Computer Analysis of Process Plant Steam Systems
Publication Date: 2012-Sep-14
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C0~UTER ~NALYSIS OF PROCESS PLP@IT STEA~M SYSTEMS
Ronald J. LaSpisa Applied Automation, Inc. Bartlesville, OK Susan F. Phillips* Applied Automation, Inc. Bartlesville, OK
Henry B. McAna!ly Pullman Kellogg Houston, TX
Computer simulation of complex dynamic systems has been an essen=ial part of the overall design process of many recent installations. In this paper we examine the kinds of results obtainable, and the methods found use- ful, during simulation of boiler and header response in the utility portion of a large plant.
* Presently on leave of absence to pursue graduate s=udies at Massachusetts Institute of Technology, Cambridge, ~.
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The "economy of scale" principle has forced process plants to con- stantly evolve into larger, more complex installa=ions. Inevitably, the steam plant facilities have also grown, supplying an ever increasing number of process units, which oftentimes must operate independently of each other. Many new design =echniques have resul=ed from these demands for higher capacity and greater integration of units. Just as complex process control and instrumentation problems have required computers for solutions, the complexities of steam system design have also required
the assistance of computers. This paper shall discuss the development of a computer program for dynamic steam plant simulation, and its use as a design tool.
Simulation and the Design Process
Steam system design starts with steady-state mass balances which are developed for almy~f~of header pressures, temperatures and configurations.
After thermodynamic analysis, nominal header pressures are set and steam users assigned to specific headers. The conceptual design evolves as boilers, turbines, and exchangers are specified, piping and relief valves are sized, and the plot plan starts to firm up. Now come the questions:
Will i~ wor~? Will ~his complex system perfo~ as desired when buil~? Sure, the design represents =he best of engineering practice, but will a trip in Process Unit 6 bring all the rest down? A tough question to be sure, and unfortunately there is only one method of ob.taining a conclusive
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yes or no answer. "However~ by developing a mathematical computer model
of the system, we may simulate this complex dynamic behavior (and many
other possible situations), and thus gain a better insight into the adequacy of the design. The advantage of such a design verification process prior to construction should be obvious. A large amount of time and money is at stake for the Engineer/Constructor. ~ •~-~ ~
About two years ago Pullman Kellogg and Applied Automation began collaborating on just such a computer model of a complex steam system with multiple boilers and process units, requiring about nine months
to complete. The program was designed to accommodate a wide variety of steam system configurations using modular modeling techniques. Some of the major equipmen...