XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3757
with the proper profile as per the mill design. Figure 1
shows the mill design simulated during the calibration run.
The site measured audit data that will be used for the
calibration of the model is presented in Table 1.
Based on the audit data and the mill design, a model of
the mill has been created using Metso ProSim plant simula-
tor. The model has been used to estimate the size distribu-
tion of the charge inside the mill slice. The size distribution
calculated from ProSim has been used to fill the slice with
solids and SPH particles corresponding to the operating
conditions of the mill. The minimum size for the DEM
particles used in the simulation was 19 mm, while the SPH
size used was 15 mm.
The simulation has been run at the beginning with
the grates blinded in order to allow the solid particle and
SPH fluid particles to settle in the grinding chamber and
to develop the charge shape. After that, the grates were
opened, and the simulation has run until a steady state has
been reached. The mill filling percentage and the percent-
age solids by weight in the discharge are controlled dur-
ing simulation by adjusting the number of solids and SPH
particles inside the mill slice. During the simulation, the
data collected was:
• Discharge flow rates for solids and water at the trun-
nion end
• Flow rates of solids and water through the grates in
both directions, inwards (from pans back into the
mill) and outwards (from inside the mill into the
pans).
• Mass hold-up in pans for solids and water.
The steady state condition was achieved when:
• Hold-ups have reached a constant mass for both sol-
ids and water.
• Mass balance has been reached. The mass balance
criteria was considered reached when the differ-
ence between the outwards and inwards flow rates
through the grates is close to the discharge flow rate
at the trunnion end.
The simulations have shown that in most cases the
steady state has been reached after 35 seconds or about 6
revolutions.
Figure 1. Design of the mill discharge system and the mill slice used for the calibration run
Table 1. Audit data for the AG mill used in the validation of the model
Mill Speed (%CS) Mill Filling (%)Solids %w/w
Discharge Rates
Solids (t/h) Water (m3/h)
76 33 78 1,056 330
with the proper profile as per the mill design. Figure 1
shows the mill design simulated during the calibration run.
The site measured audit data that will be used for the
calibration of the model is presented in Table 1.
Based on the audit data and the mill design, a model of
the mill has been created using Metso ProSim plant simula-
tor. The model has been used to estimate the size distribu-
tion of the charge inside the mill slice. The size distribution
calculated from ProSim has been used to fill the slice with
solids and SPH particles corresponding to the operating
conditions of the mill. The minimum size for the DEM
particles used in the simulation was 19 mm, while the SPH
size used was 15 mm.
The simulation has been run at the beginning with
the grates blinded in order to allow the solid particle and
SPH fluid particles to settle in the grinding chamber and
to develop the charge shape. After that, the grates were
opened, and the simulation has run until a steady state has
been reached. The mill filling percentage and the percent-
age solids by weight in the discharge are controlled dur-
ing simulation by adjusting the number of solids and SPH
particles inside the mill slice. During the simulation, the
data collected was:
• Discharge flow rates for solids and water at the trun-
nion end
• Flow rates of solids and water through the grates in
both directions, inwards (from pans back into the
mill) and outwards (from inside the mill into the
pans).
• Mass hold-up in pans for solids and water.
The steady state condition was achieved when:
• Hold-ups have reached a constant mass for both sol-
ids and water.
• Mass balance has been reached. The mass balance
criteria was considered reached when the differ-
ence between the outwards and inwards flow rates
through the grates is close to the discharge flow rate
at the trunnion end.
The simulations have shown that in most cases the
steady state has been reached after 35 seconds or about 6
revolutions.
Figure 1. Design of the mill discharge system and the mill slice used for the calibration run
Table 1. Audit data for the AG mill used in the validation of the model
Mill Speed (%CS) Mill Filling (%)Solids %w/w
Discharge Rates
Solids (t/h) Water (m3/h)
76 33 78 1,056 330