Hybrid and digital computation results in multicomponent distillation simulation

Abstract

Many paper have been published during the last five years on the relative advantage of hybrid computation over digital computation, particularly for simulation of counter-current industrial processes. However, few authors have attempted a quantitative analysis of the times of either technique, nor even a comparison. This paper discusses computation results for a large set of first-order differential equations representing the mass balance of a commercial crude oil distillation unit. The equations are solved on the hybrid computer in the Cambridge Control Engineering Group and the three separate digital computers for comparison purposes. A realistic comparison cannot be based on run-time considerations alone although this is the prime factor; accordingly, development ‘costs’ are discussed in addition to some techniques available for improving both hybrid and digital solution times. The major conclusion is that, for the particular equation set considered, conventional hybrid computer simulation is marginally faster than digital computer simulation.