SCR Performance Evaluations in Relation to Experimental Parameters in a Marine Generator Engine
Round 1
Reviewer 1 Report
This paper presents a work that could be of interest to the reading audience of the Journal of Marine Science and Engineering. However, the current presentation needs great editing before it is ready for publication.
The paper aims to study SCR performance evaluations changing experimental parameters in a marine engine.
GENERAL
1. Title. Please remove ‘720 kW.’
2. Abstract. No real conclusion was drawn.
3. List of symbols. Please add all acronyms and symbols that the authors use in the figures, tables, and equations. Adding the list allows the authors to remove the information below the figure caption in Figure 1 (for example).
4. Introduction. In the introduction, some ‘modelling methods’ are developed. However, section 2 does not describe what modelling methods have been used in this study (in theory, the authors do not use any of them). Also, the introduction section does not include comparisons of emissions in heavy-duty engines similar to the one used in the study. The introduction should be rewritten, collecting results from other studies with similar engines.
5. Section 2. Please explain the section correctly. Do not repeat information.
6. Results. Some results are not correctly explained. In some cases, it does not even know what they represent. The results are not compared with any previously published document.
7. Conclusion. It is unknown how the authors reach certain conclusions.
SPECIFIC
8. Line 25. ‘Currently, the most efficient diesel engine is mainly used for power generation facilities and cargo transportation.’ This is not true, for example in Europe. The diesel cars (light-duty diesel engine) are still the majority. Please modify this sentence (add heavy-duty, f.e.) and add some references.
9. Line 37: ‘Similarly, the authors of this study….’. Please add some references at the end of the sentence.
10. Table 1. Lines 57-64 have been overwritten on Table 1.
11. Line 52. ‘Many studies….’ This sentence ends with a single reference (which is not a revision document). Please add more references.
12. Figure 2 should be explained in more detail in the text.
13. Figure 3. This figure is not necessary. The explanation of the figure is repeated.
14. Lines 85-88 and Lines 105-108 contain the same text. Please, do not repeat. Explain correctly in Figure 2.
15. Table 2. ‘Area ratio’ Units? What mean ‘(1)’, ‘(2)’ and ‘(3)’? What mean ‘3D’, ‘4D’ and ‘5D’? What mean ‘Area ratio’?
16. Table 2. Why have these angles been used in the nozzle? Any reference?
17. Table 4. What are the main properties of the fuel used?
18. Line 138. What mean ‘DCU’?
19. Section 2.2. Please add the engine age (or similar information). If this engine complies some European or American (or equivalent) emission regulations, please indicate it.
20. Section 2.2. What type of injector has been used?
21. Line 194. The parameter 'space velocity' should be explained before the results shown in Figure 12.
22. Figure 13. What mean ‘outlet NOx’ and ‘inlet NOx’?. The Y axis of Figure 13 (a top), should be called ONLY 'NOx (ppm)' and the Y-axis of Figure 13 (b, bottom) only 'NOx (g / kWh)'. Please explain correctly the figure and what is represented in it.
23. Line 225. For the third time, the authors repeat the lines 85-88 (lines 225-228), which do not clarify anything. Please remove.
24. Conclusion. (1) ‘…The performance of the components was verified through the single component performance test for the detailed design components, and the total nitrogen oxide reduction efficiency was predicted using the proven system…’ Where?
Author Response
Review 1
This paper presents a work that could be of interest to the reading audience of the Journal of Marine Science and Engineering. However, the current presentation needs great editing before it is ready for publication.
The paper aims to study SCR performance evaluations changing experimental parameters in a marine engine.
GENERAL
1. Title. Please remove ‘720 kW.’
Answer) Thank you for your comment. I would like to modify as followed;
SCR performance evaluation in relation to experimental parameters in a marine generator engine.
2. Abstract. No real conclusion was drawn.
Answer) Thank you for your good comment. I would like to revise as followed;
Abstract: Many researchers are conducting experiments on the position and nozzle conditions in the exhaust pipe for the stage/swirl mixer, and the injection position required to satisfy the International Maritime Organization (IMO) regulations. In this study, the SCR system was designed through basic and detailed designs. The performance of the components was verified through the single component performance test for the detailed design components, and the total nitrogen oxide reduction efficiency was predicted using the proven system. Subsequently, it was applied to the actual engine, and the performance was verified according to the engine operating conditions using the experimental variables. NOx reduction rate and NH3 slip characteristics in relation to MCR conditions using the optimised SCR system show that NOx reduction rate was more than 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system meets the IMO regulatory requirements.
3. List of symbols. Please add all acronyms and symbols that the authors use in the figures, tables, and equations. Adding the list allows the authors to remove the information below the figure caption in Figure 1 (for example).
Answer) I would like to add acronyms as your comments
Acronyms
EGR Exhaust Gas Recirculation
SCR Selective Catalytic Reduction
IEM Internal Engine Modification
DWI Direct Water Injection
HAM Humid Air Motors
FEW Fuel-Water Emulsion
LNG Liquefied Natural Gas
4. Introduction. In the introduction, some ‘modelling methods’ are developed. However, section 2 does not describe what modelling methods have been used in this study (in theory, the authors do not use any of them). Also, the introduction section does not include comparisons of emissions in heavy-duty engines similar to the one used in the study. The introduction should be rewritten, collecting results from other studies with similar engines.
Answer) Thank you for your comments. I would like to rewire the introduction as followed;
1. Introduction
Currently, the most efficient diesel engine is mainly used for power generation facilities and cargo transportation. Compared with most other engines along the lines of durability, rugged design, and low fuel consumption, diesel engines are more attractive. Since its invention in 1892, the diesel engine has greatly improved in power, efficiency, fuel economy, and reliability. The performance of diesel engines has been improved through a number of studies to reduce exhaust emissions from physical and chemical processes through combustion in the engine.
Lee [1,2] evaluated the performance of Urea-SCR system applied the axillary marine diesel engine in accordance with performance parameters which are composed of ammonia slip, pressure drop of SCR system and NOx reduction with space velocity (1/h). Through experiments with this auxiliary marine Urea-scr system, the ammonia slip, selective catalyst reduction system pressure drop, and NOx reduction rate in accordance with engine load were investigated under incremental and random experimental conditions, the ammonia slip of this urea-selective catalyst reduction system is below 3 ppm, which satisfies International Maritime Organization Tier III regulations. Magnusson et al. [3] researched the influence of sulfur, water and low temperature on commercial SCR V2O5– WO3–TiO2 catalyst in marine applications, using urea as reducing agent. It was concluded that high NOX reduction could be above 90% at temperatures above 300oC.
Zheng [4] used high concentration of oxygen active particle prepared by strong ionic discharge injecting marine diesel engine channels, the results showed NOX removal efficiency greater than 95%.When Yu [5] researched on NTP used into desulfurization and denitrification of marine diesel engines, the experiment result showed that with the plasma power supply fully opening, 17% oxygen content in the air, adding humidifier water, activating wet scrubbing device, NO removal rate was over 70% while SO2 removal efficiency exceeded 90%.
Nitrogen oxides (NOx) released into the atmosphere are the main cause of exhaust emissions that cause optical smog, acid rain, ozone generation and greenhouse effect. The International Maritime Organization (IMO) has announced the regulation of nitrogen oxides in marine engines since January 1, 2016 [6].Recently, Since the NH3-SCR system is very effective in reducing nitrogen oxides, studies have been focused on expanding the active temperature range of the catalyst [7–9]. Vanadia-based catalysts are used predominantly in selective catalytic reduction (SCR) applications for marine applications, such as excellent sulfur resistance and long term stability, and have advantages over zeolite-based catalysts [10].
5. Section 2. Please explain the section correctly. Do not repeat information.
Answer) I would like to modify as your comments.
2.1. Development process of the selective catalytic reduction system
Figure 2 shows the performance of the SCR system obtained from the basic design and the detailed design by comparing it with the numerical method and the Temperature programming diagram (TPD) test results for the catalyst. The SCR system finally obtained through the numerical analysis results is optimised in accordance with experimental variables by conducting a performance evaluation in the actual engine. The final determination of the design was carried out by component analysis, as shown in Figure 2, 3 and 4, by dividing experimental and performance variables by numerical analysis results.
The final SCR system is divided into experimental and performance variables, and the performance of the reduction of nitrogen oxides is tested according to the experimental conditions in the actual engine following the same experimental method and procedure. The performance optimisation of the SCR system is performed through experimental parameters as shown in Figure 4. Table 2 shows experimental parameters for: nozzle characteristics, mixer, and reactor geometry.
6. Results. Some results are not correctly explained. In some cases, it does not even know what they represent. The results are not compared with any previously published document.
7. Conclusion. It is unknown how the authors reach certain conclusions.
Answer) I would like to rewrite the conclusion as your comments
4. Conclusions
In this study, the main components of the development engine are designed with the layout of the SCR system and the exhaust gas flow conditions as the basic design. The components in the SCR system are urea dosing system design, urea nozzle, urea injection quantity, mixer, and SCR reactor. Secondly, a detailed design of all components was carried out. The detailed design creates specific designs for the mixer, nozzle, and urea dosing control system, SCR reactor optimisation, and soot blower. The results of this research are as follows:
(1) From analysing the characteristics in relation to the injection angle of the nozzle, it was found that a urea nozzle having an angle of 40° is suitable for the experimental apparatus of this study, and the mixture characteristic of the exhaust and ammonia gases. It was verified that the urea nozzle of 40° has uniform ammonia distribution.
(2) Optimisation experiments on the SCR reactor shape in relation to the ratio of the exhaust inlet area to the catalyst inlet area showed that when the area ratio is 4.2, the catalyst length is 0.83D, and the space velocity is 8000 (1/h). It was established that this condition is excellent.
(3) NOx reduction rate and NH3 slip characteristics in relation to MCR conditions using the optimised SCR system show that NOx reduction rate was more than 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system meets the IMO regulatory requirements.
SPECIFIC
8. Line 25. ‘Currently, the most efficient diesel engine is mainly used for power generation facilities and cargo transportation.’ This is not true, for example in Europe. The diesel cars (light-duty diesel engine) are still the majority. Please modify this sentence (add heavy-duty, f.e.) and add some references.
Answer) Thank you for your kind comments.
Currently, the most efficient diesel engine is mainly used for power generation facilities. Compared with most other engines along the lines of durability, rugged design, and low fuel consumption, diesel engines are more attractive. Since its invention in 1892, the diesel engine has greatly improved in power, efficiency, fuel economy, and reliability. The performance of diesel engines has been improved through a number of studies to reduce exhaust emissions from physical and chemical processes through combustion in the engine [1].
9. Line 37: ‘Similarly, the authors of this study….’. Please add some references at the end of the sentence.
Answer) I would like to modify your questions. As followed;
Lee [2] evaluated the performance of Urea-SCR system applied the axillary marine diesel engine in accordance with performance parameters which are composed of ammonia slip, pressure drop of SCR system and NOx reduction with space velocity (1/h). Through experiments with this auxiliary marine Urea-scr system, the ammonia slip, selective catalyst reduction system pressure drop, and NOx reduction rate in accordance with engine load were investigated under incremental and random experimental conditions, the ammonia slip of this urea-selective catalyst reduction system is below 3 ppm, which satisfies International Maritime Organization Tier III regulations. Magnusson et al. [3] researched the influence of sulfur, water and low temperature on commercial SCR V2O5– WO3–TiO2 catalyst in marine applications, using urea as reducing agent. It was concluded that high NOX reduction could be above 90% at temperatures above 300oC.
Zheng [4] used high concentration of oxygen active particle prepared by strong ionic discharge injecting marine diesel engine channels, the results showed NOX removal efficiency greater than 95%.When Yu [5] researched on NTP used into desulfurization and denitrification of marine diesel engines, the experiment result showed that with the plasma power supply fully opening, 17% oxygen content in the air, adding humidifier water, activating wet scrubbing device, NO removal rate was over 70% while SO2 removal efficiency exceeded 90%.
10. Table 1. Lines 57-64 have been overwritten on Table 1.
Answer) I would like to modify as followed;
Table 1. NOx limits in MARPOL Annex VI [15]
Tier | Effective Date | NOx Limit (g/kWh) where, n is rpm | ||
130 ≤ n ≤2000 | ||||
Tier 1 | 2000 | 17 |
| 9.8 |
Tier 2 | 2011 | 14.4 | 7.7 | |
Tier 3 | 2016 | 3.4 | 1.96 | |
11. Line 52. ‘Many studies….’ This sentence ends with a single reference (which is not a revision document). Please add more references.
Answer) This section is meant to introduce the various techniques in Figure 1. Various technologies for reducing nitrogen oxides is an explanation that SCR is the most attention-grabbing technology in the subject.
12. Figure 2 should be explained in more detail in the text.
Answer) I explain the Figure 2 as followed;
Figure 2 shows the performance of the SCR system obtained from the basic design and the detailed design by comparing it with the numerical method and the Temperature programming diagram (TPD) test results for the catalyst. The SCR system finally obtained through the numerical analysis results is optimised in accordance with experimental variables by conducting a performance evaluation in the actual engine. After the actual design is achieved based on the exhaust gas and nitrogen oxide of the target engine, the optimisation of the SCR system is performed as flow-charter in Figure 2. First, in the basic design, the major components of the development engine are designed according to the layout of the SCR system and exhaust gas flow conditions. The components in the SCR system are urea dosing system design, urea nozzle, urea injection quantity, mixer, and SCR reactor. Secondly, a detailed design of all components was carried out. The detailed designs were for the mixer, nozzle, and urea dosing control system, SCR reactor optimisation, and soot blower. The final determination of the design was carried out by component analysis, as shown in Figure 2 and 3, by dividing experimental and performance variables by numerical analysis results.
The final SCR system is divided into experimental and performance variables, and the performance of the reduction of nitrogen oxides is tested according to the experimental conditions in the actual engine following the same experimental method and procedure. The performance optimisation of the SCR system is performed through experimental parameters as shown in Figure 3. Table 2 shows experimental parameters for: nozzle characteristics, mixer, and reactor geometry.
13. Figure 3. This figure is not necessary. The explanation of the figure is repeated.
Answer) I would like to delete this figure 3.
14. Lines 85-88 and Lines 105-108 contain the same text. Please, do not repeat. Explain correctly in Figure 2.
Answer) I would like to modify as followed;
In this study, the main components of the development engine are designed with the layout of the SCR system and the exhaust gas flow conditions as the basic design. The objective of the final SCR system is to optimise the components by conducting a performance evaluation on the reduction of nitrogen oxides in relation to the experimental conditions in the actual engine by classifying the experimental variables and the performance parameters according to the experimental methods and procedures.
15. Table 2. ‘Area ratio’ Units? What mean ‘(1)’, ‘(2)’ and ‘(3)’? What mean ‘3D’, ‘4D’ and ‘5D’? What mean ‘Area ratio’?
Answer) Table 2 shows experimental parameters for: nozzle characteristics, mixer, and reactor geometry. Where, the meaning of area ratio is (Dh/DN)2 which of meaning is ratio between mixing pipe(DN) and hydraulic diameter(Dh).
16. Table 2. Why have these angles been used in the nozzle? Any reference?
Answer) Thank you for your comment.
Figure 4 shows the definition of spray angle in the used multi-hole urea nozzle.
Figure 3. The definition of spray angle in the used multi-hole urea nozzle
17. Table 4. What are the main properties of the fuel used?
Answer) the fuel in this study used MDO(marine diesel oil)
18. Line 138. What mean ‘DCU’?
Answer) A NOx sensor was used to provide feedback information to the DCU (Dosing control unit; Urea dosing strategy) components such as the SCR controller. Additionally, AVL FTIR was used to monitor NH3 and NOx emissions at the tailpipe of the SCR reactor, as shown in Figure 6. Table 4 shows the experimental condition in this research.
19. Section 2.2. Please add the engine age (or similar information). If this engine complies some European or American (or equivalent) emission regulations, please indicate it.
Answer) Figure 6 shows a schematic diagram of the development SCR system applied marine auxiliary generator engine which of power is 720kW.
20. Section 2.2. What type of injector has been used?
Answer) I suggest the type of urea nozzle which is used the multi-hole urea nozzle as shown in Figure 4.
Figure 4. The definition of spray angle in the used multi-hole urea nozzle
21. Line 194. The parameter 'space velocity' should be explained before the results shown in Figure 12.
22. Figure 13. What mean ‘outlet NOx’ and ‘inlet NOx’?. The Y axis of Figure 13 (a top), should be called ONLY 'NOx (ppm)' and the Y-axis of Figure 13 (b, bottom) only 'NOx (g / kWh)'. Please explain correctly the figure and what is represented in it.
Answer) I would like to modify as followed;
Figure 13. NOx characteristic in relation to the variation of MCR conditions
23. Line 225. For the third time, the authors repeat the lines 85-88 (lines 225-228), which do not clarify anything. Please remove.
24. Conclusion. (1) ‘…The performance of the components was verified through the single component performance test for the detailed design components, and the total nitrogen oxide reduction efficiency was predicted using the proven system…’ Where?
Answer) I would like to rewrite the conclusion as followed;
4. Conclusions
In this study, the main components of the development engine are designed with the layout of the SCR system and the exhaust gas flow conditions as the basic design. The components in the SCR system are urea dosing system design, urea nozzle, urea injection quantity, mixer, and SCR reactor. Secondly, a detailed design of all components was carried out. The detailed design creates specific designs for the mixer, nozzle, and urea dosing control system, SCR reactor optimisation, and soot blower. The results of this research are as follows:
(4) From analysing the characteristics in relation to the injection angle of the nozzle, it was found that a urea nozzle having an angle of 40° is suitable for the experimental apparatus of this study, and the mixture characteristic of the exhaust and ammonia gases. It was verified that the urea nozzle of 40° has uniform ammonia distribution.
(5) Optimisation experiments on the SCR reactor shape in relation to the ratio of the exhaust inlet area to the catalyst inlet area showed that when the area ratio is 4.2, the catalyst length is 0.83D, and the space velocity is 8000 (1/h). It was established that this condition is excellent.
(6) NOx reduction rate and NH3 slip characteristics in relation to MCR conditions using the optimised SCR system show that NOx reduction rate was more than 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system meets the IMO regulatory requirements.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors provided SCR performance evaluations in relation to experimental parameters in 720 kW marine generator engine. A major revision is suggested for the authors to improve the quality of this manuscript.
- There have been papers on the research of SCR, please provide a detailed literature review on this.
- Is there any photo of the experimental test rig?
- What is the characteristics of the urea injection, e.g. injection rate, injection amount…?
- The novelty of this research needs to be further addressed.
Author Response
Review 2
The authors provided SCR performance evaluations in relation to experimental parameters in 720 kW marine generator engine. A major revision is suggested for the authors to improve the quality of this manuscript.
- There have been papers on the research of SCR, please provide a detailed literature review on this.
- Is there any photo of the experimental test rig?
: I am sorry for not showing the test rig. I would like to show the schematic diagram.
- What is the characteristics of the urea injection, e.g. injection rate, injection amount…?
- The novelty of this research needs to be further addressed.
Answer) Thank you for your comments.
Urea nozzle specifications as followed figure
Figure 4. The definition of spray angle in the used multi-hole urea nozzle
Reviewer 3 Report
In this study the main components of a marine engine are designed with the layout of the SCR system and the exhaust gas flow conditions, as basic design. The seconde stage is a detailed design in order to create specific designs for the mixer, nozzle, and urea dosing control system, SCR, and the reactor optimization.
The paper is clear and well written. The results are shown in appropriate way and the conclusions are suffragate by the performed analysis. The only main comment is to check the abstract because is not properly "in line" with the main aspects investigated in the paper.
Finally, a general revision of the english language has required.
Author Response
In this study the main components of a marine engine are designed with the layout of the SCR system and the exhaust gas flow conditions, as basic design. The seconde stage is a detailed design in order to create specific designs for the mixer, nozzle, and urea dosing control system, SCR, and the reactor optimization.
The paper is clear and well written. The results are shown in appropriate way and the conclusions are suffragate by the performed analysis. The only main comment is to check the abstract because is not properly "in line" with the main aspects investigated in the paper.
Finally, a general revision of the english language has required.
Thank you for your kindly comment. I would like to revise as followed abstract
Abstract: Many researchers are conducting experiments on the position and nozzle conditions in the exhaust pipe for the stage/swirl mixer, and the injection position required to satisfy the International Maritime Organization (IMO) regulations. In this study, the SCR system was designed through basic and detailed designs. The performance of the components was verified through the single component performance test for the detailed design components, and the total nitrogen oxide reduction efficiency was predicted using the proven system. Subsequently, it was applied to the actual engine, and the performance was verified according to the engine operating conditions using the experimental variables. NOx reduction rate and NH3 slip characteristics in relation to MCR conditions using the optimised SCR system show that NOx reduction rate was more than 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system meets the IMO regulatory requirements.
Round 2
Reviewer 1 Report
The R1 version of the document has improved compared to the initial version. The document continues to have many deficiencies, but such shortcomings could be solved.
GENERAL
3. List of symbols. This indication has been partially resolved. Please add these acronyms: DN, Dh, xD, TPD, DCU, FTIR, MCR, MDO, SV, IMO
6. Results. Some results are not correctly explained. In some cases, it does not even know what they represent. The results are not compared with any previously published document.
SPECIFIC
21. Line 194. The parameter 'space velocity' should be explained before the results shown in Figure 12.
23. Line 225. For the third time, the authors repeat the lines 85-88 (lines 225-228), which do not clarify anything. Please remove.
Author Response
Review 1
The R1 version of the document has improved compared to the initial version. The document continues to have many deficiencies, but such shortcomings could be solved.
GENERAL
3. List of symbols. This indication has been partially resolved. Please add these acronyms: DN, Dh, xD, TPD, DCU, FTIR, MCR, MDO, SV, IMO
Answer) Thank you for your comments
I would like to inset the comment items as followed;
Acronyms
EGR Exhaust Gas Recirculation
SCR Selective Catalytic Reduction
IEM Internal Engine Modification
DWI Direct Water Injection
HAM Humid Air Motors
FEW Fuel-Water Emulsion
LNG Liquefied Natural Gas
DN Pipe Diameter
xD Position of mixer located xD away from reactor inlet
Dh Hydraulic Diameter
TPD Temperature Programming Desorption
DCU Dosing Control Unit
FTIR Fourier Transform InfraRed spectrometer
MCR Maximum Continuous rating
MDO Marine Diesel Oil
SV Space Velocity (1/h)
IMO International Maritime Organization
6. Results. Some results are not correctly explained. In some cases, it does not even know what they represent. The results are not compared with any previously published document.
Answer) I would like to correct your comment as followed;
In this study, the main components of the development engine are designed with the layout of the SCR system and the exhaust gas flow conditions as the basic design. The components in the SCR system are urea dosing system design, urea nozzle, urea injection quantity, mixer, and SCR reactor. Secondly, a detailed design of all components was carried out. The detailed design creates specific designs for the mixer, nozzle, and urea dosing control system, SCR reactor optimisation, and soot blower. The results of this research are as follows:
(1) Nozzles were selected considering the nitrogen oxide conversion and NH3 uniformity characteristics according to the spray angles of the Urea nozzles. Through the temperature distribution characteristics considering the spray characteristics of sprayed urea, uniform distribution of temperature and reduction of nitrogen oxides were obtained when the spray angle was 40 °.
(2) To optimize the urea nozzle position, mixer position and reactor aspect ratio, the NH3 slip was optimized for the total differential pressure of the system. From the results of this study, the swirl mixer is located 5D away from the reactor and the area ratio of the reactor is 4.2.
(3) NOx reduction rate and NH3 slip characteristics in relation to MCR conditions using the optimised SCR system show that NOx reduction rate was more than 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system meets the IMO regulatory requirements.
SPECIFIC
21. Line 194. The parameter 'space velocity' should be explained before the results shown in Figure 12.
Answer) Thanks for your comment. I would like to explain at the 2.1. Development process of the selective catalytic reduction system. As followed;
2.1. Development process of the selective catalytic reduction system
Figure 2 shows the performance of the SCR system obtained from the basic design and the detailed design by comparing it with the numerical method and the Temperature programming diagram (TPD) test results for the catalyst. The SCR system finally obtained through the numerical analysis results is optimised in accordance with experimental variables by conducting a performance evaluation in the actual engine. After the actual design is achieved based on the exhaust gas and nitrogen oxide of the target engine, the optimisation of the SCR system is performed as flow-charter in Figure 2. First, in the basic design, the major components of the development engine are designed according to the layout of the SCR system and exhaust gas flow conditions. The components in the SCR system are urea dosing system design, urea nozzle, urea injection quantity, mixer, and SCR reactor. Secondly, a detailed design of all components was carried out. The detailed designs were for the mixer, nozzle, and urea dosing control system, SCR reactor optimisation, and soot blower. The final determination of the design was carried out by component analysis, as shown in Figure 2 and 3, by dividing experimental and performance variables by numerical analysis results.
The final SCR system is divided into experimental and performance variables, and the performance of the reduction of nitrogen oxides is tested according to the experimental conditions in the actual engine following the same experimental method and procedure. The performance optimisation of the SCR system is performed through experimental parameters as shown in Figure 3. Table 2 shows experimental parameters for: nozzle characteristics, mixer, and reactor geometry. Where, the meaning of area ratio is (Dh/DN)2 which of meaning is ratio between mixing pipe(DN) and hydraulic diameter(Dh). Figure 4 shows the definition of spray angle in the used multi-hole urea nozzle. The space velocity (equation 1) represents the flow rate of the incoming exhaust gas divided by the volume of the catalyst, which indicates how many reactor volumes can be processed per unit time:
(1)
23. Line 225. For the third time, the authors repeat the lines 85-88 (lines 225-228), which do not clarify anything. Please remove.
Answer) Thank you for your comment. I would like to revise the conclusion as followed;
4. Conclusions
In this study, the main components of the development engine are designed with the layout of the SCR system and the exhaust gas flow conditions as the basic design. The components in the SCR system are urea dosing system design, urea nozzle, urea injection quantity, mixer, and SCR reactor. Secondly, a detailed design of all components was carried out. The detailed design creates specific designs for the mixer, nozzle, and urea dosing control system, SCR reactor optimisation, and soot blower. The results of this research are as follows:
(1) Nozzles were selected considering the nitrogen oxide conversion and NH3 uniformity characteristics according to the spray angles of the Urea nozzles. Through the temperature distribution characteristics considering the spray characteristics of sprayed urea, uniform distribution of temperature and reduction of nitrogen oxides were obtained when the spray angle was 40 °.
(2) To optimize the urea nozzle position, mixer position and reactor aspect ratio, the NH3 slip was optimized for the total differential pressure of the system. From the results of this study, the swirl mixer is located 5D away from the reactor and the area ratio of the reactor is 4.2.
(3) NOx reduction rate and NH3 slip characteristics in relation to MCR conditions using the optimised SCR system show that NOx reduction rate was more than 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system meets the IMO regulatory requirements.
Reviewer 2 Report
I am happy with the corrections.
Author Response
Thanks for your comments
I would like to revise the manuscript as attached file.
