99.9% chemical results, page-24

To achieve 99+% via single flotation and caustic bake is good, acid leaching is not so good - adds to cost and is not environmentally friendly (this process has caused all the problems in China) Most graphite can be upgrade to 99+% using acid leaching........

What every investor needs to know about investing in graphite

osted on October 17, 2013 by admin

Based in Geneva, Switzerland, the company has 75,000 employees and operates over 1,500 offices and laboratories worldwide. In short, SGS is the Rolls Royce of inspection, verification, testing, and certification.
In keeping with my quest to know all that one man can (or should) possibly know about graphite, I wanted to speak to the man whose name I see frequently at the bottom of numerous new releases announced by various junior graphite explorers touting 96% to greater than 99.9% graphitic carbon purity — Mr. Oliver Peters, M.Sc., P.Eng, MBA, — SGS Canada’s Consulting Metallurgist and President of Metpro Management Inc. Mr. Peters has extensive experience in the development of metallurgical processes and has personally managed the majority of the graphite testing programs conducted at SGS in recent years.
Ty Dinwoodie (TD): I understand that you specialize in graphite?

Oliver Peters (OP): That’s one of the areas, yes, but I also have been involved with many other commodities such as copper, nickel, platinum group metals, lead, zinc, diamonds, gold, and silver — just to name a few.
TD: You test graphite samples submitted to SGS?
OP: Essentially, I manage the process development for new mine prospects. The scope of work of the programs generally includes the development of a metallurgical process to recover the valuable minerals into a high-grade flotation concentrate. In the case of graphite that generally means producing a concentrate grading greater than 95% carbon. The concentrate would then be subjected to further characterization work to determine its marketability. But if the client targets battery grade, then the graphite flotation concentrate has to upgraded in a chemical or electro-thermal purification process.
TD: Do you base your process ultimately on what the client is targeting for its graphite’s end use?
OP: Well obviously the battery application — ultra high-purity graphite — is the hot topic these days, so generally most clients are proceeding with some purification testing to determine the maximum grades that can be achieved for their graphite. But whether or not the commercial plant will include a purification circuit, that’s a different question. At 95% to 96%, sometimes even up to 98% flotation concentrate grade the product can be readily sold without the need to purify the graphite further.
TD: So you don’t have to keep trying to optimize it to get to the 99.9%?
OP: The revenue from the ultra-pure concentrate is substantially higher compared to a 95% to 97% carbon flotation concentrate, but it’s also associated with much higher processing costs. At the end of the day, it comes down to economics. In order to develop the process with the highest NPV, all options need to be explored, including purification tests to battery grade. However, depending on the specific deposit, this may not be the most economic approach.
TD: In your experience, what is a high percentage of purity achieved when just using conventional flotation?
OP: Around the 97% to 98% carbon range — and that’s mostly for the coarser flakes. If you look at some of the press releases from some of the more advanced projects, they have also very good results for the fine flakes — so it really depends on the graphite and how it upgrades in the process. As a general rule, the coarser flakes upgrade quite easily to 96% carbon and in some cases even up to 98% C. Maximizing the flotation concentrate grade while minimizing flake breakage is the key challenge in the process development programs.
TD: But to achieve 99.9% or, in some cases, greater than 99.99% requires a more sophisticated chemical process?
OP: Yes, because impurities are attached to the surfaces and in the crevasses of the flakes that cannot be removed with a mechanical process such as grinding and flotation.
TD: The conventional flotation process is more mechanical?
OP: Yes. It is based on liberating valuable and waste minerals in crushing and grinding stages followed by separating the two streams with the aid of reagents and air.
TD: What would you call the process that requires chemicals or acids to achieve high purity, greater than 99%?
OP: This approach is referred to as a hydrometallurgical process. Two common routes are a hydrofluoric (HF) leach process or a caustic bake. In addition, a graphite flotation concentrate can also be upgraded through electro-thermal purification. So there are different routes.
TD: So there are two routes to pursue when a graphite company is attempting to achieve ultra high purity?
OP: There are two main processing routes — chemical and electro-thermal purification. I’ve mentioned two chemical purification methods before, but there are other options and with the revived focus on graphite in recent years. More process development in the hydrometallurgical field is currently being conducted.
TD: Do all two high-purity paths that can be pursued all involve acid?
OP: Not the electro-thermal. Electro-thermal purification exposes graphite materials to temperatures up to 3,000°C to remove any impurities.
TD: Is the electro-thermal process a more expensive path? Meaning is it something that would be less likely to be commercially viable on a larger scale?
OP: Well, for example, one of the North-American major off-takers for graphite employs electro-thermal purification on a commercial scale — so it is definitely viable. The more economically attractive route will depend on many factors such as the location of the deposit, on the flake-size distribution, the amenability of the flakes to purification, and the maximums grade that can be achieved with flotation only. Both purification routes are not cheap and that’s why flotation is essential to upgrade the ore from 2% to 25% carbon head grade to the maximum grade that you can achieve before introducing the chemical or electro-thermal purification. Every impurity that has to be removed by the purification process is going to cost substantially more money compared to flotation.
TD: Most companies would want to go for the cost effectiveness of flotation?
OP: You will have to as a first upgrading stage. Although you can technically leach ore at 10% or even 2% graphitic carbon, the project CAPEX and OPEX will render it economically unfeasible.
TD: How old is this technology?
OP: The purification methods were developed in the last few decades and are still being refined and optimized. The basic flotation process employed to upgrade the graphite ore is over 100 years old. It’s as old as mining really.
TD: This isn’t late-breaking technology, so to speak.
OP: Flotation certainly isn’t. The trick is in the development of the process flowsheet and in that sense each ore is different. There are so many different variables in the development of a flowsheet, so you can’t just subject a new ore to an existing flowsheet. It might work, but the process will not be optimized; you’re likely going to destroy larger flakes and/or yield lower concentrate grades compared to an optimized process. Each graphite deposit is different and the process has to be tailored to that specific ore.
TD: The issue isn’t just to achieve ultra high purity; it’s to get the graphite to the highest purity in the most cost-effective, viable way?
OP: Absolutely.
TD: One can achieve 99% graphite purity if one willing to spend lots of money and use more acid?
OP: Yes, for most flake graphite deposits as long as the impurities are attached to the mineral surface rather than embedded in the mineral matrix. However, it again comes down to economics, as it’s easier to upgrade the ore to high-purity concentrate for some deposits than it is for others.
TD: So any type of natural flake graphite can be made into ultra high purity, but if it’s not a reasonable grade to begin with, it’s very expensive to do.
OP: Correct, at least based on my current experience with over a dozen graphite projects. However, there is no standard definition for “ultra high purity”. The concentration and type of impurities will differ between different deposits and a purified graphite concentrate from one deposit may be suitable for a specific ultra high-purity application, while another is not. But it is still an expensive process and the hydrofluoric acid route has a significant health & safety and environmental concern. That’s why the caustic bake is, at least from a health and safety point of view, less problematic.
TD: Caustic bake sounds like the most advantageous and cost effective of the three methods for achieving ultra high purity, is that correct?
OP: Well, it’s one route. You would not likely go with hydrofluoric in a commercial process if you can avoid it. Electro-thermal purification is carried out on a commercial scale – so that’s certainly an option too. It essentially comes down to how the graphite behaves and economics.
TD: Is there a reason why a graphite company — that has pretty potent graphite coming out of the ground — wouldn’t use caustic bake over the thermal process. Could that be more cost effectiveness or just a preference of the engineer?
OP: If the company is planning on carrying out the purification themselves in the commercial process, the chemical purification route may be easier to implement. Also, there are a number of off-takers of graphite concentrate that carry out the purification process in house, i.e. they would be interested in purchasing a flotation concentrate only with the highest grade possible to minimize the cost of their purification process.
TD: The simple caustic bake is not inherently expensive or unusual. Is that what you would normally be doing with any company that gives you conventional flake graphite when you’re trying to achieve ultra high purity?
OP: That’s why it is commonly employed as first pass — it is just a simple test with a set number of process variables. However, in order to determine the CAPEX and OPEX of your circuit, these process variables will have to be optimized as you don’t get sufficient information from a single test. It’s certainly not a cheap process, but can it be economic? Absolutely, although it’s obviously also affected by the market price for a purified product. In order to obtain the very high-grade concentrate grades, one of the purification approaches will have to be taken. That’s why battery grade graphite has a premium price over any other type of graphite — because there is additional processing involved and the processing costs are substantial. Flotation is definitely much cheaper in that regard and gives an indication of how well the graphite upgrades.
TD: What are the steps taken when a graphite sample is presented to SGS for testing?
OP: First you have to produce a flotation concentrate, which you would then subject to the purification process. You would not take the run of mine ore and subject that to a caustic bake (although it’s technically feasible it does not make economic sense). So the first step is to develop at least a conceptual flowsheet to generate a flotation concentrate. The exploratory purification test then only uses a few grams of this flotation concentrate. In the purification process reagent addition rates and process conditions are chosen conservatively to make sure that as many impurities as possible will be removed. So it’s not optimized, but at least you know how well the flakes will upgrade.
TD: And is that a good indication of purity — or is it just too preliminary?
OP: Well, it’s a valid result. Can you further increase those numbers? Possibly. Can you optimize the process from a reagent consumption point of view? Absolutely. With any project development you start with some preliminary tests and if those are encouraging you start refining your process more and more. Obviously you wouldn’t carry out the full program before you have some indication that the ore is behaving reasonably well, because you wouldn’t want to spend hundreds of thousands of dollars on process development if the ore is not yielding promising results. That’s why it is a multi-stage process where you first carry out initial scoping level testing. If the test results are encouraging, the next phase would be some process optimization and that continues on all the way through to a pilot plant scale and generation of process design criteria for engineering and CAPEX and OPEX estimates.
TD: When a graphite company is pursuing ultra high purity or battery-grade graphite, it would go to a third party like SGS, which I understand is a world leader in this field.
OP: Yes, because many of the companies all around the world — especially the ones with projects that are fairly well advanced – use the services of SGS due to the level of expertise that was obtained over the past 3 years. I was leading the development of the process flowsheet for a number of the more advanced graphite exploration companies such as Northern Graphite, Focus Graphite, Mason Graphite, and Energizer Resources. Zenyatta also awarded SGS in Lakefield the process development for their graphite deposit and numerous other graphite exploration companies are using the analytical and metallurgical services provided by SGS in Lakefield.
TD: So SGS does everything from initial purity trials to pilot plant testing?
OP: Yes, SGS does carry out all of the tests from the exploratory level lab scale to the pilot plant scale. The flowsheet development and subsequent pilot plant testing are all done at the same site. The analytical and mineralogical services are located on the same site as well, which helps to streamline the entire development process. The advantage of having all groups on the same site is that they can easily communicate with each other and, as importantly, have access to the same data.
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