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Case Studies: Introduction of Safe Practices in Mercury Use
Training Miners in the Use of Retorts in Senegal
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Experience has shown that the biggest barrier to the uptake of safer technology is educational.
A project was implemented in the Tambacounda Region of eastern Senegal to break the cycle of dangerous mercury use by supplying artisanal, or small scale gold miners with the education and technology needed to minimize their exposure to mercury and its release into the environment.
The project is a collaborative effort of the Global Mercury Project, Africaclean, USEPA and the Government of Senegal.
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| Reports |
| Artisanal Gold Mining in the Tambacounda Region of Senegal: Second Report on the Reduction of Mercury Emissions Through Appropriate Technologies Training-Summary Report; Full Report (French) |
| Technology Demonstration for Reducing Mercury Emissions from Small-Scale Gold Refining Facilities, ANL/EVS/TM/08-6 (English, Spanish) |
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Technology for Capturing Mercury Emissions from Gold Processing Shops
Gold mined using mercury-based artisanal and small scale mining (ASM) methods typically contains 5-40% mercury when sold to "gold shops" (small scale gold purchasing and refining shops). The uncontrolled removal of the residual mercury in gold shops using high temperature evaporation can be a significant source of mercury emissions in urban areas where the shops are located. The emissions from gold shop hoods during a burn can exceed 1000 mg/m3, and are typically vented to the environment at, or near, street level in high density central business district areas.
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The USEPA, with technical support from the Argonne National Laboratory, has completed a project to design and test a technology to remove the dominant aerosol component in the emissions from gold shops. Baseline evaluations conducted showed that the dominant mercury component of the exhaust is in the form of aerosol or liquid particles.
The project's objective was to demonstrate a technology that could be manufactured at low cost using only locally available materials and manufacturing capabilities. Six prototypes designed by Argonne were locally manufactured, installed, and tested in gold shops in the towns of Itaituba and Creporizao, located in the Tapajos gold producing region in Para State, Brazil.
An initial prototype design used a pebble bed to collect mercury aerosols, and achieved mercury collection efficiencies of over 90%. In a second prototype design, the pebble bed was replaced with slotted steel baffle plates to further simplify construction, and lower weigh and cost. Various installations of the baffle plate design resulted in measured mercury collection efficiencies of 40-80%.
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The combined cost of construction and installation of the prototype with baffle plates was approximately US$400. The cost of system operation could be reduced by resale of collected mercury by the system's collection drains. The system can be installed in various hood configurations commonly found in gold shops globally. A water-based system for installation in smaller shops was also tested and shown to be effective for certain applications.
A sampling procedure that is a combination of particle filter and vapor analyzer was demonstrated as an effective procedure for analyzing both the aerosol and vapor components of the mercury concentrations. (See Section 5 of the Full Report.)
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