Oil ITJ Interview—Wesley Persad, BP

BP Chemicals’ Saltend, UK, plant produces bulk chemicals such as acetic acid and acetic anhydride. The Saltend training simulator is a flagship installation for both owner-operator BP and supplier AspenTech. In this interview with BP’s Wesley Persad we explore how simulator use is extending from training to process optimization—a move closely watched by the offshore production industry.

OITJ—What’s special about Saltend?

Persad—This is BP’s flagship simulator. This week alone we have had three lots of visitors to the facility. We’ve also had visits from the offshore production sector. A new simulator costs many hundreds of thousands of dollars, mostly in man hours for a good team of simulation engineers. To build a ‘high fidelity’ model you need as much information as to build the plant.

OITJ—What is your role?

Persad—I maintain the simulator, keeping it in step with changes to the real plant. We have to avoid the situation where the plant ‘drifts away’ from what is configured in the simulator. I also manage project teams from AspenTech and Honeywell, who do the actual model building. BP’s role is to operate the site, we don’t have the resources to build a big model ourselves.

OITJ—What is in the simulator?

Persad—The simulator models the plant down to component parts such as valves and pumps, built from standard software building bricks. These are customized with the actual equipment specifications used in the plant. AspenTech’s HySys is our main simulator environment but we also use AspenTech’s Otiss, Fantoft’s D-Spice and ABB Simcon’s Gepurs.

OITJ—How do you compare simulator and plant? What’s the ‘reality check’?

Persad—It’s all in the testing. We put together a test team made up of people from the various engineering disciplines, who know all aspects of a real plant. All flows, temperatures and pressures have to match the real plant for acceptance testing, with a good match of both steady state and dynamic behavior. Operators are important here—they can spot differences between the simulator and a real plant. They get sucked into testing the simulator. It becomes ‘real’ and they’re sweating at the end of a session! We put them though start up, shut down, and test, test and test again! This can take many weeks to do properly. Ultimately, the confidence in the final model is given by the operators.

OITJ—Is simulation used in plant design and process optimization?

Persad—There is a lot of scope for the using the simulator as a design tool. In 1989, on our first ever simulator, the simulator design found several instances where the plant design was wrong. The tanks were too small, the liquid density too high. We went back to the engineering prime contractor with suggested changes that enabled the actual plant start-up to be free of these problems. But in process control, the simulator is still not used as much as it should be. I reckon we could save weeks of production downtime. Packages like AspenPlus are used in the steady state design process. But with dynamic simulation, there is a greater potential to improve process. In fact, the technology has evolved to make this possible since many plants were designed.

OITJ—How is the simulator is used to optimize operations?

Persad—Typically to practice plant startup and shutdown. These plants can run steady for very long periods (2 to 3 years), so starting and stopping them is a big deal and needs to be planned and practiced. One of the most significant cost savings is the avoidance of plant ‘trips,’ when the plant is forced to shutdown by the Emergency Shutdown System. This happens before a potentially unsafe condition arises. Such a forced shutdown may result in a 12 hour loss of production, with a much greater monetary value than the cost of the simulator!

OITJ—How exactly do you avoid such conditions arising?

Persad—The experienced operator sees things coming where an inexperienced operator doesn’t. By training operators with the scenarios mentioned above we help them anticipate unsafe conditions.

OITJ—Do you have a ‘graying’ industry like the upstream?

Persad—Do we ever! In fact simulators are used to maintain skill levels , especially as we restructure the site and potentially lose valuable skills and knowledge. The simulator becomes a way of capturing the knowledge. We anticipate problems as the baby boomers retire. We need to get hidden knowledge out of operator’s heads and into the simulator.

OITJ—When is a simulator operator training and when is it simulation and design? Aren’t these facets of the same problem?

Persad—Yes, this is what the vendors now call the ‘lifecycle model.’ It is getting more and more important.

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