"Optimizing" energy use means very different things to different people. To me it means making cut of a specified quality (defined by a quality like "volume interchange " (a measure of the amount of material above max cut point and/or below min cut point in the actual cut while using the minimum possible amount of energy.

A desired cut can be often made with less energy by increasing the number of trays. Adding stripping steam (and dedicated stripping towers) will also improve the cut quality. This stripping steam can be made from low pressure steam that has little or no value but many academics often do not recognize the difference in value between high and low level heat in their analysis.

In general more trays and less reflux will decrease firing requirements but it will cost much more to build. Preheating combustion air and enriching O2 content of combustion air (for example with a membrane) is often a good way upgrade low level heat to high level heat services and reduce total energy use.

I think you need to be more specific about how you value energy and how much you are willing to spend to reduce energy cost,

Thanks a lot for valuable answer my meant regarding energy is specific energy of compressors.

Optimization of distillation columns is a problem of mixed integer no linear programming type. In-house optimization methods of both Aspen and Hysys can't handle integer variables like # of trays, feed stage and among others (i.e side outlet streams). Therefore, I recommend the use of external algorithms, either of deterministic nature such as BARON (highly recommended) or stochastic nature like Genetic Algorithms (NSGA II, highly recommended), for handle integer variables.

Optimization problem statement is a key step for ensure good performance of optimization algorithms. I suggest cost of distillation column (including equipment cost around distillation column such as compressors, pumps, and heat exchangers) like objective function to minimize because all variables have economic influence.

There are different tools to ease optimization tasking by external algorithms using Aspen plus or Hysys simulations. For example, in the following link, you can find Matlab code to connect Aspen Plus and Matlab through COM technology and use widely used Matlab optimization algorithms:

https://www.mathworks.com/matlabcentral/fileexchange/69464-aspen-plus-matlab-link

Its possible connect Aspen plus or Hysys to any programming language with COM capabilities.

I could send you and example of Hysys - Matlab Connection.

Best Regards,

Thanks for your helpful comment

Your question is unclear. What mixture are you trying to distill? What product qualities are you trying to achieve? How much money are you willing to spend an additional hardware (more trays, compression, pumping etc.) in order to reduce reboiler and stripping requirements? If you give us a more complete description of your process it will be easier for us to determine the correct tradeoff between separation quality and investment and operating costs.

Alam Nawaz On the AspenTech support website there is an example of optimizing the feed tray location in a tower. You can also use the optimization/derivative utility to define an objective function and optimize that way. Press F5.

The actual number of trays in a continuous comercial distillation colum should be quite a bit higher (usually 40-50%) than the perferct column predictions from a simulator.

Can anyone send me an example of hysys+MATLAB optimisation?