Gasification of Densified Biomass (DB) and Municipal Solid Wastes (MSW) Using HTA/SG Technology

Round 1

Reviewer 1 Report

The paper is of interest for the scientific community and shows an improvement of the technology of gasification.

The introduction and the aim of the work are clear and well written, as well as the methods, discussion and conclusions. The process and the methods are very detailed, and the results are clearly compared to the numerical modelling.  I think it can be accepted with minor revisions.

There are only some typing errors and some minor corrections:

Lines 156 and 158: add some references to the equations. Correct Carasse into Carrasse.

Line 238: full stop instead of two points.

Line 242: explain what are Tb1 and Tog 1, and the reference to the figure.

In the legend of fig. 3 there are some typing errors;

Line 291 there is a point after (Figure 6).

Line 307-308: keep separated the two paragraphs.

Line 330. Please add some reference about the software used.

Figure 8: There are some typing errors in the legend.

Line 422: figure 10 instead of figure 6.8.

Line 522: There is a typing error.

Author Response

Response to Reviewer 1 Comments

Thank you for review of the article.

Lines 156 and 158: add some references to the equations. Correct Carasse into Carrasse.

Thank you for your suggestion. It is corrected.

Line 238: full stop instead of two points.

Thank you for your suggestion. It is corrected.

Line 242: explain what are Tb1 and Tog 1, and the reference to the figure.

Thank you for your suggestion. The explanation of symbols is added.

In the legend of fig. 3 there are some typing errors;

Thank you for your suggestion. The legend is fixed with the figure 3.

Line 291 there is a point after (Figure 6).

Thank you for your suggestion.

Line 307-308: keep separated the two paragraphs.

Thank you for your suggestion. It is corrected.

Line 330. Please add some reference about the software used.

Thank you for your suggestion. It is corrected.

Figure 8: There are some typing errors in the legend.

Thank you for your suggestion. It is corrected.

Line 422: figure 10 instead of figure 6.8.

Thank you for your suggestion. It is corrected.

Line 522: There is a typing error.

Thank you for your suggestion. It is corrected.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors:

I am glad to review your submitted article. Please see the following comments and suggestions for your paper.

• In Title, HTA/SG is not a common term for the new readers. Please specify it when it first appears.
• Please rearrange the "Author Contributions" and "Acknowledgments" after the reference section.
• In line 18, change low calorific value into the Lower Calorific Value (LCV).
• In the abstract, please add the major findings of your study. For instance, using 1 or 2 sentences for the problems, 2-3 sentences for methods, 3-4 for results and findings.
• Re-write the sentence between lines 33-35 because there is a grammar error.
• Reformat line 46.
• Please introduce the biomass as follows and cited the suggested reference. Biomass mainly consists of wood (or forestry crop) and wood processing residues (e.g., firewood and wood chips), agricultural crops and residues (e.g., rice, corn, wheat, soybeans, and algae), dedicated energy crops (e.g., switchgrass, miscanthus, fast-growing willow, and poplar), municipal solid waste (e.g., paper, cotton, and plastic), animal waste (e.g., poultry litter and pig manure), sewage, and industrial waste (e.g., black liquor and peelings and scraps from fruit and vegetables) [1, 2].
  • [1] Brassard, P.; Palacios, J.H.; Godbout, S.; Bussières, D.; Lagacé, R.; Larouche, J.P.; Pelletier, F. Comparison of the gaseous and particulate matter emissions from the combustion of agricultural and forest biomasses. Bioresour. Technol. 2014, 115, 300–306.
  • [2] Qian, X.; Xue, J.; Yang, Y.; Lee, S.W. Thermal Properties and Combustion-Related Problems Prediction of Agricultural Crop Residues. Energies 2021, 14, 4619.
• Please rearrange the equations from Lines 150-172.
• You may need to add the objective of the study before 4. Experimental Setup Section.
• Please also add a few more closely related studies on the gasification of biomass using the simulation approach into the "2. State-of-the-art Gasification of Biomass and Waste".
• In Line 127, Please read, add the definition of the Higher Heating Value (HHV) and Lower Heating Value (LHV) by citing the following two references.
  • [1] Qian, X.; Lee, S.; Soto, A.-m.; Chen, G. Regression Model to Predict the Higher Heating Value of Poultry Waste from Proximate Analysis. Resources 2018, 7, 39.
  • [2] Sheng, C., & Azevedo, J. L. T. (2005). Estimating the higher heating value of biomass fuels from basic analysis data. Biomass and bioenergy, 28(5), 499-507.
• For the instrumentations, such as thermocouples, gas chromatograph, flow meters, please add model number, manufacture, accuracy.
• Please add the general process of the gasification process after Line 238.
• In Figure 2, add the overall dimension and unit for the gasifier. Change the off-gas outlet into the syngas outlet. Add an explanation of the different temperature points, such as T_b2? T_FeG?
• In Figure 3, The symbol of H₂ and CH₄ are missing. What are the I, II, II, and IV?
• In Figure 5, how did you change and maintain the molar fraction of steam during the gasification? why the increased molar fraction of H₂ causes the lower H₂?
• In Figure 6, how do you interpret the amount of mass flow for the flue gas as increasing?
• In Figure 6, Please use the dotted lines for the LHV that we can simply observe. What's the ratio of steam effect on the LHV?
• For the numerical simulations, how did you validate your results? Conditions in Table 1 were not tested in the experimental tests.
• Again, there were no strong literature reviews to convince me why you select these conditions during the simulation in Table 1. There, please add more closely related literature for the simulation studies.

Overall, you tested and evaluated your gasification process based on variable conditions. However, there were no clear results or findings summarized in either the abstract or conclusion. Please update them.

I hope this manuscript will be updated with suggested comments.

Best regards,

Reviewer

Author Response

Response to Reviewer 2 Comments

Thank you for review of the article.

In Title, HTA/SG is not a common term for the new readers. Please specify it when it first appears.

Thank you for your suggestion. It is corrected.

Please rearrange the "Author Contributions" and "Acknowledgments" after the reference section.

Thank you for your suggestion. It is corrected. The "Author Contributions" and "Acknowledgments" are put before References according to MDPI authors’ guideline.

In line 18, change low calorific value into the Lower Calorific Value (LCV).

Thank you for your suggestion. It is corrected.

In the abstract, please add the major findings of your study. For instance, using 1 or 2 sentences for the problems, 2-3 sentences for methods, 3-4 for results and findings.

Thank you for your suggestion. The problems are stated in the beginning of the abstract and contain more than 1-2 sentences. Also the methods which are used in the study are described below the problems. The results were added at the end of the abstract.

Re-write the sentence between lines 33-35 because there is a grammar error.

Thank you for your suggestion. These lines were deleted because the information is not important.

Reformat line 46.

Thank you for your suggestion. It is corrected.

Please introduce the biomass as follows and cited the suggested reference. Biomass mainly consists of wood (or forestry crop) and wood processing residues (e.g., firewood and wood chips), agricultural crops and residues (e.g., rice, corn, wheat, soybeans, and algae), dedicated energy crops (e.g., switchgrass, miscanthus, fast-growing willow, and poplar), municipal solid waste (e.g., paper, cotton, and plastic), animal waste (e.g., poultry litter and pig manure), sewage, and industrial waste (e.g., black liquor and peelings and scraps from fruit and vegetables) [1, 2].

[1] Brassard, P.; Palacios, J.H.; Godbout, S.; Bussières, D.; Lagacé, R.; Larouche, J.P.; Pelletier, F. Comparison of the gaseous and particulate matter emissions from the combustion of agricultural and forest biomasses. Bioresour. Technol. 2014, 115, 300–306.

[2] Qian, X.; Xue, J.; Yang, Y.; Lee, S.W. Thermal Properties and Combustion-Related Problems Prediction of Agricultural Crop Residues. Energies 2021, 14, 4619.

Thank you for your suggestion. The proposed articles present the combustion process which is another form to renewable/fossil fuels conversion. The article presents the gasification process possibility to incineration of biomass and municipal wastes.

Please rearrange the equations from Lines 150-172.

Thank you for your suggestion. The formulas/equations are presented according to MDPI authors’ guideline.

You may need to add the objective of the study before 4. Experimental Setup Section.

Thank you for your suggestion. It is corrected.

Please also add a few more closely related studies on the gasification of biomass using the simulation approach into the "2. State-of-the-art Gasification of Biomass and Waste".

Thank you for your suggestion. It is added.

In Line 127, Please read, add the definition of the Higher Heating Value (HHV) and Lower Heating Value (LHV) by citing the following two references.

Thank you for your suggestion. It is added in the text and references.

[1] Qian, X.; Lee, S.; Soto, A.-m.; Chen, G. Regression Model to Predict the Higher Heating Value of Poultry Waste from Proximate Analysis. Resources 2018, 7, 39.

[2] Sheng, C., & Azevedo, J. L. T. (2005). Estimating the higher heating value of biomass fuels from basic analysis data. Biomass and bioenergy, 28(5), 499-507.

For the instrumentations, such as thermocouples, gas chromatograph, flow meters, please add model number, manufacture, accuracy.

Thank you for your suggestion. It is added.

Please add the general process of the gasification process after Line 238.

Thank you for your suggestion.

In Figure 2, add the overall dimension and unit for the gasifier. Change the off-gas outlet into the syngas outlet. Add an explanation of the different temperature points, such as T_b2? T_FeG?

Thank you for your suggestion. It is corrected.

In Figure 3, The symbol of H₂ and CH₄ are missing. What are the I, II, II, and IV?

Thank you for your suggestion. It is corrected. The symbols I, II, III and IV represent the selected stages of the gasification process.

In Figure 5, how did you change and maintain the molar fraction of steam during the gasification? why the increased molar fraction of H₂ causes the lower H₂?

The molar fraction of steam was changed using different set of steam generator capacity which was supplied with feeding gas. The increased molar fraction of steam in feeding gas resulted increased concentration of hydrogen production during gasification process (pink bar).

In Figure 6, how do you interpret the amount of mass flow for the flue gas as increasing?

Thank you for your suggestion. The flow rate of the gaseous fuel produced during the gasification process with a mixture of air and steam is much lower than when only air is used as the feed gas. Adding steam to feed gas causes slightly increasing of calorific value due to increased concentration of H₂ produced.

In Figure 6, Please use the dotted lines for the LHV that we can simply observe. What's the ratio of steam effect on the LHV?

Thank you for your suggestion. The continuous line of LHV can be more visible than dotted line.

For the numerical simulations, how did you validate your results? Conditions in Table 1 were not tested in the experimental tests.

Thank you for your remark. The validations of the numerical results are presented in Figure 9. The numerical simulations’ boundary conditions are taken from an experimental data measurements.

Again, there were no strong literature reviews to convince me why you select these conditions during the simulation in Table 1. There, please add more closely related literature for the simulation studies.

Thank you for your remark. The relevant literature was added in this subchapter and references.

Overall, you tested and evaluated your gasification process based on variable conditions. However, there were no clear results or findings summarized in either the abstract or conclusion. Please update them.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Authors:

I am glad to review your revised manuscript. The overall quality was improved a lot than the previous one. Please see the following additional comments to further improve the manuscript quality:

• Add future study in the conclusion part.
• Section 6.4 should be included either Conclusion or 6.1 to 6.3.
• Please double-check the spelling, grammar, and writing styles for the manuscript.
• Please lable the different color lines in Figure 1.
• Figure 3, please indicate the difference between I and IV.
• Please add discussion why there is difference between gases with diffeernt molar fraction of steam in the feed gas.

I hope these comments will be useful.

Best regards,
Reviewer

Author Response

Response to Reviewer Comments

Thank you for review of the article.

1.Future work (study)

Add future study in the conclusion part.

Thank you for suggestion. The future study was added in the Conclusions.

Section 6.4 should be included either Conclusion or 6.1 to 6.3.

Thank you for suggestion. The section 6.4 was attached in the Conclusions.

Please double-check the spelling, grammar, and writing styles for the manuscript.

Thank you for suggestion. The whole text was checked by English native speaker.

Please label the different color lines in Figure 1.

All lines’ colors were labelled in Figure 1 in visible places respectively. For example steam is green color labelled, air is blue color labelled, etc.

Figure 3, please indicate the difference between I and IV.

Thank you for suggestion. The difference description is added.

Please add discussion why there is difference between gases with different molar fraction of steam in the feed gas.

Thank you for suggestion. It was changed.

Author Response File: Author Response.docx