Low-Temperature NH₃-SCR Technology for Industrial Application of Waste Incineration: An Overview of Research Progress

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The presented manuscript is a complete, integral work, which has a clearly formulated purpose and fairly unambiguously described conclusions. The work can be useful to specialists in the field of knowledge application. However, there are a number of points, the correction of which can improve the perception of the work:

- Questions about the quality of the English language are placed in a separate section

- Line 41: "... non-selective catalytic reduction (SNCR) and selective catalytic reduction (SCR). SCNR is used to ..." - SCNR or NSCR? Anyway, the acronims are not used no longer across the manuscript

- Table 1: units of mg/Nm³ may be placed into the heading of the table.

- Figure 2 is veeeery difficult to read upside down

- Line 116: "Mn⁴⁺/Mn was relatively stable" - Mn⁴⁺/Mn⁰ or Mn⁴⁺/Mn³⁺? Or what? It should be mentioned correctly

- Figure 3b: H₂O should have symbol 2 as subscript for bottom right part

- Table 2: Units of mg/m³ should be placed from the bottom line of table into heading, near SO₂

- By the way, are the units mg/m³ and mg/Nm³ mean identical things?

- "with high content of H2O and SO2 under or below 180℃." - what do you mean "under or below" if the Figure 7 shows data for points 175 and 200?

- The image quality in Figure 10 needs to be greatly improved. in this form, it is absolutely unacceptable

- line 151 and 417 - why Vanadium and not vanadium?

In general, I had no questions about the scientific component of the manuscript, so I recommend a minor revision. Fortunately, the genre of the review does not impose so many restrictions on the authors - it is enough just to impartially summarize everything known at the moment

Comments on the Quality of English Language

I strongly recommend that you give the manuscript to either a native speaker or a person with extensive experience of communicating in English. There are many points in the work that seem to be understandable in meaning, but stylistically and syntactically incorrect.

Many subscripts in formulas are not specified as subscripts.

Line 417 "Vanadium-based catalysts, Mn-based catalysts, Ce-based catalysts, etc." I think it would be better to write "V-based, Mn-based, and Ce-based catalysts..."

Author Response

Response to reviewers,

We gratefully value all the professional comments from the Reviewers. The manuscript has now been carefully revised according to your suggestions. The detailed responses to your comments are listed below point by point. The corresponding revisions on the manuscript has been highlighted in the file of “catalysts-327499-revised”.

Response to reviewers’ comments

Reviewer # 1

The presented manuscript is a complete, integral work, which has a clearly formulated purpose and fairly unambiguously described conclusions. The work can be useful to specialists in the field of knowledge application. However, there are a number of points, the correction of which can improve the perception of the work:- Questions about the quality of the English language are placed in a separate section.

Response: Thanks for your suggestions. We have inspected and revised spelling mistake, words choice errors, grammar errors, etc. And marked them in the revised paper. We believe that the revised manuscript has been improved and meets approval standards. 

Question 1. Line 41: "... non-selective catalytic reduction (SNCR) and selective catalytic reduction (SCR). SCNR is used to ..." - SCNR or NSCR? Anyway, the acronims are not used no longer across the manuscript

Response: Thanks for your comments! Sorry about the wrong spelling. We corrected it as “SNCR is used to…”

 

Question 2. Table 1: units of mg/Nm3 may be placed into the heading of the table.

Response: Thanks a lot! We placed unit of mg/m³ into the heading of the table.

Emission of flue gas	GB 18485-2014 (mg/m3)	New facilities in Shenzhen (mg/m3)	Existing facilities in Shenzhen (mg/m3)
Total dust	20	8	10
Organic matter as total C	/	10	10
CO	80	30	50
NOx	250	80	80
SO2	80	30	50
HCl	50	8	10
HF	/	1	1
Hg	0.05	0.02	0.05
Total Cd, Ti	0.1	0.04	0.05
Total Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V	1.0	0.3	0.5
PCDD/PCDF(TEQ-Vaule) doixin	0.1	0.05	0.05

 Question 3. Figure 2 is veeeery difficult to read upside down

Response: Thanks a lot for your comments! Sorry about the unsuitable figure, we corrected this figure.

 

Question 4. Line 116: "Mn4+/Mn was relatively stable" - Mn4+/Mn0 or Mn4+/Mn3+? Or what? It should be mentioned correctly

Response: Thanks a lot for the comments! We totally agree with your suggestion. We correct it as: “And content of Mn⁴⁺/Mn⁴⁺+Mn³⁺+Mn²⁺ was relatively stable, which decreased the poisoning of manganese sulfate and manganese sulfite.” 

Question 5. Figure 3b: H2O should have symbol 2 as subscript for bottom right part.

Response: Thanks a lot for the comments. We have corrected this problem. “H₂O” was changed to “H₂O” in figure 3b.

 

Question 6. Table 2: Units of mg/m3 should be placed from the bottom line of table into heading, near SO2

Response: Thanks a lot for the comments. Unit of the concentration of SO₂ in other references refers to ppm, and unit of the concentration of SO₂ in reference 45 refers mg/m³. So we convert the Units of mg/m³ to ppm about reference 45. And unit of ppm was placed at heading of Table 2, near SO₂.

Catalyst	Temperature (℃)	SO2 (ppm)	NOx conversion	Notes	Refs
C-O2-MF-O2 Mn/Fe =1:0	150	50	60%	calcined under two-stage air atmosphere	[30]
CoMn2O4/Ce0.5Ti0.5Ox	150	50/100/150	90%		[31]
Mn-Ce-Sb0.2/TiO2	150	800	81%		[32]
Mn0.6Ce/GAC−CNTs	150	50	93%	GAC, CNTs	[33]
Mn-BTC-335℃ MOF nanorod	150	100	60%		[34]
MnFeNb0.2Nd0.1Ox nanobelt	120	100	54%	electrospinning method	[35]
Ce-Ti/MnO2 Dual single-atom	150	50	90%	ball-milling and calcination	[36]
MnCe-N	100-350	250	90%	MnCe nanowire aerogel	[37]
MnSb0.156/PG	150	200	80%	Mn-Sb0.156/palygorskite	[38]
NixMn3-xO4/T	150	200	80%	carbonaceous
CeO2/CNTs-GAC	150	50	89%	Wet impregnation method	[39]
Ce-MnO2	150	250	70%	hydrothermal method	[40]
Mn3O4@GA	160	50	80%		[41]
Mn-Fe-Ce-Al-O	100	50	80%	Monolithic catalyst	[42]
Mn2NiO4-CP	125	150	60%	co–precipitation (CP) method	[43]
Mn(2)Ni(1)Ox-UHHS	125	50	75%	Urea hydrolysis hydrothermal synthesis	[44]
Mn-Fe-2/γ-Al2O3	150	87	84%	wet impregnation method	[45]

 Question 7. By the way, are the units mg/m3 and mg/Nm3 mean identical things?

Response: Thanks a lot for the question. Sorry for some misunderstandings about the unit here. We think the meaning of units mg/m³ and mg/Nm³ are same in this manuscript. The unit mg/Nm³ was used in Table 3, which means the concentration of dry flue gas under standard condition. The unit mg/Nm³ was usually used in industrial application compared with the concentration of flue gas under working condition. The unit mg/m³ used in the Table 2 still means the concentration of dry flue gas under standard condition in lab experiments. And other positions mentioned mg/m³ still means the concentration in actual application. Consequently, We corrected the unit mg/Nm³ as mg/m³ according to the original standard article avoid making misunderstandings.

Emission of flue gas	GB 18485-2014 (mg/m3)	New facilities in Shenzhen (mg/m3)	Existing facilities in Shenzhen (mg/m3)
Total dust	20	8	10
Organic matter as total C	/	10	10
CO	80	30	50
NOx	250	80	80
SO2	80	30	50
HCl	50	8	10
HF	/	1	1
Hg	0.05	0.02	0.05
Total Cd, Ti	0.1	0.04	0.05
Total Sb, As, Pb, Cr, Co, Cu, Mn, Ni, V	1.0	0.3	0.5
PCDD/PCDF(TEQ-Vaule) doixin	0.1	0.05	0.05

 Question 8."with high content of H2O and SO2 under or below 180℃." - what do you mean "under or below" if the Figure 7 shows data for points 175 and 200?

Response: Thanks a lot for the question. Apologize for this unsuitable sentence for this article in Figure 7. The meaning we wanted to express is that the NO conversion of catalysts was not satisfied when the content of H₂O over 10 vol%. We corrected this part as: “Experiments indicated that NO conversion of MnO_x-CeO_x catalysts did not change line-arly with temperature, and H₂O alleviated SO₂ poisoning effect under 100℃, which was opposite to NO conversion under 150℃. Combined with mechanism analysis, they pro-posed poisoning of H₂O and SO₂ was related to temperature, and hydroxyl species facil-itated more sulfite species, which was beneficial to preserve Lewis acid sites and for-mation of nitrites for high catalytic performance. However, 15 vol%H₂O still caused sharp decrease in NO conversion, and obtained 40% in the following 8 h.” 

 

Question 9. The image quality in Figure 10 needs to be greatly improved. in this form, it is absolutely unacceptable.

Response: Thanks a lot for the comments. We modified the figure 10 with higher image quality.  

 

Question 10. line 151 and 417 - why Vanadium and not vanadium?

Response: Thanks a lot for the comments. We changed “Vanadium” to “vanadium” in line 151 and 417.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer’s Comments

The authors summarized catalytic properties for the application of NH3-SCR. I think that the manuscript should be modified for reader-friendly before the publication.

 

Questions and Comments

 

1. Line 18, you used the abbreviated term “PCDD/Fs” without explanation. Please write the actual term when it is first described.
2. Line 30, the same with the above regarding “GB18485-2014”. What is this? Please carefully read your manuscript again and modify the term without explanation.
3. Fig. 3 D, I couldn’t find the explanation on this figure. What do you want to explain?
4. Fig. 9 A, what is the reason for the catalysts showing durability even at elevated H2O concentration at 175°C?

Author Response

Response to reviewers,

We gratefully value all the professional comments from the Reviewers. The manuscript has now been carefully revised according to your suggestions. The detailed responses to your comments are listed below point by point. The corresponding revisions on the manuscript has been highlighted in the file of “catalysts-327499-revised”.

Reviewer # 2

The authors summarized catalytic properties for the application of NH3-SCR. I think that the manuscript should be modified for reader-friendly before the publication. 

 

Question 1. Line 18, you used the abbreviated term “PCDD/Fs” without explanation. Please write the actual term when it is first described.

Response: Thanks a lot for your comments. According to your suggestion, we added the explanation about the abbreviated term “PCDD/Fs”. We corrected it as “polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs).” 

 

Question 2. Line 30, the same with the above regarding “GB18485-2014”. What is this? Please carefully read your manuscript again and modify the term without explanation.

Response: Thanks a lot for the comments and suggestions. Apologize for making confusion for reading and understanding. We added the explanation about this term as: “(GB18485-2014 ( a standard for pollution control on the municipal solid waste incinera-tion in China, Table 1)”. Also, we explained another standard “SZDB/Z 233-2017” with “one of local standards in Shenzhen, China,”.  

 

Question 3. Fig. 3 D, I couldn’t find the explanation on this figure. What do you want to explain?Response: Many thanks for the comments. Apologize for making confusion for reading and understanding. We added right explanation about Fig 3D, reference 29: “V₂O₅/TiO₂-SiO₂-MoO₃ catalysts was synthesized for NH₃-SCR experiments. FT-IR spectra of used catalysts exhibited peaks at 975, 1042 and 1136 cm-1, and intensities increased at 160℃ compared with catalysts in 200℃ because of the poisoning of SO₂”

 

 Question 4. Fig. 9 A, what is the reason for the catalysts showing durability even at elevated H2O concentration at 175℃?

Response: Thanks a lot for the comment. According to the experimental results, the effect of water vapor became less when the temperature was increased over 175℃, indicating water vapor inhibition was negligible when the temperature became higher and closed to 200℃. The XRD analysis indicated that the catalysts of low crystallinity or high dispreads, which improved Low-temperature NH₃-SCR performance. Also, the dominate active phase is hematite(α-Fe₂O₃) and Mn₃O₄, which benefited the absorption of NH3 and E-R reaction of low-temperature NH₃-SCR. It has been proved that the similar catalysts without PTFE could achieve 90% around catalytic performance under 175℃^[1].[1] Putluru, S. S. R., Schill, L., Jensen, A. D., Siret, B., Tabaries, F., & Fehrmann, R. Mn/TiO₂ and Mn-Fe/TiO₂ catalysts synthesized by deposition precipitation—promising for selective catalytic reduction of NO with NH₃ at low temperatures. Applied Catalysis B: Environmental, 2015, 165, 628-635.

Author Response File: Author Response.pdf