Monday, 9 August 2010

Pyromet versus bio and hydromet

There have been great developments in bio and hydrometallurgy in recent years. This is the most researched area of minerals engineering, and is the only minerals engineering discipline to have its own dedicated peer-reviewed journal. I am sure there will be many papers from this field at next month’s IMPC, and November’s Biohydromet ’10 has a very full and exciting programme, with abstracts still coming in.

In contrast pyrometallurgy is perceived to be a dirty, expensive process, so I open for discussion: is non-ferrous pyrometallurgy likely to be superseded in the foreseeable future by the new wave of hydrometallurgical and biohydrometallurgical processes?


  1. All three technology areas offer excellent opportunities. They have in fact been under discussion for 100 years, with many successful examples
    My concern is the noted recent inability of process developers to get their technologies running. Look at the high profile failures - Hismelt, the three PAL plants in Australia, the copper concentrate pressure leach in Morenci, Lonmin's platinum furnace problems, Magnola, Alcoa Smelting Process, Iron Carbide and many more.
    For example, in 20 years of treating EAF dust, virtually every new process (save one or two) has been an abject failure. The old reliable, waelz kilns, still tops the list of go-to processes. There is a reason for this, which has been discussed elsewhere (Steel Times International, March 2010, for example) and it is not a comforting or encouraging picture.
    For most options in almost any field, if it has never been done before you can almost 100% count on commercial failure. The processes are flawed - they will not work sufficiently well to be an economic success. Cost and technology comparisons depend on the processes running as desired. Something most of these processes simply will not do. It's like most recycling options, if they are not subsidized by government they cannot be commercially successful. So feel-good, friendly processes are usually not self-sustaining.
    As one steel company recently noted regarding a new alternative iron technology they had built, four things can happen with a new technology and three of them were bad - (1) the technology will not work at all, (2) the process does not work as well as desired, and (3) the process works just fine but it is not a commercial success.
    There have been many examples trying a new idea without knowing if it has ever been tried before, or if there are similar technologies which failed, and no truly objective, thorough and competent due diligence has been done on the process. Another problem is an insufficient bankroll to keep at it long enough to solve problems. In short the development programs have been a disgrace of simplistic approaches, inattention to details, incomplete data collection and short run lengths, lack of understanding of what makes a process work and what makes it not work. All the sorts of things a good development program is supposed to address.
    An example of how to do it correctly is Freeport Sulfur's Moa Bay project, one of the first PAL's for nickel and cobalt, started up in 1960 in Cuba. Two years before startup, prior to fully begining design, the team (owner plus engineering-design-construction firm) decided they needed more process information. So they conducted an additional research program, cost $6 million in 1958 dollars. Not trivial. Yet it paid off, because everything studied was critical to good operation.
    Figure how much money it costs if the plant won't run, all those salaries to be paid, all that raw material flooding in, all that product of too poor quality to sell, no easy way to test solutions and equipment changes at such a large scale, money going out the door and nothing coming in.
    Is this really the best our technologists and design-construction firms can do? I'm afraid so, in far too many cases.
    In most cases, if you succeed, you will have earned it the hard way. There are no shortcuts and "just build it and we will make it run" is a fallacy. A steel mill can make a new melting furnace work, or a brilliantly innovative casting techniques, because those are in line with their existing businesses. We're talking making iron in low efficiency furnaces from little more than dirt, using suspect metallurgical concepts, with iron furnaces subject to slag chemistry constraints and heat/mass transfer, fluid dynamics and reaction kinetics at present little understood. All these are not within their technology familiarity zone, as the lack of successes have shown.
    Larry M. Southwick, L.M. Southwick & Associates, USA

  2. I think the final choice of process route depends upon (1) Chemistry (2) unit energy consumption. (3) kinetics One needs to select the right balance for a particular ore.
    Nevill Rice, UK

  3. There is a bit too much generalization here, both in Barry's initial post and Larry's comment. The ability to innovate varies greatly according to the mineral being processed. Take nickel, for example. Some HPAL processes work, and some don't for sulfides. For latterites, each one is different and the processing technology is re-invented for each deposit. Copper is a little more forgiving when looking at hydro vs . pyro, but again things will vary with the chemistry of the deposit.

    For anyone who has a chance to see it, JinSchuan Nickel in China has a virtual museum of processing technologies. They have experimented with everything, including the only application of waelz kilns to nickel sulfides I am aware of.
    David Wood, Russian Federation

  4. Thanks David.

    It is true that some processes work on certain minerals and not on others. My point however was that a plant being built on the mineral for which it does not work is due to a faulty development program. They should have learned it would be a failure during development.

    Alternately, plants have been built on minerals for which they should have succeeded, yet they did not. That too was due to faulty development. They should have found out how to make the process work. So in your Jin Schuan example, which were failures because of the mineral involved and in those cases then why was the plant built? And how many of their projects should have succeeded but did not?

    My point was finally that based on current examples far too many new processes are failing when under proper development they would be succeeding. That is not a generality, that is a fact. You can try to explain why – to me the unscientific mush coming out of environmental regulations is symptomatic of the mush in design and development work.

    One of the major recent successes appears to me to be Resolute Mining’s gold project in Mali. Taking over from another investor who had become stonewalled, then making a paying proposition of a new technology with a difficult orebody. But they are the rare case.

    All the ones I mentioned earlier probably should never have been built, or else built differently. Hismelt should have spent time with AusMelt (and Korea Zinc), and maybe success would have followed. Morenci should have done a better due diligence up front, and maybe it too would not have been built. Tonkin Springs (a bioleach for gold) did not do their homework on heat balances and so they too failed. The HPAL’s in Australia were a misch of ideas borrowed from the aluminum industry and elsewhere, for which a better understanding of the differences between those minerals, HPAL vs. Bayer process, equipment details, and the pressure leach processes involved would have aided development of the Australian projects.

    The bottom line is that if a new plant fails, and most new technologies have been lately, they have not done a thorough, objective due diligence and have not really understood how their technologies worked. Good, closely managed, thorough science wins every time. Most EAF dust facilities should have never been built – upfront analyses indicated that troublesome areas had been ignored. Using zinc splash condensers in a chloride loaded and dusty environment, trying hydromet without reduction first, compounded by not understanding how to put together a process flow sheet based on real data in the first place. Faulty development of rotary hearth furnaces for dust resulted partly from a flawed analysis of design parameters with an early unit. Not realizing the competition was as good as it was led to a particularly embarrassing failure. Regulators having faulty technology understanding and selection methodology led many astray. All contributed their bit to wholesale failure.

    Success comes to those who know what they are doing. Failure comes to those who do not, who wish not to admit they do not, and who do not wish to take the time to learn why their plans are flawed. The latter are in the ascendance these days. At a time when our tools and understanding should be at its zenith. You might call this a general truth.
    Larry M. Southwick, L.M. Southwick & Associates, USA

  5. Cost and availability of process water and its treatment , cost and availability of energy, purity of the concentrate to be treated (Presence of contaminants) are primary consideration I believe..Plant availability is also better in hydro met plants.
    Rangarajan Srinivasa, RAK Minerals & Metals Investments, UAE

  6. Having worked in smelters for over 10 years and been involved in the commercialisation and development of the Goldfieds (Genmin/Gencor) BIOX technology, I think I agree with Nev'. (By the way hi Nev, I don't think we've spoken in nearly 30 yrs, class of '80). Just about every project I have worked on has required a certain degree of custom metallurgical development. Subtle differences in mineralogy may predicate radically different approaches. For many projects the logical approach is to produce a concentrate for sale to a smelter, in order to minimize capital and operating costs and also permitting requirements. However, it is often not possible to produce a concentrate of sufficient grade to carry the transport costs at an acceptable recovery. In these cases you are pursuaded to look at potential hydromet routes which are generally more applicable to lower grade ores. Just make sure you have plenty of tons. It would be rare indeed for two radically different process options to come in at the same costs for which you would be faced with a simple choice. Besides you would never chose a process based on costs alone. So, from my perspective the Pyro' - Hydro' debate is unproductive, the ore will tell you what you need to do.
    Andrew Carter, Wardrop Engineering, UK

  7. These blog discussions seems to have a tendency to veer off subject!

    First pyro vs hydro (I consider bio to fall under hydro). The question Barry poses is a contrived one, all major processes in PGM, base and light metal use/need both hydro and pyro. I think of Cu, Zn, Pb, Ni ,Co, Mn, Al, Mg, etc. Name me an existing, economic choice between pure pyro and pure hydro for any project. It is what makes extractive metallurgy so interesting, combining (stepouts of) known processes and applying them to new mineral deposits. And, don't forget vapometallurgy (carbonyl, zinc, etc). Vale-Inco just announced first nickel production at GORO, New Caledonia (it's actually nickel oxide, but no matter). That's made by nickel chloride pyrohydrolysis where a nickel chloride solution is processed in a fluid bed wherein hydrocarbons are combusted to provide heat at 825 C, nickel chloride is dried, vapourized and deposited as nickel oxide on a bed of 1 mm nickel oxide prills. Is this hydro, pyro or vapo?

    With regard to Larry's comments, we really should start a blog on why the mining industry does not have Chief Engineering Officers (the other CEO's). I agree with Larry, the road to a successful new technology is lined with shuttered pilot plants. There must be at least 50 processes piloted to replace the iron blast furnace. In the meantime the latter have grown bigger, become pressurized, adopted agglomerated feeds to optimize throughput,replaced coke with fuel injected in the tyueres, mixed ilmenite in the feed to protect the hearth, etc, etc. As Larry implied, it's hard to kill a 100 year old giant.
    There are some other factors why pilot plants are abandoned, though, apart from a lack of technological discipline and experience. It takes 10 years to develop a new technology from concept to plant. No MBA trained executive will allot money on such a time scale, so it's like defence projects, they are shaded to a quick solution and started as such. Unlike defence projects they get killed after 3, 4, 5 years. If enough mony had been put into some of them, their technology would have been applied. The other reason for lack of new technologies is that they are not needed currently, the world has become a much more stable place after the various governments got out of resource operation - largely (it was replaced by recycling and environmental phobias). Look at Chili, nobody worries about investing there, anymore! The risk to investors in new metal commodities is political, economic, not so much technical. Present technologies will do fine for the new deposits, and the banks agree....
    Gus Van Weert, University of British Columbia, Canada

  8. Hi Gus.
    Like your new CEO definition! Would have perhaps saved some of the failed Mg project (MagCan, Magnola, AMC), to bring a sence of humiliy in place of arrogance. When it comes to piloting I certainly agree to take your time, even if it is a matter of spending the same budget over longer timeline. There is just no way to short circuit these things. If the pilotting is allowed to take it's course, it will give the data needed, although in some of the past projects the managers just shot the messenger, for bringing the bad news!
    Mazi Rejaee, Novopro Projects Inc, Canada

  9. Obviously, careful assessment/choice of appropriate technologies for particular types of ores is the must. However, I agree that even with a right choice, development, adaptation and establishment of processing for each particular case require 5-10 years of a thorough work. In reality, industries prefer cheaper and faster developments followed by “trials & errors”, adjustments – waste of time and money. No hopes to see any alteration of such practice in a foreseen future.

    For new process developments for Zn, Pb, Fe recovery from EAF dust, please, follow Integrated Ezinex® process combining Indutec® technology with Ezinex® system, Ausmelt processes, Enviroplus, SABIC developments, etc.
    Marina Korotkin, University of Toronto, Canada

  10. Thanks for the input Marina. These all represent interesting developments and possibly a full-sized plant in the near future. Ezinex has had its original plant in Italy since 1996, though idled for part of that time, and Ausmelt’s process has been under development with considerable testing for over 15 years. These efforts by the latter include a pilot plant in the US (now dismantled) and successful large scale tests in a LBF slag fumer at Korea Zinc (reported at the Sohn conference in 2006), as well as of course tests dating from the early 1990’s inhouse. And so it goes.

    There will be a workshop at the CIM meeting in Vancouver in October on lead and zinc recycling, including EAF dust – in North America and elsewhere. Be there or be square. My coverage of NA will focus mostly on large scale tests or commercial sized facilities. No bio, but plenty of pyro and hydro (oxide precipitation as well as electrowinning), plus solidification (fixation) and fusion (abrasive frit), with something new thrown in.

    Only pyro so far (virtually all Waelz kiln, with one flame reactor) have really succeeded in commercially recovering zinc as a byproduct here. And of course fixation, though the major landfill operator there sold out his contracts to the major Stateside pyro processor. As well as out from under his erstwhile processing partner. Competition is the name of the game, who does it well, meets steel mill pricing demands, and can still make money wins. Everyone complies the regs.
    Larry M. Southwick, L.M. Southwick & Associates, USA

  11. Pressure hydrometallurgy is the most recent development in hydrometallurgy - - it is the technology of the future. The fact that a fire took place at the new pressure leaching of copper concentrates at Morenci plant in Arizona which resulted in plant closure does not mean that the technology is a failure and should be abandoned. Here are some examples showing that pressure leaching has displaced successfully some pyrometallurgical processes that were used for many years.

    [1] For centuries, metallic zinc was produced by roasting its main sulfide mineral to get zinc oxide, which was reduced at high temperature to get the metal. Although many modifications were made to improve this technology it was only during World War I that hydro- and electrometallurgical concepts were applied to develop a new process that competed with the old technology and finally displaced it in the 1970s. However, the new process introduced other problems that have to be solved, such as treatment of side products and disposal of waste residues. Finally, in the 1980s, a new process was invented that leached directly the sulfide concentrate under pressure and electrolyzed the solution to get the metal.

    [2] Bauxite is the major raw material for producing alumina needed for producing the metal. It was first sintered with sodium carbonate at high temperature then leached with water to obtain a solution from which aluminum hydroxide was precipitated, filtered, and calcined to get pure Al2O3. Towards the end of the nineteenth century a new pressure leaching process was invented that displaced the sintering process because it was more economical. The process has been applied ever since without any major change except improving its engineering aspects.

    [3] Nickel was produced from sulfide ores mainly by pyrometallurgical route involving smelting, converting, and refining. The recent INCO nickel plant in the Canadian North has adopted pressure leaching of the sulfide concentrate. Nickel laterites have been treated successfully for half a century in Cuba by pressure leaching.

    [4] Other examples of successful pressure leaching are known, e.g., molybdenite and scheelite concentrates, uranium concentrates, etc. Not only pressure leaching has been successful but also precipitation of metals by hydrogen under pressure has been equally successful.

    Fathi Habashi
    Laval University, Quebec City, Canada

  12. Hi All,

    Just found this blog. Finally some reality in the world of extractive metallurgy developments. I have looked at dozens of processes in my 25 years in the business and have to say, we keep trying because we are all dedicated to lowering the cost and and improving the efficiency of metals recovery. I just recently looked at 2 recycling processes in depth, one was for recycling nickel bearing wastes and the other was another hydro process for EAF dust. Well the first was due diligence involving the sale of an operating asset. My major take away was the process only works economically because some engineers at the company 20 years ago realized that certain wastes just beginning to enter the waste stream had enough nickel in them to recover economically. Today, the plant economics are marginal unless this certain waste is also run through to sweeten the feed. The company gets the waste for next to nothing, but it is responsible for a substantial portion of the profit.

    The second process was a great concept, but suffered from the same issue, economy of scale. The inventors had devised a way of recovering basically every constituent metal found in EAF dust but were not able to make the commercial aspects work. Enough said.

    It seems most of the processes developed try to hard to do it all. There are very few examples of processes that have done it in a completely new way, but rather incremental technical change has been what drives the costs down.

    Most of the developers of new technology are looking at replacing the existing processes from beginning to end and this is where the failures occur. There are just too many steps to be taken to get these projects completed to commercial reality.

    BTW, I have looked at carbothermic reduction of alumina, iron carbide, various iron smelting technologies, high purity titanium sponge, one step Hunter process for titanium, ZincOx, Zeros, Zia, Horsehead Flame reactor,(for EAF dust), plasma smelting, hydro production of copper powder from oxide ores, processes to recover spent catalysts, process to recover metals from batteries, electolytic lead processes, among them.

    All were at least technically viable, but the economics always caused problems. Frankly, a lot of the processes we have today are economically questionable. Has anyone looked at the cost of a greenfield aluminum smelter today? Not a good investment.

    Dr. Habashi makes a good point, pressure leaching is one of a select few processes that have made a significant difference in our working lives.

    Joe Sabatini
    The Innovation Network, LLC
    Lexington, MA USA

  13. April 3, 2012: Here we are a year and a half later and no new postings. A very thought provoking flash of comments while it lasted.

    A concern was made as to general statemens vs. specifics. That is rather to be expected given the limited space for comments. For example, much of my comments related to the inability of new technology developers to make the grade with their work. A case in point is the use of rotary hearth furnaces in the pyro-processing of carbon steel EAF dust.

    I discussed one such example at considerable length in a recent article in Steel Tech, January, 2012 issue, an Indian journal for the iron and steel industry. While there are still space constraints, an indepth discussion was provided of what had been done before along those lines, what new was being tried, and why it was doomed to failure. The plant being considered is now in startup, so one can follow along with the trainwreck as it occurs.

    Larry M. Southwick, P.E.
    Cincinnati, Ohio


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