Numerical Investigations for the Two-Phase Flow Structures and Chemical Reactions within a Tray Flue Gas Desulfurization Tower by Porous Media Model
Round 1
Reviewer 1 Report
The list of my objections is below:
- The simulation parameters should be described more specifically (the name of used models, methods, functions, etc. - You used Fluent one of the most famous CFD programs). The simulation must be presented so that it is as simple as possible to reproduce.
- Some part of the equations does not play a significant role eg. (1), (2), (16).
- The article is quite extensive but a lot of presented considerations seem redundant. You should consider throwing out content that adds nothing and is widely known or can be significantly shortened (e.g. section 2.3 can be presented in 5-10 lines, and not in 25).
- The nomenclature section should be added.
- Figures and Tables should be in the text, not at the end.
- The Y+ value should be added.
- It is (probably) a transient simulation? Then the time step of simulation should be added.
- Why firstly You used Case A (tables 4 and 5) and explain it later (table 6). First, enter the designation and then use it.
- ....
The article is written chaotic. Its layout is unclear and various parts are scattered throughout the work. The simulation and models are described in a terrible way. The simulation description is not detailed, despite the fact that the authors discuss the formulas. I can not imagine how much work needs to be done to recreate the simulation described and find the simulation data carefully hidden in the text. The analysis of the simulation is not interesting. The article should be rewritten, shortened, and put in order. Reading it was a punishment, not a reward.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript investigates numerically the flue gas desulfurization tower by means of a porous media model. The core of the study is a theoretical investigation based on the computational fluid dynamics approach. The results are clearly presented and provide a practical reference for engineering applications. The obtained results may provide a design guideline for the FGD tower in relevant industries such as fossil-fuel power and steel plant. The contents of this paper lay well within the aims and scopes of the journal. The subject matter is interesting and potentially useful to readers.
1) The introduction needs to be better organized in order to show the new contribution of the paper. Please clearly define a novelty statement in the introduction.
2) The conclusion section needs to be improved (main findings and practically oriented suggestions should be listed).
3) There is a need for careful proofreading as typos/errors occur. In some places, the manuscript style does not meet the requirements of the journal.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 3 Report
With the two-phase flow model and desulfurization chemical reaction being employed, this study presents the numerical simulation results for the flue gas desulfurization (FGD) tower including perforated sieve trays. The results were validated with measured data in terms of SO2 removal efficiency in a small scale tower. Furthermore, the porous media model for the reduction of computational cost successfully replaces the perforated sieve structure of complexity showing comparable results. The model replacement was extended to the simulations of full-scale tower of more practicality and was validated with the experimental results, too.
This study may provide the relevant industries or community an insightful information for the FGD tower design.
A few typo-errors needs to be corrected as follows:
Line #167: medial -> media
Line #306: Equation (4) -> Equation (15)
Line #422: framework from consists -> framework consists
Nomenclature (List of Symbols) needs to be included.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Below is a list of my objections:
- Figures are still at the end of the paper not in main text. I am quoting: 'All Figures, Schemes and Tables should be inserted into the main text close to their first citation and must be numbered following their number of appearance (Figure 1, Scheme I, Figure 2, Scheme II, Table 1, etc.).' (see https://www.mdpi.com/journal/applsci/instructions#figures)
- Line 305: Reynolds number equation has no = symbol.
- Line 354: You miss ')'
- Why do you used SIMPLEC (not SIMPLC in line 353) algorithm to the transient simulation and not a PISO? How much was a convergence?
- Justify the choice of these and not the other time steps? How was they calculated?
- Why is the mesh in second tower (this without the sieve trays) so poor? If is not important why is simulated?
- Please add the source from which the experimental data was taken in table tittle (table 4 and 5).
- Line 357: 'Although the time dependent computation is considered, the solution finally reaches a steady state for a small-scale tower.' - maybe easier use the steady simulation?
Author Response
Please see the attachment.
Author Response File: Author Response.docx
