s a resource we can build the operation. But our view is that, as big as our own project is, there is probably a potential of two or three times our projects’ potential in the broader Australian landscape.
MIRU: You have much resources in Australia, like pyrite including cobalt, is it right?
Kaderavek: Exactly, that’s right. But particularly in our district of Broken Hill, we have a unique cobalt in pyrite. So, within 30 or 40 km of this town of Broken Hill, we’ve got cobalt in pyrite resources.
Q2.
MIRU: Your process of extracting cobalt sulphate is roasting the pyrite at the first stage of the process, and you could get an electric power from a boiler through gas. Is that correct?
Kaderavek: Our process uses a furnace, but the furnace is approximately 700℃, but the furnacing is done in a bed of nitrogen, because we do not want to introduce oxygen to the pyrite. And, as a result, we decompose. So, if you think of, pyrite is an atom of iron and two atoms of sulphur, we actually, effectively decomposing that. And by doing so, we make elemental sulphur, we avoid acid ---
MIRU: So, you mean that you will melt down the pyrite in the temperature of 700℃?
Kaderavek: Well – the word melt is a usual term, rather we decompose. We force the molecule, which is pyrite to effectively fracture into a new molecule which is pyrrhotite, and we liberate, we flush off an atom of sulphur.
Chart1
(Provided by Cobalt Blue Holdings)
Q3.
MIRU: We are very much surprised on the result of your feasibility study, frankly. So, what’s the difference between your project and other companies’ projects on cobalt in Australia? There are many Australian projects on extracting copper, and extracting cobalt or nickel. You said, “very effective in the point of investment” in the feasibility study, seems very different from other projects on the same page.
Chart 2
(Provided by Cobalt Blue Holdings)
Kaderavek:Let me give you a very broad answer and then we can provide detail on particular parts of my answer as you see fit.
Very simply, about 20 % of our ore is pyrite. And in the pyrite, about 0.5 of a percent is cobalt. So, the first part of our step, because we’re a sulphide ore body, we’re not a laterite, the first part of our processing is very simple. We crush and we float the sulphide. And the crush size is 1mm, so it’s very coarse, the float is a sulphide float circuit, which is a standard float. But one of the biggest steps in terms of low capital intensity is the fact that we return 80 % of the ore back into the pit with just crushing. In other words, the reject is sent back to the mine. Our concentrate is 95 % or more pyrite and our job is made very easy because our cobalt is only in one mineral. It’s only in the pyrite.
If you compare it to copper, or other mines where the copper might be in two or three or four minerals, they’re much more complicated. So, our cobalt is entirely in pyrite, our pyrite is removed from waste with a very simple crush and float, which is on Chart 1, and we use very simple gravity spirals for that, and here is one of the reasons why our plant is a fraction, our project is a fraction of the cost of laterite. It’s simply because 80 % of my waste was removed at crush, therefore my refinery is only 20 % of the size of my mine. So, my refinery is 1/5th size of my mine. If I’m a laterite, then I’m largely processing everything I mine, which makes my backend, which is where all the capital is, much bigger, if I’m a laterite.
We mine just over six million tons of ore, the concentrate is about a million tons, when we thermally decompose, when we furnace the pyrites, we liberate elemental sulphur as a gas, which is very clean as you can imagine, and what we are left as a calcine is a pyrrhotite. Technically, the formula for pyrrhotite is Fe7S8, whereas pyrite is FeS2, so you can see that you’ve stripped some of the sulphur off the pyrite, in order to release the sulphur.
Pyrolysis: FeS2 = Fe7S8 + S (gas)
Then Fe7S8 + O2 = Fe2O3 (iron Hematite used for steel making) + S (solid)
Pyrrhotite is extremely leachable.
The other advantage in our process versus a nickel laterite, I’ve already said that we are one fifth of the refining size, the other advantage is, pyrrhotite is very leachable. We are leaching at 130℃ and 10 atmospheres. As someone in my engineering staff recently said, we are leaching at about the same parameters as a coffee machine in your kitchen. It’s a very low aggressive environment.
A nickel laterite would leach at 250 ℃, and 50 atmospheres. And be a much bigger circuit, a much more aggressive circuit. So, we are a very small circuit and not very aggressive.
MIRU: You mean, the leaching process is an autoclave or something?
Kaderavek: Yes, it’s an autoclave. The leaching step is done in an autoclave in a pressure vessel. But, my point is that our pressure and temperature are a fraction of the aggressiveness of nickel laterite. We typically have a residence time of about 30 to 40 minutes, in other words, the pyrrhotite needs to be in there for 30 minutes in order for the cobalt to be leached. In nickel laterite HPAL circuits, that could be 3 to 4 hours. So, much more aggressive environment, much bigger vessels, and all of that leads to much bigger capital for lateritic ores.
Q4.
MIRU: How difficult is it to filtrate the iron oxide, ferric oxide? Is it easier on filtration?
Kaderavek:
It’s a good question – I need to refer to my technical people to give you an exact answer. What I can tell you is that once we’ve leached the pyrrhotite, we then extract effectively the cobalt, and a very small amount of nickel - we have a very small amount of nickel. The sulphur is then floated, because 130℃ is the melting point of sulphur, so it floats, and we extract sulphur. So, on the diagram you see there (Chart1), you see more sulphur being emitted at the leach step.
The residue, because it’s an oxide, is a hematite residue. We are looking at ways to make the hematite commercial, there are two challenges for our hematite. One is, it’s a very fine product. Typically, by the time it’s through leach, it’s at 30 microns. I am told that that’s not a big deal, that’s still commercial because we can agglomerate the hematite. The main problem is the sulphur. There’re still, percentage points of sulphur left sticking to the hematite, and steel makers don’t like the sulphur, above their processing limits. So, at the moment, there is no commercial value in the leach residue in the hematite, but we are looking at it.
（To be continued in Vol.2）
(Interviewers: Yuji Tanamachi & Tomoki Katagiri, Transcription by A.Crnokrak)
