Computational Fluid Dynamics Study of a Pharmaceutical Full-Scale Hydrogenation Reactor

Round 1

Reviewer 1 Report

The paper could be interesting to the reader if it writes in a clear way! The main issue is that the fluid and cases are not clear. The cases is not defined clearly. Please don’t describe anything regarding the mesh and turbulent study in the main sections. Describe the mesh study in appendix 1, and turbulent (k-w and k-e) in appendix 2.

RT in line 94 is Rushton turbine?

Figure 4 and Table 4 about the mesh are not necessary. 

It’s not clear from ‘’number of phase’’, is there a change in the phase or not? Please clarify the change of the hydrogen gas or liquid in the simulation? Is it because the mixing process in the tank, could affect changing the pressure and as results change the phase?

Turbulence modeling: Please give the reference to why the RANS modeling gives good accuracy with the LES model, Also, what is the turbulent intensity in the simulation?

Line 202, is the gravity important in simulation or we can ignore or maybe use the Boussinesq approximation?

Line 204, Please give the reference why using the MRF model for the study of impeller? Could we use the Blade Element Model?

In eq 5, Rd must change to Re_d,

Table 5 change GaussSeidel to ‘’ Gauss–Seidel’’. Please give more details about the solver of GAMG

BCs are not clear at all. Please show all the BCs in Figure 3 or add a new picture. Please add the equation of the fixedFluxPressure and alphaContactAngle with the help of the Open Foam. Are there any inlet and pressure outlet BCs in the domain? What is the volume fraction in the other BCs?

Line 250 what is the density material here? Is it air or hydrogen?

Line 297, is it the time-averaged? Please describe the time step and simulation. 

Figure 6 is not clear. The maximum and minimum range of the pressure are the same! The figure should be titled with A) and B). Also, please plot the concentration and volume fraction of the fluid.

Please describe the ‘’ phase-averaged’’ eq in the introduction section.

Line 391, in section 1, you used the rho_w as the density of the water. Please used another symbol. 

Methanol density is 762, the air is 1.2, water is 998, and hydrogen is 0.2 in the total pressure of 2.75 bar, and by increasing the pressure it could be higher than air pressure. Is not clear whether this difference between the density of fluids and pressure could affect the concentration of fluid and change the phase? 

Figure 9 what is A-D?

Line 405 is solvent is methanol?

Figure 10 range is not correct.

Line 450, what is the liquid phase here?

Line 505, what is the fluid, or solvent?

There are not any good results in conclusion. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The poaper discusses an application of CFD into the pharam industry. 

page 3: some details on the mesh generation is not required and makes the paper seem like a technical report rather than a paper.

section 3.3 details of solver settings are not required and does not add to the paper and better to be removed. again the paper is more like a technical report.

section 5: discussion of results may be combined with presentation of results

A major issue is that the solution was shown to be dependent on turbulence models. therefore, some Y+ illustrations and boundary layer profile resolution need to be demonstrated and discussed.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors present a study of a full-scale hydrogenation reactor. A CFD model is developed and compared to existing results in the literature (mainly an experimentally validated CFD study itself). The authors then extend their model to a full-scale application. The work is generally well presented and seems to contain findings of practical interest. Below are some comments for the authors to consider:

1.       In the introduction, the authors state that a key objective of the work is the study an existing reactor that contains two vertically mounted impellers. However, the influence of the two impellers is not directly discussed in the results at all. A short comment or two on any observations or findings due to the use of two impellers could potentially help provide generality to the specific results presented in this study.

2.       Similarly to the above, are there any comments by the authors on the influence of the two impellers on the developed correlations?

3.       In the dot point on “Turbulence modelling” (lines 188-191 specifically), it is claimed that the conclusions regarding 2-eq. turbulence models are supported by the “literature review in Section 1”. However, the literature review purely mentions the various turbulence models without any additional details regarding their advantages/disadvantages. This should be added to the literature review.

4.       Comments on Figure 6. In the (left) figure, the impeller is white; however, there seems to be another white section at the bottom left of this figure. Is this another part of the impeller? In the (right) figure there seems to be some artefact below, in the bottom left corner (some overlapped text it seems). Figure (right) would also benefit from similar axes and legend titles and formatting that (left) has.

5.       Figure 7 shows that the model utilized within this paper is not accurate over the entire radial domain. Are there any comments of how such inaccuracies could influence the conclusions/correlations of the paper?

Minor comments:

-          Sentence starting on line 68 would benefit having a reference to the literature.

-          Sentence from line 113-115 would also benefit from a reference.

-          Formatting issue on line 124 and Figure 2.

-          Line 209, should the “physic” be “physical”?

-          Start of line 221, should the “Being” be “Where”.

-          Line 222, uneven spacing around the “=” in the in-line equation.

-          First paragraph in Section 3.3 would benefit from references.

-          Line 260, should “N” be “N_p”?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thanks for your response. 

Reviewer 2 Report

The authors have addressed my concerns