25 MERCURY LOSS Spillage during amalgamation Poor amalgam distillation Disposal of amalgamation tailingsFurther processing of sponge goldit is estimated that for every gram of gold recovered at least 0.43g of mercury escapes
26 ALTERNATIVE PROCESSES TO AMALGAMATION Physical methods Shaking tables , special sluices, Centrifugal concentrators.Chemical methods Coal gold agglomeration IGoli Haber process Cyanide leaching Direct Smelting
27 SLUICING Method Equipment/ Process Principle Applicability Physical SluiceGravity concentration leading to production of a rough concentrate that has to be cleaned furtherUsed in virtually all small scale mining centres as a conventional rougher concentration unit.
28 COAL-GOLD AGGLOMERATION MethodEquipment/ProcessPrincipleApplicabilityPhysico-chemicalCoal-Gold AgglomerationAgglomeration of the gold particles and coal, followed by flotation with diesel, kerosene and other oils. The float concentrate has to be processed and smeltedThe process has been tested in Australia, South Africa, Brazil and Tanzania. It appears that despite its apparent attractions, it was never actually put in to operation and more research is required.
29 Igoli Process Method Equipment/ Process Principle Applicability ChemicalIGoli processLeaching with HCl and NaOCl followed by filtration and precipitation with sodium metabisulphite. The slimes precipitated are calcined and smeltedThe process has been applied in South Africa and Tanzania. Due to the safety hazards involved in working with acids and the miners lack of training in chemistry. Mintek insists on miners attending a training course. It is currently more suited to organised medium scale rather than artisanal and small scale mining operations.
30 CYNIDATION Method Equipment/ Process Principle Applicability Chemical CyanidationLeaching with sodium Cyanide and oxygen followed by adsorption onto activated carbon, elution, electrowinning and smelting. Concentrated solution that requires further processingCyanidation has been applied by small scale miners in Colombia, Bolivia, Brazil and Zimbabwe. The method is not fast enough for processing concentrates. It is poisonous and illegal in some countries like Ghana
31 HABER PROCESS Method Equipment/ Process Principle Applicability Haber Leaching with a concentrated solution that requires further processingThe leaching reagent is proprietary. For this process artisanal miners have to take their ore to processing centres where it is processed. This is not applicable to the artisanal mining environment as:too costly and too complex for individuals or small groupsuses a proprietary chemical thus locking the miners into a foreign third party supplierhas major issues of trust and keeping track of an individual’s ore
32 DIRECT SMELTING Method Equipment/ Process Principle Applicability ChemicalDirect SmeltingMelting black sand concentrates to produce pure goldSmelting is applied in most small scale centres and miners are familiar with the method as it is being used for purifying sponge gold. It has been developed, tested and commercialised in Ghana. It can be used for all types of ores and comparatively cheaper than amalgamation.
33 CRITERIA OF SUITATBLE ALTERNATIVE FOR GALAMSEYERS EffectiveEasy - requires no special equipmentQuickCheapSuitable for processing small batches of concentrateVisible - the miners can see their products throughout the whole processLocally available
34 CHOICE OF DIRECT SMELTING Fulfils all main criteriaUses non-toxic, cheap chemicals: borax, sodium carbonate, silica sand
35 SMELTINGSmelting is a high-temperature melting process used to recover metals from ores and concentratesFluxes are added to the concentrate to assist melting and react with impurities so that the metal separates outThe final products are pure metal and a glassy slag containing the unwanted components
36 SMELTING VS AMALGAMATION Smelting gave 99.9% recoveryIn the lab amalgamation gave around 97% recoveryIn the field amalgamation gave around 88% recovery
42 DIMENSIONS OF GAS FURNACES ITEMDIMENSIONSSmall Size (1)Large Size (4)Height280 mmExternal Diameter240 mm405 mmInternal diameter170 mm375 mmThickness of insulation30 mm60 mmThickness of metal shell50 m50 mmLength of LPG inlet pipe190 mmAir slot length95 mmAir slot width10 mmNumber of air slots34242
48 COST ELEMENTS OF LARGE SIZE GAS FURNACE SNItemQuantityUnit Cost (GH¢)Total Cost (GH¢)1Casing290.002Lining120.003Ring5.004Clips0.100.205Hose (4 m)6.006Valve3.007Regulator20.008Hood30.009Miscellaneous5.80Total480.004848
49 COST ELEMENTS OF SMALL SIZE GAS FURNACE SNItemQuantityUnit Cost (GH¢)Total Cost (GH¢)1Casing220.002Lining90.003Ring5.004Clips0.100.205Hose (4 m)6.006Valve3.007Regulator20.008Hood30.009Miscellaneous5.80Total380.004949
50 COST OF KIT WITH LARGE SIZE GAS FURNACE SNItemQuantityUnit Cost (GH¢)Total Cost (GH¢)1Gas furnace (L/S)480.002Gas cylinder (15 kg)70.003Gas (15 kg)12.004Fire extinguisher (4 kg)50.005Tongs7.0014.006Cupels15.0030.007Hammer3.008Gloves2.004.009Goggles10Spoons0.200.4011Weighing scale80.0012Crucibles10040.0013Flux reagents200.0014Mixing bowlTotal991.405050
51 COST OF KIT WITH SMALL SIZE GAS FURNACE SNItemQuantityUnit Cost (GH¢)Total Cost (GH¢)1Gas furnace (S/S)380.002Gas cylinder (15 kg)70.003Gas (15 kg)12.004Fire extinguisher (4 kg)50.005Tongs7.0014.006Cupels15.0030.007Hammer3.008Gloves2.004.009Goggles10Spoons0.200.4011Weighing scale80.0012Crucibles10040.0013Flux reagents200.0014Mixing bowlTotal891.405151
61 CHALLENGES Retrieval of loan balances How is the money accruing from the sale of the kits to be used?Formation and sustenance of Small Scale Miners’ AssociationsSustenance of the Mercury Abatement Programme (accessibility & affordability)Further follow-up to sustain the momentum of the use of the technology.6161
62 THE WAY FORWARD - GHANAEnsure that the kits are readily available and accessible virtually at the door steps of the ssm;Monies accruing from the sale of the kits should serve as revolving fund;Outstanding loan balances should be retrieved by the respective District Offices of the MC;6262
63 THE WAY FORWARD - GHANA CONT’D Encourage the formation and strengthening of the SSM AssociationsMonitoring and follow-up should be continued for at least two (2) years;Use of the direct smelting method should be made a condition for the acquisition of license where amalgamation is used6363
64 THE WAY FORWARD - GLOBAL To achieve this feat it is recommended that the:ACP country should provide a budget or secure donor funds to launch the project possibly using the Ghana Project as model (at least €200,000.00);ACP country should organise a Management Unit (Ministry of Mines, University, NGOs, etc) to manage the project;ACP country should recruit local consultants with experience in artisanal and small scale mining of gold to undertake the project
65 THE WAY FORWARD – GLOBAL CONT’D Menart Geoventures Ltd, University of Mines and Technology, Tarkwa – Ghana, could be contracted to provide fabrication plans and a complete kit;Menart Geoventures Ltd, University of Mines and Technology, Tarkwa - Ghana may be contacted to provide high level consultants to supervise the project.
66 ACKNOWLEDGEMENT MINISTRY OF FINANCE & ECONOMIC PLANNING, GHANA EUROPEAN UNIONMINERALS COMMISSION, GHANAPROJECT MANAGEMENT UNIT, GHANABRITISH GEOLOGICAL SURVEYUNIVERSITY OF MINES & TECHNOLOGY, TARKWA (UMaT), GHANAACP GROUP6666