Nozzles for Spraying Coal–Water Fuels

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The review provides the analysis of eight variants of coal-water fuel nozzles presented in modern literature to show the influence of their designs on the principle and conditions of operation like characteristics of spraying.

Resulting that that nozzles for spraying coal-water fuel with quasi-internal mixing of fuel and spraying agent are the most attractive from the point of view of performance efficiency.

It should be interesting to complete with tests and direct measurements to make the comparison more objective being made under same conditions and with similar process for measuring the results.

 

The Mistyping / mistakes to be fixed before publishing final version:

- page 4, line 131: "fuel nozzles in the" instead of "fuel nozzles In the"

- page 8, Figure 9: "CWF" insterad of "CWP" in the text of the drawing

 

Author Response

The authors thank the reviewers for paying attention to our manuscript. The authors tried to take into account all the criticism when reprocessing the manuscript. More detailed answers to all questions and comments are provided below. The corresponding changes and additions have been made to the text manuscript. The authors also express their gratitude to the editor of the Applied Sciences.

Reviewer 2 Report

Comments and Suggestions for Authors

This paper reviews the modern devices for spraying coal-water fuels, it will be useful for researchers studying the processes of spraying coal-water fuels. But, as a review paper, the usage of CWF should be introduced more in detail, like in gasifier. Other comments are listed below.

1. Introduction is too long, and the shortcomings of previous research results are not reflected.

2. The introduction of the part “CWF injectors” and “Generalization of information” is very confusing. In my opinion, the four criteria should be introduced clearly.

Author Response

The authors thank the reviewers for paying attention to our manuscript. The authors tried to take into account all the criticism when reprocessing the manuscript. More detailed answers to all questions and comments are provided below. The corresponding changes and additions have been made to the text manuscript. The authors also express their gratitude to the editor of the Applied Sciences.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

This paper examines new devices used for spraying coal-water fuels. These devices can either create injectors for these fuels or modify existing boilers to use them. However, there are some important issues that need to be addressed.

·                 The authors discuss factors such as the high viscosity of CWF, resulting in larger droplets after spraying, and the significant ignition delay times due to the presence of water in CWF drops. Can you explain why such high viscous CWF mixture are used.

·                 The passage highlights that the presence of fine coal in CWF can lead to premature wear of the nozzle channels, primarily impacting the specific areas where this wear occurs and causing an increase in the diameter of the outlet nozzle. Simultaneously, it asserts that the fuel channels of the injectors may become obstructed by large coal particles or CWF agglomerates. Then, how can we determine the optimal particle size in this context.

·                 Elaborate further on the significance and potential applications of studying the behavior of different variants of coal-water fuel nozzles in the literature. Also, further highlights the novelty to signify the importance of study.

·                 Figure 3. Nozzle for CWF spraying with ceramic orifice and figure 5 Pneumatic nozzle for spraying slurry fuels: increasing the font size of the diagram for better visibility and clarity.

·                 There are multiple typographical errors and grammatical mistakes present in the manuscript, which require correction.

·                 What criteria do the authors use to determine whether certain design features of the nozzle type are considered simple or complicated? Please explain the specific criteria employed for this classification.

·                 The authors used several criteria to access the efficiency of CWF spraying devices such as simplicity of design, susceptibility to fuel channel clogging, durability erosion wear of the nozzle, dispersion of the jet. Additionally, the material used in the construction of these devices also be an important factor that must be considered. However, the authors do not include this very important aspect. Discuss whether or not the material is a significant criterion and also its potential impact on the device's performance and durability.

Comments on the Quality of English Language

As above

Author Response

The authors thank the reviewers for paying attention to our manuscript. The authors tried to take into account all the criticism when reprocessing the manuscript. More detailed answers to all questions and comments are provided below. The corresponding changes and additions have been made to the text manuscript. The authors also express their gratitude to the editor of the Applied Sciences.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The paper provided a review to assess various coal-water fuel spraying devices based on criteria like design simplicity (A), susceptibility to fuel channel clogging (B), resistance to nozzle channel erosive wear (C), and jet dispersion (D). The study recommends coal-water fuel nozzles with quasi-internal mixing for efficient operation, especially when combined with refractory or ceramic materials and a large fuel channel diameter, which reduces erosion and clogging risks while maintaining fine droplet dispersion. It emphasizes that narrowing the fuel channel is an unfavorable design choice. This analysis benefits researchers studying coal-water fuel spraying processes and designers working on coal-water fuel injectors or boiler conversions.

The paper overall showed a good format in terms of organization and writing. To accept it as a journal paper, the following points are listed for authors to consider.

Introduction

The introduction provided a comprehensive overview of coal-water fuel (CWF), its advantages, and the challenges associated with its combustion. It effectively sets the stage for the subsequent discussion on CWF spraying and burning. The use of citations to reference sources lends credibility to the content. However, the introduction could benefit from a more concise and structured presentation to enhance readability. Consider breaking it into smaller paragraphs, each focusing on a specific aspect of CWF, its advantages, and the combustion challenges. This would make the information more digestible for the reader.

There are a couple points that could be improved or clarified:

·         The introduction sets the stage for discussing the challenges of CWF combustion but doesn't explicitly state the research's primary goal or the problem it aims to address. Adding a sentence that clearly defines the study's objective could provide better guidance for the reader

·         The introduction uses terms like "CWF" and "coal-water fuels." Ensuring consistency in terminology will enhance clarity.

·         While the introduction offers valuable information, it could be further improved by organizing the information into distinct sections, such as "Challenges in CWF Combustion" and "Objective of the Study." This would create a more structured flow. Just a suggestion.

CWF injector

Overall, the section offers valuable insights into CWF injectors but may require some minor revisions to enhance clarity, avoid repetition.

·         The text sometimes repeats certain disadvantages, like the narrowing of the fuel channel or the potential for clogging. While it's important to emphasize these issues, too much repetition can be redundant. Consider summarizing common issues across the various injector designs.

·         The descriptions of injector designs are well-presented, but including more technical specifications, such as flow rates, operating pressures, and materials used, could provide a more comprehensive understanding of each injector's capabilities and limitations. This additional technical information can help researchers and engineers make more informed decisions when choosing injectors for specific applications.

·         The concept of hydraulic resistance is mentioned in the context of narrowing fuel channels. Including quantitative assessments of hydraulic resistance for each injector type would help engineers evaluate the impact on overall system performance.

Generalization of information

This section provides a detailed analysis of various CWF spraying devices based on several key criteria. It offers valuable insights into the strengths and weaknesses of each design. Here are some comments and considerations:

·         While the assessment criteria (A, B, C, D) are informative, consider adding some quantitative data where applicable. For example, when discussing the size of fuel channels, include the actual dimensions. Providing numerical values can make the assessment more concrete.

·         How much energy is required for spraying, and how does it affect the overall energy balance in a combustion system? Energy efficiency is a crucial consideration in real-world applications.

·         The potential challenges or limitations associated with each design may be worth to be discussed. This could include conditions where a specific design might not be suitable or areas where further research is required.

Conclusion

The conclusion summarizes the findings of the analysis and highlights key points effectively. It provides a clear takeaway regarding the most efficient design of CWF nozzles, and it emphasizes the importance of key factors in their operation.

While the conclusion summarizes what has been learned from the existing literature, it might also briefly suggest directions for future research. This can provide additional value to readers who may be interested in advancing the field.

 

 

 

Comments on the Quality of English Language

The paper overall showed a good format in terms of writing. 

Author Response

The authors thank the reviewers for paying attention to our manuscript. The authors tried to take into account all the criticism when reprocessing the manuscript. More detailed answers to all questions and comments are provided below. The corresponding changes and additions have been made to the text manuscript. The authors also express their gratitude to the editor of the Applied Sciences.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

It can be accepted now.

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript revised according to suggestions.