Selection of Optimum Separation Sequence for Multicomponent Distillation
Round 1
Reviewer 1 Report
The authors are requested to rework on the manuscript. The subject is interesting but the presentation and the organization of the content is unlike a research work. Also it would be nice if the authors do validity range of their model and do a sensitivity analysis too.
Author Response
In our paper we try to stick only to basic thermodynamic assumptions. The column is what is known as a simple column. Main assumptions are given in the paper. The sensivity analysis is a great thing, but not a subject of a paper. Authors would like to have more detalized comments.
Some minor changes are made in the text attached.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is well written and the results are clearly presented. There are some minor corrections that the authors should attended it:
L.14: …”(for example [1-4] and others)” – it means “which ones”? – in my opinion, this sentence should be removed;
L.26: “This paper…” – which one? - it needs citation;
L.54: …”pressure ,…” - it was not marked in Figure 1 - the decision about the correction I leave to the authors;
L.62: The symbol ... "ith" ... I suggest replacing it with "i-th";
The equation between L.64 - L.65 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
The equation (4) should be corrected – “ ….” - what does it mean?
In the text of the manuscript should be described, what the symbol (R) means - equations (6) and (7);
Line below the equation (8) - symbol ... "jth" ... I suggest replacing it with "j-th";
L.100: The indications of “lhs” and “rhs” should be written in brackets - as given in lines (91) and (92);
L.106 - 108: The fragment “If the separation sequence …. the value of C” - I treat it as a citation, so it is necessary to give the references;
In the inequality (11), the (+) (-) signs should be on the left and right side of its segment - as in equation (5). In addition, it should be clarified in the text of the manuscript, what means the ratio of “T12”;
The inequality: T1 < T12 < T2 < T23 < T3 (p. 5) should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
L.109 – 111: The fragment “If the first column …. of next stages” - I treat it as a citation, so it is necessary to give the references;
L.114: The indication of “lhs” should be written in brackets;
The equation between L.115 - L.116 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript. This number should be given in L.116a after the symbol (F);
The equation before L.117 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
L.129: Please check the symbol – (k) or (ki);
The equation between L.139 - L.140 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript.
L.148a: The indication of “rhs” should be written in brackets;
L.149c:The equations should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
L.155c: The symbol ... "jth" ... I suggest replacing it with "j-th";
L.155d: The equation should be numbered;
L.158: The indication of “rhs” should be written in brackets;
In my opinion, "Abbreviations" should be removed. They are known or explained in the text of the manuscript (except for LVC).
Author Response
L.14: …”(for example [1-4] and others)” – it means “which ones”? – in my opinion, this sentence should be removed;
It is corrected.
L.26: “This paper…” – which one? - it needs citation;
Changed to “Our current paper”
L.54: …”pressure ,…” - it was not marked in Figure 1 - the decision about the correction I leave to the authors;
Leaved as is
L.62: The symbol ... "ith" ... I suggest replacing it with "i-th";
Fixed throughout a paper.
The equation between L.64 - L.65 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
Corrected
The equation (4) should be corrected – “ ….” - what does it mean?
Corrected
In the text of the manuscript should be described, what the symbol (R) means - equations (6) and (7);
Section for Notation added
Line below the equation (8) - symbol ... "jth" ... I suggest replacing it with "j-th";
Corrected
L.100: The indications of “lhs” and “rhs” should be written in brackets - as given in lines (91) and (92);
Corrected
L.106 - 108: The fragment “If the separation sequence …. the value of C” - I treat it as a citation, so it is necessary to give the references;
Changed to emphasis
In the inequality (11), the (+) (-) signs should be on the left and right side of its segment - as in equation (5). In addition, it should be clarified in the text of the manuscript, what means the ratio of “T12”;
Corrected
The inequality: T1 < T12 < T2 < T23 < T3 (p. 5) should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
Corrected
L.109 – 111: The fragment “If the first column …. of next stages” - I treat it as a citation, so it is necessary to give the references;
Changed to emphasis
L.114: The indication of “lhs” should be written in brackets;
Corrected
The equation between L.115 - L.116 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript. This number should be given in L.116a after the symbol (F);
Corrected
The equation before L.117 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
Corrected
L.129: Please check the symbol – (k) or (ki);
Corrected, it is k.
The equation between L.139 - L.140 should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript.
Corrected
L.148a: The indication of “rhs” should be written in brackets;
Corrected
L.149c:The equations should be numbered. This is related to the change in the numbering of subsequent mathematical formulas and appropriate corrections in the text of the manuscript;
Corrected
L.155c: The symbol ... "jth" ... I suggest replacing it with "j-th";
Corrected
L.155d: The equation should be numbered;
Corrected
L.158: The indication of “rhs” should be written in brackets;
Corrected
In my opinion, "Abbreviations" should be removed. They are known or explained in the text of the manuscript (except for LVC).
Removed, added sections for Notation and Indices
Author Response File: Author Response.pdf
Reviewer 3 Report
The comments are included int the "Comments" to the manuscript pdf file.
Comments for author File: Comments.pdf
Author Response
Most of the corrections are marked red in the new revision.
1. No explanation of symbols and units used in the text.
Word "flux" is erronously used, acutally the "stream" is suitable throughout the text.
Corrected
2. The first sentence is not true, this process is well known and studied for many years. If authors devote a bit more effort in background
Corrected
3. These three sentences are not clear and not well explained.
Corrected, clarification added
4. Citation needed.
Changed to "our current paper"
5. Authors assume negligible entropy yet they define the equation (3) below that accounts for that. Some clarification required.
Only the entropy generation due to the mixing is negligible. Other cases are taken into account.
6. What type of energies do authors exactly understand by q+, q- and q?
These are heat streams. It is clarified in a newer revision.
7. (14) is the set of three formulations, the minimum refers to all of them?
This sentence means that one need to select the minimum value from (14).
8. Mass or heat transfer?
The equation (17) expresses the total entropy generation, both for heat and mass transfer. Minor remark is made in a newer revision.
9. Is the VLE calculated only for reboiler (no trays inculded)?
Yes, we consider the VLE only for condenser and reboiler.
10. This rule should be presented in this part in more clear way.
Corrected
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Accept in the present form
Author Response
Thank you for your review.
Reviewer 3 Report
There are still some small typographical errors in the text (indicated in the file).
To be honest - the problem presented is rather simple one and could be a good didactic task for students.
For instance: in the two examples provided the equations are presented in the form of student's script style with all the numbers substituted. It is not typical for scientific articles, but maybe some readers/students would find it helpful.
I wanted to underline that the work is correct and I would accept it as a student's semester project. So my overall impression is that the text is prepared in a teaching student's form, and I doubt a bit if it is really suitable to be published in scientific journal.
There are of course corrections provided by the authors. But in the light of the above I am setting the "Major revision" mark again and I leave the final decision to the Editor to whether to proceed with this manuscript.
Comments for author File: Comments.pdf
Author Response
Every author hopes that his/her result will be someday used as a basis for student projects. The "Results" sections of our paper presents the following new results obtained:
The estimate of the capacity of the binary distillation column is the quadratic function of its energy consumption.
The above-mentioned function is concave and characterized by only two generalized parameters.
We have shown that the efficiency of an irreversible column increase monotonously as a function of the efficiency of a reversible one. The efficiency corresponding to the operating mode with maximum capacity is equal to the half of the reversible efficiency.
Only basing on the statements described above, we deduced the exceptionally simple rule for selection of optimum separation sequence.
We would be glad if dear Reviewer 3 told us who and when used these results for students' projects and if our results are not novel for him, who and where did publish it? We hope that our results will be of use to dear Reviewer 3.
Thank you for minor corrections within the body of the paper.
