Improving the Carbon Capture Efficiency for Gas Power Plants through Amine-Based Absorbents

Round 1

Reviewer 1 Report

This manuscript deals with carbon-capturing for gas-powered power plants. In general, the quality of the manuscript is good and the manuscript flows very well. Few comments as follow:

1-Some typos are found. For example, “hem” should be “them” (line 202). Please correct them throughout the paper. Please also check lines 98 to 102

2-Please add a section to discuss the limitations of this study.

3-The intro and literature review should be improved slightly to be more "clear". In the current form, it gives a very good introduction to the background but fails to establish the novelty/contribution of the paper.

4-Is there any way to make the manuscript shorter e.g. by moving some part to the supplementary section?

Author Response

Reviewer 1

1-Some typos are found. For example, “hem” should be “them” (line 202). Please correct them throughout the paper. Please also check lines 98 to 102

The (line 202) has been changed to “them”.

The lines 98 to 102 have been checked and are changed accordingly in the text, changes are also shown below:

“…Therefore, it is appropriate to begin discussing the various CO₂ capture approaches and their associated technologies, such as Post-combustion, pre-combustion, oxy combustion, and chemical looping combustion [7,11,10, 9,12].

2- Please add a section to discuss the limitations of this study.

The limitation of this study has been added to the conclusion:

Limitation of the study

The limitation of this study is that it focused on typical natural gas-powered plant alone without consideration to fuel-switch between natural gas and other fuels such as Diesel etc, this was to ensure constant flue gas from the plant. Other limitations include steady-state analysis considered compared to the transient operations where plant start-up and shut-down generate different flue gas composition. 

3- The intro and literature review should be improved slightly to be more "clear". In the current form, it gives a very good introduction to the background but fails to establish the novelty/contribution of the paper.

The Introduction has been clearer, and the novelty of the study was added.

You can see table 3 has been moved to Appendix, and the chemical formula removed figures for MEA, DEA, and MDEA, and the general reaction has been removed from literature, I add the comparison between solvents,

 

4-Is there any way to make the manuscript shorter e.g. by moving some part to the supplementary section?

The manuscript has now been made shorter by removing parts that are not very relevant while certain charts were moved to the appendices.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors

I think the research topic you present is of interest for the Journal, however, it needs deep revisions, starting from the title that is too long. I would write something like this: Improving the carbon capture efficiency for gas power plants through amine-based absorbents.

The abstract also can be shorter starting from row 14 (going immediately to the point, we know from the title the flue gas is from the gas power plant)

Lines:53 “to persuade users of co2 to reduce their co2 emissions” – not clear, and there other sentences like this in the text, so please review it carefully.

Chapter 2 is well designed in the 3 chapters, but every one of them is too long. No need to report table 3, fo instance, just put this in a reference and point out in the test which of all those physical properties are the ones involved in the absorption process with amines.

No need to report general reactions of amines with formulas, these are known processes; stress instead in why they are good/or not  for the CO2 capture

Add a graph (or more) to table 8, to compare at glance the differences in the response of the used amines

The paper aims to highlight which of the examined amines are the better ones in the decarbonizing flue gas. However, Sustainability is not a Journal dedicate only to the chemical aspect, and for instance, it is good to discuss amine prices, but it also would be good to add some evaluation of the cost or a real capture plant.

Author Response

Reviewer 2

 

• I think the research topic you present is of interest for the Journal, however, it needs deep revisions, starting from the title that is too long.

The title has been changed to :

Improving the carbon capture efficiency for gas power plants through amine-based absorbents.

• The abstract also can be shorter starting from row 14 (going immediately to the point, we know from the title the flue gas is from the gas power plant)

The abstract has been reviewed with clearer sentences as shown in the text from line 14.

 

• Lines:53 “to persuade users of CO₂ to reduce their CO₂emissions” – not clear, and their other sentences like this in the text, so please review it carefully.

This sentence has been changed to this below sentence:

This study also presents trade-off option of CO2 capture versus amine recirculation required and cost for amine solvents (MEA, DEA, and MDEA). Therefore, the most significant problem which must be determined and considered is the percentage of oxygen in the flue gas, which is affected the amine solvents and caused degrade its.

• Chapter 2 is well designed in the 3 chapters, but every one of them is too long. No need to report table 3, for instance, just put this in a reference and point out in the test which of all those physical properties are the ones involved in the absorption process with amines.

The Table 3 has been moved to Appendix section and applied property Table generated has also been added onto the appendix to indicate comparison of the properties for amines absorption.

 

• No need to report general reactions of amines with formulas, these are known processes; stress instead in why they are good/or not  for the CO₂ capture

The general reactions of amines with formulas has been deleted while their relevance to amine absorption has been critically discussed.

 

• Add a graph (or more) to table 8, to compare at glance the differences in the response of the used amines.

A graph has been added.

• The paper aims to highlight which of the examined amines are the better ones in the decarbonizing flue gas. However, Sustainability is not a Journal dedicate only to the chemical aspect, and for instance, it is good to discuss amine prices, but it also would be good to add some evaluation of the cost or a real capture plant.

The  capital cost for CO₂ capture facility is $223million and capture cost ($/tonne CO₂)  ranges between $(36-70) for MEA  for a typical gas-powered powrr plant incorporated with Cabon capture using MEA shown in Table 11[19,35].

 

Table 11. The cost of MEA for one a real company for post capture of CO₂.

Study	[19,35]
Industrial source	Combined stack gas
CO2 capture technology	PCC MEA
CO2 capture efficiency (%)	90
CO2 captured (Mt CO2/y)	1.04
Project life (years)	20
Currency	US
Cost year	2007
External power plant or fuel	Natural gas
Capital cost for capture facility ($million)	223
Capture cost ($/tonne CO2 avoided)	36-70

 

Author Response File: Author Response.docx

Reviewer 3 Report

The work uses simulation in attempt to compare the efficiency of MEA, DEA and MDEA as solvents or absorbents for CO₂ capture from flue gas emitted from gas powered plants. The novelty of the work is not very high but the work could provide very useful preliminary insight for researchers in the area. The content of the manuscript is extensive and literature has been adequately reviewed. However, some revision is required before the paper can attain an acceptable or publishable status. The following suggestions could improve the work.

1. The introduction is very exhaustive. However, there are a few sentences that require revision. Line 51, Line 54-56, Line 66, Line 97-102, Line 165, Line 182-183, Line 202, Line 344-345. These sentences and phrases must be thoroughly rewritten.
2. Materials and methods section should be rewritten. Although the analytical method was purely based on simulation, the authors don't need to explain how the software works. Where to click and how to start and run the software is not a publishable methodology. The methodology should involve the theoretical calculations done at the backend of the software. The software is just a tool that accepts input data, conducts some computations and gives output data. The calculation steps at the backend of the computer, which is theoretical is what should go into the methodology. Therefore the entire methodology and computational algorithm should be revised thoroughly. 
3. Underlying assumptions of the modelling work were not clearly stated. The assumptions and limitations of the work must be clearly stated. Every data used in the simulation must be justified. The reasons for choosing the process data should be stated and justified.
4. Results were not adequately described and explained. From Table 8, when the concentration of MDEA was increased from 10% to 15%, the amount of CO2 in the clean flue gas actually increased from 8.4559 to 8.5816. However, similar increments in the concentration of MEA and DEA resulted in decrease in CO2 content of the flue gas. This data needs further explanation because it is contrary to conventional knowledge. Bar charts could be used to compare the performance of these three solvents adequately, after all that is the main objective of the paper.
5. Discussion of the results is inadequate. Line 559 - 563 is the main paragraph that seems to discuss the observed results. Every output of the simulation must be adequately discussed. First, key parameters for comparing the performance of the solvents must be established in the methodology. Then, after the simulation, the output must be discussed parameter by parameter to show clearly which solvent has the most efficient performance overall. 

In conclusion, the work has very useful application if it is presented well. I strongly believe that if the authors implement the above suggestions, the paper should be accepted and published as it will contribute meaningfully to research in the area. 

Author Response

Reviewer 3

 

• The introduction is very exhaustive. However, there are a few sentences that require revision. Line 51, Line 54-56, Line 66, Line 97-102, Line 165, Line 182-183, Line 202, Line 344-345. These sentences and phrases must be thoroughly rewritten.

 

Changes have been made to each of the lines and paragraph as detailed below:

 

Line 51, this is some change in the line 51,

Currently, chemical solvents using absorption process consider use the technology of the post-combustion CO₂ capture of technologies, considered one of the best technology for capturing CO₂, in addition to pre-combustion capture that has been used to remove CO₂ and H₂S from natural gas components in a refinery [5,6,7].

 

Line 54-56,  have been changed to

This study also presents trade-off option of CO₂ capture versus amine recirculation required and cost for amine solvents (MEA, DEA, and MDEA).Therefore, the most significant problem which must be determined and considered is the percentage of oxygen in the flue gas, which is affected the amine solvents and caused degrade its

Line 66 has been changed to this:

There are two considerations to be made prior to CO₂ capture , which are:

(a) how to deal with the huge amount of carbon dioxide from fossil fuels formed during combustion; 

(b) how to separate the impurities of the stream in flue gas.

 

Line 97-102

Therefore, it is bringing significant attention to the research community in understanding  CO₂ capture approaches and their associated technologies for gas-powered plants, such as Post-combustion, pre-combustion, oxy combustion, and chemical looping combustion [7,11,10, 9,12]:

 

Line 165 has been changed

The rich amine solution leaves via the bottom of the absorber, which is then heated to about 100 °C across the amine-amine exchanger (lean/rich amine heat exchanger)

 

 

Line 182-183 has been changed more information to:

because of the equilibrium isotherm and loading (mole of CO₂ / mole of amine) transfer from higher (rich amine)to lower loading (lean amine or treated amine), leading to high cost of energy recovery for solvent  

Line 202,

“hem” changed to “them”.

Line 344-345

Has been changed to this:

the low loading capacity of CO₂; could still lead to high energy consumption and  corrosion rate; which in turn makes equipment size  high.

• Materials and methods section should be rewritten. Although the analytical method was purely based on simulation, the authors don't need to explain how the software works. Where to click and how to start and run the software is not a publishable methodology. The methodology should involve the theoretical calculations done at the backend of the software. The software is just a tool that accepts input data, conducts some computations and gives output data. The calculation steps at the backend of the computer, which is theoretical is what should go into the methodology. Therefore the entire methodology and computational algorithm should be revised thoroughly.

The materials and methods section have been updated according.

• Underlying assumptions of the modelling work were not clearly stated. The assumptions and limitations of the work must be clearly stated. Every data used in the simulation must be justified. The reasons for choosing the process data should be stated and justified.

 

Assumptions and limitations of the study have been added.

 

• Results were not adequately described and explained. From Table 8, when the concentration of MDEA was increased from 10% to 15%, the amount of CO2 in the clean flue gas actually increased from 8.4559 to 8.5816. However, similar increments in the concentration of MEA and DEA resulted in decrease in CO2 content of the flue gas. This data needs further explanation because it is contrary to conventional knowledge. Bar charts could be used to compare the performance of these three solvents adequately, after all that is the main objective of the paper.

Results have now been adequately described.

• Discussion of the results is inadequate. Line 559 - 563 is the main paragraph that seems to discuss the observed results. Every output of the simulation must be adequately discussed. First, key parameters for comparing the performance of the solvents must be established in the methodology. Then, after the simulation, the output must be discussed parameter by parameter to show clearly which solvent has the most efficient performance overall. 

The key parameters such as absorbent concentrations, recirculation rate and the percentage of CO2 in the exit stream have now been adequately discussed.

Round 2

Reviewer 2 Report

Dear Authors

 

The paper has been improved a lot thanks to all the reviewers suggestions.

It can be published din th epresent form

Best

Author Response

Thanks for your review I really appreciate that as you said below

The paper has been improved a lot thanks to all the reviewers suggestions.

It can be published din the represent form

Best

Reviewer 3 Report

The manuscript compares the efficiency of three amine-based absorbents (MEA, DEA and MDEA) for CO2 capture from flue gas. This is a major revision after first round of review. The major suggestions from the first round of review has been implemented and the paper has been improved to a large extent. However, there remain some minor work to be done to get the paper up to publication standard. The following are suggested:

1. English language editing was conducted but some of the newly written texts need a major editing. I have highlighted some of the areas in the attached manuscript for consideration. Some of the sentences don't make scientific sense and need to be rewritten. The authors should take time to go through every sentence to make sure all sentences make sense. 
2. Assumptions and limitations are inadequate. Only one sentence (page 17) is written about underlying assumptions of the work. I don't think steady state flow is the only assumption of the work. Create a new heading for assumptions and limitations and state all assumptions and expected limitations of the work.
3. Inappropriate positioning of the limitations of the work. The authors have stated the limitations of the work after the conclusion. This has the tendency to undermine the findings of the work. State the limitations in the same section where you have written the assumptions of the work since they go together. It is based on the assumptions that we get the limitations.
4. Figure 20 and 21 are not publishable charts. Review and prepare the charts to meet scientific standards for publication. The figures should be clear and clean.
5. Inadequate discussion of results. The authors have improved their discussion but it is not enough. Every data in the work should be useful and if it is useful you need to write about it. Tell us how every data contribute to answering the research question. It is not enough to simply publish the output from the software. Interpretation of every data and its contribution to the work must be written.
6. Figure 22 is not a figure but a table. Prepare it into a publication worthy table. I understand that this is just a screenshot from the software. Use the data to prepare the table. 

Generally the work has been improved and that is good. The usefulness of the work has never been in doubt. I strongly believe that if the above listed minor work is done meticulously, the paper will be good for publication. 

Comments for author File: Comments.pdf

Author Response

1. English language editing was conducted but some of the newly written texts need a major editing. I have highlighted some of the areas in the attached manuscript for consideration. Some of the sentences don't make scientific sense and need to be rewritten. The authors should take time to go through every sentence to make sure all sentences make sense. has been change
2. Assumptions and limitations are inadequate. Only one sentence (page 17) is written about underlying assumptions of the work. I don't think steady state flow is the only assumption of the work. Create a new heading for assumptions and limitations and state all assumptions and expected limitations of the work. the limitation has been shifted to assumption section
3. Figure 20 and 21 are not publishable charts. Review and prepare the charts to meet scientific standards for publication. The figures should be clear and clean. the figures are reploted
4. Inadequate discussion of results. The authors have improved their discussion but it is not enough. Every data in the work should be useful and if it is useful you need to write about it. Tell us how every data contribute to answering the research question. It is not enough to simply publish the output from the software. Interpretation of every data and its contribution to the work must be written. some information has been change and add.
5. Figure 22 is not a figure but a table. Prepare it into a publication worthy table. I understand that this is just a screenshot from the software. Use the data to prepare the table. 

the figure 22 change to table 13.

\my regards and thanks I hope you like my change this time thanks alot

 

Author Response File: Author Response.docx