Reducing NOx Emissions through Microwave Heating of Aftertreatment Systems for Sustainable Transport in the Inland Waterway Sector
, Robert Cristian Marin 1,*, Andrej David 2, Adrian Bebe Olei 1, Ilie Dumitru 3, Daniela Tarnita 4, Andrea Maternova 2 and Ionel Dănuț Savu 1Round 1
Reviewer 1 Report
(1) In Table 2, the displacement of the engine is 59.21cm3. This is too small. Please check it.
(2) Figure 3 is not clear. Please redraw it.
(3) Does the MW-SCR device work only at cold start of the engine？
(4) There are some grammatical errors. They need to be revised.
Author Response
Response to Reviewer 1 Comments
Point 1: In Table 2, the displacement of the engine is 59.21cm3. This is too small. Please check it.
Response 1: Thank you for comment. The error was corrected in the revised version of manuscript. The correct value is 59.21 m3.
Point 2: Figure 3 is not clear. Please redraw it.
Response 2: Thank you for comment. I remarked that the Figure 3 was not clear due to the resolution of the picture. Please find it below at higher resolution. If is necessary to redraw the figure in order to be more clear in terms of devices and components, I will do it.
Point 3: Does the MW-SCR device work only at cold start of the engine？
Response 3: Thank you for comment. The MW-SCR works for all operating regimes of the ship. However, the research was focused on cold start taking into consideration that the NOx emissions presents the highest values when the engine is cold. Starting from this, the MW-SCR functioning has been tested for idling regime as well as nominal operating regime.
Point 4: There are some grammatical errors. They need to be revised
Response 4: Thank you for comment. The entire manuscript has been subject of english language revision.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this study, the effects microwave heating of aftertreatment systems for sustainable transport on reducing the NOx emissions in inland water way sector were investigated. This is a relatively complete study, so I recommend that this article can be accepted after minor revision as follows:
- As for the technology of reducing NOx emissions from diesel engines, in addition to using aftertreatment system such as SCR, fuel additives such as alcohols and optimizing fuel injection timing are also one of the methods to reduce NOx. The following literature can help the authors improve them: Comparative study of pilot–main injection timings and diesel/ethanol binary blends on combustion, emission and microstructure of particles emitted from diesel engines. Fuel, 2021, 122658. Comparative Evaluation on Combustion and Emission Characteristics of a Diesel Engine Fueled with Crude Palm Oil Blends. Applied Sciences, 2021, 11.23: 11502. Optimization of palm oil biodiesel blends and engine operating parameters to improve performance and PM morphology in a common rail direct injection diesel engine. Fuel, 2020, 260: 116326.
- The analysis on the Figures should appear in front of the Figure.
- The analysis on Figure 8 needs to be detailed.
- The analysis on Figure 9 is missing.
- The NOx generation mechanism should be analyzed in detail.
Author Response
Response to Reviewer 2 Comments
Point 1: As for the technology of reducing NOx emissions from diesel engines, in addition to using aftertreatment system such as SCR, fuel additives such as alcohols and optimizing fuel injection timing are also one of the methods to reduce NOx. The following literature can help the authors improve them: Comparative study of pilot–main injection timings and diesel/ethanol binary blends on combustion, emission and microstructure of particles emitted from diesel engines. Fuel, 2021, 122658. Comparative Evaluation on Combustion and Emission Characteristics of a Diesel Engine Fueled with Crude Palm Oil Blends. Applied Sciences, 2021, 11.23: 11502. Optimization of palm oil biodiesel blends and engine operating parameters to improve performance and PM morphology in a common rail direct injection diesel engine. Fuel, 2020, 260: 116326.
Response 1: Thank you for comment. The scientific results presented in the articles published in Fuel and Applied Sciences are very interesting and therefore they have been introduced in section Introduction as well as in section References.
Point 2: The analysis on the Figures should appear in front of the Figure.
Response 2: Thank you for comment. The analisys of the Figures 5, 6 and 8 have been moved in the front of figures. The analysis of Figure 7 has been placed after the figure due to the comparative analisys of different operating regimes and microwave injected powers.
Point 3: The analysis on Figure 8 needs to be detailed.
Response 3: Thank you for comment. The Figure 8 has been explained in detail by introducing the following text:
“Figure 8 also provides information related to correlations between engine output power and NOx emissions when MW-SCR system is activated. The graph shows that for idling regime and low power of naval engines, the NOx emissions present the highest values. The model is similar with those without microwave activation of selective catalytic reduction system. The conclusion related to influence of microwave energy on the reduc-tion of NOx emissions is that the microwave power contributes only to the reducing of heating time. The NOx reduction mechanism is not determined by the level o microwave injected power.”
Point 4: The analysis on Figure 9 is missing.
Response 4: Thank you for comment. The Figure 9 has be analyzed and the following text has been added:
“Figure 9 presents the evolution of NOx emissions for different operating regime of the ship engine compared with Stage V limitations. The NOx emissions without MW-SCR system decrease when the engine speed increases. On the other hand, the NOx emissions reduc-tion through microwave heating of SCR device is not affected by the engine speed. Only for very low engine speed (700 and 800 rpm) the NOx emissions depend by speed and mi-crowave injected power. Beyond 900 rpm, the reduction of NOx depend only by the heat-ing speed of cordierite core.”
Point 5: The NOx generation mechanism should be analyzed in detail.
Response 5: Thank you for comment. The research did not targeted the NOx generation mechanism. All values related to NOx emission have been measured on the exhaust pipe and the research was focused on fast activation of a commercial SCR by introducing an additional thermal source provided by microwave energy.
Author Response File: Author Response.docx
Reviewer 3 Report
The present work treats about reducing the NOx emissions through microwave heating of aftertreatment systems for sustainable transport in inland waterway sector. The topic is interesting and the manuscript is well written. I recommend the following modifications:
- Review the English language.
- Line 47, change “Sulphur” to “Sulphur”
- Line 53, change “Seddiek, & Elgohary” to “Seddiek and Elgohary”. Idem in lines 55 and 72.
- Line 59, change “Van Dingenen et al.” to “Van Dingenen et al. [3]”.
- Line 63, change “Pecho, et al. [4]” to “Pecho et al. [4]”.
- Line 67, change “Chirica, et al. [5]” to “Chirica et al. [5]”.
- Line 95, change “Yuanwang D. and his coollaborators [10]” to “Yuanwang et al. [10]”. Idem in lines97, 101, 111, 115, 124 and 128.
- Use the same text size in Figure 3. Idem in Figure 5.
Author Response
Response to Reviewer 3 Comments
Point 1: Review the English language
Response 1: Thank you for comment. The English language has been check and grammar errors were corrected.
Point 2: Line 47, change “Sulphur” to “Sulphur”
Response 2: Thank you for comment. The recommended modification has been applied.
Point 3: Line 53, change “Seddiek, & Elgohary” to “Seddiek and Elgohary”. Idem in lines 55 and 72.
Response 3: Thank you for comment. The recommended modifications have been applied.
Point 4: Line 59, change “Van Dingenen et al.” to “Van Dingenen et al. [3]”
Response 4: Thank you for comment. The recommended modification has been applied.
Point 5: Line 63, change “Pecho, et al. [4]” to “Pecho et al. [4]”.
Response 5: Thank you for comment. The recommended modification has been applied.
Point 6: Line 67, change “Chirica, et al. [5]” to “Chirica et al. [5]”
Response 6: Thank you for comment. The recommended modification has been applied.
Point 7: Line 95, change “Yuanwang D. and his coollaborators [10]” to “Yuanwang et al. [10]”. Idem in lines97, 101, 111, 115, 124 and 128
Response 7: Thank you for comment. The recommended modifications have been applied.
Point 8: Use the same text size in Figure 3. Idem in Figure 5.
Response 7: Thank you for comment. The sizes of the text in both figures have been increased in order to obtain a better visualization of the parts. If the text will be reduce, it will be very difficult to understand the notations from figures. Thank you.
Author Response File: Author Response.docx
