Copper Mountain RecoveryExpert™ , Flotation Expert Control
The copper mountain project demonstrates the effectiveness if RecoveryExpert™ solutions on flotation cells. Overall recovery increased by 3-4% on average while maintaining the desired concentrate grade.
Rougher Flotation Control Strategy
Maximize rougher flotation recovery at an acceptable rougher concentrate grade without exceeding the limitations of the rougher flotation circuit or downstream unit operations such as the cleaner circuit.
The rougher control strategy has a control mode that can be selected from the operator DCS screen. The rougher strategy is typically invoked every ten minutes. The frequency that the strategy is executed can be modified based on the dynamics of the circuit and the frequency of feedback from the on-stream analyzers. If PlantVision is used, the frequency may be increased slightly.
Rougher Process Variables
Process variables are input values from the flotation process that are measured, calculated, or controlled by the DCS. For the Rougher flotation circuit, the process variables are listed below:
• Pulp Level
• Air Flow
• Concentrate Flow
• Frother Dosage
• Collector Dosage
• Secondary Reagent Dosage
• Rougher Concentrate Grade
• Rougher Feed Grade
• Rougher Tails Grade
• Rougher Recovery
Additionally PlantVision provides the following flotation data:
• Froth Velocity
• Froth Color (Red, Green, Blue, Luminescence)
• Bubble Size
The goals for the rougher area are to maximize recovery, maintain acceptable rougher concentrate grade and to minimize reagent consumption.
Flotation Overload Recovery Strategy
1st – High Sump Levels: Evaluate the rougher concentrate sump level and lower pulp levels when the sump level is above the high limit.
2nd – Regrind Overloaded: Evaluate the regrind circuit and lower pulp levels when the regrind circuit is overloaded. The regrind circuit status will be “overloaded” if the regrind sump is above the sump level high limit or the cyclone feed pump current is above the amperage high limit or the cyclone header pressure is above the pressure high limit.
These rules are ordered by their priority and the degree of their control action. The implementation of this part of the strategy will be “crisp rules” so that responses to emergency conditions will focus upon recovering from the overload.
Control Branch Rules (Optimize Flotation Performance)
If it was determined in the overload detection rules that no overload conditions exist in the rougher area, then the control branch (optimization) rules are invoked.
1st -Evaluate the froth velocity in every bank and adjust the pulp level when the froth velocity is above or below acceptable limits. This is extremely important when there are multiple rows being controlled using combined assay values, and allows for optimization of each bank.
2nd – Evaluate the rougher concentrate grade and lower the pulp level in every bank when the grade is below the low acceptable limit. If the pulp level in every bank is near its low limit, reduce the air flow. If the air flow is near its low limit, lower secondary collector dosage. If the secondary collector dosage is near its low limit, then lower primary collector dosage. If the primary collector dosage is at its low limit, lower frother dosage.
3rd- Evaluate the recovery and increase the pulp level in every bank to improve recovery. If the pulp level in every bank is near its high limit, increase the air flow. If the air flow is near its high limit, increase the secondary collector dosage. If the secondary collector dosage is near its high acceptable limit, then increase the primary collector dosage. If the primary collector dosage is near its high limit, increase the frother dosage.The froth velocity measurement can be used to ensure each cell bank is pulling concentrate as well as the location where additional frother may be needed. For example if the pulp level is near its high limit but the froth velocity is low and air flow is high, additional frother may be needed. The froth velocity measurement can be used to adjust the pulp levels of individual banks. For example if the concentrate grade is low the general action would be to lower the pulp levels. However, if a bank has a low froth velocity and is not pulling, the individual action would be to raise the level on that specific bank. This type of strategy is essential when many rows must be controlled using shared assay information.
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