Tank bioleaching is an established and competitive technology for treating refractory gold sulfide concentrates, but despite extensive research and development and considerable expenditure, the technology has had limited commercial application for treatment of base metal concentrates. Heap bioleaching is extensively used for commercial treatment of secondary copper ores but is still to be established for recovery of copper from primary chalcopyrite ores.
In the first keynote lecture at Biomining '20 in Falmouth, Dr. David Dew, of Dewality Consultants Ltd, UK, will review tank bioleach technology developed for treating base metal concentrates and discuss the process and engineering factors that determine the design and scale-up, identifying the limiting factors that affect commercial competitiveness. The development of chemical and bioleaching processes for heap leach treatment of primary copper sulfide ores will also be reviewed identifying challenges that limit bioleach performance.
Dr. Dew feels that the hydrometallurgy component of biohydrometallurgy is often largely ignored at conferences concerned with bioleaching, despite the fact that downstream iron removal, metals recovery and waste disposal are key elements that determine the viability of the overall process. He will review some of the standard methods used for metals recovery and the challenges that are imposed on the overall process, particularly relevant to heap leach operations. Considering the limitations and challenges identified, he will then present a case for opportunities where biohydrometallurgy may add value and identifies focus areas for development.
David Dew has 30 years international experience in the development of biohydrometallurgical processes for application in the extraction of base and precious metals. He joined Gencor Ltd., South Africa, in June 1983; in 1990, as Principal Research Metallurgist, he joined the project team responsible for development of the BIOX Process. He took a lead role in the improvement and design of the bioleach reactors, reducing power costs and establishing a methodology for pilot testing and commercial plant design. He was later appointed Manager Process Development at Billiton Plc responsible for leading research in this area. In 2001 Billiton merged with BHP to become BHP Billiton and David was appointed as Global Technology Manager at the Johannesburg Technology Centre, primarily responsible for technology development for the Base Metals Division. David became an independent consultant in 2012 and formed his own company, Dewality Consultants Limited, which he operates from his home in Cornwall. In May 2018 David joined the College of Engineering , Mathematics and Physical sciences, University of Exeter, as a Postdoctoral Research Fellow working part-time for the Horizon 2020 NEMO project, funded by the European Union. The project re-establishes his links with the Camborne School of Mines, from where he graduated in 1979.
David's keynote is something to look forward to, but in the meantime I am sure that he would appreciate your views on the future of biohydrometallurgy for the treatment of base metal sulphide ores.
David's keynote is something to look forward to, but in the meantime I am sure that he would appreciate your views on the future of biohydrometallurgy for the treatment of base metal sulphide ores.
#Biomining20 for the latest updates on the conference.
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How about bioleaching application in the urban mining?
ReplyDeleteThe application of bioleaching for treatment of urban waste and particularly electronic waste is an area receiving interest, because of the potential to treat waste on a small scale local to the source. Biohydrometallurgy for treatment of electronic waste faces familiar issues: acid consumption (dissolution metals and oxide material), unwanted iron dissolution, ability to recover of precious metals and safe disposal of waste residue and iron precipitates that may contain toxic metal impurities. The outcome of research in this field and the application of patented methods will be tested in the years ahead. As yet, I am not aware of any major commercial operations where bioleaching is a key element for treatment of urban waste; but others may have examples where the method has shown a competitive edge?
DeleteDave Dew, Dewality Consultants Ltd, Cornwall, UK
The "brick wall" of tank bio-oxidation (needed for sulphide ores) is the (power) cost of oxygen transfer from air to slurry. The only technology which avoids this is the 2NO + O2 ---> 2NO2 reaction. That moves the brick wall to the recovery of NO/NO2 from magnesium nitrate. Gus Van Weert.
ReplyDeleteIt is fair to argue that the application of bioleaching is limited by solids throughput and that is strongly related to oxygen supply and energy cost (capital and operating) as throughput is increased, plus limitations of maintaining active microbial growth as solids content is increased. I would agree that alternative methods such as the Nitox Process® offer potential advantages.
DeleteDave Dew, Dewality Consultants Ltd, Cornwall, UK
We have been hearing and reading on bioleaching and biohydrometallurgy for years; but seem to have not taken off in a bigway. Is it environmental issues/cost/ ??? What are the real issues in going from lab and or small scale to major operations , I am sure more focused research and practical issues would be attended to if these are fully understood. These are very attractive(if not only) technologies to be adopted to recover values from lean and difficult to treat ores,particularly sulphides. Are there any engineering challenges?
ReplyDeleteThe above is more for my better understanding.
The application of bioleaching for treatment of base metals depends very much on the mineralogy of the ore, and the efficiency and cost of the downstream process to recover base metals, including separation and disposal of excess iron and impurities. Improvement of reactor agitator design in the past 5-10 years has reduced operating cost for oxygen transfer. Despite this, the main challenge limiting application for large scale treatment of base metal ores by bioleaching remains solids throughput. Operating costs (energy, acid consumption, nutrients and solution neutralisation) and capital cost (reactors, agitators and downstream plant for metals recovery and waste neutralisation). The latter may prove prohibitive for larger operations due to throughput constraints. Treatment of low grade ore and waste materials by heap leaching remains an area where bioleaching shows a clear commercial advantage.
DeleteDave Dew, Dewality Consultants Ltd, Cornwall, UK
Very clear picture and appreciate--looks we need multidisciplinary approach--biology,thermodynamics, reactor design---exciting !
ReplyDeleteSo many challenges and opportunities to recover values from finite natural resources.
I have just come across this thread, so I don't know if anyone is reading it anymore! Bioleaching is, in my opinion, a very niche application. As Dr. Dew alludes to, the main problem is downstream processing, and it is the same for all sulfate-based processes, namely that for every tonne of S oxidised, you create 5 tonnes of gypsum (assuming lime neutralisation). Similarly for iron, every tonne oxidised creates 1.5-2 tonnes of iron (oxy) hydroxide residues. Thus, the residue fall is substantially more than the ore originally mined. Due to the use of lime, the process also has a small carbon footprint, and it is also unable to recoup any of the intrinsic energy in the ore. On the other hand, I am a great fan of bio-remediation, especially "ecologoical engineering" wherein microbes are used to return waste rock piles to their former natural state. This is much to be preferred to liming in perpetuity, and I would rather see the bio community focus on this than leaching. Bryn Harris
ReplyDelete