Aspen simulation of regenerative tower circulation problems
Thread Content
To facilitate convergence of the entire carbon capture system, I separated the regeneration and absorption sections, and used the parameters of the rich liquid obtained from absorption as input to simulate the regeneration section separately. The following warning appeared: * WARNING: The calculated feed temperature for the hot side (3.8736951D+02) does not match the value of its inlet stream (3.8787725D+02). Possible cause: loose flash tolerance, or an upstream block with different phase specifications or property methods. The calculated value will still be used in the calculations. I’ve checked some existing posts, but in my process flow the property methods for the upstream and downstream sections are the same, and the convergence tolerance is set very low (-5 power). I still can’t figure out how to adjust things so that this warning related to the heat exchanger disappears. I’d like to ask for any suggestions you might have to guide me. Interestingly, when I opened an MDEA/PZ CO2 absorption process using Aspen’s built-in amine package (the ele-nrtl method), it still showed such a warning regarding the heat exchanger; could there be an issue with this amine package as well?
According to the warning message, a possible reason is that during the simulation of the regeneration section, the calculated hot-side feed temperature does not match the value of the incoming stream. This may be due to an excessively high flash tolerance setting, or the upstream modules using different phase specification or property methods. You have confirmed that the property methods for the upstream and downstream processes are selected consistently, and that the convergence tolerance is set low, but the problem still persists. I suggest you try the following steps to resolve this issue: 1. Check whether the parameter inputs for the rich liquid flow in the absorption section are correct. Ensure that the input property values and flow rates correspond to the actual conditions. 2. Check for any other warning or error messages in the simulation of the regenerated section. There may be other issues affecting the simulation results of the regenerated portion. 3. To eliminate simulation errors, you can try using more accurate but more computationally expensive methods to simulate the regeneration portion, such as changing material properties or adjusting calculation parameters. 4. If your model involves flashing operations, you can try reducing the flashing tolerance, that is, lowering the convergence tolerance setting, to improve the accuracy of the simulation. The same warnings apply to the built-in amine absorption model, likely due to the limitations of the model itself. If you have doubts about the accuracy of the model, you can consider using other amine packages or simulating the absorption section through a custom model. Finally, if the problem persists, it is recommended that you contact Aspen Plus’ technical support team, describe your issue to them, and provide more detailed information on the simulation settings and procedures, so as to receive professional assistance and guidance. .