Control Systems for
Iron Ore Pellet Plants
At Metso Minerals Cisa, we know that pellet quality and optimization of
production costs are major concerns for iron ore pellet producers nowadays. To
address these concerns, we implement advanced control systems.
It's an area we know well and where we are quite active, with references at CVRD
(we have a contract covering the seven pellet plants at Vitoria, ES), and Samarco
in Brazil, Corus in Holland and LKAB in Sweden.
Our offering in this realm consists of:
- Advanced control systems for pellet induration plants,
- VisioPellet systems to measure the size distribution and other parameters of "green" pellets.
Our advanced (optimizing) control systems
are characterized by a few unique features:
1) Metso Minerals Cisa the only team in the world who have developed and successfully
installed a phenomenological online dynamic model of induration machines (grate
kilns as well as straight grates). Our on-line dynamic model is a phenomenological
population balance model. It relies on the physics of the process and accounts
for mass and heat transfers associated with:
- combustion of carbon,
- oxidation of magnetite,
- evaporation/condensation,
- calcination of limestone and dolomite.
The model provides on-line information which never before had been accessible
in real time, including, but not restricted to:
- temperature profile inside each zone of the grate, including the cooling zones,
- moisture and iron oxidation profiles inside the grate, including the cooling
zones,
- parameters related to pellet quality, especially Cold Compression Strength.
The coupling of the model with an Extended Kalman filter (adaptive tuning algorithm
for non linear models) ensures that the variables inferred by the model remain
known accurately over time. Selected gas temperature measurements are used as
observations of the process for correcting model predictions on-line.
If/When a company has developed some proprietary know-how in modeling its pelletizing
process, we can embed this know-how in the equations of our model, and preserve
the confidentiality of this specific know-how.
2) Our advanced optimizing control systems are hosted by our OCS© software, which makes it possible to seamlessly add the strengths of an expert system with combined fuzzy and crisp logic (where we capture the human expertise which is necessary to operate the plant and is not reflected in the model equations), with the on-line dynamic model, the vision module (VisioPellet) and potentially other algorithms such as our neural network. There are more than 50 OCS© -based advanced control systems in operation in the mineral processing industry worldwide.
Considerable benefits were measured both at CVRD and at Samarco, where
full systems are in operation.
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VisioPellet is a new product. Like our already successful VisioFroth (more than 300 cameras installed in a year and a half) it is based on the USB technology and the vision algorithm is embedded in OCS© Vision Module.
VisioPellet is a new generation image analysis system dedicated to on-line continuous measurement of properties of green pellets of iron ore oxide concentrate, with several industrial USB cameras connected to one PC computer. Typically one camera on each balling disc or drum. VisioPellet USB cameras and lightings typically mount directly above the conveyor at the outlet of a balling disc (alternatively, locations above a critical part of the disc may be explored but are not standard), and the camera signal is remotely connected to the processing computer, normally located in the plant control room.
VisioPellet continuously estimates the proportion of green pellets produced in several size classes, for each disc, with up to 30 images analyzed per second. VisioPellet also allows visualization of the green pellets produced by each disc from the control room and automatic archiving of time stamped digital images of the green pellets. Numerous properties of the images (related to color, velocity and aspect) are also calculated. All information is displayed on the VisioPellet computer screen, and is processed by OCS©, with an appropriate combination of statistical tools, and OCS© expert system rules with fuzzy logic, to derive conclusions about the operation of the circuit. All data and conclusions are displayed on the VisioPellet computer, but they can also be used by an advanced control strategy, with the same computer and/or transmitted to the DCS.
A unique strength
of VisioPellet comes from the fact that the VisioPellet algorithm is embedded
in OCS© and therefore the information generated
by VisioPellet is immediately connected to the OCS© advanced capabilities,
expert system, fuzzy logic, neural network, easy configuration, statistics
and graphical interface.
