• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
S. Al-Hassan & R. K. Amankwah & R. S. Nartey, University of Mines and Technology, Ghana, Direct Smelting of Gold Concentrates as an Alternative to Amalgamation in Small-scale Gold Mining Operations
 

S. Al-Hassan & R. K. Amankwah & R. S. Nartey, University of Mines and Technology, Ghana, Direct Smelting of Gold Concentrates as an Alternative to Amalgamation in Small-scale Gold Mining Operations

on

  • 4,609 views

 

Statistics

Views

Total Views
4,609
Views on SlideShare
4,602
Embed Views
7

Actions

Likes
0
Downloads
404
Comments
0

1 Embed 7

http://www.slideshare.net 7

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    S. Al-Hassan & R. K. Amankwah & R. S. Nartey, University of Mines and Technology, Ghana, Direct Smelting of Gold Concentrates as an Alternative to Amalgamation in Small-scale Gold Mining Operations S. Al-Hassan & R. K. Amankwah & R. S. Nartey, University of Mines and Technology, Ghana, Direct Smelting of Gold Concentrates as an Alternative to Amalgamation in Small-scale Gold Mining Operations Presentation Transcript

      • Direct Smelting of Gold Concentrates as an Alternative to Amalgamation in Small-scale Gold Mining Operations
      • S. Al-Hassan & R. K. Amankwah & R. S. Nartey
      • UNIVERSITY OF MINES AND TECHNOLOGY, GHANA
      • presented at the workshop at
      • CASM CONFERENCE, BRASILIA, BRAZIL
      • October 6 – 12, 2008
    • Today’ s Presentation
      • Objective
      • ASSM Mining methods in Ghana
      • Available alternatives
      • Direct smelting – the technique
      • Laboratory and field trials
      • Challenges
      • Conclusions
    • Objective
      • Identify and introduce techniques or processes to eliminate the use of mercury by artisanal and small-scale gold miners (ASM) in Ghana
    • Map of Africa showing position of Ghana
      • Area is about 230 020 km 2
      • Population is about 21 million
      • Climate is tropical
    • Geological map of Ghana showing rock formations that contain gold
    • Location of Small-scale Mining District Centres, Ghana Upper East Bolgatanga Eastern Akim Oda Central Assin Fosu, & Dunkwa-on-Offin Western Tarkwa, Bibiani, & Asankragua Region District Centres Location
    • ASSM Gold & Diamond Production 1989 Gold 2% Diamonds 40% 2001 Gold 6% Diamonds 95% 2007 Gold 12% Diamonds 98% SSM Contribution Total Ghana Production Source: Minerals Commission, Ghana 839,235 2,628,290 2007 972,991 2,342,722 2006 1,065,923 2,138,944 2005 905,344 2,031,971 2004 904,089 2,274,627 2003 963,493 2,236,833 2002 1,090,072 2,381,345 2001 878,011 2,457,152 2000 Diamond Prodn (carats) Gold Prodn (oz) Year
    • ASSM Mining Methods in Ghana
      • Washing and Panning (alluvials along rivers)
      • Shallow pitting (near surface placers)
      • Underground mining (reefs)
      • Tailings and waste dumps (of old closed mines)
    • Mining in Dry Area (Eluvial) 90% greater than 1 mm
    • Concentration (Dry Area) Winnowing Washing
    • Mining of Alluvial Deposits
    • Mining Hard Rock (Reefs)
    • SSM Dredging in Ghana (Suction)
    • Milling (Hard Rock)
    • Flow sheet for operations
      • Ore (hard rock)
      • crushing/grinding
      • gravity concentration
      • mercury  amalgamation
      • filtration of excess mercury  liquid mercury
      • burning of amalgam  mercury vapor
      • sponge gold
      • smelting
      • bullion
    • Sluicing
    • Panning
    • Gold concentrate in a pan
    • Amalgamation
    • Squeezing excess mercury from amalgam
    • Fireplace for burning amalgam
    • Spongy gold
    • Gather and sell
    • Open hearth for smelting gold
    • Mercury Loss
      • Spillage during amalgamation
      • Poor amalgam distillation
      • Disposal of amalgamation tailings
      • Further processing of sponge gold
      • it is estimated that for every gram of gold recovered at least 0.43g of mercury is escapes
    • Alternatives
      • Physical methods Shaking tables , special sluices Centrifugal concentrators
      • Chemical methods Coal gold agglomeration IGoli Haber process Cyanide leaching Smelting
    • Alternative suitable for galamseyers
      • Effective
      • Easy - requires no special equipment
      • Quick
      • Cheap
      • Suitable for processing small batches of concentrate
      • Visible - the miners can see their products throughout the whole process
      • Locally available
    • Choice of direct smelting
      • Fulfils all main criteria
      • Uses non-toxic, cheap chemicals, borax, sodium carbonate, silica sand
      • Technology not developed for artisanal use
    • Smelting
      • Smelting is a high-temperature melting process used to recover metals from ores and concentrates
      • Fluxes are added to the concentrate to assist melting and react with impurities so that the metal separates out
      • The final products are pure metal and a glassy slag containing the unwanted components
    • Smelting vs amalgamation
      • Smelting gave 99.9% recovery
      • In the lab amalgamation gave around 97% recovery
      • In the field amalgamation gave around 88% recovery
    • Furnace (sika bukyia) Removable chimney Steel shell Refractory bricks Stabilizer bar Combustion chamber Pipe for exhaust fan
    • Direct Smelting
    • Mixing charge and feeding crucible
    • Feeding the furnace
    • Heating crucibles in furnace
    • Temperature control
    • Removing crucible after smelting
    • Pouring of molten material
    • Cooling of melt in a mould
    • Separation of gold from slag Gold
    • Gold beads
    • Field trials
    • Demonstration of Method
    • Cost of Direct Smelting 1.6 Total 0.8 12 kg Charcoal 0.4 2 Crucibles 0.4 200 g Flux Cost (GH¢) Weight/number Item
    • Cost comparism 3.20 5.50 Total 1.50 Smelting 0.50 Heating of amalgam 3.20 4 crucibles (2 operations) 4.00 Half teaspoonful of mercury (27 g) Cost, GHC Direct smelting Cost, GHC Amalgamation
    • Challenges (alternative fuels) PALM KENNEL
    • Challenges (concentrate pretreatment)
      • Sulphidic concentrates
      • Concentrates with high metal content
    • Challenges (alternative fuels) GAS Crucibles Gas cylinder Furnace
    • Challenges (alternative fuels) GAS
    • Challenges (integrity of crucibles)
    • Conclusions
      • Direct smelting can be used to replace amalgamation
      • It is cheaper on consumables
      • It takes a similar length of time
      • It uses no hazardous reagents
      • It is suitable for small batches
      • It is visible
    • Cost estimates for kit CHARCOAL
    • Cost estimates for kit GAS
    • Acknowledgements
      • The on-going direct smelting studies is being sponsored by the EU. The great support given by GBS and Wardell Armstrong is worth commending. I am grateful to the organizers of this CASM Conference for sponsoring me for this presentation.
    • RIDE A CROCODILE AT PAGA GHANA THANK YOU OBRIGADO