Learning Forum

[soheil]

 

Hi,

I am trying to model particle formation by a crystallization process with Fluent based on the following chemical reaction:

• CaCl2(aq) + H2CO3(aq) --> CaCO3(s) + HCl(aq)

 

EXPERIMENT:

 

Based on the reaction, CO3(aq) ions are added to a small-scale mixing tank containing Ca2+. Mixing is done by a magnetic stirrer. Tank is initially “half-filled” with solution of CaCl2(aq) , and low volumes of reagent will be added. Tank dimensions: (dia.=66 mm, H=95 mm). 

3D SIMULATION:

The overall outline of the simulation is as follows (?), however, I am not clearly sure..

 A. STEADY: To obtain flow hydrodynamics 

1    Since the tank is “half-filled”, then Eulerian Multiphase is activated to Patch the region of Water in the tank. PHASE 1: Water (later will be Mixture Template), PHASE 2: Air [As shown in the Figure].

2.   Steady-state simulation of “half-filled” tank with Water to obtain Flow & Turbulence (k-e) & Volume Fraction. Boundary Condition for the Tank Lid is set as Pressure Outlet. MRF is adopted for Stirrer modeling.

B. Switching to TRANSIENT

1.       Another phase should be added for “Solid Crystals” formation? (Particles don’t affect the flow).

2.       Species Transport should be activated [Volumetric, Finite-Rate/No TCI].

3. Materials should be defined through Mixture Template. Reaction is defined.

4. In the Phase Interaction dialogue box, Reaction can be defined (Figure is attached).

5. Population Balance with Discrete Method is set for Phase 3 (Crystals).

6. Switching Inlet BC to Velocity Inlet during Transient mode.

C.   Is there any way to avoid solving equations for Air from the very beginning? As there is no interest on that; it just increases the time of the simulation. For instance, using Transforming/Dynamic Mesh to compensate for the addition of material and Continuity. Tank is NOT 100% filled with liquid/solution; it’s only half-filled.

I think the rest could be manageable if these key steps are set correctly. I DO APPRECIATE any help.

Best Regards,

- Soheil

 

 

[Rob]

Without the free surface you can't add material without breaking the continuity equation. Assuming you don't add much material there's no reason for having as much head space: you're wasting a lot of mesh. 

If you want PBM you'll need Eulerian grannular model. An alternative is DPM but you'll need UDFs to transfer from the liquid to Lagrangian phase. 

[DraiusX]

Hi Soheil, I'm doing a same simulation and I wanted to know if you have finished this simulation and found the answers or not? And if yes did you changed the setting above?nI Truly appreciate any help you can give me. In my task I'm trying to find the diameter changes of crystals. nI would be greatly thankful for your help!nn