Multiapproach Design Methodology of a Downscaled Wet Scrubber to Study the Collection of Submicronic Particles from Waste Incineration Flue Gas

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

“ Multiapproach design methodology of a downscaled wet  scrubber to study the collection of submicronic particles from  waste incineration flue gas”

The study proposes a design methodology of a downscaled wet scrubber at a municipal waste incineration plant to be fed with real flue gas and study its efficiency towards the removal of submicronic particles.  Also, Computational fluid dynamics simulations were conducted to analyze the gas flow structure within the device.

 

Overall it is a nice study. Please consider the recommendations below to improve the quality:

 

-Importance of the topic can be explained also in the abstract section for the readers who are not familiar. The risks associated by dust emissions are well explained in the into section. I think a broader perspective can be also given at the abstract and conclusion section, and the importance of the topic can be highlighted by a couple of sentences.

 

-Please include an abbreviation section.

 

-Please improve the literature review, relataed studies about the topic.

-Please present the novelty of the study, the research gap more clearly.

-Please give the units for the parameters being used in the equations. And give a number for each equation

-Please give the main findings of the study at conclusion section.

Comments on the Quality of English Language

-The quality of English is good but can be improved. 

Author Response

We are glad you find our study nice and greatly appreciate your feedback to improve its quality. We confirm that the article has been updated to include your remarks. Please find our responses to your comments below.

 

Comments 1: Importance of the topic can be explained also in the abstract section for the readers who are not familiar. The risks associated by dust emissions are well explained in the into section. I think a broader perspective can be also given at the abstract and conclusion section, and the importance of the topic can be highlighted by a couple of sentences.

Response 1: Thank you for your comments. We agree with your suggestion and we have made the following corrections:

Abstract (limited to 200 words): "Although these devices are not particularly performant at capturing submicron particles, which are associated with health and environmental hazards, their collection efficiency can be improved by optimizing operating conditions." (L11)

Conclusion: "In the long term, the established suggestions can be used by industry to avoid the emission of submicron particles that may represent a risk to our health and the environment." (L506)

 

Comments 2: Please include an abbreviation section.

Response 2: We are sorry for omitting the nomenclature and the abbreviation list. This have been included in the revised version (L526).

 

Comments 3: Please improve the literature review, relataed studies about the topic.

Response 3: We are glad to improve our literature review. We included 2 new references regarding the design of scrubbers based on different approaches (references [22] and [23], from L84 to L92) and one additional reference regarding an in situ study with a downscaled scrubber for the collection of dust and other pollutants from waste incineration fumes under conditions similar to ours (from L94 to L101).

 

Comments 4: Please present the novelty of the study, the research gap more clearly.

Response 4: Thank you for your constructive comment. The novelty of the study lies in the use of multiple criteria in the design of the pilot to reproduce on a reduced scale both local and global phenomena encountered in industrial reality. The novelty of the study and the gaps in the research are now clearly stated in the introduction (L124 - L126).

 

Comments 5: Please give the units for the parameters being used in the equations. And give a number for each equation

Response 5: Thank you for pointing out this error. Correction have been made on the revised version: the units are indicated in the nomenclature table in L526 and each equation has its own number.

 

Comments 6: Please give the main findings of the study at conclusion section.

Response 6: The conclusion has been updated to better highlight the work that had been done and the main findings, especially regarding the theoretical particle collection efficiency (L494 - L496).

Reviewer 2 Report

Comments and Suggestions for Authors

Please see attached file.

Comments for author File: Comments.pdf

Author Response

Thank you very much for reviewing our paper. We greatly appreciate your pertinent remarks, which have helped us improve its quality. We would like to confirm that the experimental investigation is ongoing, and the results will be published after analysis.

 

Comments 1: Page 7. Line 261. “The 3D domain was meshed into 2 million polyhedral cells…” Please justify the selection of such mesh. 

Response 1: Thank you for valuable comment and we recognized the lack of information regarding the mesh selection. Indeed, we selected this mesh following a comparison of different mesh density that indicated a high mesh sensitivity. We opted then for a non-uniform mesh with variable sizing based including refinement near walls. The polyhedral mesh was chosen for its efficiency, as it requires less computation time than a tetrahedral mesh. The manuscript has been updated to include the above information (Page 8, L289 - L291). 

 

Comments 2. Page 13. Line s408-409. “These results were then compared to the CFD simulations (Figure 9), revealing good agreement along the radial axis of the wet scrubber…” It is not possible to agree that this is a “good agreement” when the difference in some cases is more than 2 times. It is not possible to understand why such big differences are. Please provide the Picture/Photo and detailed description of the probe in the chapter 3.3. 

Response 2: We apologize if our discussion of the agreement between the CFD and experimental results was not clear. The double filter, intended to break the jet, resulted in a recirculation flow downstream. This recirculation creates a zone with a minimum velocity (<0.2 m/s) that coincides with the level where the largest discrepancies between measured and simulated occur. This effect is especially prominent at y = 2 m (in the low-flow region) but is also found close to the walls, where velocity approaches to 0 m/s. We have included a diagram showing the velocity vectors inside the device and describing the measurement protocol as well as the probe specifications (Figure 8(e), Page 14). From this diagram, we can clearly identify the dead zone, that by the way is not a problem for our future measurements. A detailed discussion about the discrepancies observed is provided and the unsuitability of the anemometer for these low velocity measurements are addressed in the manuscript (Page 13, lines 431 to 443, and Page 14, lines 464 to 474). Thank you for your comment, which certainly improves the quality of our research.

Comments 3: Page 14. Conclusions. Please include the statement concerning collection efficiency calculation results.

Response 3: The conclusion has been updated to better highlight the theoretical collection efficiency results (L494 to L496).

Reviewer 3 Report

Comments and Suggestions for Authors

 

The comments for this text after reading are as follows:

1.      In L141, the research methodology authors mention the use of an electron microscope (SEM) with the EDX module. There is no more detailed description of its type and parameters.

2.      In L151, the authors quote the results of analyses from the literature, with the particle sizes at 1-1000nm (nanometers). Meanwhile, in the authors' design assumptions (Table 1), the particle size is 600 um (micrometres), - that is 3 orders of magnitude difference.

3.      In L279, the elemental composition of particles obtained from EDX is provided - for what purpose if this information is not used further?

4.      In the formula, the quantity "dp" appears after L172. Neither this formula nor subsequent formulas where this quantity appears describes what it means.

5.      No information was provided on how the photo from Figure 2 was taken. It would be helpful to provide information about the camera used, magnification, etc…

6.      The term "spectral efficiency" is used in many places in the text (L146, L247, Fig. 3, L438). The authors did not write what they meant by this term.

7.      Commenting on the content of Figure 9, the authors used the term "revealing good agreement (…) particularly at heights 1m and 2.5m". This agreement is debatable for both the remaining cases (1.5m and 2m). Even for those indicated heights (1.5m and 2.5m), the differences between the numerical experiment and the measurement are at the level of 15-20% - therefore, it can be discussed whether it is a "good agreement".

8.      The text presents only the theoretical effectiveness of the constructed wet scrubber. There is no experimental measurement of the effectiveness, neither total nor interval efficiency (as the authors call it "spectral").

 

Author Response

Thank you for taking the time to review our paper and for your valuable comments, which were very useful in its improvement. Below, we have provided some responses to your questions.

 

Comments 1: In L141, the research methodology authors mention the use of an electron microscope (SEM) with the EDX module. There is no more detailed description of its type and parameters.

Response 1: For SEM EDX, we used a high-resolution JEOL JSM 5800LV. This information has been added to the manuscript (L163). We regret that we don’t have all the technical parameters available, as the measurements were realized at the Nantes Materials Institute.

 

Comments 2:  In L151, the authors quote the results of analyses from the literature, with the particle sizes at 1-1000nm (nanometers). Meanwhile, in the authors' design assumptions (Table 1), the particle size is 600 um (micrometres), - that is 3 orders of magnitude difference.

Response 2: We apologize for any misunderstanding. The 600 µm measurement refers to the droplet diameter, while the particle size range from 1 to 1000 nm refers to the particle diameters studied by Adah et al. (2022). A list with the nomenclature and symbols is included in the revised version (L526).

 

Comments 3:  In L279, the elemental composition of particles obtained from EDX is provided - for what purpose if this information is not used further?

Response 3: The analysis of the elemental chemical composition of the particles allows us to anticipate technical difficulties with our experimental set up (e.g. blockages of the lines due to the presence of silica). The solubilization of salts that change the pH of the recirculated water may also have an impact on the efficiency of our scrubber and should be taken into account during its operation. Finally, the theoretical calculations of particle collection efficiency integrate the particle density term. The density of the particles, directly linked to their chemical composition, can then be estimated from this information. A sentence summarizing the interest of doing this analysis was added in the text (L165 to L167).

 

Comments 4: In the formula, the quantity "dp" appears after L172. Neither this formula nor subsequent formulas where this quantity appears describes what it means.

Response 4: The quantity "dp" refers to the particle diameter. We apologize for omitting this important information. It has been made explicit in the text (L198) and the nomenclature table with all quantities and units has been added (L525). 

 

Comments 5: No information was provided on how the photo from Figure 2 was taken. It would be helpful to provide information about the camera used, magnification, etc…

Response 5: The camera that we used is a NIKON D7200 coupled with a Sigma 150-600 mm f/5-6.3 lens, set at a focal length of 150 mm. This information has been added in the caption of Figure 2 as well as a scale.

Comments 6: The term "spectral efficiency" is used in many places in the text (L146, L247, Fig. 3, L438). The authors did not write what they meant by this term.

Response 6: Spectral efficiency refers to the collection efficiency for a specific particle diameter. Although the term "spectral" efficiency was initially used, we believe that fractional efficiency is more appropriate and have updated our text accordingly. The meaning of the term has also been defined in the text (L71).

 

Comments 7: Commenting on the content of Figure 9, the authors used the term "revealing good agreement (…) particularly at heights 1m and 2.5m". This agreement is debatable for both the remaining cases (1.5m and 2m). Even for those indicated heights (1.5m and 2.5m), the differences between the numerical experiment and the measurement are at the level of 15-20% - therefore, it can be discussed whether it is a "good agreement".

Response 7: We apologize if our discussion of the agreement between the CFD and experimental results was not clear. The double disruptor device, intended to break the jet, resulted in a recirculation flow downstream. This recirculation creates a zone with a minimum velocity (<0.2 m/s) that coincides with the level where the largest discrepancies between measured and simulated occur. This effect is especially prominent at y = 2 m (in the low-flow region) but is also found close to the walls, where velocity approaches to 0 m/s. We have included a diagram showing the velocity vectors inside the device and describing the measurement protocol as well as the probe specifications (Figure 8(e), Page 14). From this diagram, we can clearly identify the dead zone, that by the way is not a problem for our future measurements. A detailed discussion about the discrepancies observed is provided and the unsuitability of the anemometer for these low velocity measurements are addressed in the manuscript (Page 13, lines 431 to 443, and Page 14, lines 464 to 474). Thank you for your comment, which certainly improves the quality of our research.

 

Comments 8: The text presents only the theoretical effectiveness of the constructed wet scrubber. There is no experimental measurement of the effectiveness, neither total nor interval efficiency (as the authors call it "spectral").

Response 8: Thank you for pointing this out. However, the current work is limited to the design and its implementation, which helps us address technical problems and closely simulate real-world conditions. The experimental studies are still in progress, and the results will be covered in a subsequent article once the data has been examined.