Simulation of large scale dynamic systems—II. A modulator simulator for the dynamics of distillation systems

Abstract

A modular dynamic simulator has been developed to simulate the dynamics of interacting distillation columns. The dynamic simulator consists of a Fortran software package with dynamic modules to simulate distillation columns, reboilers, condensers and control systems. The modules can be modified to simulate special reboilers, condensers and control systems. User input to the simulator consists of the system description, constants, physical property data and an optional initial state. Two example problems have been used to test the simulator: (1) A 5 component, 29 stage distillation column with controllers, and (2) An atmospheric crude unit with 4 side strippers. Each of the side strippers and the main column are simulated independently. Steady-state conditions for the crude unit are computed by following a policy which approximates crude unit start-up procedures. We illustrate the type of results obtainable from the simulator by presenting several dynamic responses of the crude unit to step disturbances. Scope—We describe a modular simulator for distillation systems built around the coordinator concept described and analyzed in Part I. Simulation of 2 substantial problems, a 29 stage distillation column, and crude unit, demonstrate the methodology. Significance—The simulator and worked examples demonstrate the validity of reducing a complex simulation to an interconnection of independent simulations tied together by a coordinator. The advent of parallel processing should enable simulation of the dynamics of extremely large, and heretofore intractable, systems using the modular approach.