Model-Based Analysis of Feedback Control Strategies in Aerobic Biotrickling Filters for Biogas Desulfurization
, Eveline Volcke 2 and David Gabriel 1,*Round 1
Reviewer 1 Report
Lopez et al. presented a PI/PID-based feedback controller strategy for desulfurization process using biotrickling filter.
My major concern regarding this manuscript is on its controller and the model
- It seems that the major model used in this study is the empirical mass transfer correlation of pack columns. Based on its equation, it does not have temporal component, but in the results section, the temporal dynamics of the close-loop system was presented (e.x., fig 5). How does the authors simulate the close-loop dynamics with this empirical correlations?
- Also, the PI/PID controllers' parameters were tuned based on the above empirical mass transfer correlations. I am not convinced that these controllers will be robust enough to control the real process since the real process is too complex to be fully described by the empirical correlation. In the literature, a model-based controller is usually formulated first by constructing a high-fidelity first-principle model and using it to derive a MPC-type controller to robustly control the real process. Please see the following references for more details. Siddhamshetty et al. https://doi.org/10.1002/aic.16031; Kwon et al. https://doi.org/10.1016/j.ces.2013.09.026; Burnak et al. https://doi.org/10.1002/aic.16981; Aumi et al., https://doi.org/10.1002/aic.12398
- In Figure 1, two control strategies were presented. One question I have is why O2 concentration should be controlled for a process where the entire process is set up to remove H2S. The motives for controlling O2 are not clear to me.
- In Figure 3, the authors attempted to validate the empirical correlations by the experiments. But, where these experimental results come from?
- There are some typos and grammatical issues need to be addressed by the authors. A few examples are given here
- Replace "if" with "of" on the line 16
- remove "s" after "Affect" on line 19
- move "significantly" after "performance" on line 19
- Replace the comma with a semicolon on the line 34
- Add "s" after "Equation" on line 67. And make the same change throughout the manuscript
- Add "ed" after "support" on line 119
- Add "s" after "correlation" on line 143 and 144
- Capitalize "t" in "Table 1" on line 177. And make the same change throughout the manuscript
- What do commas mean in Table 4?
- Add a semicolon after "affected" on line 408
- remove "and" and add a comma after "therefore" on line 409
- remove "that" on line 413
- Add a comma after "minimum" on line 467
- Add a period after "changes" on line 625
- Why does the conclusion break into so many short sentences?
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Please look at the attached document for my comments. The marked up manuscript is attached after my comments.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have addressed my comments appropriately.
Author Response
No response provided since the reviewer provided no comments
Reviewer 2 Report
The manuscript is much improved. There is still some English that needs to be changed to improve readability. There are two technical issues that I am still confused about which is explained in the attachment.
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.docx
