Efficiency Separation Process of H2/CO2/CH4 Mixtures by a Hollow Fiber Dual Membrane Separator
, Pei Gao 1, Yan Dai 1,2, Xuehua Ruan 1, Xiaobin Jiang 1, Xuemei Wu 1, Yuanxin Fang 1 and Gaohong He 1,2,*
Round 1
Reviewer 1 Report
In this manuscript authors have designed and manufactured a hollow fiber dual membrane separation equipment integrated polyimide (PI) membrane and polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membrane for the separation of the mixture of gases H2 / CO2 / CH4. They studied the effects of stage cut, operating temperature, operating pressure, and membrane area ratio on separation performance of dual membrane separator in comparison to single membrane separator. Manuscript is written well and I believe it will be interest to readers.
Author Response
Dear Reviewers and Editors,
We appreciate for Editors/Reviewer’s warm work earnestly, and thank you for your encouragement and recognition of our research work. We tried our best to improve the manuscript and made some changes in the manuscript. We hope that the revised version of
the manuscript is more acceptable for publication in your journal.
Response to Reviewer 1 Comments
Rewritten the introduction to make it more logical in its flow. In the fourth paragraph of the “Introduction” (lines 57-78 of page 2 in the manuscript), the development of the mathematical model and experimental research were first discussed. Then introduced the research of the dual membrane contactor. At last, put forward the area that needed to be supplemented and improved.
Re-explained the effects of operating temperature on the performance of PI membrane and PDMS/PEI membrane. H2, CO2 and CH4 have different diffusion activation energy or apparent activation energy, resulting in different sensitivity to temperature. In PI membrane, the diffusion activation energy of CO2 is higher than that of H2, so at high temperatures, the CO2 permeation rate increased more. In PDMS/PEI membrane, the apparent activation energy of CO2 is lower than that of H2, so the CO2 permeation rate did not change much with temperature, but the H2 permeation rate increased significantly. More detailed explanation was added in section 3.2.2, red part. Related references were listed in the text ([25][27]).
Thank you very much for your time and considerations.
I look forward to hearing from you soon.
Yours sincerely
Wu Xiao and co-authors
Reviewer 2 Report
Authors present a hollow fiber dual membrane separator, reporting how its efficiency and general performances are affected by several parameters which are important also in view of an industrial use.
The paper is well written and well conceived and the results are interesting; in my opinion the manuscript is publishable. I have some suggestions for the authors to improve the clarity of the manuscript:
- In the "Materials and Method" section, they should better explain which were the crosslinking agents and the catalysts used for the membrane preparation
- At the beginning of section 3.1 they report that: “PI is glassy, while PDMS is rubbery” (line 153). This should be supported by a reference at least.
- Also first paragraph of section 3.2.2 (lines 184-189) should be improved, since these lines could be better explained.
- Finally, the link between results reported in figure 9 and in table 2 should be explained in more details.
Author Response
Dear Reviewers and Editors,
We would like to thank the respected reviewers and the editor for the rigorous and constructive comments and suggestions.
The manuscript has been revised taking into account all of the helpful comments and suggestion. The details of the comments and their responses are also presented in the following. We hope meet with your approval. And we hope this revision can make our paper more acceptable.
The point to point responses to the reviewer’s comments are listed below this letter.
Point by point responses to the reviewers:
Response to Reviewer 2 Comments
Point 1: In the "Materials and Method" section, they should better explain which were the crosslinking agents and the catalysts used for the membrane preparation.
Response 1: Thank you for your suggestion. Required information on cross-linking agents and catalysts was added in section 2.1. Information on polydimethylsiloxane (PDMS) and i-octane used in the experiment also provided. (Red paragraph in “Materials and Method” section).
Point 2: At the beginning of section 3.1 they report that: “PI is glassy, while PDMS is rubbery” (line 153). This should be supported by a reference at least.
Response 2: Related references have been listed in the text. (line 166, [25] and [26])
Point 3: Also first paragraph of section 3.2.2 (lines 184-189) should be improved, since these lines could be better explained.
Response 3: Re-explained the effects of operating temperature on the performance of PI membrane and PDMS/PEI membrane. H2, CO2 and CH4 have different diffusion activation energy or apparent activation energy, resulting in different sensitivity to temperature. In PI membrane, the diffusion activation energy of CO2 is higher than that of H2, so at high temperatures, the CO2 permeation rate increased more. In PDMS/PEI membrane, the apparent activation energy of CO2 is lower than that of H2, so the CO2 permeation rate did not change much with temperature, but the H2 permeation rate increased significantly. More detailed explanation was added in section 3.2.2, red part. Related references were listed in the text ([25][27]).
Point 4: Finally, the link between results reported in figure 9 and in table 2 should be explained in more details.
Response 4: Fig. 9 presented the influence of membrane area radio (R) on the purity and recovery of dual membrane separator at different feed rate. Table 2 showed the permeation rate and selectivity of PI membrane at a fixed feed rate of 100 ml/min. The relationship between Figure 9 and Table 2 has been explained in detail in the first paragraph of 3.2.4., red part.
Thank you very much for your time and considerations.
Yours sincerely
Wu Xiao and co-authors
Reviewer 3 Report
For the most part this is well written, I think however the introduction should be rewritten to make it more logical, ideas seem to me to be jumbled around. The authors have a problem with English articles and a capable native English-speaking editor could easily resolve this problem. I am going to recommend minor revisions but these changes should be made.
Minor
.. a dual membrane separator has obvious advantages over a single... be careful of your use of articles.
At 25 ℃, a dual membrane separator
I don’t think it is correct to say H2 production plays a key role in IGCC, not in that sense. It is produced but unless the goal is synthesis its production is part of the processes, not key to it. You only shift if you want to produce H2, but for some processes at least that is not the major goal and the shift processes is expensive. I think IGCC is potentially a way to produce hydrogen, not the other way around. The normal way of producing hydrogen is steam reforming of natural gas, not IGCC.
Pg. 2, line 46, 47 rewrite this sentence.
The research on dual membrane… don’t say researchers carried out various studies and then give no references to them. Also, there is a clear break of thought here and you begin to discuss mathematical models, and then the next sentence starts to discuss membrane comparisons?
Rewrite the introduction to make it more logical in its flow.
I don’t regard cm of Hg as an SI unit, check the journal’s requirements here.
Pg. 4, line 139 The stage cut…
The membrane ratio
In membrane separators, membrane performances directly affect the gas separation efficiency. Why do we need such a statement, to me it reads like a motherhood statement, something that is obvious and therefore unnecessary..
and which led to .. and which leads to
Be consistent in your references if you bold the year do it for all references:
Chemical Society Reviews, 2019, 48(10):2783-2828.
Do not change the title of your reference, for reference 19 you have: Ternary gas separation using 2 different membranes, but the paper itself is entitled: Ternary gas separation using two different membranes
This may seem trivial to you but it is quite wrong. Please check all your references.
Author Response
Dear Reviewers and Editors,
We would like to thank the respected reviewers and the editor for the rigorous and constructive comments and suggestions.
We tried our best to improve the manuscript and took into account all of the helpful comments and suggestion. The details of the comments and their responses are also presented in the following. We hope meet with your approval. And we hope this revision can make our paper more acceptable.
The point to point responses to the reviewer’s comments are listed below this letter.
Point by point responses to the reviewers:
Response to Reviewer 3 Comments
Point 1: a dual membrane separator has obvious advantages over a single... be careful of your use of articles.
At 25 ℃, a dual membrane separator
Response 1: Thank you for your attention. Above mistaken are corrected (lines 21-24 of page 1 in the manuscript).
Point 2: I don’t think it is correct to say H2 production plays a key role in IGCC, not in that sense. It is produced but unless the goal is synthesis its production is part of the processes, not key to it. You only shift if you want to produce H2, but for some processes at least that is not the major goal and the shift processes is expensive. I think IGCC is potentially a way to produce hydrogen, not the other way around. The normal way of producing hydrogen is steam reforming of natural gas, not IGCC.
Response 2: Thank you for your attention. This is our mistake. H2 is an important raw material for refineries and a clean energy for IGCC power plants. CO2 recovery is conducive to reducing greenhouse gas emissions. H2/CO2 separation process is an important part in these factories. The advantage of the dual membrane separator is that H2 and CO2 products could be obtained at the same time. Revised the “Abstract” section (lines 14-15 of page 1 in the manuscript) and the first paragraph of the “Introduction” section(lines 35-36 of page 2 in the manuscript).
Point 3: Pg. 2, line 46, 47 rewrite this sentence.
The research on dual membrane… don’t say researchers carried out various studies and then give no references to them. Also, there is a clear break of thought here and you begin to discuss mathematical models, and then the next sentence starts to discuss membrane comparisons?
Rewrite the introduction to make it more logical in its flow.
Response 3: The research progress of the dual membrane separator has been rewritten, the logic of this part has been rearranged, and the annotations of references in the manuscript have been added. In the fourth paragraph of the “Introduction” (lines 57-78 of page 2 in the manuscript), the development of the mathematical model and experimental research were first discussed. Then introduced the research of the dual membrane contactor. At last, put forward the area that needed to be supplemented and improved.
Point 4: I don’t regard cm of Hg as an SI unit, check the journal’s requirements here.
Response 4: Thank you for your attention. This unit is allowed in many journals in related fields. References are as follows:
[2] Merkel, T. C.; Zhou, M.; Baker, R. W. Carbon dioxide capture with membranes at an IGCC power plant. Journal of Membrane Science, 2012, 389,441-450.
[4] Chen, B.; Yang, T.; Xiao, W.; Nizamani, A.K. Conceptual design of pyrolytic oil upgrading process enhanced by membrane-integrated hydrogen production system. Processes, 2019,7,284.
[25] Dai, Y.; Ruan, X.; Bai, F.; Yu, M.; Li, H.; Zhao, Z.; He, G. High solvent resistance PTFPMS/PEI hollow fiber composite membrane for gas separation. Applied Surface Science, 2016, 360,164-173.
[26] Sanders D. F.; Smith Z.P.; Guo R.; Robeson L. M.; McGrath J. E.; Paul D.R.; Freeman B.D. Energy-efficient polymeric gas separation membranes for a sustainable future: A review. Polymer, 2013, 54,4729-4761.
Point 5: Pg. 4, line 139 The stage cut…
The membrane ratio
Response 5: Thank you for your attention. Above mistaken are corrected.
Point 6: In membrane separators, membrane performances directly affect the gas separation efficiency. Why do we need such a statement, to me it reads like a motherhood statement, something that is obvious and therefore unnecessary.
Response 6: Thank you for your attention. The unnecessary sentences have been removed in the manuscript.
Point 7: and which led to .. and which leads to
Response 7: Thank you for your attention. This mistaken was corrected.
Point 8: Be consistent in your references if you bold the year do it for all references:
Chemical Society Reviews, 2019, 48(10):2783-2828.
Do not change the title of your reference, for reference 19 you have: Ternary gas separation using 2 different membranes, but the paper itself is entitled: Ternary gas separation using two different membranes. This may seem trivial to you but it is quite wrong. Please check all your references.
Response 8: Thank you for your attention. All references have been carefully checked, and errors in the titles and format of the references have been revised.
Once again, thank you very much for your comments and suggestions.
I look forward to hearing from you soon.
Yours sincerely
Wu Xiao and co-authors
Reviewer 4 Report
To authors
This paper is very well ready to be accepted for Process journal as showing the separation of H2/CO2. The hydrogen and CO2 are very important for clean and sustain Earth. Therefore, it must be accepted without any consideration.
Sincerely
Chul Ho Park
Author Response
Dear Reviewers and Editors,
We appreciate for Editors/Reviewer’s warm work earnestly, and thank you for your encouragement and recognition of our research work. We tried our best to improve the manuscript and made some changes in the manuscript. We hope that the revised version of
the manuscript is more acceptable for publication in your journal.
Response to Reviewer 4 Comments
Rewritten the introduction to make it more logical in its flow. In the fourth paragraph of the “Introduction” (lines 57-78 of page 2 in the manuscript), the development of the mathematical model and experimental research were first discussed. Then introduced the research of the dual membrane contactor. At last, put forward the area that needed to be supplemented and improved.
Re-explained the effects of operating temperature on the performance of PI membrane and PDMS/PEI membrane. H2, CO2 and CH4 have different diffusion activation energy or apparent activation energy, resulting in different sensitivity to temperature. In PI membrane, the diffusion activation energy of CO2 is higher than that of H2, so at high temperatures, the CO2 permeation rate increased more. In PDMS/PEI membrane, the apparent activation energy of CO2 is lower than that of H2, so the CO2 permeation rate did not change much with temperature, but the H2 permeation rate increased significantly. More detailed explanation was added in section 3.2.2, red part. Related references were listed in the text ([25][27]).
Thank you very much for your time and considerations.
I look forward to hearing from you soon.
Yours sincerely
Wu Xiao and co-authors
