ECSPXPCaseStudy4

7/30/2019 ECSPXPCaseStudy4

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CASE STUDY 4: Committed to Optimization in CIMPOR Portugal

Cimentos de Portugal, SGPS, S.A., or CIMPOR as it is known, is the largest cementcompany in Portugal. CIMPOR operates in eleven countries worldwide, includingPortugal, Spain, Mozambique, Morocco, Brazil, Tunisia, Egypt, Cape Verde, SouthAfrica, Turkey and China. CIMPOR manufactures and markets cement, hydrauliclime, concrete and aggregates, precast concrete and dry mortars. CIMPORs totalclinker production capacity is close to 28 million tonnes per year.

CIMPOR has four plants in Portugal. The Cabo Mondego plant produces hydrauliclime, while the remaining three are cement plants, with a combined capacity ofseven million tonnes per year. The four facilities are well distributed across thecountry, with Alhandra just outside Lisbon, Cabo Mondego and Souselas in the North

near Coimbra and Loul in the Algarve.

CIMPOR has been using advanced control solutions from FLSmidth Automation(FLSA) for more than a decade. Alhandra and Souselas initially used FLSAs previous-generation control system, which consisted of ECS/FuzzyExpert based on a DigitalVMS platform, in various sections of the plants. When FLSA launched the newgeneration of the system, ECS/ProcessExpert (PXP), the Loul plant and Line 3 at theSouselas plant began using the new technology.

Cimpor plants in Portugal

This article focuses on the implementation of PXP at Souselas Line 3 sector, andreviews the project from start to finish, outlining the processes, solutions and projectexecution.

The need for automation and controlLine 3 at the Souselas plant consists of one upgraded SLC-D kiln with a cross-barcooler, one vertical roller mill for raw material grinding, and two closed-circuit ballmills for cement grinding. The kiln uses a mix of 50 percent coal and 50 percent pet-coke as fuel in both the calciner and the main burner.


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The pyro department faced significant process-related problems. These included:

high temperatures producing excessively fine clinker

the formation of large build-ups in the precalciner and tertiary air duct kiln instability due to several factors, including tertiary air duct blockage, a

lack ofoxygen in the kiln inlet (due to sulphur build-up in the smoke chamberand riser duct), snowman formation, and hot clinker leaving the cooler.

The production management considered it crucial to significantly enhance kilnstability and boost the quality of the clinker-free lime. The average production rateand plant availability needed to be increased.

From the control point of view, the ID-fan was identified as a significant bottleneck inthe pyro section. It was crucial for the advanced control system to maximiseproduction in spite of this constraint.

Kiln and tertiary air duct at line 3, Souselas, Portugal.

The grinding department also required improvements. The plant managementwanted an expert control system that could control the fineness and the quality ofthe cement. This was ground-breaking as it was the first time the grinding divisionhad achieved such a high level of automatic control.

In general, the Souselas plant needed modernisation. The management wanted toincrease automation, reduce the operators workload in the control room, andhomogenise production by unifying the plants operations. It was clear that investingin PXP technology was the best way to achieve these goals.

PXPs unique flexibility was highlighted by the fact that the plants control systemwas based on the Siemens WinCC system with Control Logix PLC. Even though theunderlying technology was different, it was possible to achieve a direct dataexchange between PXP and the process using PXPs built-in I/O drivers.


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How the ECS/ProcessExpert (PXP) system works

PXP is the latest generation of FLSAs advanced control platform for high-level

process control and optimisation solutions. The platform offers a number oftechnologies that support the most appropriate control solution for a given process.Based on its predecessor, PXP is more flexible thanks to its ability to combinedifferent technologies and easier to maintain.

Known as an autopilot in cement plants, PXP not only controls and optimises theprocess under normal conditions, but can also handle irregular circumstances thatrequire different control strategies in order to avoid process drift and instability. Tohelp identify specific problem situations and plan effective solutions, FLSA worksclosely with plant operators and production engineers to discuss needs, requirementsand conditions.

Each PXP application includes a number of key performance indicators for each

process, allowing operators to easily monitor process performance at any given time.Monthly performance assessment reports enable production management and FLSAsafter-sales service and support staff to evaluate the overall process and controllerconditions. This helps to ensure that operations run smoothly.

Irregularities in the kiln

In addition to developing and customising the normal control strategy for theSouselas Line 3 kiln, FLSA also implemented a number of strategies for handlingirregular conditions. One such strategy is the calciner control scheme, which includeshigh-priority actions in calciner fuel control in case of temperature increase in thelower cyclones.

This means that the normal calciner controller level is overruled by the high-prioritycontroller if the cyclone 4 temperature increases for any reason. Another high-priority controller strategy for this kiln deals with handling of high CO levels in thepreheater. A high-priority controller can take appropriate action based onobservation of the CO dynamics in order to maintain balanced feed, air and fuellevels. In this way it is able to override the production and quality optimisationcontroller if deemed necessary.

PXPs high-priority controllers ensure that actuator use is managed according togiven process conditions, even in conflicting directions. The result is a higher degreeof controller availability. especially in abnormal conditions when operators tend toswitch the controller off in order to rectify the process.

The kiln application also has a soft sensor, which is designed to produce kiln inletgas analysis results for the controller in case of a temporary lack of online resultsdue to hardware maintenance.


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Operator user-interface of PXP-kiln controller

Implementing PXP in the mills

Installing the PXP application for the vertical roller mill was a straightforwardprocess. The installed application is FLSAs standard Model-based Predictive Controlsystem, which controls total feed and separator speed based on measurements frommill differential pressure, vibrations, product fineness, mill power and reject elevatorload. The purpose of the controller is to maximise the production while maintainingthe product fineness.

PXP also controls the feed ratio by basic, single input and output, and ensures qualitycontrol. The total feed directly determines the clinker feed, and the gypsum andlimestone feed are both controlled as a feed ratio of the clinker. So the gypsum andlimestone amounts are based on main clinker feeder. These amounts only changewhen a new laboratory value is introduced. There is an additional control thatregulates the gypsum and limestone feeders, maintaining the required level of SO3and LOI based on the minimum amount of clinker in the overall mix.

The combined results of these process controllers benefit the entire plant and itsoutput. In particular, the PXP system has improved mill stability at Souselas andincreased the operators confidence in monitoring mill performance and control.


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Operator user-interface of PXP-VRM controller

A smooth implementation process

The PXP project was made up of three phases:1) A pre-commissioning visit to discuss process issues and control strategy and

plan implementation practicalities2) Introducing operators to PXP and providing user training3) Implementing the kiln, cooler, raw mill and cement mills applications

The three-phase implementation process took 20 weeks in 2007. Applications wereinstalled in four different sections of the plant.

Post-commissioning services is a fundamental aspect of FLSAs capabilities. Thisguarantees that the PXP system functions perfectly, regardless of where it has beenimplemented. Souselas management has initiated a service agreement to ensure aclose partnership between CIMPOR and FLSA in the future. The agreement coversvarious types of service including both remote and on-site tuning, and a

comprehensive maintenance programme.

An immediate improvement in kiln performance

Enhanced kiln control at Souselas produced direct improvements in the multi-levelcalciner control scheme results. Overall kiln stability is highly dependent on stablecalciner operation, and the operators were positively surprised by PXPs influence onthe calciners performance and the impact on general kiln stability.

The production managers were also impressed by the PXP effect. They praised theimprovement in kiln stability and reliability and the significant reduction in clinkerquality variation. As the table below illustrates, prior to the PXP installation there wasa standard deviation of free lime of up to 1.42. However, in the months following the


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installation, the standard deviation of free lime was reduced to between 0.3 and0.75, with an overall standard deviation reduction from 0.88 to 0.55 for the whole

April to July period.

The average free lime standard deviation between April and July 2007 was 2.08.From August to mid-November, it was only 1.68. The free lime target for PXP is 1.6.

Free lime std.

dev.

Production

April-July (before PXP) 0,88 259 t/hourAugust-November (afterPXP)

0,55 268 t/hour

Improvements 37,5% 3,5%

Preliminary average results of the PXP kiln 3 controller.

The management aimed for a minimum hourly feed rate of 260 tonnes in the pyrodepartment. The average kiln feed during April to July was 259 tonnes per hour,while the kiln feed from August to the middle of November was 268 tonnes per hour.This shows that PXP not only caused the standard deviation to decrease, but alsosignificantly boosted the kiln feed.

The run factor figures showing system utilisation in daily operation are verysatisfactory. Even in the last stages of pyro department commissioning, the systemrun factor in September 2007 was as high as 78 percent. The operator set PXP tooff-line mode for 18 percent of operation time in this month. The remaining onepercent indicates situations when PXP automatically switched off because it wasunprepared. After some minor tuning, the run factor was significantly improved in

October 2007. By experience, increased operator confidence will result in evenhigher run factor in the near future.

The road to success

The PXP implementation work at Souselas was considered as a successful processboth from plants and FLSAs view points. The success was due to a variety ofdifferent factors.


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Communication is always crucial in this type of project. Close discussion betweenFLSA engineers and Souselas staff about the process control strategies, control

variables and actuators was a priority. FLSAs on-site PXP training was essential forhelping operators understand system behaviour and giving them the confidence theyneeded to use the autopilot system effectively. The combination of training andconsultations provided plant supervisors with a thorough understanding of PXPsflexibility, tuning and maintenance options thus removing any ambiguity andensuring that they could get the best out of the new system.

The success of the Souselas implementation was based on the following factors:

- In the first training session, one person per shift was responsible forfacilitating the commissioning period for the whole production team. Theproduction team and those responsible for implementation kept in closecommunication.

- High levels of equipment availability and schedule flexibility.

- Both companies worked as a team, forming a strong relationship based ontrust and shared knowledge.

- Remote access connection to FLSA after the commissioning period.

From the commissioners point of view, a successful project requires:

- Good interaction between the production management, the operators and theFLSA implementation team. Commissioners need to feel that they are part ofthe team and have the freedom to work the necessary hours. For example,commissioners may need to work cement mills at off-peak times, whenelectricity is cheaper, allowing more time for tuning.

- Operators explaining the strategy behind the application, so that the reasonsfor using it are clearly understood.

- Commissioners working closely with operators so they benefit from eachothers specialised knowledge.

It is clear that at Souselas, the CIMPOR/FLSmidth partnership is based on trust andprofound compatibility!

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