USING ASPEN HYSYS OPTIMIZER

Problem Statement

This is one of the hands-on lesson from Udemy Oil and Gas Process Simulation/Modelling Using Aspen HYSYS course

Given required settings for the distillation column:

• Number of stages : 10

• Feed stage: 5

• Condenser type : Total Condensation

• Condenser Pressure : 103.00kPa

• Reboiler Pressure: 107.00kPa

The feed stream is 3700kg/hr mixture consist of 44% THF and 56% Toluene, entering the column at 10°C and 140kPa

We want the mixture to be seperated via distillation to get THF with 99.5% purity and Toluene with 94.0% purity

With the given feed price, toluene and THF selling price, cooling and heating cost, how can we optimise the setup to maximise our profit?

We set a range between 0.99 to 0.999 for the THF purity limit and 0.9 to 0.99 for the toluene purity limit. Use Wilson Fluid Package

Execution

After setting up the environment and the column, we go to the Monitor section and define the THF and Toluene purity. But before that, we need to uncheck the Reflux Ratio and Distillate Rate at the [Active] tab, creating 2 Degree of Freedom.

Then we go to [Add Spec...] to add Column Component Fraction for THF and Toluene, we specify 0.995 for THF mass fraction and 0.9400 for toluene mass fraction

The next step is we go to the [Optimizer] and navigate to [Variable] tab to add variable THF Purity and Toluene Purity. As shown below, we defined the upper bound and lower bound of the substance based on the given problem statement

After that, we go to the [OptimizerSpreadsheet] and define the required parameters and the formula of the profit as shown below

As you can see, from the inital setup, we can yield $6.8 profit. Is there anyway we can maximise it? The Optimizer will sort that out

We go back to the Optimizer and go to [Functions] and select the cell value we want to maximise

You now notice that the value change from $6.8 to $61.21!! A significant increase in value! Let's take a look once again at the OptimizerSpreadsheet

You may notice a slight change in Bottom Prod. Rate, Duty, and the THF Purity is at 0.99