A system for simulating chemical process dynamics and control

A system, known as PRODYC, for aiding in the analysis and design of chemical process control systems has been developed. The system is capable of simulating the dynamics of an entire plant including the control function. A modular approach was used to develop subroutines for handling various chemical processes. Each subroutine derives sets of algebraic and differential equations, referred to as the default model, which describe the dynamics of a particular process. An overall executive routine supplies information necessary to tie all of the models together. The result is a set of CSMP statements which simulate the dynamics of the entire plant. The present system has subroutines for handling mixers, dividers, continuous stirred tank reactors, valves (with controller), transmission delay, and simple distillation. The control function is a general feedback control loop. The control valve and the sensor can be located in streams independently. There are two control algorithms, one for a standard three mode analog controller, and one using sampled data and clamp functions to simulate a digital controller. The problem of property evaluation for dynamic simulations is discussed. A simple weighting by mol fractions is used by the system for evaluating stream properties. If more accuracy is required, methods for accomplishing this are discussed. The structure of the PRODYC system, the input requirements and the expected results are clearly defined. Techniques for expanding the system are explained.Chemical and Biomolecular Engineering, Department o