Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I found this paper provides a comprehensive review.  The proposed mechanisms partially explain the mineral phases associated with iron in coal ash.  I do have several comments on this study

1. Should diffusion control mechanism be more dominant on a coarse particle? The diffusion of gas takes longer time to transfer through the pores compared to that on a fine particle.    
2. It would be more comprehensive to include discussions on the interactions between pyrite and other forms of iron (for example, siderite and jarosite).  I would suggest the authors modify the title of this paper to reflect the lack of this discussion.  
3. In addition to the analytical methods that the authors mentioned in the manuscript, X-ray photoelectron spectroscopy (XPS) can be a useful tool to evaluate the oxidate states of Fe and S under particular conditions.  
4. The manuscript needs to be revised for minor editorial inconsistency.  For example, lines 642 and 643.  There is no need to start another paragraph here.  

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This MS presents a systematic investigation into the thermal transformation behavior of pyrite in coal, proposing a "competition-coupling mechanism" and constructing a unified phase diagram. The work possesses significant academic value and innovation, and is characterized by a clear structure, substantial data, and coherent logic. The following revisions are recommended to further enhance the manuscript:
1.The abstract should be streamlined, retaining the core logic (Problem-Mechanism -Solution-Significance) while reducing specific data details. It should more explicitly state that the proposed "competition-coupling mechanism" successfully reconciles the long-standing controversies in the literature regarding the wide discrepancies in reported apparent activation energies and contradictory reaction pathways, leading to the construction of a unified phase diagram. Briefly mention the industrial application potential of this diagram as a predictive tool for optimizing combustion systems and controlling sulfur emissions and ash deposition/slagging.
2.The keyword "coal pyrite" should be split into two independent keywords: "coal" and "pyrite". This aligns with academic conventions and improves accuracy in literature retrieval.
3.The statement in the Introduction, "Despite extensive research...", is too general. It is recommended to specify the limitations of previous research more concretely in one or two sentences. For example: "Although considerable research has been conducted, most studies have analyzed pyrolysis and oxidation as isolated processes, failing to deeply reveal their complex interactions under non-equilibrium conditions. This has led to significant disagreements in the understanding of dominant reaction pathways and kinetic parameters."
4.The transition between Section 2 (Thermodynamics) and Section 3 (Kinetics) is somewhat abrupt. To enhance coherence, add a bridging paragraph at the end of Section 2.3 or the beginning of Section 3. For instance: "The aforementioned thermodynamic analysis identifies the stable phases under equilibrium conditions. However, the actual transformation process is kinetically controlled and exhibits far more complex behavior. The following section will re-examine the kinetic data to reveal the origins of the discrepancies between thermodynamic predictions and experimental observations."
5.The use of FactSage software is mentioned, but the specific databases employed are not stated. Please supplement this information, including the suitability of the selected databases (FToxid, FTsulf, FactPS). For example: "The thermodynamic equilibrium calculations were performed using FactSage software (v8.4) and its associated databases (FToxid, FTsulf, and FactPS). These databases cover a wide range of oxides, sulfides, and gaseous species, making them suitable for simulating the behavior of the Fe-S-O system at high temperatures."
6.Optimize Data Presentation in Tables 2 and 3: The content of Tables 2 and 3 is substantial but the format is crowded. It is recommended to simplify or split these tables to highlight key information such as the Eₐ range, controlling mechanism, and critical experimental conditions. Consider adding a summary statement below the tables emphasizing the dependence of the Eₐ values on the experimental conditions.
7.While multiple kinetic models are summarized, there is a lack of comparative discussion. It is suggested to add a paragraph in the summary sections (3.1.4 and 3.2.3) discussing the applicability of the different kinetic models. Explain why different models are applicable under different conditions (e.g., particle size, atmosphere) in the context of this integrated analysis, as this itself is a kinetic manifestation of the "competition-coupling mechanism".
8.The conclusion is comprehensive but could have greater impact. It is recommended to further emphasize the theoretical contribution of this study (e.g., providing a unified theoretical framework that resolves long-standing controversies) and its practical significance (e.g., the constructed phase diagram serves as a predictive tool and provides theoretical guidance for controlling sulfur emissions and ash deposition/slagging in clean coal utilization technologies).

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,
The authors' self-citation should support the Review manuscript because it demonstrates the authors' research expertise in the relevant fields.
Since the self-citation of authors does not support the Review Manuscript, my recommendation is REJECT. 
If you import some relevant self-citations, I will reconsider my decision. 

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The review covers a remarkable range of studies (thermodynamic modeling, experimental kinetics, morphology, and combustion implications) from early work in the 1940s to recent publications. This is extremely comprehensive and well-referenced, indicating substantial effort. With tighter synthesis, better focus on the competition–coupling framework, and improved figure originality, it could become a highly useful review for the field. To make the review impactful, the authors should streamline redundant content, highlight conceptual insights, and critically evaluate controversies rather than merely restating past work.

1. The manuscript exceeds 35 pages, much of which reproduces literature verbatim. In addition, many figures are “reproduced from” existing publications; the review would be stronger with original schematic summaries illustrating trends, rather than numerous reprinted plots.
2. The review summarizes hundreds of studies but rarely evaluates or contrasts them in depth. A high-quality review should identify why discrepancies exist, which data are more reliable, and how the proposed mechanism resolves contradictions. For example, the “competition–coupling” concept is described narratively but not validated via energy diagrams, rate equations, or comparison to experimental trends.
3. Sections 2 and 3 read like an experimental results paper, presenting individual datasets in detail rather than integrating them into higher-level conclusions. To strengthen the manuscript as a review article, these sections should be condensed and restructured to highlight comparative insights rather than isolated results.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for explaining the connection between your previous research study and the presented review manuscript. Recommendation is to publish.