Structural Characterization of Low-Rank Coals in the Ningdong Coalfield Under the Control of the First Coalification Jump

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have carried out extensive and in depth research on the First Coalification Jump on the low rank coals. The key findings reflects the possibilities of formation of CH₄ and CO₂, degree of metamorphism. 

1. The introduction section is well written and the relevant literature have been discussed.
2. The sample preparation, different experiments conducted on the prepared samples are precisely explained.
3. Can the demineralized base be explained mentioning their effect on coal efficiency/effectiveness? (Table 1)
4. How the C skeleton structure influences the coal structure? (line 199-200)
5. Improve the figure quality (mainly the font sizes) of Figure 3 and 6.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editor,

The manuscript (processes-3660731) entitled ‘‘Structural Characterization of Low-Rank Coals in the Ningdong Coalfield Under the Control of the First Coalification Jump’’ can be published in the Processes after minor revision.

 

My suggestions:

• In line 299-326, The FTIR spectrum of coal is typically divided into four regions: the hydroxyl functional group absorption region (3600-3000 cm^-1), the aliphatic structure absorption region (3000-2800 cm^-1), the oxygen-containing functional group region (1800-1000 cm^-1), and the aromatic structure region (900-700 cm^-1).

Please reorganize the functional group zones: The FTIR spectrum of coal is typically divided into four regions: the hydroxyl functional group absorption region (3700-3120 cm^-1), the aliphatic structure absorption region (3000-2800 cm^-1), the oxygen-containing functional group region (1800-1000 cm^-1), and the aromatic structure region (900-700 cm^-1, out of plane bend).

The aromatic C-H (sp²) vibration frequency comes in the range 3000-3120 cm^-1, so let's pay attention to the area calculation after noting this in the main text. Let's support these peak values with the reference I suggested.  Applied Catalysis A: General, 464, 322-331, 2013. As far as I understand, it doesn't affect your calculations much. 

• In line 433-435, the numbers 2 and 3 in sp2 and sp3 should be upper indices or superscript (sp² and sp³).
• In line 577, The FCJ occurs at approximately 350 °C. If you increase FCJ temperature more, how much the amount of oxygen decreases, i.e. from about 20% in the composition to how much?
• In Table 4, you have started each chemical with a capital letter, then capitalize the first letter of ash (Ash).
• When we examine Table 7, we see a high proportion of pyridine (11.74%) and protonated-pyridine (17.99%), but when we examine Figure 11a, we do not see it separately in the fitting curve.

 

 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The Manuscript is thematically suitable for the Processes Journal. The paper presents the results of detailed studies which provides a theoretical foundation for the evolution of microstructures before and after FCJs under the same geological conditions.

However, I have the following major comments:

1. Introduction section: there is no information about the novelty of the research.

2. Materials and Methods section:

a) There is no information about the seams from which samples were taken. There is no map with the sampling points.

b) How were the samples taken, what were their masses, how were they averaged. Were these representative samples?

c) How the samples were prepared for microscopic observation?

d) Too general information about reflectance experiments and microscopic component analysis, providing a standard is definitely not enough. No information is provided about measurement uncertainties and accuracy of other methods.

3. Results and Discussion section: no photos from microscopic observations.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The article has been revised according to my comments.