CHEN 4460 – Process Synthesis, Simulation and Optimization

1. Optimization Software CHEN 4460 – Process Synthesis, Simulation and Optimization Dr. Mario Richard EdenDepartment of Chemical EngineeringAuburn University Lab Lecture No. 5 – Introducing LINGO October 16, 2012

2. Optimization Software • LINGO • Should be available on computers • If not, download zip file from class webpage • Program is started using C:\LINGO\LINGO.EXE

3. Optimization Software • LINGO • To start entering a new optimization problem type: • Model: • Enter the objective function by typing: • min = ……; or max = ……; • Then enter the constraints. • Each line must end by a semi-colon ; • The final statement in the problem should be “end”

4. Optimization Example • Hydrogen Sulfide Scrubbing • Two variable grades of MEA. • First grade consists of 80 weight% MEA and 20% weight water. Its cost is 80 cent/kg. • Second grade consists of 68 weight% MEA and 32 weight% water. Its cost is 60 cent/kg. • It is desired to mix the two grades so as to obtain an MEA solution that contains no more than 25 weight% water. • What is the optimal mixing ratio of the two grades which will minimize the cost of MEA solution (per kg)?

5. Optimization Example • Hydrogen Sulfide Scrubbing (Cont’d) • Objective function min z = 80x1 + 60x2 • Constraints • Water content limitation 0.20x1 + 0.32x2 ≤ 0.25 • Overall material balance x1 + x2 =1 • Non-negativity x1 ≥ 0 • x2 ≥ 0 Variables (Basis 1 kg solution) x1 Amount of grade 1 (kg) x2 Amount of grade 2 (kg) z Cost of 1 kg solution (cents)

6. Optimization Example • Solve using LINGO Press this to solve problem

7. Optimization Example • Solve using LINGO Press this to switch to results