3766 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
wear readings and other flow through the grate simulations
that the lifter bar design and/or the position of the open-
ings in relation to the lifter bar can affect the flow through
the grates. It is probably the combined results of the pulp
lifter and the position of the slots relative to it that matters.
On the other hand, the relative position of the openings to
the pulp lifter affects the flow back into the mill and thus
the net discharge rates.
SUMMARY AND CONCLUSIONS
The effect of the grates position on the discharge efficiency
of an AG mill has been studied using a series of simula-
tions ran with a DEM+SPH coupled in-house software.
The simulations have been carried out on two different dis-
charge systems, namely radial and curved. All the operating
conditions for the AG mill and the designs of the discharge
system and mill slice have been kept unchanged in order to
focus our analysis on the grates’ position only.
The simulations shown that the position of the grates
have an important role on the efficiency of the AG mill,
especially on the discharge rates and flow through the grates
rates. When the holes are closer to the mill shell, the dis-
charge rates are larger than in any other position. As the
holes move towards the center of the mill, the discharge
rates decrease up to a position where there is no slurry
discharge anymore. Obviously, that specific position will
depend on the amount of slurry inside the mill and the
operating conditions for the mill.
Under the current operating conditions used for the
simulations, it has been shown that the slurry is mainly dis-
charged through the grates positioned between 8 o’clock
and 10 o’clock, while the solids have a wider range between
6 o’clock and 10 o’clock. This has been observed in other
experimental work for medium discharge rates similar to
our mill operating conditions.
The curved discharge design was showing to be more
efficient than the radial design at higher discharge rates. The
main reason for this might be the fact that the curved design
has the openings spread widely than the radial design allow-
ing for more particles and slurry to pass through the grates.
These higher discharge rates corresponded to the two lower
positions of the grates, namely Radial1(Curved1) and
Radial2(Curved2). At lower discharge rates the two designs
perform almost the same with slightly differences in case
of solids.
REFERENCES
Asakpo, E, Heath, A R. and Chaffer, S, 2018. Results from
Installing Turbo Pulp Lifter (TPL) in Ahafo SAG Mill,
paper presented to Comminution 2018 Conference,
Cape Town, 16–19 April.
Bordi, D, Heath, A and Pasternak, E. A method for model-
ling grate flow characteristics in autogenous and semi-
autogenous grinding mills, 9th Australasian Congress on
Applied Mechanics (ACAM9), 27–29 November 2017.
Campbell, C S, 1997. Computer Simulation of Powder
Flows, in Powder Technology Handbook, (ed: Gotoh),
pp 777–793, (Dekker: New York).
Ciutina, S and Soriano, R J, 2014. Curved Pulp lifters—can
they save energy?, paper presented to 12th AUSIMM
Mill Operators’ Conference, Townsville, Australia, 1–3
September.
Cleary, P W, 2001. Recent advances in DEM modelling of
tumbling mills, Minerals Engineering, 14: 1295–1319.
Cleary, P W, 2004. Large scale industrial DEM modelling,
Engineering Computations, 21: 169–204.
Cleary, P W, Sinnott, M D and Morrison, R D, 2006.
Prediction of slurry transport in SAG mills using SPH
fluid flow in a dynamic DEM based porous media,
Minerals Engineering, 19: 1517–1527.
Cleary, P W, 2009. Industrial particle flow modelling using
DEM, Engineering Computations, 26(6): 698–743.
Cleary, P W, Hilton, J E and Sinnott, M D, 2017.
Modelling of industrial particle and multiphase flows,
Powder Technology, 314: 232–252.
Gutierrez, A, Ahues, D, Gonzalez, F and Merino, P, 2018.
Simulation of material transport in a SAG mill with
different geometric lifter and pulp lifter attributes
using DEM, Mining, Metallurgy &Exploration, 36(2):
431–440.
Herbst, J A, Lo, Y C and Rajamani, K, 1985. Population
balance model predictions of the performance of large
diameter mills, Minerals and Metallurgy Process, 2(2):
114–120.
Herbst, J A and Nordell, L, 2001. Optimization of the
design of sag mill internals using high fidelity simula-
tion, in Proceedings SAG 2001 (ed: A Barratt and M
Mular), pp 150–164.
Latchireddi, S and Morrell, S., 2003. Slurry flow in mills:
grate-only discharge mechanism (Part-1), Minerals
Engineering, 16(7): 625–633.
wear readings and other flow through the grate simulations
that the lifter bar design and/or the position of the open-
ings in relation to the lifter bar can affect the flow through
the grates. It is probably the combined results of the pulp
lifter and the position of the slots relative to it that matters.
On the other hand, the relative position of the openings to
the pulp lifter affects the flow back into the mill and thus
the net discharge rates.
SUMMARY AND CONCLUSIONS
The effect of the grates position on the discharge efficiency
of an AG mill has been studied using a series of simula-
tions ran with a DEM+SPH coupled in-house software.
The simulations have been carried out on two different dis-
charge systems, namely radial and curved. All the operating
conditions for the AG mill and the designs of the discharge
system and mill slice have been kept unchanged in order to
focus our analysis on the grates’ position only.
The simulations shown that the position of the grates
have an important role on the efficiency of the AG mill,
especially on the discharge rates and flow through the grates
rates. When the holes are closer to the mill shell, the dis-
charge rates are larger than in any other position. As the
holes move towards the center of the mill, the discharge
rates decrease up to a position where there is no slurry
discharge anymore. Obviously, that specific position will
depend on the amount of slurry inside the mill and the
operating conditions for the mill.
Under the current operating conditions used for the
simulations, it has been shown that the slurry is mainly dis-
charged through the grates positioned between 8 o’clock
and 10 o’clock, while the solids have a wider range between
6 o’clock and 10 o’clock. This has been observed in other
experimental work for medium discharge rates similar to
our mill operating conditions.
The curved discharge design was showing to be more
efficient than the radial design at higher discharge rates. The
main reason for this might be the fact that the curved design
has the openings spread widely than the radial design allow-
ing for more particles and slurry to pass through the grates.
These higher discharge rates corresponded to the two lower
positions of the grates, namely Radial1(Curved1) and
Radial2(Curved2). At lower discharge rates the two designs
perform almost the same with slightly differences in case
of solids.
REFERENCES
Asakpo, E, Heath, A R. and Chaffer, S, 2018. Results from
Installing Turbo Pulp Lifter (TPL) in Ahafo SAG Mill,
paper presented to Comminution 2018 Conference,
Cape Town, 16–19 April.
Bordi, D, Heath, A and Pasternak, E. A method for model-
ling grate flow characteristics in autogenous and semi-
autogenous grinding mills, 9th Australasian Congress on
Applied Mechanics (ACAM9), 27–29 November 2017.
Campbell, C S, 1997. Computer Simulation of Powder
Flows, in Powder Technology Handbook, (ed: Gotoh),
pp 777–793, (Dekker: New York).
Ciutina, S and Soriano, R J, 2014. Curved Pulp lifters—can
they save energy?, paper presented to 12th AUSIMM
Mill Operators’ Conference, Townsville, Australia, 1–3
September.
Cleary, P W, 2001. Recent advances in DEM modelling of
tumbling mills, Minerals Engineering, 14: 1295–1319.
Cleary, P W, 2004. Large scale industrial DEM modelling,
Engineering Computations, 21: 169–204.
Cleary, P W, Sinnott, M D and Morrison, R D, 2006.
Prediction of slurry transport in SAG mills using SPH
fluid flow in a dynamic DEM based porous media,
Minerals Engineering, 19: 1517–1527.
Cleary, P W, 2009. Industrial particle flow modelling using
DEM, Engineering Computations, 26(6): 698–743.
Cleary, P W, Hilton, J E and Sinnott, M D, 2017.
Modelling of industrial particle and multiphase flows,
Powder Technology, 314: 232–252.
Gutierrez, A, Ahues, D, Gonzalez, F and Merino, P, 2018.
Simulation of material transport in a SAG mill with
different geometric lifter and pulp lifter attributes
using DEM, Mining, Metallurgy &Exploration, 36(2):
431–440.
Herbst, J A, Lo, Y C and Rajamani, K, 1985. Population
balance model predictions of the performance of large
diameter mills, Minerals and Metallurgy Process, 2(2):
114–120.
Herbst, J A and Nordell, L, 2001. Optimization of the
design of sag mill internals using high fidelity simula-
tion, in Proceedings SAG 2001 (ed: A Barratt and M
Mular), pp 150–164.
Latchireddi, S and Morrell, S., 2003. Slurry flow in mills:
grate-only discharge mechanism (Part-1), Minerals
Engineering, 16(7): 625–633.