Simulating Aroma Extraction: Using Aspen Plus Efficiently

Aroma extraction is a process used to recover aroma compounds from essential oils. This process can be simulated using software such as Aspen Plus, which is particularly useful for modelling more complex processes. To simulate aroma extraction in Aspen Plus, it is necessary to have accurate data on the true boiling point (TBP) and gravity specifications for the feed, raffinate, and extract streams. Additionally, the creation of a reactor/extractor cascade may be required to model reactive extraction accurately.

Liquid-liquid extraction

When simulating liquid-liquid extraction in Aspen Plus, the selection of the thermodynamic method is critical. Three types of models can be used to represent highly non-ideal liquid mixtures at low-pressure systems: the non-random two-liquid (NRTL) model, the universal quasi-chemical (UNIQUAC) model, and the UNIQUAC functional-group activity coefficient (UNIFAC) model.

The NRTL model is often chosen over other activity coefficients, such as UNIQUAC and Wilson, due to its superior performance in simulating liquid-liquid equilibrium data for the separation of aliphatic-aromatic systems.

To simulate liquid-liquid extraction in Aspen Plus, follow these steps:

• Ensure that data is imported correctly from your database. Go to the "Pure component" parameters folder in the Properties view to check this.
• Make sure Aspen estimates any missing binary parameters. You can do this by running the estimation option and checking that Aspen can determine the molecular formula. If not, you may need to provide a chemical structure.
• Choose a suitable property model or method. In the options for the LL extraction column, try various methods, including NRTL, UNIQUAC, and NRTL-LL. It is important to research which model has been used for your specific type of components in the literature.
• Define the desired pseudo-components in the Aspen Plus simulator by adding their properties, such as density, molecular weight, normal boiling temperature, and viscosity.
• Estimate additional properties, such as viscosities, heat capacities, and surface tensions of the desired pseudo-components using the default methods implemented in the Aspen Properties system.

By following these steps, you can effectively simulate liquid-liquid extraction in Aspen Plus.

Reactive extraction

In Aspen Plus, you cannot specify reaction conditions in an extraction column or specify extraction parameters in a reactor. Instead, you can create a reactor/extractor cascade to model the reactive extraction.

Equilibrium data

The NRTL activity coefficient model was used to correlate the liquid-liquid equilibrium data. The choice of NRTL over other activity coefficients such as UNIQUAC and Wilson was informed by a number of studies that revealed the superiority of NRTL in simulating LLE data for separation of aliphatic-aromatic systems. The NRTL model presents superiority in the simulation of liquid-liquid equilibria.

The NRTL model was used to correlate the experimental LLE data and good agreements between theoretical and experimental results were obtained. The NRTL model was used for modeling the liquid-liquid equilibrium (LLE) of the system, and the binary interaction parameters (BIP) were determined by regression with the phase equilibrium data.

Extraction parameters

To simulate aroma extraction in Aspen Plus, you must first define the relevant components and their properties. This includes defining the solid components and their enthalpy of formation, as well as any necessary thermodynamic properties. Once the components are defined, you can set up the extraction process.

For liquid-liquid extraction problems, you will need equilibrium data for the raffinate and extract phases. You can then use Aspen Plus to plot this data and calculate the percentage of the solute extracted. When setting up the EXTRACT column, you will need to specify the True Boiling Point (TBP) and gravity specifications for the feed, raffinate, and extract streams.

If you are simulating a reactive extraction process, you cannot specify reaction conditions in an extraction column in Aspen Plus. However, you can create a reactor/extractor cascade to model the reactive extraction.

For salting-out extraction processes, you can use the ELEC-NRTL model in Aspen Plus. You will need to determine the binary parameters for the system by conducting experiments or retrieving literature data.

Overall, the key to simulating aroma extraction in Aspen Plus is to define the components and their properties accurately, utilise the appropriate models, and specify the necessary process conditions and data.

Aspen Plus setup

To simulate aroma extraction in Aspen Plus, you'll need to follow these steps:

Step 1: Define the Problem

Firstly, you need to clearly define the problem you're trying to solve. In this case, it's simulating the extraction of aromas from a feed stream using a solvent. The specific compounds and their concentrations will vary depending on your particular application.

Step 2: Gather Data

Before setting up the simulation in Aspen Plus, you'll need to gather relevant data. This includes the true boiling point (TBP) and gravity specifications for the feed, raffinate, and extract streams. Additionally, you may need to define new components in Aspen Plus if they are not already in the database. This involves providing information such as thermodynamic properties, molecular weight, and boiling point.

Step 3: Create a New Case in Aspen Plus

Open Aspen Plus and create a new case file. You'll be prompted to select a simulation type. Choose "Simulation" and then select the appropriate thermodynamic package (e.g., UNIFAC, NRTL, etc.) for your system.

Step 4: Set Up the Flowsheet

In the Aspen Plus interface, navigate to the "Flowsheet" tab. Here, you'll add the necessary unit operations to model your process. For liquid-liquid extraction, you'll typically need to include an extractor (or multiple extractors in series) and a separator. Connect the streams accordingly, ensuring that inlet and outlet streams are properly defined.

Step 5: Specify Stream Information

Double-click on each stream to open the stream property dialog box. Here, you'll input the composition and thermodynamic properties of each stream, including the feed, solvent, extract, and raffinate. Ensure that you provide the assay information for each stream, including the key components and their concentrations.

Step 6: Define Operating Conditions

Next, you'll need to define the operating conditions for each unit operation. For the extractor, specify the number of stages, the flow rates of the feed and solvent, and the temperature and pressure conditions. Similarly, for the separator, define the conditions such as pressure and temperature.

Step 7: Run the Simulation and Analyze Results

Once you have set up the flowsheet and defined the stream information and operating conditions, you're ready to run the simulation. Click on the "Run" button, and Aspen Plus will perform the calculations. After the simulation is complete, you can view the results by double-clicking on the streams to see the outlet compositions and other relevant information. Compare these results with your expected outcomes and adjust your process conditions as needed.

It's important to note that Aspen Plus may have limitations when dealing with certain complex processes or specific types of extractions. In such cases, you may need to create a reactor/extractor cascade or consider using alternative software specifically designed for those applications.

Frequently asked questions