27th Jul 2007 07:00
Alexander Mining PLC27 July 2007 27 July 2007Alexander Mining plc New business formed to commercialise innovative new mineral processingtechnology Alexander Mining plc ("Alexander", the "Company"), the AIM-listed copper, goldand silver mining company with projects in Argentina and Peru, is pleased toannounce an innovative new mineral processing technology. • Alexander has developed a new ammonia heap leaching process for copper oxide deposits at its Leon copper project in Argentina • Significant potential for use on other base and precious metals. Initial laboratory testwork results for zinc are highly promising, with the potential for a breakthrough in the development of a new low cost solvent extraction, electrowinning processing route • AmmLeachTM Limited, a wholly owned subsidiary has been incorporated in the British Virgin Islands, to develop and commercialise the ammonia leaching technology • Alexander has already demonstrated significant operating cost and environmental advantages compared with conventional acid heap leaching • Provisional patents application and trade marks filed • Mutual confidentiality agreement signed with a major mining company to explore the possibility of exploiting the technology; with meetings arranged with a number of other major companies Dr. Matt Sutcliffe, Chairman and Chief Executive Officer, said: "Alexander's newAmmLeachTM process has serious commercial potential. Approximately 40% of theworld's copper is produced using the acid heap leaching method and the price ofacid is at record highs. The AmmLeachTM process can significantly reduce theoperating cost of the heap leaching process. In addition, it has the potentialfor a major breakthrough in the processing of previously untreatable zinc oxidedeposits, with the development of the first heap leach zinc mines. Alexander ismoving rapidly to maximise the commercial value of this exciting new process." For further information please contact: Matt Sutcliffe, Chairman and Chief Executive OfficerAlexander Mining plc1st Floor35 PiccadillyLondonW1J 0DW Tel: +44 (0) 20 7292 1300Fax: +44 (0) 20 7292 1313Mobile: +44 (0) 7887 930 758Email: [email protected]: www.alexandermining.com Nominated Advisor and BrokerAlasdair Younie/John PriorArbuthnot Securities Limited,Arbuthnot House,20 Ropemaker Street,London, EC2Y 9ARTel: +44 (0) 20 7012 2000 Public/Media RelationsTim BlackstoneBritton Financial PR,62 Britton StreetLondonEC1M 5UY Tel: +44 (0) 20 7251 2544Mobile: +44 (0) 7957 140 416 Introduction In the course of conducting the feasibility study work at its Leon copperproject in Salta Province, northwest Argentina, Alexander has developed a newammonia heap leaching process, which it has named AmmLeachTM. Not only doesAmmLeachTM have specific benefits for treating the Leon copper oxide deposit butit also has potentially significant advantages for treating other copper oxideand base metals deposits, especially those deposits where existing mineralprocessing methods do not work or are uneconomic. These advantages includeoperational, economic and environmental criteria and are more fully detailedbelow. In order to maximise the commercial value of its intellectual property (IP),Alexander has filed a provisional patent and AmmLeachTM trade mark application.In addition, it has incorporated in the British Virgin Islands a wholly ownedsubsidiary, AmmLeachTM Limited, to develop and commercialise the technology. Initial work has commenced on the application of the AmmLeachTM process to otherbase metals. In particular, the initial laboratory testwork results on zinc havebeen highly promising and have the potential for a significant breakthrough inthe development of a new low cost solvent extraction, electrowinning processingroute. The AmmLeachTM Process The AmmLeachTM process is a new process for the extraction of base metals,especially copper, zinc, nickel and cobalt from ore deposits. The processutilises ammonia-based chemistry to selectively extract metals from ores. Thetarget ores will typically be high acid consuming, although AmmLeachTM is alsoan alternative to acid leach processes as it is far more selective and offers anumber of benefits. The technology consists of the same three major stages as acid processes i.e.leaching, solvent extraction and electrowinning. The leaching occurs in twosteps, an ore-specific pre-treatment which converts the metals into a solubleform and the main leaching step, which uses recycled raffinate from the solventextraction stage. Solvent extraction is used to separate and concentrate themetals whilst also changing from ammoniacal media to acid sulphate media fromwhich metals can be directly electrowon using industry standard unit operations.One of the key benefits of the AmmLeachTM process is that unlike some newtechnologies it requires no special purpose built equipment. AmmLeachTM technology is suitable for both low grade heap leaching and highergrade tank leaching; the choice is dictated by the grade and deposit economics.Polymetallic deposits can be readily handled using standard solvent extractionand solution purification techniques. The difference from acid leaching is that the leaching is conducted inmoderately alkaline solution with ammonia present as a complexant. The use ofalkaline conditions allows the use of AmmLeachTM on high-carbonate ores whereacid consumption would be prohibitive. The AmmLeachTM process has an extremely high selectivity for the target metalover iron and manganese, which are insoluble under AmmLeachTM conditions.Calcium solubility is also significantly suppressed by the presence of carbonateand extremely low sulphate levels in the leaching solutions. These featuresensure that there are no potential problems due to jarosite or gypsumprecipitation reducing permeability in the heap or scaling problems in thesolvent extraction plant. Additionally, silica is also insoluble in the AmmLeachTM process, removing problems associated with formation of unfilterableprecipitates within an acid leach plant during pH adjustment and the need tohandle high viscosity solutions. Ammonia unlike acid, doesn't react withaluminosilicates and ferrosilicates, whose products can cause drainage andpermeability problems in heaps. Compared with previous ammoniacal processes, almost any ore mineralogy can betreated as the pre-treatment step is specific to each orebody. The wholeAmmLeachTM process is tailored to individual ore bodies and consequently hassubstantially lower ammonia losses than earlier processes. In theory, all theammonia can be recovered, however in practice small losses do occur. Decommissioning of the heap is extremely simple as no neutralisation isnecessary and the potential for acid mine drainage is virtually eliminated.After final leaching the heap is simply washed to recover ammonia and then leftto revegetate with the residual ammonia acting as a fertiliser. The alkaline residue allows immediate application of cyanide leaching of goldand silver in ores where there is an economic precious metal content afterremoval of high cyanide consuming metals Potential Applications Alexander believes that its AmmLeachTM technology has considerable commercialpotential in the global mining industry. It plans to maximise this potential byseeking to develop relationships with other companies and has already commenceddiscussions. This may be by joint relationships on advancing the IP of thetechnology and/or targeting 'problem' ore bodies which hitherto are uneconomicusing existing mineral processing technology and metallurgy. The following metals are particular targets for the AmmLeachTM process: • copper and silver in stratabound carbonate and weathered oxide deposits;• zinc in mixed oxide deposits;• nickel and cobalt in lateritic deposits;• gold, silver and copper in leached porphyries; and• polymetallic base metal deposits, especially uranium. Of these, the copper process has already been demonstrated at pilot plant scaleat Alexander's Leon project. The zinc process has been trialled successfully ona bench scale and larger scale testwork is planned for late-2007. The nickel andcobalt process is still under development but early experiments show promise. Because of the tailored pre-treatment step, almost any ore type is amenable tothe AmmLeachTM process. Thus far it has been demonstrated on predominantly oxideores but sulphides have also been shown to leach after appropriatepre-treatment. Polymetallic ores can also be processed by AmmLeachTM with separation achievedusing solvent extraction to separate metals and produce multiple revenuestreams. The minimisation of ammonia transfer allows these metals to berecovered directly from their strip solution by precipitation, crystallisationor electrowinning. The use of ammonium carbonate will allow the simultaneous recovery of uraniumand base metals from roll-front deposits, with the carbonate extracting theuranium and the ammonia the base metals. Current technology does not allowrecovery of both. The alkaline conditions used in the AmmLeachTM process allow precious metals tobe recovered from the base metal depleted heap using a secondary leach step. Theheap can simply be washed to recover ammonia and subjected to standard alkalinecyanidation to recover gold and silver. Work is currently underway toincorporate precious metal recovery within the AmmLeachTM process. Preliminarywork on the leaching of cyanide consuming metals prior to precious metalleaching with cyanide looks very promising. Comparison of AmmLeachTM with acid leaching of copper+---------------+------------------------------+-------------------------------+|Parameter |Acid |AmmLeachTM |+---------------+------------------------------+-------------------------------+|mineralogy |oxides, carbonates, silicates,|almost any - dependant upon || |some sulphides |curing stage |+---------------+------------------------------+-------------------------------+|curing |concentrated H2SO4 |tailored to ore mineralogy |+---------------+------------------------------+-------------------------------+|selectivity |Low- iron, manganese, calcium |High- no iron, manganese, || |and silica are likely problems|calcium or silica dissolution |+---------------+------------------------------+-------------------------------+|rate of |limited by acid strength and |ammonia concentration in leach ||extraction |diffusion |solution matched to leaching || | |rate |+---------------+------------------------------+-------------------------------+|recovery |80% of leachable |> 75% in || | |approximately 60-120 days |+---------------+------------------------------+-------------------------------+|heap lifetime |55-480 days |approximately 60-120 days |+---------------+------------------------------+-------------------------------+|sulphate |reduced permeability in heap, |calcium and iron solubilities ||precipitation |break down of clays and plant |too low for precipitation, also|| |scaling due to precipitation |low sulphate levels in leach || |of gypsum and jarosite |solution |+---------------+------------------------------+-------------------------------+|leachate |depends upon carbonate content|depends on concentration used ||consumption |3.7-27 kg/t reported |< 5kg/t in preliminary trial || | |heap (field trials show less || | |than 1kg/t) |+---------------+------------------------------+-------------------------------+|precious metals|heap to be neutralised before |neutralisation not required, || |cyanidation |potential for simultaneous || | |recovery using thiosulphate or || | |sequential leaching using || | |cyanide |+---------------+------------------------------+-------------------------------+|decommissioning|heap requires washing, |heap can be washed and left, ||& environmental|neutralisation and long term |residual ammonia acts as || |monitoring to avoid Acid Mine |fertiliser for vegetation || |Drainage (AMD) |regrowth, minimal likelihood of|| | |AMD. |+---------------+------------------------------+-------------------------------+ This information is provided by RNS The company news service from the London Stock ExchangeRelated Shares:
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