Copyright © 2013, Industrial Management Enhancement
e‐mail: [email protected] // www.imeSolutions.biz Page 1 of 4
CaseStudy:QualityMineralbeneficiation
Introduction
Case Study 2 originates from a mineral processing plant. Primary crushing and milling precedes the
flotation circuit. All processing prior to the flotation circuit is about getting material in the correct
format to maximise recovery of minerals. Incorrect flotation circuit operation results in significant
losses.
This assessment quantifies the impact of Rougher Mass Pull in relation to flotation circuit
performance.
Control samples, sampled every two hours, provide feedback regarding quality. A combination of
process data (flow rates, motor current, pH, feed rates, etc.) and control samples describe
process conditions.
The aim is to understand how process conditions relate to flotation performance that is reported
retrospectively (i.e. control samples lagging the real‐time process by a minimum of 2 hours). This
assessment provides insight into operating conditions that have the highest probability of
realising the desired performance (expressed in terms of recovery, grade and production rate).
Once agreement is reached on the baseline state, it will be possible to generate a TISM to describe
Rougher Mass Pull in real‐time. The latter serves as an early warning system when the process is
drifting away from the baseline state thereby facilitating pro‐active management of the process.
Information produced during this assessment facilitates root cause analysis, tracks the impact of
performance improvement initiatives, and facilitate training / development of operational
personnel.
Opportunity Description
Rougher Mass Pull has a direct impact on recovery. In this particular case, 1% loss in recovery per
day is equivalent to about USD12000 revenue loss – that is mineral not recovered and pumped to
tailings.
Key Process Influencing Factors identified for this flotation circuit include Mill Feed Rate, Pulp
Density, Reagent Dosing, Circulating Load, Rougher Concentrate Tank Level, Froth Depth, and
Volumetric Air Flow on Mechanism. Although a control system (PLC) controls process variables
against set points, operational decision‐making rated as the most significant factor contributing
toward Rougher Mass Pull Control.
Guidelines were put in place regarding appropriate manner the rougher circuit should be operated.
Irrespective of the latter, mass pull regularly operated outside the target range resulting in
spillage and recovery losses as the residence time in the Cleaner / Re‐cleaner circuit goes outside
defined limits.
Copyright © 2013, Industrial Management Enhancement
e‐mail: [email protected] // www.imeSolutions.biz Page 2 of 4
The need existed, firstly, to determine whether existing process parameters could provide insight
into operating conditions delivering best performance. Secondly, utilize Performance Maps to
determine how long the Rougher Mass Pull operated within desired limits – this is to quantify the
operational risk exposure. Thirdly, utilize Performance Maps to align all stakeholders regarding
the correct operating procedure. In other words, standardize the Rougher Circuit method of
operation.
Approach
Figure 1 is an extract of the Performance Maps constructed to characterize process conditions
associated with Rougher Mass Pull.
Figure 2 maps the relationship between process conditions and Recovery. The bold and underlined
conditions represent highest recovery. (The selection took other constraints such tailing grade,
feed grade, motor currents, levels, etc. into account. In other words, if any of the qualifying Key
Process Influencing Factors were outside their respective ranges, it disqualifies the position to be
included as an ‘ideal’ condition.)
Figure 1 - Performance Map for Rougher Mass Pull
Copyright © 2013, Industrial Management Enhancement
e‐mail: [email protected] // www.imeSolutions.biz Page 3 of 4
Figure 4 contains the matching conditions selected in Figure 2. Figure 4 contains a clear definition of
what operating conditions constitutes ideal operation. In other words, the probability of
achieving higher recovery substantially improves when operating within the selected condition.
The ability to link a performance indicator to operating conditions using process measurements
confirms that it is possible to utilize process parameters to detect operating conditions (this was
the first objective of the study).
Figure 3 confirms that the Rougher operated for only 9.2% within the target state. This Performance
Map took 20 days of operation into account. During ideal conditions, recovery was 71% versus
non‐ideal conditions that reported 64% (weighted average). This is equivalent to a 7% drop in
recovery over 18.2 days. In monetary terms, this is equivalent to USD1.5m loss (second
objective).
Figure 2 - Recovery
Figure 3 - Time-in-State
Copyright © 2013, Industrial Management Enhancement
e‐mail: [email protected] // www.imeSolutions.biz Page 4 of 4
KPIF Decision Rationale
Stakeholders participated in this assessment. Performance Maps linked process measurements to
recovery. During interactive discussions, operational personnel gained insight into the
contribution of various Key Process Influencing Factors. This understanding provided a common
approach to Rougher Mass Pull control (objective number three).
Conditions outlined by Performance Maps provide a quantitative assessment of process conditions
facilitating efficient decision‐making.
Summary of Results and Benefits
A follow‐up study conducted three weeks after aligning stakeholders revealed that the average
Time‐in‐State (ideal state) increased from 9.2% to 65%. Recovery increased at the same time by
an average of 2.1% after discounting feed grade changes.
Figure 4 – Rougher Mass Pull – ‘Ideal’ conditions
Top Related