Low Activity of Regenerated Carbon and Fine Particle Issues at a Gold Mine in Victoria, Australia
Low Activity of Regenerated Carbon and Fine Particle Issues at a Gold Mine in Victoria, Australia
Introduction
With over 50 years of experience in the Activated Carbon Manufacturing Industry, Haycarb focuses on sustainable practices and provides high-performance activated carbon products that meet the rigorous demands of modern gold extraction processes. In addition to our advanced manufacturing techniques and quality control systems, our experienced multidisciplinary technical teams comprising of Chemists, Process Engineers and Metallurgists offer a wide range of services including tests and assays on Activated Carbon from our fully equipped laboratories together with the following suite of technical services for effective carbon selection and management.
With over 50 years of experience in the Activated Carbon Manufacturing Industry, Haycarb focuses on sustainable practices and provides high-performance activated carbon products that meet the rigorous demands of modern gold extraction processes. In addition to our advanced manufacturing techniques and quality control systems, our experienced multidisciplinary technical teams comprising of Chemists, Process Engineers and Metallurgists offer a wide range of services including tests and assays on Activated Carbon from our fully equipped laboratories together with the following suite of technical services for effective carbon selection and management.
Routine
Testing
Evaluating the condition of plant carbons, regeneration efficiency and process carbon management.
Technical
Troubleshooting
Identifying and resolving issues related to activated carbon systems.
Activated Carbon Plant
Audits
Conducting comprehensive evaluations of activated carbon plants to ensure optimal performance.
Plant Operator
Training
Providing specialized training for plant operators on effective carbon management.
Routine Testing
Evaluating the condition of plant carbons, regeneration efficiency and process carbon management.
Technical Troubleshooting
Identifying and resolving issues related to activated carbon systems.
Activated Carbon Plant Audits
Conducting comprehensive evaluations of activated carbon plants to ensure optimal performance.
Plant Operator Training
Providing specialized training for plant operators on effective carbon management.
The following is an example of how our Technical trouble shooting and mine audit process of a Gold Mine in Victoria, Australia that faced with 2 main issues: low activity of regenerated carbon and unexpectedly fine particle distribution, was assisted by our team to identify the root cause and recommend solutions that overcame the problem successfully.
Upon brief investigation by our engineers, it was found that the main cause for operational inefficiencies and carbon attrition was the impaired function of the screw feeder in the regenerated kiln.
Problem Identification
Problem Identification
The sample of regenerated carbon showed an activity level of just 59.7%, which is significantly lower than with new activated carbon. This indicates ineffective regeneration, adversely affecting the overall efficiency of gold recovery. Ideally, the activity of regenerated carbon should fall within the optimum range of 85% to 95%.
The low activity observed in regenerated carbon is often not due to the regeneration process itself, but rather the quality of water used for Quenching. If the quench tank water is of poor quality (e.g. using process water with a higher percentage of contaminants), the regenerated carbon may adsorb contaminants at this stage, including both organic and inorganic substances.
As evidenced by ICP analysis, the quench water sample showed higher concentrations of inorganic contaminants. This significantly reduces the carbon’s activity, affecting its kinetic properties, gold adsorption capacity, and overall recovery rates. However, this issue does not occur in all gold processing operations.
In this process, froth flotation utilizes organic reagents to recover gold concentrate. However, these reagents often carry over into the CIL process, contaminating the activated carbon and diminishing its gold adsorption efficiency. This indicates that the activated carbon regeneration process was flawed.
In this case, regeneration must be performed under more stringent conditions and at higher temperatures than usual because some reagents, particularly Potassium Amyl Xanthate (an organosulfur compound), bind very strongly to the carbon pores.
The low activity observed in regenerated carbon is often not due to the regeneration process itself, but rather the quality of water used for Quenching. If the quench tank water is of poor quality (e.g. using process water with a higher percentage of contaminants), the regenerated carbon may adsorb contaminants at this stage, including both organic and inorganic substances.
As evidenced by ICP analysis, the quench water sample showed higher concentrations of inorganic contaminants. This significantly reduces the carbon’s activity, affecting its kinetic properties, gold adsorption capacity, and overall recovery rates. However, this issue does not occur in all gold processing operations.
In this process, froth flotation utilizes organic reagents to recover gold concentrate. However, these reagents often carry over into the CIL process, contaminating the activated carbon and diminishing its gold adsorption efficiency. This indicates that the activated carbon regeneration process was not fully successful.
In this case, regeneration must be performed under more stringent conditions and at higher temperatures than usual because some reagents, particularly Potassium Amyl Xanthate (an organosulfur compound), bind very strongly to the carbon pores.
The sample had a high concentration of fine carbon which led to increased carbon loss and consequently, gold loss. The regenerated sample contained 36.5% fine carbon (% mass finer than 1.7 mm), which exceeds acceptable norms for efficient carbon circuits. To minimize gold loss, it’s recommended to keep fine carbon content below 10%, as fine carbon can pass through interstage screens and be discharged into tailings. This is the root cause.
Root Cause
In this process, froth flotation utilizes organic reagents to recover gold concentrate. However, these reagents often carry over into the CIL process, contaminating the activated carbon and diminishing its gold adsorption efficiency. This indicates that the activated carbon regeneration process was not fully successful.
In this case, regeneration must be performed under more stringent conditions and at higher temperatures than usual because some reagents, particularly Potassium Amyl Xanthate (an organosulfur compound), bind very strongly to the carbon pores.
In this process, froth flotation utilizes organic reagents to recover gold concentrate. However, these reagents often carry over into the CIL process, contaminating the activated carbon and diminishing its gold adsorption efficiency. This indicates that the activated carbon regeneration process was not fully successful.
In this case, regeneration must be performed under more stringent conditions and at higher temperatures than usual because some reagents, particularly Potassium Amyl Xanthate (an organosulfur compound), bind very strongly to the carbon pores.
Solutions
The sample had a high concentration of fine carbon which led to increased carbon loss and consequently, gold loss. The regenerated sample contained 36.5% fine carbon (% mass finer than 1.7 mm), which exceeds acceptable norms for efficient carbon circuits. To minimize gold loss, it’s recommended to keep fine carbon content below 10%, as fine carbon can pass through interstage screens and be discharged into tailings. This is the root cause.
As the mine acquired the appropriate kiln tube and increased the kiln temperatures, they managed to achieve activities greater than 90%
The sample had a high concentration of fine carbon which led to increased carbon loss and consequently, gold loss. The regenerated sample contained 36.5% fine carbon (% mass finer than 1.7 mm), which exceeds acceptable norms for efficient carbon circuits. To minimize gold loss, it’s recommended to keep fine carbon content below 10%, as fine carbon can pass through interstage screens and be discharged into tailings. This is the root cause.
As the mine acquired the appropriate kiln tube and increased the kiln temperatures, they managed to achieve activities greater than 90%
Immediate replacement of the worn screw feeder was recommended. The materials used should be mild steel or stainless steel, with a preference for stainless steel (SUS 316L) due to its superior resistance to corrosion and wear. To enhance control capabilities, it was suggested to implement variable frequency drives like the Techno Variable Driver – 1HP. Additionally, it is crucial to maintain the clearance below 2.00 mm, with a maximum allowance of 5.00 mm.
Following changes to the screw feeder, there was a significant reduction (40-50%) in fine carbon content. This improvement underscores the importance of continuous monitoring and adjustments to the feeder systems to maintain optimal performance.
Immediate replacement of the worn screw feeder was recommended. The materials used should be mild steel or stainless steel, with a preference for stainless steel (SUS 316L) due to its superior resistance to corrosion and wear. To enhance control capabilities, it was suggested to implement variable frequency drives like the Techno Variable Driver – 1HP. Additionally, it is crucial to maintain the clearance below 2.00 mm, with a maximum allowance of 5.00 mm.
Following changes to the screw feeder, there was a significant reduction (40-50%) in fine carbon content. This improvement underscores the importance of continuous monitoring and adjustments to the feeder systems to maintain optimal performance.
Improve Kiln
Parameters
Optimize kiln settings to achieve higher carbon activity levels and more efficient gold adsorption.
Optimize
Particle Size
Ensure that the carbon supplied adheres to the standard 6/12 mesh specification to reduce fines and enhance retention.
Enhance Screw
Feeder Design
Utilize stainless steel feeders with variable frequency drives and maintain appropriate clearance to minimize attrition and ensure consistent feed rates.
Regular
Maintenance
Have a thorough maintenance schedule to monitor and fix wear and tear and avoid damage from foreign materials.
Improve Kiln Parameters
Optimize kiln settings to achieve higher carbon activity levels and more efficient gold adsorption.
Optimize Particle Size
Ensure that the carbon supplied adheres to the standard 6/12 mesh specification to reduce fines and enhance retention.
Enhance Screw Feeder Design
Utilize stainless steel feeders with variable frequency drives and maintain appropriate clearance to minimize attrition and ensure consistent feed rates.
Regular Maintenance
Have a thorough maintenance schedule to monitor and fix wear and tear and avoid damage from foreign materials.
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