Model Predictive Control for the Process of MEA Absorption of CO₂ Based on the Data Identification Model

Round 1

Reviewer 1 Report

Absorption of CO2 by ethanolamine is an important process in the post-combustion CO2 capture system. I suggest the following issues be addressed to improve the quality of this paper.

 

1. Novelty and importance 

It is not clear what the novelty of this paper is. And why was Aspen Plus and Aspen Plus Dynamics used? Was this the best choice? The authors need to make this clear.

 

2. Major findings, figures, and tables

What is the major finding of this study? It is not very clear. And I think the number of figures can be significantly reduced. The figure legends also need to contain significantly more information. It is difficult to comprehend the contents of the figures in its current form. The same comment applies to the tables - the number needs to be reduced and the legend needs more detail.

 

3. Implication

What is the implication of this study? This needs to be made much clearer in the Abstract and Conclusion. 

 

4. Presentation and expression

The English expression needs to be significantly improved. And the abbreviations need to be explained when used for the first time within the paper. There are many cases where this is missing.                      

 

Author Response

Dear editor and reviewer:
Thank you for your comments and suggestions. We have revised the manuscript based on your comments and marked it in the file attachment . Thanks again for your valuable comments.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

1. Line 18 - 20: The sentence is too long and unclear.
2. What is PCCP in Line 28? Please provide a list of abbreviation at the end of the manuscript. Other unknown abbreviations such as MPC, PI are also stated in the manuscript.
3. Line 42: The phrase "Validate factory data by the steady state" is unclear. Are the authors referring to process simulation of steady state operation with the validation from the industrial setting?
4. Line 71 - 72: The best choice for the CO₂ adsorbent with its absorptivity of up to 90%. This sentence is merely a claim unless a reference is given. Besides, what does 90% here refers to (i.e. normalized with what basis)?
5. Line 92: It should be written as N₂. There is a typo.
6. In Section 2.1, please indicate what assumptions are used in this simulation. For example, in this simulation, did the authors assumed that MEA is not decomposed (or loss) throughout the simulation, as in Figure 2, water is replenished in the system to maintain the water balance in the system due to the potential loss in the product gas or bottom stripper. Besides, the author also assumes that all the impurities (e.g. SO₂ are not feeding it to the absorber/stripper column). Please confirm such assumptions are reasonable/practical to be compared with industrial operation.
7. The equation font size for equation 1 and 2 is too small.
8. Line 95 - 96: What is the meaning of cross heat exchanger? (Cross-flow/Counter-flow heat exchanger?)
9. Line 99 - 100. More elaboration on the reboiler unit should be stated (e.g. to desorb the absorbed CO₂)
10. Line 106: Is there any particular reason why the flow rate of lean solvent is set at 0.458 kg/s?
11. Line 106: Similarly, why CO₂ capture rate is fixed at 70%? Do the CO₂ capture rate is similar to the absorptivity (as mentioned in Line 71 - 72 by the authors) of 90% by the author? If it is the same, please confirm this discrepancy and explain.
12. Line 114 - 115: Is there any literature studies that support the claim mentioned by the authors (i.e. dynamic simulation in Aspen Plus Dynamics does not support the rate level model)
13. Line 135: "double-membrane" refers to?
14. Figure 5, 7 and 9 are too small. For Figure 8, please change the label in the y-axis. Please also check the labelling in the text carefully (e.g. "figure 7" in line 163 should be labelled as upper case (i.e. Figure 7)). Please make a consistent formatting for all the figures provided. I recommend to shift some non-critical figures to the supplementary information to make the overall content neater (e.g. not explanation on Figure 12 and Figure 15).
15. Line 142 - 143: Provide references for the statement provided.
16. The 160 - 161: The information in Table 3 is corresponded to Equation 1 and 2 as mentioned by the authors? Are the numbers stated the coefficients? What is object A, B, C and D in this case?
17. Line 163: Change the subscript to CO₂
18. Line 176 - 177: rather than stating as formula (8), formula (9); it should be stated as equation (8), equation (9). Please make the changes.
19. I am unsure the reason that the x-axis uses "second(s)" as the unit. It may be better to change it to hours (hr) so that the values are smaller and more representative (at times, it is difficult at a first glance to have a impression on how long 65000 s is.
20. References formatting are not consistent.
21. Line 300: What is the meaning of the sample availability?

Author Response

Dear editor and reviewer:
Thank you for your comments and suggestions. We have revised the manuscript based on your comments and marked it in the file attachment . Thanks again for your valuable comments.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper with a few corrections to stating acronyms such PCCP and MPC can be presented at the Journal. More data insight would of course be helpful, but the state space model makes sense. 

Author Response

Dear editor and reviewer:
Thank you for your comments and suggestions. We have revised the manuscript based on your comments and marked it in the file attachment . Thanks again for your valuable comments.

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The issues raised previously have been addressed sufficiently.