New developments in chemical process simulation-FLOWSIM

Abstract

FLOWSIM is the first of a new generation of chemical process flowsheet simulators which are based on the solution of a mathematical model of simultaneously solved equations. A chemical process is described using a modular input format. Analysus and verification of the input data are performed and a set of equations is automatically generated which represents the process. A sparse matrix representation of the equations are generated and the equations are ordered to produce a nonzero diagonal. Automatic initialization of the process variables is performed and the process model is evaluated and solved. The equation-oriented approach overcomes most of the disadvantages found in modular chemical process flowsheet simulators. Data imput and output remain in a form familiar to the current modular concept used in chemical engineering. A graphics pre- and postprocessor is planned to enhance the I-O capability. The solution package uses less computer memory and computer time than a modular simulator with comparable ability. FLOWSIM contains 20 basic units with a large list of options to specify. Additional user defined units are allowed, plus the ability to design groups of the basic units into macros. These macros may represent more complex units, or sections of a chemical plant and can be treated exactly like the basic units used to construct them. A verification task determines whether the process being modelled is correctly specified and informs the user of under or over-specifications that are detected. The solution task is accompanied by a plug-in thermodynamic data package. FLOWSIM is constructed so that it can accept physical properties data from another source by reprogramming only an interface routine built for that purpose. The current version of FLOWSIM can handle a chemical process able to be modelled by 1600 equations or less. The number of units in the process is limited only by the number of equations needed to model it. The current version of FLOWSIM has most of the capabilities and features available in the best modular flowsheet simulators, plus some not available anywhere else. Improvements are under development now to handle tasks that are impractical in a modular flowsheet simulator.