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Knelson Concentrators, a corporate partnership dba Knelson Gravity Concentration at Ashanti Goldfields BIOX Plant Obuasi Mine; Ghana, W. Africa.

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Presentation on theme: "Knelson Concentrators, a corporate partnership dba Knelson Gravity Concentration at Ashanti Goldfields BIOX Plant Obuasi Mine; Ghana, W. Africa."— Presentation transcript:

1 Knelson Concentrators, a corporate partnership dba Knelson Gravity Concentration at Ashanti Goldfields BIOX Plant Obuasi Mine; Ghana, W. Africa

2 CONTENTS 1. Introduction - Knelson Concentrator - Overview - Obuasi STP-Biox Plant Flowsheet 2. Testwork - Results from lab scale testing 3. Construction and Installation - Materials of Construction 4. Circuit Metallurgy - Operating parameters of the circuit - Impact of the Knelson Concentrator 5. Summary

3 ASHANTI - OBUASI OPERATIONS Pompora Treatment Plant (PTP)1.8Float, Roast,CIL Sulphide Treatment Plant (STP)2.9Float, Biox, CIL Oxide Treament Plant (OTP)2.9CIL Tailings Treatment Plant (TTP)1.9CIP Heap Leach1.1Agglomerated PLANT CAPACITY(Mtpa) PROCESS Grind Re-grind Flotation BIOXCCD CIL Flot. Tail Conc.

4 On-site Lab Test Work 1. Three Streams Tested a) CCD Thickener #5 U/F b) Biox-CIL Tailings c) Final Tailings (from flotation) 2. Considerations - severe corrosion of the lab test machine - corrosive nature of the Biox process (pH ) 1. Three Streams Tested a) CCD Thickener #5 U/F b) Biox-CIL Tailings c) Final Tailings (from flotation) 2. Considerations - severe corrosion of the lab test machine - corrosive nature of the Biox process (pH ) - free gold - easily visible Objective: To determine the presence of free gold in the STP Biox circuit. - fine free gold - visible under the microscope - flat gold flakes - easily visible - flat shape attributed to grinding

5 1. Photomicrographs and visual observations indicated the presence of free gold in all of the streams tested. 2. Free gold passed through the CIL circuit without complete leaching. 3. Internal work by Ashanti indicated that free gold is liberated in the Biox Process % of the liberated gold particles are <20 micron. 5. Any installation of a Knelson Concentrator in the Biox/CCD circuit would have to address the corrosive nature of this slurry (pH ). Lab Test Work Summary

6 CIL No. 5 Thickener No. 6 Thickener Cyclone Thickener Feed Box Knelson Concentrator Concentrate Hopper Table

7 Modifications to the Knelson Concentrator Materials of Construction Evaluated a) Hastelloy C-276 b) Incolloy 825 c) Stainless Steel 904L d) Stainless Steel 304L - Ashanti indicated that 304L had performed very well for other equpiment located in that part of the plant. - The other alloys would have at least doubled the cost of manufacture compared to the standard unit. Materials of Construction Evaluated a) Hastelloy C-276 b) Incolloy 825 c) Stainless Steel 904L d) Stainless Steel 304L - Ashanti indicated that 304L had performed very well for other equpiment located in that part of the plant. - The other alloys would have at least doubled the cost of manufacture compared to the standard unit.

8 Materials of Construction Materials of Construction General Assembly Stainless Steel (304L) - Tail. Launder Linatex Rubber Lined - Motor Cover - General Assembly - Upper & Lower Frame Assemblies - Conc. Launders Electroless Nickel Plated - Upper & Lower Bearing Exteriors - Drive Sheave/Bushing

9 Knelson Concentrator Hourly Tonnage tonnes Pulp Density of Knelson Feed % (w/w) Temperature of Knelson Feed30 o C Slurry pH2 - 3 Size distribution of Knelson Feed90% passing 45 microns Concentrating Cycle Time3 hours/cycle Knelson Fluidization Flow (USgpm)130 gpm Operating Parameters

10 Plant Au Recovery Prior to KC Installation87% Plant Au Recovery After KC Installation % Percentage of Total Gold Recovered by KC4 - 5% CIL Tails Grade Prior to KC Installation2 - 3 g-Au/t CIL Tails Grade After KC Installation g-Au/t Process Improvements

11 Knelson Concentrator Installation at AGC Obausi Mine; Ghana, W. Africa

12 SUMMARY & CONCLUSIONS 1. Lab testing identified free gold present in the CCD circuit, CIL tails and final tails. 2. Free gold passed through the CIL circuit without complete leaching. 3. Decision to install a Knelson Concentrator in the CCD circuit after the Biox process. 4. The materials of construction were modified to 304L stainless steel to withstand the severely corrosive nature of the slurry. 5. Installation was extremely successful with significant improvents to gold recovery.


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