Co-Combustion of Food Solid Wastes and Pulverized Coal for Blast Furnace Injection: Characteristics, Kinetics, and Superiority

Round 1

Reviewer 1 Report

In this paper, the combustion characteristics and kinetics of food solid waste (FSW), pulverized coal (PC) and their mixtures were studied by non-isothermal thermogravimetric method.This provides a new idea for the treatment of food solid waste.This study shows that the combustion characteristics of food solid waste are better than those of pulverized coal, and its calorific value is comparable to that of pulverized coal. Food solid waste can be injected into the blast furnace in place of part of the pulverized coal. Food solid waste is a type of biomass whose combustion produces zero net CO2 emissions. It replaces pulverized coal and can reduce carbon dioxide emissions from blast furnace ironmaking.The article is well written, but some content needs to be revised. It is recommended to be accepted after revisions.
1.The title of Figure 2 should be 'SEM of PC, FSW and their different mixtures'.The name of the mixture should be fully marked in Figure 1 and 2, such as 20%FSW+80%PC.
2.It is recommended to discuss the contents of Table 2 in the main text, such as the difference between the fixed carbon and calorific value of the two fuels.
3.The content of conclusion (3) and (4) is too cumbersome, and it is recommended to simplify the text.
4.The abscissa of Figure 7 should be the mass fraction of FSW in the mixture. In Figure 7, it is not clear which Y-axis the lines and bars belong to, and it is recommended to be clear.

Author Response

Dear editors and reviewer,

Thanks for your kind interest and the considerable reviewer comments about our manuscript “sustainability-1700224”. We are pleased to inform you that these comments have been considered as follows. Also, the revisions have been made in yellow in our new manuscript.

Reviewer # 1:

In this paper, the combustion characteristics and kinetics of food solid waste (FSW), pulverized coal (PC) and their mixtures were studied by non-isothermal thermogravimetric method. This provides a new idea for the treatment of food solid waste. This study shows that the combustion characteristics of food solid waste are better than those of pulverized coal, and its calorific value is comparable to that of pulverized coal. Food solid waste can be injected into the blast furnace in place of part of the pulverized coal. Food solid waste is a type of biomass whose combustion produces zero net CO2 emissions. It replaces pulverized coal and can reduce carbon dioxide emissions from blast furnace ironmaking. The article is well written, but some content needs to be revised. It is recommended to be accepted after revisions.

Question 1: The title of Figure 2 should be 'SEM of PC, FSW and their different mixtures'. The name of the mixture should be fully marked in Figure 1 and 2, such as 20%FSW+80%PC.

Answer: The title of Figure 2 and the name of mixture in Figure 1 and 2 have been revised.

Question 2: It is recommended to discuss the contents of Table 2 in the main text, such as the difference between the fixed carbon and calorific value of the two fuels.

Answer: Differences in fixed carbon and calorific value of the two fuels have been compared in the main text.

‘The fixed carbon and ash content of FSW are lower than that of PC, and the ash content of FSW is only 10.36% of that of PC. The volatile content of FSW is 2.55 times that of pulverized coal, the hydrogen content is 4.32 times that of pulverized coal, and its LHV is slightly higher than that of PC.’

Question 3: The content of conclusion (3) and (4) is too cumbersome, and it is recommended to simplify the text.

Answer: The contents of conclusions (3) and (4) have been simplified, shown in the revised manuscript.

Question 4: The abscissa of Figure 7 should be the mass fraction of FSW in the mixture. In Figure 7, it is not clear which Y-axis the lines and bars belong to, and it is recommended to be clear.

Answer: The abscissa of figure 7 have been revised. The Y-axis of bars and lines are indicated by arrows in the graph.

 

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

Reviewer 2 Report

Manuscript entitled “Co-combustion of food solid wastes and pulverized coal for blast furnace injection: characteristics, kinetics and superiority” submitted by Jian Yang, Zhenying Li, Rufei Wei, Di Zhou, Hongming Long, JiaxinLi, Chunbao Charles Xu, can be considered for  publication in Sustainability Journal, after a major revision.

 

Here is a list of my specific comments:

1. General comment: The utility of this study should be clearly highlighted in the manuscript.
2. Page 1, Abstract: Include in this section the most important experimental results to highlight the importance of this study.
3. Page 1, 1. Introduction: (a) This section should be reorganized. The most important aspects related to this topic should be clearly presented in accordance with the state of art in this field. (b) Add references, when are mentioned studies from literature (see line 35, 42, 49, etc.). (c) At the end of Introduction, the main objectives of this study should be clearly presented.
4. Page 3, line 117: “The industrial analysis standard of FSW…”. Add here the references.
5. Page 5, 3.1 Analysis of physical and chemical characteristics: The results included in this section must be clearly presented and detailed discussed.
6. Page 7, line 214: “According to the TG-DTG curve in Figure 3,…”. These observations should be more detailed discussed.
7. Page 11, line 293: “Since PC absorbs the heat released by…”. The same observation as above.
8. Page 15, 4. Conclusion: This section is too long and should be systematized. Delete (1), (2),…and provide a clear presentation of the most important experimental results and findings included in this study.
9. Page 16, References: The number of references is too low and must be increased.

Author Response

Dear editors and reviewer,

Thanks for your kind interest and the considerable reviewer comments about our manuscript “sustainability-1700224”. We are pleased to inform you that these comments have been considered as follows. Also, the revisions have been made in yellow in our new manuscript.

Reviewer # 2:

Here is a list of my specific comments:

Question 1: General comment: The utility of this study should be clearly highlighted in the manuscript.

Answer: Through the research of this study, the co-combustion characteristics and kinetics of FSW and PC are revealed, which provides a theoretical basis for injecting the mixture of FSW and PC into blast furnace. Because FSW is a kind of biomass, its injection in blast furnace can reduce the carbon dioxide emission of blast furnace ironmaking. The utility of this study has been highlighted in the manuscript.

 

Question 2: Page 1, Abstract: Include in this section the most important experimental results to highlight the importance of this study.

Answer: The importance of this study has been highlighted in the abstract.

‘In general, the combustion performance of FSW is better than that of PC. The mixed injection of FSW and PC can improve the overall combustion efficiency and reduce CO₂ emission in iron-making process.’

 

Question 3: Page 1, 1. Introduction: (a) This section should be reorganized. The most important aspects related to this topic should be clearly presented in accordance with the state of art in this field. (b) Add references, when are mentioned studies from literature (see line 35, 42, 49, etc.). (c) At the end of Introduction, the main objectives of this study should be clearly presented.

Answer: (a) Thank the reviewers for your comments, we have revised the introduction. The introduction is divided into four paragraphs. The first paragraph mainly writes that the combustion of fossil fuels leads to greenhouse gas CO₂ emissions. Biomass energy is an important energy to replace fossil fuels and reduce CO₂ emissions, while food solid waste is an important biomass energy. The second paragraph mainly describes the current situation of the treatment and utilization of food solid waste. The third section introduces the current situation of injecting combustible solid waste into blast furnace, and discusses the research status of injecting FSW. The fourth section introduces the problems existing in the injection of FSW into blast furnace, and puts forward the research content of this paper.

(b) We have added references on lines 35, 42 and 49, the references as following:

‘Vassilev, S.V.; Baxter, D.; Vassileva, C.G. An overview of the behaviour of biomass during combustion: Part I. Phase-mineral transformations of organic and inorganic matter. Fuel. 2013, 112, 391– 449.’

‘Vishakha; Mishra, N.K.; Bhardwaj, N. Biofuels: A Renewable and Sustainable Way to Conserve the Fossil Fuels in India. Invertis Journal of Renewable Energy. 2018, 8(3):151-156.’

‘Xue, M.; Xu, F.F.; Yuan, J.; Zong, P.J.; Wang, B.; Li, J.; Qiao, Y.Y.; Tian, Y.Y. Thermal degradation of food waste by TG-FTIR and Py-GC/MS: Pyrolysis behaviors, products, kinetic and thermodynamic analysis. Journal of Cleaner Production. 2020, 244(C):118713-118713.’

‘Melikoglu, M. Reutilisation of food wastes for generating fuels and value added products: A global review. Environmental Technology & Innovation. 2020, 19.’

(c) We have clearly presented the main objective of this study.

‘In this paper, the co-combustion characteristics of FSW and PC are studied by non isothermal thermodynamic method, and the combustion kinetics of FSW and PC mixture is analyzed by Coats-Redfern calculation. It is expected to provide theoretical support for mixed injection of PC and FSW in blast furnace.’

 

Question 4: Page 3, line 117: “The industrial analysis standard of FSW…”. Add here the references.

Answer: We have added three references as followings:

‘General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. GB/T 28731-2012, Proximate analysis of solid biofuels. Beijing: China Coal Industry Press. 2012.’

‘General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. GB/T 212-2008, Proximate analysis of coal. Beijing: China Coal Industry Press. 2008.’

‘General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. GB/T 31391-2015, Ultimate analysis of coal. Beijing: China Coal Industry Press. 2008.’

 

Question 5: Page 5, 3.1 Analysis of physical and chemical characteristics: The results included in this section must be clearly presented and detailed discussed.

Answer: We have revised this section, and the results has been clearly presented and detailed discussed.

‘The infrared characteristic peaks of FSW and PC have a large difference in peak shape between 900-700 cm^-1, and the peak intensity of PC is higher and the content of C-H bonds is higher. The characteristic peaks of FSW and PC are between 1700-900 cm^-1, indicating that the content of C-O, C=C and C-O-C is high in both. The peak shapes of FSW and pulverized coal between 2970-2860 cm^-1 are basically similar, but the peak intensities are different, and the peak intensity of FSW is larger, indicating that the C-Hn bond content of FSW is high.’

 

Question 6: Page 7, line 214: “According to the TG-DTG curve in Figure 3,…”. These observations should be more detailed discussed.

Answer: We have revised this section, and the observation has been more detailed discussed.

‘From the curves of FSW and PC in Fig. 3, it can be seen that under the constant heating rate of 2.5 K/min, 5 K/min, 10 K/min and 20 K/min, the heating rate will affect the weight loss process of FSW and PC. Due to thermal hysteresis, the TG and DTG curves of FSW and PC shifted to high temperature with increasing heating rate. However, the changing trends of the respective curves of PC and FSW are basically the same. The weight loss process of PC can be divided into two stages. The temperature range of the first stage is in the range of room temperature to 550K, and the weight loss rate in this stage is low. When the temperature exceeds 550K, until the end of the sample combustion, this is the second stage. Due to the combustion of volatile substances in PC, a large amount of heat is released, resulting in the combustion of fixed carbon. When the weight of the PC is not changing, the combustion process ends. The weight loss rate of PC at this stage is relatively large (84%).’

 

Question 7: Page 11, line 293: “Since PC absorbs the heat released by…”. The same observation as above.

Answer: We have revised this section.

‘Since PC absorbs the heat released by the combustion of FSW and increases the reaction rate of PC, FSW promotes the combustion of PC in the fixed carbon stage of the co-firing process. This synergy due to the thermal effect is easily affected by the oxygen concentration and the heating rate, and both low oxygen concentration and low heating rate will weaken the thermal effect.’

 

Question 8: Page 15, 4. Conclusion: This section is too long and should be systematized. Delete (1), (2),…and provide a clear presentation of the most important experimental results and findings included in this study.

Answer: We have revised the conclusion and thank the reviewer for your suggestions

 

Question 9: Page 16, References: The number of references is too low and must be increased.

Answer: The number of references in the paper has been increased, from 22 references to 38 references.

 

The authors are grateful to the reviewers for your kind comments, discussion and recommendations.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

Author Response File: Author Response.docx

Reviewer 3 Report

This paper studied the co-combustion of FSW and coal in TGA, though the objective is utilization in blast furnace, due to the great difference between TGA and the real one, the results are common and the suitability is not substantially validated. More discussion and information are needed to provided before considering acceptance.

1； line 86-106, why not considering the high water content and low heating value of FSW? how to maintain the self heating combustion of FAW to realize 2000 purely burning it? At same time, the reason for impossible pure combustion is not the product is not enough, it is FSW can not meet the pure combustion requirement.

Table 2 please add the water content, air dried basis is not dry basis, there must be water content. if the LHV of FSW is higher than that of coal, how to reduce the water content is more important.

 

2: line 103, actually, the study on mixing combustion of biomass or waste and coal in TGA is too many, what is the main difference between FSW and other biomass or waste? beside blast furnace?

 

3: line 136, only 9 mg sample, how to guarantee the representativeness of the mixing.

4: line 138, how to prove 30ml/min air is enough to delete the limitation of external diffusion.

5: table 6, it is better to compare the data with publication, at least for FSW and PC coal/40kj.mol for coal is relative lower than that with similar Vad

6: section 3.4, besides the merit, the adversity of FSW should be also mentioned, such as the cost to drying, prepare, the variation in content and heating value, the real operation in not so simple as lab test.

Other minors

Line 72, what means PC?

Line 96, grammar

Author Response

Dear editors and reviewer,

Thanks for your kind interest and the considerable reviewer comments about our manuscript “sustainability-1700224”. We are pleased to inform you that these comments have been considered as follows. Also, the revisions have been made in yellow in our new manuscript.

Reviewer # 3:

This paper studied the co-combustion of FSW and coal in TGA, though the objective is utilization in blast furnace, due to the great difference between TGA and the real one, the results are common and the suitability is not substantially validated. More discussion and information are needed to provide before considering acceptance.

Question 1: line 86-106, why not considering the high water content and low heating value of FSW? how to maintain the self heating combustion of FAW to realize 2000 purely burning it? At same time, the reason for impossible pure combustion is not the product is not enough, it is FSW can not meet the pure combustion requirement.

Table 2 please add the water content, air dried basis is not dry basis, there must be water content. if the LHV of FSW is higher than that of coal, how to reduce the water content is more important.

Answer: Thank you for the positive comments. As the reviewer said, the high-water content of FSW limits its industrial application. But drying FSW can improve its energy density. So, the dried FSW is chosen as fuel for blast furnace injection together with PC.

The combustion position in the blast furnace is located in the tuyere raceway. The heat of the tuyere raceway comes from three aspects: coke combustion, pulverized coal combustion and physical heat brought by high-temperature hot air, as shown in fig.1. Coke is the main combustion material inside the blast furnace, it provides the main heat. The hot air at about 1200 ℃ also brings a lot of heat into the tuyere. The theoretical combustion temperature of tuyere is about 2500 ℃.Therefore, after FSW and PC are injected into the air inlet together, they can reach 2000 ℃ through combustion.

The samples in this work were dried in a drying oven at 378K for 24h before the experiment. The sample is considered to be completely dried and the moisture content of the sample is near to 0%.

Fig.1 The combustion in the tuyere raceway.

 

Question 2: line 103, actually, the study on mixing combustion of biomass or waste and coal in TGA is too many, what is the main difference between FSW and other biomass or waste? beside blast furnace?

Answer: As the reviewer said, there is a lot of researches on the mixed combustion of substances (straw, husks, wood, etc.) and PC. There are also some researches on the combustible solid waste (waste plastic, waste leather, etc.), but there are few researches on the mixed combustion of FSW and PC, especially under blast furnace conditions. The blast furnace is the main reactor for iron making, and metal iron is obtained by burning coke, PC and other fuel in the blast furnace to provide heat and reducing agents. Under such process conditions, the combustion characteristics of PC and FSW has not been reported.

 

Question 3: line 136, only 9 mg sample, how to guarantee the representativeness of the mixing.

Answer: The samples were pulverized with a pulverizer and then sieved through a sieve with a particle size of less than 120 mesh (0.125 mm). Powder particles with such a small particle size can be mixed evenly in the grinding process. This method and sampling quality has been accepted by researchers in previous studies. So 9 mg sample is representative for TGA detection.

 

Question 4: line 138, how to prove 30ml/min air is enough to delete the limitation of external diffusion.

Answer: For thermogravimetric experiments, the gas flow range that researchers often use in previous studies is 30ml/min-80ml/min. For this experiment, we used a gas flow rate of 30ml/min. Before the experiment, air was introduced at a flow rate of 30ml/min for 30min, and then the experiment was carried out. In addition, the instrument we use has good air tightness. Therefore, we believe that the experiment is unlikely to be disturbed by external diffusion.

 

Question 5: table 6, it is better to compare the data with publication, at least for FSW and PC coal/40kj.mol for coal is relative lower than that with similar Vad

Answer: We compare the data with publication. The activation energy of PC with volatile components similar to this experiment is within 33.59 kJ/mol-54.9 kJ/mol. The activation energy of PC in this paper is 40 kJ/mol, which is correct.

‘https://doi.org/10.1007/978-3-319-48764-9_26’

‘https://doi.org/10.1007/978-3-540-76694-0_232’

 

Question 6: section 3.4, besides the merit, the adversity of FSW should be also mentioned, such as the cost to drying, prepare, the variation in content and heating value, the real operation in not so simple as lab test.

Answer: The reviewer suggestions are very good. We have added the problems that may be encountered in FSW industrial applications.

Compared with PC, the energy density of FSW is low, mainly due to the high water content of FSW. The high water content of FSW limits its application as a replacement for fossil fuels. The dried FSW is easier to store and can provide more convenience for its subsequent industrial applications, but its transportation, storage and drying costs must be considered. In addition, the chemical composition of PC is not much different, and the composition of FSW will be different according to the eating habits of various regions, so it needs to be classified and processed, which increases the management cost.

 

Question 7: Line 72, what means PC? Line 96, grammar

Answer: PC is the abbreviation of pulverized coal.

The grammar has been revised. “However, the demand for injection fuel in blast furnace ironmaking is huge.”

 

 

The authors are grateful to the reviewer for your kind comments, discussion and recommendations.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

Author Response File: Author Response.docx

Reviewer 4 Report

The review is available in the attachment.

Comments for author File: Comments.pdf

Author Response

Dear editors and reviewer,

Thanks for your kind interest and the considerable reviewer comments about our manuscript “sustainability-1700224”. We are pleased to inform you that these comments have been considered as follows. Also, the revisions have been made in yellow in our new manuscript.

Reviewer # 4

Recommendation:

The topic discussed in this paper is an important and interest to the readers of the Sustainability journal. The aim of the research has been clearly defined. The applied thermogravimetric analysis was valid, and the kinetic analysis was carried out correctly. Some issues require clarification, improvement and corrections. The manuscript can be approved for publication in the journal, only after the revisions.

Question 1: It is worth checking the case of letters in the content, "Song et al. Studied" - lines 63, 133, 167, 168, 317, etc. Please use the same notation: "non isothermal" or "non-isothermal".

Answer: ‘Studied’ in lines 63 and 89, ’Characteristics’ in line 133, ‘K’ in line 167 and 168, ‘coats’ in lines 317, ‘Compost’ in line 62, and ‘H2’ in line 85 have been revised to ‘studied’, ’characteristics’, ’k’, ‘Coats’, ’compost’ and’H₂’, respectively. ‘non isothermal’ in line 105 has been revised to ‘non-isothermal’.

Question 2: Line 140: "sample from 323 K to 1000 K." - but the results of the TG analyzes for pulverized coal (Figure 3) and the FSW-PC mixture (Figure 4) were made up to 1050K.

Answer: ‘sample from 323 K to 1000 K" in line 140 has been advised to "sample from 323 K to 1050 K’ in the paper.

Question 3: For what purpose, the authors refer to Equations (2) and (3) describing the flammability index and characteristic index. Were these equations used in the manuscript?

Answer: The flammability index and the characteristic index are usually used to evaluate the combustion performance of the sample. The higher the value of these two indices, the better the combustion performance of the sample. In Table 5, the combustion performance of FSW, PC and their different mixtures is compared using these two indices.

Question 4: Figure 2 shows the photomicrographs at different magnifications: x250, x500, and x1000. Such a statement may mislead the recipient.

Answer: Photomicrographs have been revised to the same magnification (×500).

Question 5: In Figure 5, the arrows for the same curve mislead the reader.

Answer: The two arrows represent different stages of the same curve. The former arrow points to the high temperature direction, indicating that the co-combustion of FSW and PC has an inhibitory effect in the volatilization stage, and the latter arrow points to the low temperature direction, indicating that the co-combustion of FSW and PC has a combustion-supporting effect in the fixed carbon combustion stage. In order to prevent misleading the reader, it has been marked with circles in Figure 5.

Question 6: Revise Figures 9a-c. Reaction rate - unit a.u.?; "Kj?"; "PCI?"

Answer: ‘a.u.’ is the abbreviation of arbitrary units, which is a dimensionless unit. ‘a.u’ in Figure 9(a) has been revised to ‘a.u.’. ‘Kj’ in Figure 9(b) has been revised to ‘kJ’. PCI is an abbreviation for pulverized coal, which has been revised to PC in Figure 9(c).

Question 7: "in ①②③ in Figure 10." - such markings are missing in Fig. 10.

Answer：①②③ has been marked in Figure 10.

 

The authors are grateful to the reviewers for your kind comments, discussion and recommendations.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

Round 2

Reviewer 2 Report

Manuscript entitled “Co-combustion of food solid wastes and pulverized coal for blast furnace injection: characteristics, kinetics and superiority” submitted by Jian Yang, Zhenying Li, Rufei Wei, Di Zhou, Hongming Long, JiaxinLi, Chunbao Charles Xu, can be considered for  publication in Sustainability Journal, after a major revision.

 

Here is a list of my specific comments:

1. Page 2, line 56: “Landfill method is a traditional…”. Add here a reference.
2. Page 2, line 81: “As the main reactor for ironmaking…”. The same observation.
3. Page 3, line 107: “The annual consumption of blast furnace…”. This paragraph should be deleted, because was already mentioned at page 2, line 46.
4. Page 7, Figure 1: The maximum wave numbers of the most important absorption bands should be added inside of figure 1.
5. Page 13, line 330: “This synergy due to…”. This synergy should be clearly explained and more arguments should be added.
6. Page 16, line 374: “From the above two relations,…”. This observation should be detailed.
7.  Page 17, line 399: “…as shown in ①②③ in Figure 10.”. These notations are not mentioned in figure 10.
8. Page 18, 4. Conclusion: This section is still too long and should be systematized. Delete (1), (2),…and provide a clear presentation of the most important experimental results and findings included in this study.

Author Response

Dear editors and reviewers,

Thanks for your kind interest and the considerable reviewer comments about our manuscript “sustainability-1700224”. We are pleased to inform you that these comments have been considered as follows. 

Reviewer # 2:

Question 1: Page 2, line 56: “Landfill method is a traditional…”. Add here a reference.

Answer: A reference have been added.

‘Jin, C.; Sun, S.; Yang, D.; Sheng, W.; Ma, Y.; He, W.; Li, G. Anaerobic Digestion: An Alternative Resource Treatment Option for Food Waste in China. Science of The Total Environment. 2021, 779, 146397. ‘

 

Question 2: Page 2, line 81: “As the main reactor for ironmaking…”. The same observation.

Answer: A reference have been added.

‘Zhang, F.M. Research and design on low-carbon and high-efficiency blast furnace. China Metallurgy. 2021, 31(11), 1-8’

 

Question 3: Page 3, line 107: “The annual consumption of blast furnace…”. This paragraph should be deleted, because was already mentioned at page 2, line 46.

Answer: Page 3, line 107: ‘The annual consumption of blast furnace…’. We think this paragraph should be retained.

Page 2, line 46: ‘The average annual output of food waste…’. This paragraph is an introduction to the output of FSW．Page 3, line 107: ‘The annual consumption of blast furnace…’. This paragraph refers to the output of FSW in the previous paragraph and compares it with the coal injection volume of the blast furnace. It can be seen that the demand for PC is much greater than the output of FSW, and FSW cannot completely replace PC as the fuel for blast furnace injection. The FSW and PC are mixed as fuel for blast furnace injection. This method can not only deal with FSW reasonably, but also reduce the carbon dioxide emission of blast furnace ironmaking.

 

Question 4: Page 7, Figure 1: The maximum wave numbers of the most important absorption bands should be added inside of figure 1.

Answer: The maximum wavenumber of the most important absorption band has been added in Figure 1.

 

Question 5: Page 13, line 330: “This synergy due to…”. This synergy should be clearly explained and more arguments should be added.

Answer: This section has been revised.

‘This synergy due to the thermal effect is easily affected by the oxygen concentration and the heating rate. The lower oxygen concentration will reduce the combustion reaction rate of FSW, and then the heat release rate will also decrease, while the lower heating rate will make the temperature difference between FSW and PC smaller. Both of these conditions will slow down the heat transfer rate between the FSW and the PC, weakening the thermal effect.’

 

Question 6: Page 16, line 374: “From the above two relations,…”. This observation should be detailed.

Answer: This section has been revised.

‘From the above two relations, it can be seen that there is a dynamic compensation effect between lnA and E. This shows that the two kinetic models have obvious kinetic compensation effects in their respective co-combustion stages, which proves the effectiveness of the two kinetic models in describing the complex co-combustion process.’

 

Question 7: Page 17, line 399: “…as shown in ①②③ in Figure 10.”. These notations are not mentioned in figure 10.

Answer: ①②③ has been marked in Figure 10.

 

Question 8: Page 18, 4. Conclusion: This section is still too long and should be systematized. Delete (1), (2),…and provide a clear presentation of the most important experimental results and findings included in this study.

Answer: We have deleted (1) and (2) and optimized the conclusion. The revised conclusions are as follows.

(1) The co-combustion of FSW and PC has an inhibitory effect in the volatilization stage, and has a combustion-promoting effect in the fixed carbon combustion stage. The interaction between FSW and PC is dominated by thermal effects.

(2) The average activation energy in the volatile phase of PC and FSW combustion is 54.34 kJ/mol, and the average activation energy in the fixed carbon combustion phase is 27.98 kJ/mol, which is lower than the activation energy of PC in the fixed carbon combustion phase.

(3) Compared with direct coal injection, the mixed injection of FSW and PC will reduce the ignition temperature of PC and improve the overall combustion efficiency. Injecting FSW into blast furnace can promote indirect reduction of iron ore, reduce coke ratio, reduce ironmaking process and reduce CO₂ emission.

 

The authors are grateful to the reviewers for your kind comments, discussion and recommendations.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

 

Reviewer 3 Report

1:there are so many preparation processes  for FAW before burning in blast furnace, which will greatly decreases the economic value of real application. the authors should add these information in the text, avoiding misleading.
if there is no water content, the base is not air dry, is dry. this is common concept in fossil fuel. 

2: question2 in 1st comments,  this answer has no positive value, the real blast is different, while, in present study, the TGA condition is same as other mixing burning test, only air as gas flow, no reducing agents. At same time, the temperature is far lower than 2000 degree.

3:  question 3 in 1st comment, actually, FSW has different content, it is hard to get even distribution inside FSW,  no matter grinding or not, especially, 0.125mm is coarse size used in TGA. 

4: question 4 , The restrict method is to test the sensitively of the gas flow rate, not just base previous studies, if previous study did the same TGA test with same FSW, what is the new in this TGA test?

Author Response

The reply letter to the reviewer is shown in the following document.

Author Response File: Author Response.docx

Reviewer 4 Report

The Authors responded my comments very well, and the manuscript was improved in a good way. I think this paper can be considered to accept.

Author Response

The authors are grateful to the reviewers for their comments in the first round and their recognition of this work.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

Round 3

Reviewer 2 Report

All my previous remarks and comments have been considered in this new version of the manuscript. In my opinion, the revised manuscript meets the criteria and can be published as original paper in Sustainability Journal.

Author Response

The authors are grateful to the reviewers for their comments in the first and second round and their recognition of this work.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]

Reviewer 3 Report

though the authors explained the questions mentioned in 1st and 2nd reviewing, while, there is nearly no amendment or improving in the test, such as the difference between TGA and Blast, the sensitivity validation of gas flow rate. TGA is a common method, so it is hard to do some novelty just following the same procedure unless doing more detail and comprehensive work.  

at same time, the authors applied many his own publications in TGA to prove feasibility  of TGA usage. 1: as common method,  why not mention other classical works? 2: how to differ this work with other previous publications besides fuel type?

Author Response

Dear editors and reviewer,

Thanks for your kind interest and the considerable reviewer comments about our manuscript “sustainability-1700224”. We are pleased to inform you that these comments have been considered as follows. Also, the revisions have been made in yellow in our new manuscript.

Reviewer # 3:

Question 1: though the authors explained the questions mentioned in 1st and 2nd reviewing, while, there is nearly no amendment or improving in the test, such as the difference between TGA and Blast, the sensitivity validation of gas flow rate. TGA is a common method, so it is hard to do some novelty just following the same procedure unless doing more detail and comprehensive work.

Answer: The difference between TGA and blast and the sensitivity validation of gas flow have been revised in the paper.

‘Laboratory thermogravimetric analysis instruments generally cannot reach the combustion temperature of blast furnace tuyere. In previous studies on the mixture of biomass and pulverized coal as blast furnace injection fuel, thermogravimetric analysis was often used to study the thermal conversion performance and combustion kinetics of biomass and pulverized coal. Thermogravimetric analysis is also recommended by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC) to study the combustion properties of biomass and pulverized coal.’

 

‘In previous experiments using thermogravimetric analysis to study the combustion characteristics of biomass, the gas flow rate was generally 30-70 mL/min. In this experiment, the gas flow rate of 30 mL/min was selected. Before the experiment, 30 mL/min of air was introduced for 30 minutes, and then the thermogravimetric experiment was carried out.’

 

Question 2: at same time, the authors applied many his own publications in TGA to prove feasibility of TGA usage. 1: as common method, why not mention other classical works? 2: how to differ this work with other previous publications besides fuel type?

Answer:

1.In the second revision, 5 papers about using TGA research material and pulverized coal as blast furnace injection fuel are listed. One of them is a research paper by our research group on the combustion characteristics of food solid waste, and the other four are papers by others on the use of TGA to study the combustion characteristics of biomass and pulverized coal.

‘Zhou, D.; Wei, R.F.; Long, H.M.; Li, J.X.; Qi, L.Y.; Xu, C.B. Combustion characteristics and kinetics of different food solid wastes treatment by blast furnace. Renewable Energy. 2020, 145, 530-541.’

‘Xu, R.; Wang, W.; Dai, B. Influence of particle size on combustion behavior of bamboo char used for blast furnace injection. J. Iron Steel Res. Int. 2018, 25 (12), 1213–1222. ’

‘Wang, P.; Wang, G.; Zhang, J.; Lee, J.-Y.; Li, Y.; Wang, C. Co-Combustion characteristics and kinetic study of anthracite coal and palm kernel shell char. Applied Thermal Engineering. 2018, 143, 736–745.’

‘Ye, L.; Zhang, J.; Xu, R.; Ning, X.; Zhang, N.; Wang, C.; Mao, X.; Li, J.; Wang, G.; Wang, C. Co-combustion kinetic analysis of biomass hydrochar and anthracite in blast furnace injection. Fuel. 2022, 316, 123299.’

‘Li, J.; Xu, R.; Wang, G.; Zhang, J.; Song, B.; Liang, W.; Wang, C. Study on the feasibility and co-combustion mechanism of mixed injection of biomass hydrochar and anthracite in blast furnace. Fuel .2021, 304, 121465.’

 

2. In previous papers, the combustion characteristics of biomass alone, or the combustion characteristics of mixtures of biomass and pulverized coal were generally studied. However, their research generally only focuses on combustion, and does not link its combustion process with blast furnaces. The combustion of FSW and pulverized coal in the blast furnace tuyere not only provides heat for the reduction reaction inside the blast furnace, but also the CO generated during the combustion process is also useful, which can be used as a reducing agent for blast furnace ironmaking and participate in indirect reduction reactions. In Section 3.4, this paper links the combustion of the blast furnace tuyere with the reduction inside the blast furnace.

‘Wang, G.; Zhang, J.; Shao, J.; Liu, Z.; Zhang, G.; Xu, T.; Guo, J.; Wang, H.; Xu, R.; Lin, H. Thermal Behavior and Kinetic Analysis of Co-Combustion of Waste Biomass/Low Rank Coal Blends. Energy Conversion and Management. 2016, 124, 414–426. ’

‘Boumanchar, I.; Chhiti, Y.; M’hamdi Alaoui, F. E.; Elkhouakhi, M.; Sahibed-dine, A.; Bentiss, F.; Jama, C.; Bensitel, M. Investigation of (Co)-Combustion Kinetics of Biomass, Coal and Municipal Solid Wastes. Waste Management. 2019, 97, 10–18.’

‘Wang, Q.; Wang, G.; Zhang, J.; Lee, J.-Y.; Wang, H.; Wang, C. Combustion Behaviors and Kinetics Analysis of Coal, Biomass and Plastic. Thermochimica Acta. 2018, 669, 140–148.’

 

The authors are grateful to the reviewers for your kind comments, discussion and recommendations.

Best regards,

 

Dr. Rufei Wei

Associate Professor, School of metallurgical engineering

Anhui University of Technology, Ma'anshan 243002, Anhui, China

Tel: +86-13365553195

Email: [email protected], [email protected]