890 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
CONCLUSIONS
Application of the Modified Torres and Casali model as part
of non-linear model predictive control algorithm was pre-
sented. Given the accurate prediction made by the model
for pressing iron ore concentrates in industrial HPGRs, its
use was assumed as a valid virtual description of the plant
operation. This was performed to allow investigations in
the present work.
Given the steady-state nature of the model, NMPC
structure relied on time discrete simulations, while product
BSA and throughput were controlled variables and operat-
ing pressure and roll peripheral velocity were the manipu-
lated variables. Advantage of the present work raises when
adopting changes in operating gap based on changes in
operating pressure, which has not been incorporated until
now for MPCs for HPGRs. To ensure a proper description
of the HPGR dynamics the NMPC was tuned with predic-
tion and control horizons of 15 and 5 s, respectively. A cus-
tomized cost (objective) function was defined to minimize
the differences between the setpoint references and model
predictions for both product BSA and throughput. A pen-
alty was also incorporated for abrupt changes in the operat-
ing conditions, thus allowing a smoother description of the
HPGR dynamics within the control algorithm adopted.
Analysis of the NMPC structure was based on two case
studies to check the controller response from changes in
the feed BSA and control strategies. Variations on the feed
BSA were modeled to follow the evolution between differ-
ent states in the time interval of 50 min, which in lined-up
with the dynamics of ball milling and classification stages
(operations found upstream from the HPGR in the present
study). Case study #1 then demonstrated the ability of the
NMPC in capturing changes in the HPGR feed and main-
taining the product BSA constant and throughput close
to the target values. In case study #2, which was proposed
to increase the target for the quality of the final product
and throughput, the NMPC was unable to achieve accept-
able results given the operational limits of the machine
investigated.
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