Application of mixed-integer programming in chemical engineering

摘要

Mixed-Integer Programming has been a vital tool for the chemical engineerin the recent decades and is employed extensively in process design and control.This dissertation presents some new Mixed-Integer Programming formulationsdeveloped for two well-studied problems, one with a central role in the area ofOptimisation, the other of great interest to the chemical industry. These are theTravelling Salesman Problem and the problem of scheduling cleaning actions forheat exchanger networks subject to fouling.The Travelling Salesman Problem finds a plethora of applications in manyscientific disciplines, Chemical Engineering included. None of the mathematicalprogramming formulations proposed for solving the problem considers fewer thanO(n^2) binary degrees of freedom. The first part of this dissertation introduces anovel mathematical description of the Travelling Salesman Problem that succeedsin reducing the binary degrees of freedom to O(nlog2(n)). Three Mixed-IntegerLinear Programming formulations are developed and the computational performanceof these is tested through computational studies.Sophisticated methods are now available for scheduling the cleaning actionsfor networks of heat exchangers subject to fouling. In the majority of these, onlyone form of cleaning is used, which restores the performance of the exchangerback to its clean level. A recent study revised the schedulingproblem for the case where there are several cleaning methods available. Thesecond part of this dissertation extends their approach, developed for individualunits, to heat exchanger networks and explores the concept of selection of cleaningtechniques further. Mixed-Integer Programming formulations are proposed forthe scheduling task, for two fouling scenarios: (i) chemical reaction fouling and(ii) biological fouling. A series of results are presented for the implementation ofthe scheduling formulations to networks of different sizes.