ASPEN’s decanter simulation for liquid-liquid phase separation problems
Thread Content
I would like to ask: at 20 degrees Celsius and 4 bar, only one liquid phase is obtained during separation using a decanter. What is the reason for this? The thermodynamic equation used is NRTL-HOC. The materials involved are as follows: dimethyl ether: 22.43 kg/h, iodomethane: 104.5 kg/h, methyl acetate: 33.98 kg/h, methanol: 16.32 kg/h, water: 90.02 kg/h, acetaldehyde: 1.66 kg/h
When using ASPEN for simulations, if only one liquid phase is separated by the decanter, the possible reasons are as follows: 1. **Temperature and pressure conditions**: At 20 degrees Celsius and 4 bar, your system may indeed be in a single-phase region. In this case, even if multiple components are introduced, all of them may stably exist in the same liquid phase due to the specified conditions (pressure and temperature). 2. **Thermodynamic model selection**: You chose NRTL-HOC as the thermodynamic equation. The NRTL model (Non-Random Two-Liquid model) is a activity coefficient model used to predict liquid-liquid equilibrium, and it is well suited for describing the behavior of non-ideal mixtures. However, the application of the model still depends on accurate interaction parameters and system composition. If the relevant interaction parameters are inaccurate or not suitable for your specific components, it may lead to incorrect predictions of phase behavior. 3. **Properties and interactions of components**: The solubilities and interactions of dimethyl ether, iodomethane, methyl acetate, methanol, water, and acetaldehyde in the material also affect the phase behavior. For example, methanol and water have high mutual solubility, which may encourage other components to remain in the same liquid phase as well. It is recommended to check the following points: - Verify that all the input component data (such as pure component properties and mixture interaction parameters) are accurate. - Consider adjusting the simulation conditions, such as temperature or pressure, to see if phase separation can be induced. - It may be necessary to adjust or reevaluate the thermodynamic model used or its parameters; alternatively, other thermodynamic models such as UNIFAC can be tried to compare the results and see if they lead to improved predictions. Ultimately, these steps can help you understand why there is only one liquid phase under the current conditions, and may help identify the conditions or methods that promote phase separation. .
First, check the liquid-liquid phase diagram to see if your composition is outside the equilibrium line. Is it homogeneous?
Indeed, it cannot be separated within the homogeneous phase. However, the data provided by the process package can be separated. . . . .
They’ll have to check it then to see where the errors are
For slightly more complex systems, whether the liquid-liquid phase separation prediction by software is reliable depends entirely on luck; in cases involving a large amount of binary data, the calculated results often differ significantly from experimental values