NO Removal by Plasma-Enhanced NH3-SCR Using Methane as an Assistant Reduction Agent at Low Temperature
, Yanghaichao Liu 1,2, Heng Wei 3, Renxi Zhang 1,2,*, Gang Luo 1,2,*, Huiqi Hou 1, Shanping Chen 4 and Ruina Zhang 4Round 1
Reviewer 1 Report
The authors have presented a very interesting work for the use of methane as an assisting agent in plasma enhanced NH3 -SCR reaction. The results presented in this manuscript clearly demonstrate that the activity of DBD-NH3-SCR for NOX conversion significantly increase at low temperature when methane was used as a assisting reductant. This manuscript is very well organized and easy to follow. This manuscript contribute towards the development of catalytic materials for NOx conversion reaction and will draw attention from a vast number of researchers working in this field. I would recommend the publication of this article in the current form.
Author Response
Response: Thank you so much for your quick response and valuable comments on our work.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Reviewer’s Report
NO removal by plasma-enhanced NH3-SCR using methane as an assistant reduction agent at low temperature
Manuscript ID: applsci-540715
In this manuscript, the authors have investigated the effect of CH4 as a reducing agent in plasma-assisted NH3-SCR. The results presented in the manuscript could be publishable after the following revisions.
1) Authors should abbreviate the DBD in the abstract.
2) The experimental procedures should be described as completely as possible. For example, details of catalyst pretreatment before the reaction.
3) At page 1, lines 35-36; “A high reaction temperature leads to expensive energy consumption and other problems”. Authors should provide the appropriate references for this statement.
4) What is “ABS” used on page 2, line 52?
5) Authors should provide the N2 selectivities in the DBD-SCR process.
6) Did you check the long-term performance and/or SO2/H2O tolerance in DBD-SCR process?
7) There are several typo/grammatical errors that should be minimized before publication.
8) The following papers on SCR catalysis would be a great help to the authors of this manuscript in order to further interpret the results and should be cited.
Catalysts 9 (2019) 349; Industrial & Engineering Chemistry Research 57 (2018) 16615-16621
Author Response
In this manuscript, the authors have investigated the effect of CH4 as a reducing agent in plasma-assisted NH3-SCR. The results presented in the manuscript could be publishable after the following revisions.
Point (1): Authors should abbreviate the DBD in the abstract.
Response: Thank you so much for your kindly comments on our manuscript. We have rectified the abbreviation in the manuscript (Track changed version: line 24 on page 1).
Point (2): The experimental procedures should be described as completely as possible. For example, details of catalyst pretreatment before the reaction.
Response: Thanks a lot for your serious suggestions. We have supplemented more experiment details in experimental part (Track changed version: line 67, line 71, line 78, line 82, line 85 and line 90 on page 2, line 94 on page 3).
Point (3): At page 1, lines 35-36; “A high reaction temperature leads to expensive energy consumption and other problems”. Authors should provide the appropriate references for this statement.
Response: Thank you so much for your suggestions and serious thinking. We have supplemented new Ref [28] and Ref [29] to support the statement of “A high reaction temperature leads to expensive energy consumption and other problems” (Track changed version: line 36 on page 1, line 324 and 327 on page 10).
Point (4): What is “ABS” used on page 2, line 52?
Response: Greatly thank you for your serious thinking. The “ABS” used on page 2 is “Ammonium Bisulfate” and we have supplemented the full name of ABS in the manuscript (Track changed version: line 53 on page 2).
Point (5): Authors should provide the N2 selectivity in the DBD-SCR process.
Response: Thank you so much for your rigorous thinking and comments on our manuscript. We had formerly researched the DBD-SCR process without reducing gas and the relevant research results had also been published in “Plasma Science and Technology” [Plasma Sci. Technol. 20 (2018) 014002 (8pp)]. According to this experiment result, when the O2 concentration was 8% and voltage was 4 kV, the N2 selectivity of DBD-SCR process was only 10.1%. Because the main point of the manuscript submitted to Applied Science focused on the effect of using CH4 as assistant reduction agent for NH3-DBD-SCR process, the results about DBD-SCR process without reducing gas was not considered in this work.
Point (6): Did you check the long-term performance and/or SO2/H2O tolerance in DBD-SCR process?
Response: Greatly thanks for your rigorous thinking and suggestions. In this research, the total discharge time of this hybrid system exceeded 10 hours and the repeated experiments were also performed. All the results showed that the steady performance of DBD-NH3-CH4-SCR system was kept.
The SO2/H2O tolerance in DBD-NH3-CH4-SCR system is indeed an important topic. The relevant research work has been investigated as an independent subject and the relevant experiment results along with the catalyst modification work would be written as a new paper to be submitted. Therefore, the work abut SO2/H2O tolerance in DBD-NH3-CH4-SCR system is not included in this manuscript.
Point (7): There are several typo/grammatical errors that should be minimized before publication.
Response: Thanks for your rigorous comments and suggestions. We have modified several typo/grammatical errors in the manuscript (Track changed version: line 50 on page 2, line 147 on page 5, line 164 and line 171 on page 6, line 225 on page 8, line 285 on page 9).
Point (8): The following papers on SCR catalysis would be a great help to the authors of this manuscript in order to further interpret the results and should be cited.
Catalysts 9 (2019) 349; Industrial & Engineering Chemistry Research 57 (2018) 16615-16621
Response: Thanks a lot for your serious comments and also thanks you so much for providing such helpful information for me. We have read these papers carefully and thought that it is really an interesting topic and wonderful prospect for our work. We have added the two articles to the references and supplemented relevant expressions in the manuscript (line 37 on page 1, line 331 and 333 on page 10).
Author Response File: Author Response.pdf
Reviewer 3 Report
The work is interesting and well written. I would suggest only removing the acronyms from title and abstract.
Author Response
Comments to the Author：
The work is interesting and well written. I would suggest only removing the acronyms from title and abstract.
Response: Great thanks for your rapid response and kindly suggestions. We have modified the relative expressions in the abstract (line 19 on page 1).
Author Response File: Author Response.pdf
Reviewer 4 Report
The manuscript titled “NO removal by plasma-enhanced NH3-SCR using methane as an assistant reduction agent at low temperature” by Zhao et al. studied NO removal using DBD reactor with the presence of NH3-SCR and NH3-CH4-SCR . It is found that NOx conversion factor was enhanced with the addition of CH4 into DBD-NH3-SCR at low temperatures (below 348 K) with O2 concentration exceeding 2%. Some products were identified using FTIR and possible mechanism for NO removal was proposed.
This manuscript needs some improvements, below is my comments:
Section 3.2, Product analysis
Did authors try to find other products, eg. : N2O3, N2O4 and N2O5?
Section 2, definition of N2 selectivity.
I would suggest authors revise denominator “ NOinlet + NH3inlet − NOoutlet − NH3inout” into denominator “ NOinlet + NH3inlet ” , “NH3inout ” into “NH3outlet”.
Typo
Page 8, line 215, CH4 + 2NO + O2 → N2 + H2O + CO2. It should be replaced by CH4 + 2NO + O2 → N2 + 2H2O + CO2
Page 10, reference 11, Burch R, 2004. “Knowledge and Knowâ (?) …
Pls. see an attachment as well.
Author Response
Comments to the Author：
The manuscript titled “NO removal by plasma-enhanced NH3-SCR using methane as an assistant reduction agent at low temperature” by Zhao et al. studied NO removal using DBD reactor with the presence of NH3-SCR and NH3-CH4-SCR. It is found that NOx conversion factor was enhanced with the addition of CH4 into DBD-NH3-SCR at low temperatures (below 348 K) with O2 concentration exceeding 2%. Some products were identified using FTIR and possible mechanism for NO removal was proposed.
This manuscript needs some improvements, below is my comments:
Point (1): Section 3.2, Product analysis Did authors try to find other products, eg: N2O3, N2O4 and N2O5?
Response: Thanks a lot for your rigorous thinking and comments on our manuscript. We had also tried to detect other NOX in products, but N2O3, N2O4 and N2O5 was not identified. I think that the possible reasons are N2O3 and N2O4 are decomposable compounds with the conversion products of NO and NO2. In addition, N2O5 might react with H2O to yield NO3-. Therefore, the products of N2O3, N2O4 and N2O5 in DBD-NH3-CH4-SCR system were not monitored.
Point (2): Section 2, definition of N2 selectivity.
I would suggest authors revise denominator “NOinlet + NH3inlet − NOoutlet − NH3inout” into denominator “NOinlet + NH3inlet”, “NH3inout” into “NH3outlet”.
Response: Great thanks for your serious thanking and suggestions. We have amended the definition of N2 selectivity and relative data in manuscript (line 104 on page 3, line 191, line 196 and line 197 on page 7).
Point (3):
Typo
Page 8, line 215, CH4 + 2NO + O2 → N2 + H2O + CO2. It should be replaced by CH4 + 2NO + O2 → N2 + 2H2O + CO2
Page 10, reference 11, Burch R, 2004. “Knowledge and Knowâ (?) …
Response: Sorry for our carelessness and thanks a lot for your serious suggestions. We have modified the typo in the manuscript (line 225 on page 8, line 285 on page 9).
Author Response File: Author Response.pdf
