Chemical & Engineering News,
March 27, 1995

Copyright © 1995 by the American Chemical Society.

Simulators seek a broader community of users

Process simulation isn't just for experts anymore. Although its use has been broadening for some time, recent developments in simulators are making them more amenable to general application in chemical engineering.

The earliest software for process modeling and simulation was developed at chemical companies and universities. By the 1980s, commercial software was becoming the norm. Today, a wide variety of software directed at process engineering is available. Among the more commonly used process modeling and simulation software in the chemical industry are systems from Aspen Technology Inc. (AspenTech), Cambridge, Mass.; Simulation Sciences Inc. (SimSci), Brea, Calif.; Hyprotech, Calgary, Alberta; and Chemstations Inc., Houston.

Major new offerings in the past year from two of the software developers - AspenTech and SimSci - underscore the thrust by software firms to make simulation easier to use and more broadly applicable. Last June, AspenTech announced Release 9 of its Aspen Plus, the core of the firm's suite of products. And in September, SimSci announced PROvision, a 32-bit Microsoft Windows environment supporting SimSci's core simulator PRO/II, which simultaneously was released in a version 4.0.

Process simulation relies on a model consisting of mathematical expressions that describe the behavior of each of the chemical processes and physical operations making up the steps of a process flowsheet. Physical and thermodynamic properties of the components in the flow streams are also important for a simulation and are typically contained in the software programs themselves, in proprietary corporate databases, or in others such as the Dortmund Data Bank of Germany's FIZ Chemie or that compiled by the American Institute of Chemical Engineers' Design Institute for Physical Property Data.

The process flowsheet provides information about the process for the model - for example, configuration of unit operations along with operating conditions and feed stream compositions and flow rates. The simulation then predicts performance of the plant by computing the flow and properties of all intermediate and product streams, the performance of every unit in the process, and the capital and operating costs of the plant. In this way, engineers can, for example, investigate design alternatives by changing the conditions of the simulation.

Steady-state simulators, such as Aspen Plus and PRO/II, have applications in a range of areas. Among them are investigating alternative process flow sheets in R&D, optimizing plant and process schemes in design work, improving yield and throughput of existing plants, and training operators.

Aspen Plus has been the centerpiece of AspenTech's software. Nevertheless, when the company announced Release 9, it extolled that release as the most significant one the company had ever delivered. Release 9, according to the company, fundamentally advanced Aspen Plus's architecture and its range of engineering. It brought new engineering features in all key areas, including equipment design and rating calculations, petroleum modeling, distillation and separations, physical properties, reactors and other unit operation models, and costing and economic evaluation, among others. It also included a new capability, Data-Fit, to help fit simulation models to plant or laboratory data, thus providing a path from raw plant data to a simulator model that matches actual operation.

The new architecture of Release 9 is derived from AspenTech's PC-based Max product launched a year earlier. It makes it possible to run Aspen Plus simulations and analyses completely interactively through the firm's ModelManager graphical user interface, which itself had undergone some new productivity enhancements. As an information aid, Release 9 provides an on-line hypertext help system.

These architecture and productivity advances as well as others, AspenTech President Joseph F. Boston points out, were all aimed at making the software accessible to a much wider population of engineers while still maintaining the reliability and rigor needed for accurate models that the engineer can trust. "Friendly technology needs to go hand in hand with technically dependable technology," he says. "Together, they are a powerful combination."

SimSci is equally enthusiastic about its new PROvision. SimSci President and Chairman of the Board Y. L. Wang terms it one of SimSci's most important developments. It is a multiplatform application designed for client-server environments running under Windows. Among its features, PROvision provides flexible flowsheet drawing and data input, interactive and batch calculation control, and on-line help. A novel approach to problem specification makes use of interactive color-coded data entry and validation to guide users through simulation setup and execution.


Flexible flowsheet drawing and data management are features of PROvision from Simulation Sciences. PROvision is the company's new multiplatform application designed for client-server environments running under Windows.

Users can easily transfer graphics and process data from PROvision to other Windows applications using the Windows Clipboard utility. In addition, PROvision supports Microsoft's OLE 2 (object linking and embedding) standard, enabling other OLE-compliant applications, such as Microsoft's Excel spreadsheet software, to be seamlessly integrated with the PROvision environment.

In January, SimSci announced that the computing environment of PROvision would be opened for other software vendors and integrators to use the flowsheet drawing features as a graphical user interface to additional process engineering applications. A PROvision application programmer's interface (API) will be available later this year.

SimSci expects that opening the PROvision environment will enable engineers to move process data easily from one application to another, will make use of in-house applications easier, and will increase utilization of in-house software libraries. Wang says the move is a response to the desire not just of process simulation users but of software users in general to have that software in an open environment.

Another AspenTech product, the recently introduced Polymers Plus, is a further move by the company toward spreading easy-to-use modeling technology to a broader constituency. Chemical and petroleum manufacturers have long been able to realize the benefits of process modeling, Boston says, but until now it hasn't been a practical approach for polymer processes.

With an eye toward simulation's future, both AspenTech and SimSci are working to make dynamic simulation easier to handle and more broadly applicable. Dynamic simulators have been used primarily for studying such operations as process control or plant start-up and shutdown. The simulators are rather difficult to use, however, and dynamic simulation has remained something of a specialty until now. That seems likely to change.

AspenTech has already announced a new product, DynaPlus, scheduled for completion this year. DynaPlus will be an integration of Aspen Plus and the company's dynamic simulator, Speedup. And SimSci has formed a consortium called PROTISS with the U.K.'s Special Analysis & Simulation Technology Ltd. (SAST) to develop a package that uses PROvision to interface between SimSci's steady-state simulator, PRO/II, and SAST's dynamic simulator, Otiss. An early, alpha version of the new software has been completed.


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