Application of the microsoft excel solver tool in the optimization of distillation sequences problems

Distillation is a very important operation for purification and separation in Chemical Engineering field. The determination of the optimal distillation sequence is key to minimize the total investment and operating cost and it can be posed as a mixed integer-linear programming (MILP) problem. To solve them and due to the high number of variables and equations, it is required the use of specific software, for example, General Algebraic Modeling System or A Mathematical Programming Language. However, these software involve long training for the student to adequately harness them. The use of non-specialized, widespread and easy to access software programs is a good opportunity to tackle the teaching of some typical optimization problems. One of them is the Microsoft Excel Solver Tool, accessible by any engineering student who usually learn its use in the first years of their degree, so that MS-Excel is already known when students deal with optimization problems. Additionally, it is scarcely known that Microsoft Excel Solver may tackle both real and binary variables, so it is possible to leverage it for solving MILP problems. This paper presents an example of distillation sequences problem aimed to separate a mixture comprising four different compounds with a minimal operational cost (which constitutes a MILP optimization problem indeed) solved using Excel Solver tool. This methodology was taught successfully to the students of the Master of Chemical Engineering of Rey Juan Carlos University and Autonoma University of Madrid.