Rapid Estimation of Sulfur Content in High-Ash Indian Coal Using Mid-Infrared FTIR Data

Round 1

Reviewer 1 Report

Very good job. It seems to me that Chapter 2 entitled "Geological setting of the study area" is superfluous. The description of the geological structure of the deposit does not provide significant information on the methods of determining the sulfur content in coals. Without it, the article will also be clear enough. Sufficient information on the sulfur content of Indian coals is given in Chapter 1 (lines 101-111). The information at the beginning of chapter 5 (lines 503 - 513) is also public knowledge and is not the conclusions of the article.

Author Response

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Reviewer 2 Report

The submitted MS entitled „Rapid Estimation of Sulphur Content in High Ash Indian Coal using Mid-Infrared FTIR data” describes the manner of estimation of sulphur content in high ash Indian coals based on numerical modelling. The Authors characterized the coal reserves from India due to their sulphur content. The estimated results were compared with the results obtained from the most popular IR method using CHNS analyser.  Both prediction models FTIR and Quasi-Newton gave satisfying results with a relatively low error level. The Manuscript is written in good English and generally has good logic. The paper contains appropriate chapters. The Authors correspond to their previous work that gives a wider understanding of the general idea of sulphur content estimation. It is evidently an advantage of the paper. 

To improve to MS outcome I can suggest some corrections:

1. Introduction is too long. Authors can consider shortening this chapter to leave only the essential clues.

2. Line 35 – sulphur content is not present, the sulphur can be present not its content

3. Lines 70-72  contain a sudden jump to coke. Previously, the authors were describing the combustion and putting here the coke and pyrolysis needs more clear explanation…first of all it is a different process and these 2 sentences do not fit there at all.

4. Lines 72-77 why is it for?  I suggest removing or rewriting if it is related to sulphur

5. Lines 80- 82 – for example? What regulation? Reference needed

6. From line 83 – are these coals commercial products or coals in seams? It should be clarified here and also in the rest of the MS. It is not understandable if talking about high-ash coals we talk about seam coals or commercial that are often washed (enriched). The coal before it goes to the power plant is washed to remove mineral matter. 

Authors should clarify the samples' character in the chapter of samples and methods chapter.

7.     Line 114 – it is better to use the term Combusted

8. Chapter 3.2 needs rewriting to keep the proper logic. It is a bit chaotic.

9. In table 3 – keep the same decimals

10. Chapter 4.3 is the difficult part of the MS. I would ask the Authors to consider simplifying the description for the readers to be able to follow more easily

Author Response

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Reviewer 3 Report

1. In the ultimate analysis, the size of the powdered samples is 72μm，while in the FTIR spectroscopy the size is 212μm. Whether the sample size will impact the experiment results? More controlled experiments should be conducted to eliminate the influence of the sample size on the results.

2. The FTIR technique has already been used for the determination of the sulfur content in the coal, so it is not a novel method.

3. In the section 4.2, the authors select 14 peaks for the identification of the major sulfur compounds. However, the reasons for why these 14 peaks are selected are not clear. Is it referenced from other studies or concluded by the authors themselves?

4. In Figure7, there is great gap between the SFTIR and SCHNS, taking sample number 14, sample number 20, sample number 42, sample number 105 and sample number 126 for example. The prediction model is not as accurate as the authors describe. The relative error between the prediction model and the experimental value should be presented.

5. Although the result of this paper performs well in highly-ash coals, it maybe not suitable for coals from various worldwide.

 

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Author Response

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Round 2

Reviewer 3 Report

The paper can be accepted without any further changes.