Abstract
A general description of digital simulation methods is given, followed by a more detailed comparison between the two most advanced programs available at present: FIFI --- a digital computer code for the solution of sets of first order differential equations and the analysis of process plant dynamics --- and DSL/90 --- a digital simulation program for continuous system modelling. The methods described were applied to the investigation of the dynamic behaviour of a gas reformer and a pilot-scale binary distillation column, whereby: (a) A digital compensator for controlling the outlet temperature of the reformer by regulating its fuel input, was designed. (b) The validity of a mathematical model for the distillation column was studied. Reasonable agreement was found between the responses of the model and those of the plant, and by introducing hydrodynamic delays to the model, an even closer prediction of the plant dynamics was achieved. Also, the model was linearised and the range over which this linearisation is valid was investigated. Finally, two new routines and a modification to the main control routine of FIFI had to be written, so that discontinuities could be introduced at any chosen time.