Learning Forum

[Emerald Ramos]

Hi, I need help with a project. It is about simulating adsorption using a porous packed bed. I can't seem to figure out how to do it.

This is what I've done so far...

I used multiphase model and species transport. For species transport, I created a mixture of water and mercury with mercury being the component adsorbed to the packed bed. For multiphase, I chose Eulerian in which my phase 1 is the mixture while the phase 2 is the porous packed bed. In phase 2, I defined it as granular and packed bed. I also enabled mass transfer mechanism (species transport) in which specie (mercury) will go to phase 2. When I try to run the simulation, it won't work as the Ansys fluent will crash. What am I doing wrong? How to properly simulate adsorption?

I've also tried to enable multiphase but without species transport and vice versa. The simulation gives a floating-point error. Sometimes, it run well but it doesn't seem to give correct results. I want to see if mercury will adsorb onto the porous bed. Also, is it possible to input adsorption isotherm in Ansys? If so, how? If no, does Ansys calculate for it? I am very new to Ansys, please bear with me. Your response will be a big help for our project. Thank you.

[Prashanth]

Hi, you can model adsorption with or without a multiphase model, with species transport, but the adsorption process is usually defined by setting up wall surface reaction here. You need to setup a reaction mechanism using species and site species that takes part in the adsorption process. Also, Fluent uses Arrehenius law for reaction rate. If you want to setup isotherms as in literatures, you need to define them using user-defined function.

[Emerald Ramos]

Hello, thank you very much for your response. I already set it up as a wall surface reaction in the species transport. However, I don't know what species should I include in the solid and site species. What is the difference between the two. I created two materials for mercury, one which is mixed with the water (selected species), while  I set the other mercury as site species, is this correct? Also, if I set up the reactants and products in the reaction mechanism, what will be the corresponding species? I am confused, should I also create a separate species for the porous packed bed, since the mercury will react/adsorb onto the packed bed? Thank you!