The “Load Simulation” tab

This is Metacontrol initial tab, where you will be able to

  • Supply an Aspen Plus simulation file;

  • Create aliases for the Aspen Plus simulation variables, to ease the study;

  • Select your relevant variables (Manipulated Variables, Controlled Variables and Auxiliary Variables);

  • Inspect information about the simulation you provided;

  • Create user-defined expressions for Objective functions, Constraints and CVs that are not natively calculated by the process simulator.

../_images/loadsimtab.png

Fig. 3 Metacontrol “Load Simulation” tab.

There are four main panels on this tab:

  • Load simulation file panel

  • Selected variables aliases panel

  • Functions definitions panel

  • Simulation info panel

Load simulation file panel

This is the panel that you will use to load the Aspen Plus simulation file.

../_images/loadsim_panel.png

Fig. 4 Metacontrol “Load Simulation file” panel.

Providing a simulation file

Clicking on “Open File”, a window will appear in your screen and you will be able to point to your Aspen Plus file location on your PC.

../_images/point_bkp.png

Fig. 5 Pointing to your Aspen Plus file Location.

Important

The supported Aspen Plus file extension is .bkp (Aspen Plus backup file). Please, save your simulation with this format before using Metacontrol.

Attention

Make sure the file supplied is not your only copy! We can not guarantee that any eventual use by the Metacontrol OLE/COM will not cause permanent modification, damage or corruption to your file.

Choosing your variables, and associating aliases for them

After pointing to your Aspen Plus simulation file location, the button “Load Variables” becomes active. After clicking on it, a screen to select simulation variables and adding aliases for them will appear. Just click on “Load Variable tree”, and the Aspen Plus engine will be loaded on background and all the variable tree will be loaded.

../_images/var_tree.png

Fig. 6 Loading Variables from Aspen Plus simulation.

After clicking “Load Variable tree” button, you will see that the variables from the simulation are available for use. They are neatly organized between Input and Output variables, and organized for each block and stream that you have modelled in Aspen Plus. If you want a specific variable, simply navigate using the loaded tree, and select it.

../_images/var_tree_filling.png

Fig. 7 Selecting the loaded Variables from Aspen Plus simulation.

Important

If you hover you mouse pointer over a variable from the tree, Metacontrol will show the description of that variable.

../_images/hover_mouse_description.png

Fig. 8 A quick reminder of what that variable actually is…

On the screen above you noticed a red form over the alias and type forms. This is intentional: Metacontrol is informing you that two variables are with the same aliases and also, that you did not classified the type of the variables that you entered. Giving proper (non-repeated) aliases and correctly classifying your variables will make the red warning disappear.

../_images/var_tree_filled.png

Fig. 9 Typing aliases for variables in Metacontrol.

../_images/var_tree_class_input.png

Fig. 10 Classifying your variables in Metacontrol - Input Variables.

../_images/var_tree_class_output.png

Fig. 11 Classifying your variables in Metacontrol - Output Variables.

Important

To create aliases in Metacontrol, only lower case alphanumeric characters are allowed.

If you forgot something from you model (a stream name, block, etc.), You can show the simulator GUI (Aspen Plus) by just checking the “Open Simulator GUI” checkbox on the upper right corner of the variable tree load window.

../_images/aspen_gui_invoke.png

Fig. 12 Forgot something (We do all the time)? Just call Aspen Plus from Metacontrol, and have a quick reminder.

After selecting, naming and classifying all the variables that you need, just click “Ok”, and you will be back on the main-screen.

Selected variables aliases panel

After selecting the necessary variables, you will see that now on the main tab, this panel reports a list of all variables from your study. This was created to make it easier for you to remember the aliases of the variables that you created and which type of variable you gave to each one of them (CV candidate, MV, Auxiliary).

../_images/selected_variables_list.png

Fig. 13 At the “Load Simulation” tab, a list of all variables that you choose.

Functions definitions panel

On this panel, you can create user-defined variables, using the variables that you previously choose from your Aspen Plus model. This is really convenient because it allows you to:

  • Create the objective function that you will optimize in Metacontrol

  • Create constraints for your optimization problem

  • Create CV Candidates that are not natively calculated by the process simulator (A difference between variables, ratios, product, etc.)

../_images/function_def_panel.png

Fig. 14 The functions definition panel.

The Function definitions panel allow several math operations and functions:

Table 1 Metacontrol supported math operations and functions.

Expression

Definition

+

Addition

-

Subtraction

*

Multiplication

/

Division

^

Potentiation

PI

PI constant

E

Euler’s number

sin(x)

Sine function

cos(x)

Cosine function

tan(x)

Tangent function

asin(x)

Arcsine function

acos(x)

Arccosine function

atan(x)

Arctangent function

log(x)

Natural Logarithm function

log(x,base)

Logarithm function with specified base

abs(x)

Absolute value of a number

ceil(x)

Round up to the closest integer

floor(x)

Round down to the closest integer

round(x)

Round to the closest integer

exp(x)

Exponential function

The functions definition panel also checks the spelling of your expressions. Missed a minus signal between two variables? Mistype the name of an alias? Metacontrol will indicate that to you, with a red color:

../_images/exp_invalid_alias.png

Fig. 15 An example of an alias mistype (missing a “t” from “fco2out” alias).

../_images/exp_invalid_math.png

Fig. 16 An example of math mistype (Math operator missing between the two parts of the expression).

Correcting the spelling/operator errors, Metacontrol validates your expressions:

../_images/exp_valid.png

Fig. 17 Valid expression becomes green!

Creating a User-Defined Objective function

  1. Click “Add Expression”:

../_images/add_exp.png

2. Create your desired expression for the Objective function (and name it) to be optimized by Metacontrol later on your study:

../_images/add_fobj.png

  1. Classify it as an Objective Function using the dropdown list:

../_images/class_fobj.png

Creating a User-Defined CV Candidate

  1. Click “Add Expression”:

../_images/add_exp.png

2. Create your desired expression for the CV candidate, based on model measurements that you associated aliases with:

../_images/add_cv.png

  1. Classify it as an CV candidate using the dropdown list:

../_images/class_cv.png

Creating a Constraint function

It is very common to have process constraints in the processes that you want to study in a plantwide (Self-Optimizing) perspective. Metacontrol supports the creation of constraints that are added to the optimization problem solved using metamodels. The constraints are always written in the form:

\[g(x) \leq 0\]

And you should provide the constraint with such syntax to Metacontrol. For instance, the following product purity CO2 constraint in a compression and purification plant:

\[x_{CO2} \geq 0.96\]

Must be provided as:

\[0.96 - x_{CO2} \leq 0\]

Within Metacontrol, you should simply type:

../_images/constraint1type.png

You can also create constraints that are expressions. For example:

../_images/constraint2type.png

which is:

\[fco2out/fco2in \geq 0.9\]

If you have an constraint interval, simply break it into two constraints (A lower bound and an upper bound constraint).

Simulation info panel

This panel serves as a “At a glance” simulation data info panel: After you load your Aspen Plus simulation, it is possible to inspect the following information:

  • Number and name of components

  • Thermodynamic Package used in your model

  • Number and name of blocks used

  • Number and name of streams in your flowsheet

  • Chemical Reactions modeled

  • If there are any sensitivity analysis, optimizations, calculators and/or Design Specifications Within your model.

Attention

You might want to disable any sensitivity analysis and optimization blocks that exist inside your simulation. Note that Metacontrol is going to perform a DOE (Design of Experiments) using your model in order to create a kriging interpolator and later optimize it. If you keep a sensitivity analysis turned on, for instance, the results of the DOE will be superseded by the sensitivity analysis. In addition, if you have an optimization block active: Aspen Plus will try to optimize at each run. We certainly do not want this.

The following image shows an example of the Simulation info panel after you load a simulation:

../_images/sim_info_panel.png

Fig. 18 Simulation info panel showing information regarding the Aspen Plus model provided.