Future of Pyrometallurgy

[nsurre]

I would like to ask all the pyrometallurgists out there how they see the future of non-ferrous pyrometallurgy in, say, 20 years time.

It seems to me to be a dirty, expensive process which is likely to be superceded by the new wave of hydrometallurgical and biohydrometallurgical processes.

Is it on the decline?

[Jacques]

Is non-ferrous pyrometallurgy in the decline? Short answer: No, I do not believe this is the case, but I do believe hydrometallurgy has broadened the metal extraction options.

In the non-ferrous industry, pyrometallurgy and hydrometallurgy are complementary rather than opposing engineering technologies. In some industries (e.g. Zn, Au, U), the hydrometallurgical process alternatives are preferred. On the other hand, pyrometallurgical processing is and will remain the preferred processing route for Cu, Ni (including laterites), PGM's, Pb, Ti, where they are extracted in large quantities and the economics of scale dictate the requirements for smelting.
In many non-ferrous industries the combination of hydro-and pyromet gives an optimal solution (the recovery of Co from waste slags at Chambishi and the subsequent leaching of the DC furnace produced alloy, or the smelting of mattes before leaching in the PGM industry are examples.
Even in Zn processing, the most common extraction method is roast-leach-electrowin...where roasting remains a pyrometallurgical operation.

Hydromet still has its fair share of challenges, including the disposal problem of environmental unstable leach residues, and aqueous effluents.

Moreover, hydromet has significant challenges in energy utilisation: any heating and cooling of the salts in solution requires heating of cooling of the solvent which is often 95-99% of the solution mass.

Are pyrometallurgical operations hot dusty environments?....yes they have been, but they are becoming less so every year as improved dust and emission control systems are installed.

Pyrometallurgy is not the preferred processing route in all cases. A good extractive metallurgist will always follow the scientific route and evaluate all options objectively. However in reality we all have our comfort zones and a pyrometallurgist will tend to prefer pyrometallurgical process option and the hydrometallurgist the hydrometallurgical options. Both should suggest their process alternatives (or combine their processes) and the best engineering solution should be developed.

The bigger problem is often (in the non-ferrous industries) that smelters are treated as "black boxes" rather than high temperature reactors which can be analysed using basic engineering principles. Measurement and control is more challenging due to the hostile conditions but newer non-contact technologies have become available to better control furnaces.

Hydromet and pyromet will (and need to) develop innovative process solutions in parallel to address the future need for metals, metallic intermediates and commodities.

[E Nield Netherlands]

There are two further general advantages of pyromet: firstly high temperature processes have much faster kinetics than cool or luke warm processing and that equates to smaller capital equipment and capital costs.

Hydromet processes which require large inputs of electric power are at a disadvantage in remote places where unit power costs are high and where the best ore deposits tend to be. Electrolysis of zinc, for example, demanding about 4000 KWHrs per tonne metal is not on at unit power costs of 10-15 US cents per KWHr - a common figure if power has to be generated in diesel sets using transported oil. Transporting Zn feed to sites where unit power costs are lower may well set impossible demands on concentration of ore to concentrates without major losses of values.

[Fathi Habashi]

Hydrometallurgy will displace inefficient pyro processes. There are at least two examples:
1) Zinc was produced for over 400 years by a fully pyro route. Since 1980, a fully hydro process was invented (Sherritt autoclave process) and four plants are now in operation using this technology
2) Alumina was first produced by a high temperature sintering process (Le Chatelier, 1855) was replaced by Bayer's hydrometallurgical process in 1892 - - the process used today world wide

[B Bailey Australia]

Mr. Habashi states categorically that hydromet will supercede pyromet. A brave man who can predict the future so confidently!!

He mentions zinc, and the fact that it was at one time produced solely by pyrometallurgy. On this topic, I seem to remember much interest in the 80s and 90s in the 'Warner Process', which was actively researched in the UK.

This process produced zinc, and other base metals, by a totally pyrometallurgical route, obviating the need for concentration and separation of the valuable minerals by froth flotation. I believe there was also recycling of heat and gases within the system.

It would appear to me that, judging by the debate at www.meionline.proboards2.com/index.cgi?board=comminution&action=display&n=1&thread=30, this process would be very pertinent to some of the highly complex and refractory base metal ores which are now being treated.

These ores need extensively fine (ultrafine) grinding, which is expensive and inefficient (in promoting liberation), and flotation is often woefully inadequate in dealing with this fine material, such that low recoveries are attained, and minerals find their way into the wrong concentrates, thus incurring extra penalties.

So my questions are, what happened to the Warner Process, and why is no-one using it?

[ZML]

Answer to final question by B Bailey, Australia.
"The Warner Process is readyand waiting for someone to carry out development throught the prototype stage to commercialisation. The basic work on the metallurgy, engineering design and economics has been done. Contact Zinc Metallurgy Ltd (ZML) through MEI to learn more.
Development of Warner Process has been slowed up by low cash flows in producer industry not being supportive of investment.

[barrywills]

Contact details are on the Business Directory at www.min-eng.com/directory/pyro/index.html

[E Nield]

For a good recent review of the Warner Process, see www.min-eng.com/pyrometallurgy/44.html

[barrywills]

Those interested in this debate on pyrometallurgy versus hydrometallurgy may be interested in the forthcoming keynote lecture, to be given by Prof. Noel Warner, at Zinc Processing '08 in Brisbane in August. For more details see www.meionline.proboards2.com/index.cgi?board=conference&action=display&n=1&thread=35&page=1

[ajohnston]

Pyromet process are also very good at making cheap sulphuric acid, which is needed by most hydromet processes. In my mind studying hydromet routes usually highlight a problem in a project, such as the inability to make a clean concentrate through flotation.
Mixed concentrates with combinations of finely disseminated pyrite, copper, lead, zinc or other minerals may not be smelter feed candidates or would be too costly to ship. Also, arsenic or other nasties in the ore could eliminate the pyromet alternative, thus making hydromet more attractive.

[hborst]

Just a thought, but is it possible that hydromet processes are so popular because they are easy to research? Almost every minerals institution has a hydromet lab- all that is needed are a few beakers and reagents. Pyromet, however is much more difficult to research at small-scale, which is why Prof. Warner should be applauded for building a full-scale pilot version of his process at the University of Birmingham, and hence proving its viability. It's a pity that the research is not ongoing as many modern deposits would be ideally suited to the Warner Process.

[ajohnston]

hborst: You might be on to something there. I don't think that they are more popular in operations for that reason, but certainly in research and papers published.

Can anyone name any significant hydromet operations that were built because they out performed pyromet? Very isolated operations and those with contaminants that attract smelter penalties not included please.

[barrywills]

This discussion continues on the MEI Blog at min-eng.blogspot.com/2010/08/pyromet-versus-bio-and-hydromet.html

[cleaningcompany]

the future will be best if see our problem