cvrd - expertune · belo horizonte vitória porto tubarão ... the level of the silo vary...

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Use of Performance Supervision Software at an Iron Ore Processing

PlantBernardo Soares Torres, M.Sc. (ATAN)

Lívia Camargos Rodrigues de Oliveira (ATAN)Leonardo Antônio da Silva (CVRD)

Roberto Dias Aquino (CVRD)Felipe Novaes Caldas (CVRD)

Vicentino Rodrigues, M.Sc. (CVRD)

CVRD

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CVRD – A broad presence around the globe

New Business

Geology

Commercial representatives

Manganese

California Steel Industries

GIIC

CVRD Location in Brazil

South System

Carajás

São Luis

Belo HorizonteVitória

Porto Tubarão

Porto Itaguai

Itabira

North System

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Conceição Mine

Location:Itabira – MG Brazil

CVRD Iron Ore Production

CVRD iron ore production grew 15% per year from 2001 to 2005. With the new investments, it is expected to reach 300 Mtpy* in 2007.

300.0

264.4

233.8

211.3

188.3

167.8

133.8 2001

2002

2003

2004

2005

2006E

2007E

* Under US GAAP

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Market shareAmérica

do Sul2,2% África

1,3%

Oriente Médio3,3%

América Norte3,6%

Brasil17,8%

Europa30,8%

Asia41,7%

Human Resources are Limited!

How to assess hundreds of control loops simultaneously?

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Empowerment

Corporate KPIsWhat is necessary to have meaningful global grades?

• Appropriate choice of KPIs, which can be distinct for different types of loops and control objectives

• Proper configuration of status bit for each loop and unit• Normalized configuration of Baselines & Thresholds between similar

groups of loops at similiar plants• Periodic review of B&Ts• Limit %T grades to a max value (CVRD Vision)

By following these steps carefully, the global grade for each loop, unit operation and plant will be representative of the process performance.

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Treemap at CVRD Control Room

Dashboards - Operational View

After the operator choose the loop in the treemap, they

can do a detailed

analysis of it.

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Treemap – Plant Comparison –Management approach

Comparison among the plants’ grades

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Operational Intelligence Center

The Importance of Comunication:Change Management

GROWTH CYCLE

RESISTANCE CYCLE

The unknown leads to

Threats and fears Defensive behavior

Increases the resistance

CHANGE

Involves and informs

Brings opportunities personal benefits

Creativity andeveryone’s participation

Increases the opening for

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Control Loop Optimization Examples: Actions taken• Standardization and correction of the PIDs’ implementation

in the PLCs;• Addition of filters in the loops that exhibit excessive noise;• Identification of the loops having saturation of the actuator

and measurement problems, which limit the controller action;• Discussion and review of the control strategies being used;• Experimental implementation of the proposed control

strategy for pulp sumps;• Analysis of the tuning of all loops audited;• Quantification of stiction and/or histeresis in the actuators of

loops presenting oscillation due to valve non-linearities.

1 - Implementation of regulatory control in the crushing feed

Source: Automation team – Conceição Mine

...

...

Primary crusher pile

Mass

Level

A B

Upper and lower limits for the level of the silo vary

frequently

Great Mass Variations

The limits of the sieves’ current are

often achieved

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Implementation of regulatory control in the crushing feed

Flow and level loops were switched to automatic mode

Possibility of throughput increase


BEFORE (uncontrolled) AFTER (controlled)

TC-3013 Feed

TC-3013 Feed

Improved control of the crushing feed

Feed interruptions

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BEFORE (uncontrolled) AFTER (controlled)

Increase in the average mass fed

TC-3013 TC-3013


Improvements:

• Increase in the crushing throughput;

• Reduction of the cost per ton produced;

• Increase in the flexibility of the operation, maintenance

and mine;

• Maximization of the asset’s use.

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2 - Flocculant injection flow loops

The flocculant fastens the particles’ decanting in the thickener

Avg Abs Error

Tuning

Flocculant injection flow loops

After the tuning, the response to setpoint changes was improved, as well as the response to load upsets.

However, the new tuning increased the valve travel due to the increased controller action.

A filter was then implemented in the loop to reduce the valve wearing and thus increase its lifetime.

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Flocculant injection flow loops

Improved response to setpoint changes

BEFORE AFTER

3 - Foam level of a flotation column loop

This loop had a satisfactory performance (low global grade), but the valve travel was high.

Valve travel

Global grade

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Foam level of a flotation column loopThe cause of the high valve travel can be histeresis or

stiction in the valve. PlantTriage identified oscillation due to valve in this loop.

The valve had 4% of stiction.Oscillating

Osc - valve

4 - Reagent’s flow in a flotation column

The loop was in manual and the setpoint was not well adjustedThe problem was identified in the Treemap

Problem

Actions taken

Improvements

There was a 25% reduction in the reagent consumption.

The loop was tuned and then switched to automatic mode;The logic implemented in the PLC to define the setpoint was altered;

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Reagent’s flow in a flotation column

BEFORE AFTER

5 - Material feed

Desired value

BEFORE AFTER

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Material feed

The maximum material flow in the conveyor belt was exceeding the setpoint

Problem

Actions takenThe fuzzy control was adjusted

Improvements

The operational safety was increased

Measurement of the improvements

Avg Abs Error

Average

The gains were measured according to the reduction in the average value of the error.

Loop LIC6346:The error decreased 28% due to the PID tuning.

Similarly, other loops had performance improvement.

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6 - New control strategy for pulp sumps

New control strategy for pulp sumps

Description of the Process:

Control loops:• Level – actuates in a pump regulating the pulp outflow to

flotation columns in order to keep the level constant • Density – actuates in a valve that adds water into the

sump to reduce the density

Disturbance: pulp feed to the sump (it depends on the upstream stages of the process)

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Previous control strategy’s P&I diagram

Process behavior with previous strategy

Disturbance in the foam level of the flotation column downstream

Level of the pulp sump

Foam level of the flotation column

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Pulp Sump Simulator

Pulp Sump Simulator

PID controllers

ProcessActuators

OPC connectivity

Configuration window

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Pulp Sump Simulator

Conceição’s plant has several pulp sumps;

The simulator is configurable (sump size, dead time and time constants, pump’s and valve’s curve, transmitters’ranges, inlet pulp flow and density, noise, tuning, etc);

The simulator was validated with real data;

It can be used to test control strategies for pulp sumps, as well as to dimension new pulp sumps (sump size, valve’s and pump’s capacity).


Description of the new control strategy:

Introduction of a slave flow loop (level and flow in cascade configuration);

Remote setpoint for the level loop (the level is allowed to vary in a certain range). To achieve this goal, the level setpoint follows the PV closely inside this range so that the control error is small;

The level loop is allowed to open the water valve (which is the actuator of the density loop) in extreme situations to avoid the ON-OFF valve to be opened.

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Remote setpoint for the level loop:

New control strategy’s P&I diagram

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Advantages of the new strategy:

The output pulp flow is more stable, thus reducing the disturbance in the flotation columns;

Non-linearities in the level loop are compensated:- Non-linearities in the actuator (pump) curve- Dependence of the outflow on the level (and not only on

the pump speed)

The ON-OFF valve does not open very often.

Results of the change in the control strategy


Foam level of flotation columns

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Results of the change in the control strategy

Previous strategy New strategy


Results of the change in the control strategyReport from PlantTriage’s web interface:

New strategy

Previous strategy

Global grade of the level of a pulp sump

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Results of the change in the control strategyAverage reduction of 26% in the variability of the flotation

columns’ froth depth

BEFORE

AFTER

Most important outcomes

• General review of the operating conditions of the plant’s control loops;

• Online availability of trends and diagnosis for a total of 500 control loops;

• Technical qualification of CVRD’s control team and creation of performance indicators as well as a methodology to monitor the loops;

• PID controllers’ tuning and the consequent reduction of the average control error of the loops at each unit operation;

• Decrease in the operations’ response time to disturbances in the process

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Bernardo Soares TorresBernardo Soares [email protected]@atan.com.br

www.atan.com.brwww.atan.com.br

Fortaleza Fortaleza –– CE CE -- BrazilBrazil

cvrd - expertune · belo horizonte vitória porto tubarão ... the level of the silo vary...

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