Michel Eltink, Protomation,

The Netherlands, looks at the benefits

that operator training simulators can

provide fertilizer plants.

High-fidelity operator training simulators (OTS) increase plant safety and on-stream time. They professionalise and boost the learning and training process of operators, which is

nowadays difficult to achieve by means of on-the-job training. Considering the losses as a result of maloperation, the payback time of the investment in an OTS can be very short.

Sorfert Algeria acquired an OTS for its 1.2 million tpy ammonia and urea plant located in the Arzew industrial complex, situated near three major Algerian ports on the Mediterranean coast in the Wahran province, approximately 350 km from the capital city, Algiers. The ammonia and urea plant

accounts for one of the largest volumes of fertilizer exports in the Mediterranean.

IntroductionPlant owners have the challenge to manage operational risks and increase operational experience and competences to minimise or avoid production losses, which in the processing industry can be substantial.

Managing a plant is always a challenge – conditions must be optimal to achieve a good performance. The two main parameters to measure that performance are safety and profitability. Although there are many factors that affect those parameters, the human one is the most critical factor.

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Operators are not standardised. Each individual is different; they get sick, retire or are newcomers. This might become a problem when the performance of the plant depends on stability. A plant running within optimal conditions and without deviations is the perfect scenario.

Training on the job has many practical limitations, since many realistic training scenarios would otherwise require shutting down a running plant. OTSs behave and look just like the actual plant. This allows dangerous and unfamiliar situations to be simulated realistically, and the operator response can be observed, trained and tested. It is the next best thing to the actual plant.

The payback time of an investment in an OTS can in fact be very short, considering that, for example, losses in a high capacity urea plant, due to an emergency shutdown with a downtime of one day, can easily go beyond €700 000.

In case of equipment damages as a result of maloperations in the plant, downtimes are often significantly longer, especially for critical equipment with long delivery time or in case of catalyst replacement.

OTSs for urea and ammoniaIn order to professionalise and boost the learning and training process of operators, which is nowadays difficult to achieve by means of on-the-job training, the Sorfert management decided to provide the operators and the

technical staff with a state-of-the-art high-fidelity OTS for the company’s ammonia and urea plant for training plant operations over the complete operating window of these plants.

The company decided to acquire the OTS from Protomation, which develops high-fidelity OTS solutions for fertilizer complexes, covering ammonia, urea, granulation, UAN, DEF and nitric acid. Protomation has the specific know how and the exclusive rights for the full range of

Stamicarbon urea and granulation technologies, and works for the Sorfert ammonia plant with ThyssenKrupp Industrial Solutions for the ammonia technologies.

The OTS allows for training of the operators performing a multitude of actions, such as performing startups, increasing production up to normal operation, shutdowns and emergency shutdowns, as well as triggering of emergency situations in the process (also by means of training scenarios) and load changes. Furthermore, the operators can be put in a whole range of plant situations, including plant upsets, malfunctions, failures, stops and start of equipment, and will be trained to act appropriately and correctly in these situations.

With the OTS, new, apprentice and experienced operators can be trained with better and aligned responsiveness in plant operation, while reducing the risk of operational errors and equipment damage and consequently improving reliable plant operation and plant safety.

The project comprises of an OTS for the ammonia plant and an OTS for the urea plant. An additional OTS for the urea granulation plant is under consideration.

OTS componentsEach OTS comprises of one instructor/field operator station and three trainee stations, as shown in Figure 1.

The OTS setup allows for training of larger groups of operators, as each trainee station can run a separate instance of the full plant model. Also, two or more trainee stations can jointly run one plant model for collaborative training, similar to controlling the plant using multiple distributed control system (DCS) operator stations.

The plant instructor controls the training by means of the instructor station, with which he can insert training scripts, assist in operating the field controls, as well as join into the training sessions to insert additional plant disturbances, instrumentation malfunctions and so on.

OTS architectureThe OTS architecture comprises of the control system, which is in this case is an emulation of the Centum VP

Figure 1. Operator training simulator (OTS) components.

Figure 2. OTS architecture.

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controllers, graphics and faceplates; the emergency shutdown system (ESD), which is emulated as well in the Process Studio OTS software; the simulated field controls, such as sensors (e.g. transmitters) and actuators (e.g. valves); the high-fidelity first-principles urea plant model and ammonia plant model.

As in the actual plant, the trainees control the simulated plant by means of the control system implemented in the OTS. The instructor can access all OTS functionality from the Instructor station, such as the field controls, in order to insert malfunctions (such as a valve suddenly fully opening or closing, a measurement having sudden zero indication or noise, stopping of a pump, or a compressor having sudden vibrations) and disturbances (catalyst deactivation, runaway reaction, heat exchanger fouling or tube leakage, filter blockage, tube rupture, or sudden change in feed gas composition) during the training session.

The field operator functionality can be run from the instructor station, as well as from a separate field operator station. This enables training of the communication between the control system operator (DCS operator) and the field operator.

The field operator functionality can be accessed by means of field operator graphics that are derived from the control system graphics and showing only those devices that can be controlled in the plant.

OTS of the urea plantThe OTS of Sorfert’s urea plant comprises all main equipment, instrumentation, controls, logics and advanced control as found in the actual plant.

The urea plant model represents Sorfert’s complete urea plant, which is Stamicarbon’s Urea2000plusTM pool condenser design, but without the granulation section, which may be added later on.

The main process equipment included in the urea model comprises of:

� Steam turbine driven four-stage compressor, hydrogen reactor and high pressure ammonia pump.

� High pressure stripper, high pressure ejector, pool condenser, reactor, high pressure scrubber and 4 bar absorber.

� Rectifying column and atmospheric flash vessel. � Low pressure carbamate condenser and high pressure

carbamate pump. � Evaporator, evaporation condenser and steam ejector. � Ammonia water tank, first and second desorber,

reflux condenser and hydrolyser. � Steam and condensate system and cooling water

system.

Figure 3. Process flow diagram urea plant (typical).

Figure 4. DCS graphic urea plant (typical).

Sorfert’s urea plant is controlled by a Centum VP control system. The OTS emulates the Centum VP controls, graphics and faceplates, with which the trainee operates the simulated plant.

Proprietary thermodynamic and reaction kineticsThe OTS makes use of the proprietary Stamicarbon thermodynamic and reaction kinetics models, which have been developed by Stamicarbon over many years. As a result of this, the OTS provides a very realistic experience.

OTS of the ammonia plantLike the OTS for the urea plant, the OTS of Sorfert’s ammonia plant comprises all main equipment, instrumentation, controls, logics and advanced control as found in the actual plant.

The ammonia plant model represents the company’s complete ammonia plant, which is ThyssenKrupp Industrial Solutions – Uhde design.

The main process sections included in the ammonia model consist of the following:

� Natural gas compression. � Process air compression. � Steam reforming.

� High temperature and low temperature CO conversion.

� CO2 removal. � Synthesis gas compression and steam system turbine. � Analysers. � Lube oil and seal gas system. � Ammonia synthesis. � Refrigeration. � Ammonia recovery. � Hydrogen recovery. � Cooling water system.

Thermodynamic and reaction kineticsThe OTS makes use of thermodynamic and reaction kinetics models which have been developed by Protomation in close cooperation with ThyssenKrupp Industrial Solutions. As a result of this, the OTS provides a very realistic experience.

ConclusionThe OTS project was started in November 2016 with a Sorfert team comprising of Sorfert employees of various disciplines from the ammonia and urea plants chosen by Sorfert top management according to specific criteria. Acceptance testing is currently in progress. The company will start training of a large group of newly hired operators directly after acceptance testing.