Virtual worlds
From simulation to concrete and steel

Well over 200 users attended an event organized by AspenTech in order to put themselves in the picture about new developments in the field of process and simulation software for plant planning. PROCESS was there.

he AspenTech user meeting worked to a busy agenda and all participants seems to be satisfied with the proceedings. The company used the opportunity to present the latest enhancements to its simulation and cost analysis software for the chemical, pharmaceutical and petrochemical industries. A series of user reports described the day-to-day industrial routine and user experience with the software. One recurrent theme during the lively discussions was the need to provide positive and negative feedback on the simulation software and to learn from each other.

Cost analysis and simulation in the optimization loop

So what is new at AspenTech? Since the introduction of the Engineering Suite in 2000, the company has been working to enhance the level of interaction between the various planning modules. The roll-out of the aspenOne applications in 2005 brought the developers another step closer to this goal. Solutions which are based on a vertical view of the process are designed to enhance plant design and improve virtual processes. Version 2006, which was released at the end of 2006, contains the first updates to the various planning tools and enhances data exchange between the individual components. Cost analysis is integrated into the simulation right from the start. It is put through the same optimization loops as the engineering design and starts at the basic flow diagram level. Aspen Plus models the process. Version 2006 uses data from the National Institute of Standards and Technology (NIST). Aspen Dynamics generates the safety and controllability parameters for the process, and Aspen IPE calculates the costs. Data continually flows between the three modules even at this level. Before basic engineering gets underway, HTFS calculates the heat exchanger parameters using the data which is available to the program at this point. The results are fed into Aspen Plus and also to the basic engineering calculations using Aspen Zyqad. The Aspen Kbase estimation tool refines the cost estimate which is based on the basic flow diagram and generates a detailed cost analysis for the individual pieces of equipment.

"Analysis is not run
just once"

Dan McCarthy, Product Manager at AspenTech, points out that "analysis is not run just once. It is an iterative process which continues until an initial version of the optimal process design and cost structure has been generated." Once this is complete, the program passes data to Intergraph’s SmartPlant Suite for the detailed engineering phase. Data is passed between Aspen Kbase and SmartPlant Suite to refine the cost optimization. When the planning exercise is complete, the planners have a 3-D diagram of the chemical plant which they can view on their monitors.

The process is still useful even after plant construction is complete, because "a process model at the basic flow diagram level helps chemical plant engineers make a lot of decisions relating to ongoing operations and new design", explained McCarthy.

Virtual plants and a wealth of
experience

There is often a big difference between theory and practice, and Aspen 2006 is no exception. It is usually the details which cause problems, and this is not news to users. When Axel Polt, Manager of the Engineering Department at BASF, asked who was already using Aspen 2006, there was no reaction from the audience. His comment was: "That is just what we thought".

In contrast to many other users, BASF is already using Apsen 2006. Polt is convinced that internal organizational issues along with the actual system modeling and the workflow-centric design of Aspen 2006 are the key to success. "Using the new functionality of Aspen 2006, we can run faster and better simulation of complex systems which are typically used in the chemical industry. Improved interaction between the programs, for example linking modeling with heat transfer design, is a real plus."

In addition to having better software, there is another aspect which assists the engineers, namely many years of experience in plant operations plus the BASF knowledge pool. Polt says that the knowledge pool should not be underestimated. "We play leading-edge video games. However, the game is not reality, and the model is not the real production system. With this in mind, we have been making conscious use of the experience we have gained in ongoing operations to design new, more cost-effective production systems."

The engineers at BASF have completed a total paradigm change in their modeling and optimization activities. During the modeling process, all of the system parameters are reduced to a single target function which they try to optimize. "Using Aspen 2006 and a BASF-specific extension, we minimize the costs as must as possible. The entire system model is available on the computer screen as a cost flow (€/a) rather than a material flow," explained Polt. This is a significant advantage in an era when energy and coolant costs continue to be very volatile. Program update cycles are so short that the standard IT processes are far too slow. Some users would like to use different software versions at the same time, but that is normally not possible. Franz-Rudolf Aßmann, Account Manager at BASF IT Services, briefly outlined a solution to the problem. "Together with the engineering team, we have developed a virtual software environment. The different programs only exist in their defined environment. This will allow us to make different versions available more quickly in the future, and users will have access to different versions of the program at the same time."

A dangerous lack
of reality

Simulation however is not an unmixed blessing. There are inherent dangers and risks. Inexperienced engineers repeatedly confuse the virtual world with reality, according to Hans Göebel who works at the engineering contractor Fluor. "I have already seen an inexperienced user accepting an unrealistic model without questioning the result because the computer cannot make mistakes." Even small errors such as selecting the wrong units of measure or failure to properly take process thermodynamics into account can cause serious problems. The computer model should always be scrutinized by an experienced engineer. Göebel described the Fluor approach as follows: "We are not finished when the model is complete. Our own independent experts check to ensure that the results make sense. Customers in the chemical industry in particular should ensure that the model reflects what they are actually trying to achieve."

Résumé: life without modeling software is unthinkable

Nevertheless, all of the users agreed that life without modeling software is unthinkable in today’s world. Simulation speeds up engineering design, provides more accurate estimates of construction and ongoing operating costs and offers various alternatives during the design phase. However, the results still must be treated with caution.