1776 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
i, respectively. In order to achieve the optimal balance
between the speed of attaining the target and the execu-
tion expense of control actions, the cost function, J, uti-
lizes penalty matrices, Q and R, as tuning parameters. These
parameters are normalized and customized to play a pivotal
role in fine-tuning the control strategy in the BrainWave
algorithms. To control and optimize the CIL leaching cir-
cuit, BrainWave leverages this concept to calculate neces-
sary dosages of reagents, such as sodium cyanide and milk
of lime, to maintain residual cyanide concentration and pH
level at the desired targets in the tank.
CIL ACE Advanced Process Control Strategy
The main objective of the CIL ACE APC strategy is to
stabilize pH level and residual cyanide concentration.
Therefore, there are two main variables to control. The first
one, which is pH, can be measured at multiple locations
depending on the number of CIL tanks and the number of
lime addition points. If an estimation of the incoming feed
to each tank and a reliable lime flow measurement are avail-
able, a BrainWave controller will control the pH to the SP
by regulating the ratio of lime addition to incoming feed.
The ratio control strategy will linearize the response and
will automatically account for feed rate disturbances. In the
absence of a reliable lime flow measurement, the ratio can
be defined as valve position divided by incoming feed.
The second objective of the CIL ACE APC strategy is
to control residual cyanide in the CIL tanks. In order to
control residual cyanide in real-time, a reliable cyanide ana-
lyzer must be available. Residual cyanide analyzers can be
placed in different tanks depending on the circuit design.
Additionally, the number of sodium cyanide addition points
also determines the APC strategy. Residual cyanide at each
location is controlled by regulating sodium cyanide dosage.
To account for incoming flow changes, the BrainWave con-
troller calculates a ratio of sodium cyanide flow to mass feed
rate. In the absence of a sodium cyanide flow meter or an
incoming feed, the BrainWave can be configured to control
the sodium cyanide valve position directly. Once variabili-
ties of the cyanide concentration and pH level are reduced,
the target residual cyanide can be decreased to reduce the
reagent consumption.
RESULTS AND DISCUSSIONS
A mine site in the United States utilizes eight CIL tanks in
series to perform gold cyanidation in the presence of carbon.
The residual cyanide concentration is controlled in Tank 1
by regulating the sodium cyanide dosage. Concurrently, the
pH level in Tank 1 of the CIL circuit is regulated through
manipulating the lime addition. This study uses plant
uptime data from October 15th to October 20th, 2023, to
evaluate the efficiency of the APC solution in maintaining
stable residual cyanide concentrations and pH levels within
the CIL circuit. During this period, the utilization of the
APC solution was maintained at a consistent 100%. In fact,
this CIL ACE solution was installed three years ago and has
been running since then. Therefore, the uptime of the APC
system is generally above 90%.
Graphical representations of the control performance
for residual cyanide and pH are shown in Figure 4 and
Figure 5, where the blue and red lines represent the PV and
SP, respectively. The values were normalized to protect the
confidentiality of the mine site. As can be observed from
Figure 4 and Figure 5, the APC solution effectively main-
tained the residual cyanide concentration and the pH level
Figure 3. Process inputs (U), Laguerre state variables (L), and predicted outputs (Y) used by BrainWave
i, respectively. In order to achieve the optimal balance
between the speed of attaining the target and the execu-
tion expense of control actions, the cost function, J, uti-
lizes penalty matrices, Q and R, as tuning parameters. These
parameters are normalized and customized to play a pivotal
role in fine-tuning the control strategy in the BrainWave
algorithms. To control and optimize the CIL leaching cir-
cuit, BrainWave leverages this concept to calculate neces-
sary dosages of reagents, such as sodium cyanide and milk
of lime, to maintain residual cyanide concentration and pH
level at the desired targets in the tank.
CIL ACE Advanced Process Control Strategy
The main objective of the CIL ACE APC strategy is to
stabilize pH level and residual cyanide concentration.
Therefore, there are two main variables to control. The first
one, which is pH, can be measured at multiple locations
depending on the number of CIL tanks and the number of
lime addition points. If an estimation of the incoming feed
to each tank and a reliable lime flow measurement are avail-
able, a BrainWave controller will control the pH to the SP
by regulating the ratio of lime addition to incoming feed.
The ratio control strategy will linearize the response and
will automatically account for feed rate disturbances. In the
absence of a reliable lime flow measurement, the ratio can
be defined as valve position divided by incoming feed.
The second objective of the CIL ACE APC strategy is
to control residual cyanide in the CIL tanks. In order to
control residual cyanide in real-time, a reliable cyanide ana-
lyzer must be available. Residual cyanide analyzers can be
placed in different tanks depending on the circuit design.
Additionally, the number of sodium cyanide addition points
also determines the APC strategy. Residual cyanide at each
location is controlled by regulating sodium cyanide dosage.
To account for incoming flow changes, the BrainWave con-
troller calculates a ratio of sodium cyanide flow to mass feed
rate. In the absence of a sodium cyanide flow meter or an
incoming feed, the BrainWave can be configured to control
the sodium cyanide valve position directly. Once variabili-
ties of the cyanide concentration and pH level are reduced,
the target residual cyanide can be decreased to reduce the
reagent consumption.
RESULTS AND DISCUSSIONS
A mine site in the United States utilizes eight CIL tanks in
series to perform gold cyanidation in the presence of carbon.
The residual cyanide concentration is controlled in Tank 1
by regulating the sodium cyanide dosage. Concurrently, the
pH level in Tank 1 of the CIL circuit is regulated through
manipulating the lime addition. This study uses plant
uptime data from October 15th to October 20th, 2023, to
evaluate the efficiency of the APC solution in maintaining
stable residual cyanide concentrations and pH levels within
the CIL circuit. During this period, the utilization of the
APC solution was maintained at a consistent 100%. In fact,
this CIL ACE solution was installed three years ago and has
been running since then. Therefore, the uptime of the APC
system is generally above 90%.
Graphical representations of the control performance
for residual cyanide and pH are shown in Figure 4 and
Figure 5, where the blue and red lines represent the PV and
SP, respectively. The values were normalized to protect the
confidentiality of the mine site. As can be observed from
Figure 4 and Figure 5, the APC solution effectively main-
tained the residual cyanide concentration and the pH level
Figure 3. Process inputs (U), Laguerre state variables (L), and predicted outputs (Y) used by BrainWave