Experimental and Numerical Analysis of a Low Environmental Impact Pyro-Gasification System for the Energetic Valorization of Waste through a Biomass Steam Power Plant

Round 1

Reviewer 1 Report

The current paper addresses the energy recovery of waste and biomass the consequent use of through a reactor pyro-gasifier.

The topic is very relevant and the way the authors explain their research is well accomplished. However, there are certain points that require a better explanation to help the reader understand the paper. Please follow the recommendations:

 

• Line 76 page 3 - In part, the statement is true. However, both the pyrolysis process and the gasification process present by-products that should not be underestimated (namely tar). Another major problem is the formation of HCl, which is not exclusive to combustion processes. Please make a small reference to some existing problems with the gasification and pyrolysis processes.

 

• Line 94 page 3 - What do you want to refer to with “a precise composition evaluation of the pulper used during the experimental tests was not carried out and the related data were characterized by wide uncertainty”. Do you refer to proximate, ultimate, calorific and inorganic analysis? Or are you referring to the synthesis gas produced during the test? Please try to explain further.

 

• Line 123 page 4 - In my opinion, it should be noted in advance that the reactor works with a methane burner.

 

• Line 123 page 4 - Another question that arises is, whether the paper pulp intake silo is closed, or is it continuous feed? I understand certain values ​​of the syngas (namely the amount of nitrogen) if the paper pulp intake silo is opened and there is an air intake in the reactor around. In Fig. 4, more precisely in the item “(DEPOLYM. In Figure 4)”, only the incoming pulp flow is represented.

 

• Line 133, page 4 - There are no references from where the values ​​of the analyzes carried out on the raw material were obtained.

 

• Line 137, page 5 - How do you explain the amount of Methane produced compared to other light hydrocarbons? And, the residual amount of Hydrogen produced? It appears that if there was any thermal cracking of the hydrocarbons, it was not reflected in the hydrogen concentration.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper concerns an important topic relative to nowadays’ concerns, offering a circular economy-related solution to a massive environmental problem. The introduction section is rather basic and general. Dedicated details and specific issues for this topic and techniques, as well as the political and legislative background would enhance the importance of the paper and raise the interest of the audience and readers. The methodological approach is sound and suitable, denoting knowledge on the numerical tools and simulations. References could be updated to more recent literature, as more than 50% of them has been published more than 5 years and this is a permanently evolving area.

Some generic comments:

- Which gasifying agent was utilised? It is possible to infer by the schemes but is not stated along the text.

- The font format is different from section 1 to the others.

 

Also, some more directed comments to the manuscript:

Page 2, line 51-52: figure 1 caption is lacking a reference for the cited data.

Page 3, lines 58-60: this sentence is not supported by the correct reference. Authors mention the World Bank report and cite different literature.

Page 3, lines 63-64: the authors state “many reports” and cite only two references. Actually, this sentence is highly debatable, and depending on the energy recovery technologies might even be false. A better explanation and justification of this sentence is necessary in order not to raise doubt and put the authors under critics. More careful is required when stating information in such a “peremptory” way.

Page 3, lines 68-69: a support reference is missing.

Page 4, line 116: RM appears for the first time but the meaning is not explained, neither listed in the acronyms and abbreviations section.

Page 5, line 135: Table 1 caption is not correct, as the proximate analysis does not describe chemical characterization.

Page 5, line 138: which laboratory? Authors cannot just state things, references must be provided.

Page 5, line 142: “uncertainty”? Wouldn’t it be more accurate to call it “parameter range” or similar? “Uncertainty” refers to a statistical feature, not a calibration parameter.

Page 6, line 164: Table 4 is lacking units for the evaluated parameter, the same for tables 7 and 8.

Page 8, line 213: MOGA appears for the first time but the meaning is not explained neither listed in the acronyms and abbreviations section.

Page 12, line 275: (red) colour should be avoided.

Page 12, line 280-304: tis section is merely descriptive, no other contextualization, explanations or comparisons are provided. The same applies to section 7, which is way too limited to be called “further analysis and considerations”.

Page 13, figure 10: decimal separator should be replaced by “.”

Page 14, line 338: equation should be numbered and a supporting reference cited. The same applies for page 15, line 345.

Page 15, lines 349-350: again, this sentence needs clarifying once depending on the boundaries of the considered system (for instance biomass processing, power source for all the parts of the plant, etc) this may not apply.

Page 15, line 357: syntax error. The same occurs in line 362.

Page 15, line 364: “which can also be applied to other systems and technologies”…where is this shown in the manuscript so that it can be stated in the conclusions?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Most of the previously reported comments were addressed by the authors. Nevertheless, some corrections are still due, namely:

• The authors state that the introduction was updated. Still, most of the references added are even older than the ones presented before (example: references 23, 24, 26, 28 and 29 refer to 2006, 2009, 2003, 2002 and 2008). Also the reference numbers are not sequential in some parts of the text (example: no reference 2 following reference 1, no reference 7 and 8 before reference 9).
• Concerning the comment on the fact that the Introduction section presents a different visual than the other sections (it is all in caps – line 29, while the titles for the other sections are not – lines 127, 154, 213, 243, 328, 362…), the authors replied that “The manuscript should have been edited by the Editor”. This is a type of sentence that should be avoided because, besides pointing a third party as “guilty” person, the authors did not fix the problem: in the revised manuscript, the issue remains.
• Regarding my former comment to the fact that Tables 4, 7 and 8 were lacking units, “mass fraction” and “volume fraction” (as added by the authors) are not units. Are the values reported in g, kg, cm³, L, %...? One can only guess!
• Relative to the comment about sections 6 and 7 (which are now incorporated in the “Optimization results and decision-making problem” section), these parts are still lacking comparison to published literature, a better contextualization and explanation of the achieved results is needed.
• Respective to the comment about Page 15, lines 349-350 in the original manuscript (now lines 359-361), although the authors state that they revised the sentence, it appears exactly as in the original manuscript. No changes are seen.

Author Response

Please see the attachment

Author Response File: Author Response.pdf