Review Reports - The Development of a Waste Tyre Pyrolysis Production Plant Business Model for the Gauteng Region, South Africa

Round 1

Reviewer 1 Report

Summary

This paper directly focused on environment concern with various factors. Also, some environmental conditions were mentioned wit detailing.

Question

Figure 1 provided the distribution of temperature factors. How to evaluate these data sets ?

Five equations in Equipment costing equations are used, it is NOT suitable that it had NOT physical properties of materials

Figure 1

Please would you like to make clear axis name.

What meaning corresponding ranges of from 20.0 to 0.1 valuable?

Section 3.1

Please would you like to introduce guide line or evaluation standards for safety in waste remaining?

Section 3.2 Line 207

It is so very high temperature about 550 degrees. How to prevent the safety of waste disposal facility from heating process ?

Figure 2

Figure quality is NOT good, please revise it.

Author Response

Dear reviewer

Firstly I would like to thank you for taking your time to read through my work and providing your critics there after.

I have tried to take all your comments and suggested changes that you have recommended. With regards to providing the latest waste tyre accumulation statistics, unfortunately that information is not easy to obtain in South Africa as there is to readily available data base. As a result, those were the latest published statistics from the different sources that I have use.

Thank you.

N Nkosi

Author Response File: Author Response.pdf

Reviewer 2 Report

The Development of a Waste Tyre Pyrolysis Production Plant Model for the Gauteng Region, South Africa

This paper deals with the issues of waste management, and more precisely of waste tyres in South Africa and proposes the technical, economic and feasibility study of a reprocessing and recovery solution based on pyrolysis process.

The paper is well written, clearly explained and deals with a topical issue. The structure of the paper is relevant.

General comments:

Although the references, and some of the data, are not the most recent, the topic and study remains interesting and relevant. Nevertheless, the authors could try to add a few current references, confirming the problem, the situation and/or the solution.

I was wondering if: “Would compliance with environmental standards (which does not necessarily seem to be the case according to the paper), in terms of increased costs, not greatly reduce the profitability of the process and therefore its economic viability? This does not seem to be taken into account in the analysis.” But the authors briefly raise this point at the end of the conclusion. However, since the dissertation dates back to 2014, have these additional analyses been carried out since then? Could supplements be provided?

Specific comments: I haven't identified any.

Author Response

Dear reviewer

Firstly I would like to thank you for taking your time to read through my work and providing your critics there after.

Thank you.

N Nkosi

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript deals with an interesting matter nevertheless it needs extensive reorganization before possible submission

points

1) what does it mean the development of a... model? a model for what?

2) in abstract you state his paper is part of the work presented in the first author’s Master’s dissertation at the University of Johannesburg [1]. this is clearly not needed in an abstract. also in abstracts we never show references

3) why you say two problems? it is not really valid

4) you state The study objectives were achieved through literature research, site visits, telephonic
19 and personal interviews and questionnaires

you never really mentioned the study objectives. also how telephone interviews can help the business model you show here?

5) you need in the abstract but also in the introduction to show why this reasearch is also important for an international audience eg if it can be incorporated elsewhere

6) I dont think that you quote the references correctly eg it is not Muzenda, E. (2014) but Muzenda (2014) etc... please see the instructions of the journal and abide by them exactly

7) I am not quite sure how relevant are the references you show in the introduction to your aim. what these authors focused on? on the viability and the bussiness plan or on the products and by-products of tyre recycling. please elaborate

8) it is ubrupt to start with the paragraphs gas fraction and liquid fraction. please link them with the previous paragraph

9) you state however, the large quantities of carbon monoxide (CO, 0 vol%) and
63 carbon dioxide (CO2, >5 vol%) hinders its blending with natural gas (2.41 vol % CO and 1.15 vol %
64 CO2) how can they be large quantities if they are 0?

10) why BTX (benzene, toluene, xylenes) is a valuable chemical? I think it is a pollutant. please elaborate

11) you state all major equipment are available and the Detailed (Quotation) Estimates, with 5 10 % precision, is
91 based on complete plant designs, acquired quotations for all equipment and detailed construction
92 costs [23] this sentence is not understandable. please rephrase in English

12) I think that 30% error margin is quite high for the Order of Magnitude Estimate. why it was used? please elaborate

13) I am not sure I understand how the correction factor in table 5 is calculated please elaborate

14) I understand that tremendous work was put into the calculations but is impossible for the reader to understand all the tables and the figures and it is of little value. eg what is the use of fig 1? you can just claim that the correction factor based on this reference is x and y. also I hope that the figure is not taken from this reference and it is drawn by the present authors because this is not acceptable. in any case I dont think it is necessary. the same about table 2 and table 3 please incorporate the data in the text and dont use these details. please also see and quote J. Open Innov. Technol. Mark. Complex. 2019, 5(3), 46 how short the cost evaluation is presented

15)I am sorry but in results and discussion I believe that you still present materials and methods eg Table 7. Pyrolysis oil specifications, table 8. also Table 11. Input assumptions is materials and methods. table 12 and 13 are very large can they be shortened. i dont see at all the telephone and personal interviews in the materials and methods or in the results. please elaborate

16) in conclusions you state Based on the pyrolysis plant business model and all relevant data collected through literature 324 analysis, questionnaires, site visits as well as telephonic and personal interviews the following 325 conclusions are made:

as mentioned before-where are the results from questionnaires etc?

17) in discussion you state

Waste tyre pyrolysis in South Africa

why is this chapter relevant here? what it has to do with your bussiness model? please shorten and keep only the relevant data that you utilized here or that you can compare with your data

also the manuscript needs editing by a fluent english speaker

Author Response

Dear reviewer

Firstly I would like to thank you for taking your time to read through my work and providing your critics there after.

I have tried to take all your comments and suggested changes that you have recommended. Your critic is very comprehensive and thorough, thus, I think it has added value to my paper and has made it more appealing to a broader audience (international). I also appreciate your attention to detain, such as the referencing error that I was making and ensuring that every aspect of the work is covered. I personally think that your reviews have made me a better researcher and writer.

Thank you,

N Nkosi

Author Response File: Author Response.pdf

Reviewer 4 Report

The paper deals with the economic feasibility assessment of a waste tyre pyrolysis production plant in the Gauteng Region (South Africa).

Due to the great number of waste tyres and the consequent issue in terms of disposal, energy recover by pyrolysis could be a successful strategy.

However, no layout, no Process Flow Diagram (PFD) and no Piping and Instrumentation Design (P&ID) is shown. Without these information, so, it is very difficult to evaluate i) tyre-pyrolysis plant sections, ii) mass and energy fluxes between sections.

Therefore, the paper lacks of the minimum technical elements to verify the economic evaluation.

Other minor lacks are also reported to the Authors as follow:

Introduction:

Lines 52-56. Authors write “The composition of the primary pyrolysis products is influenced by process operating parameters such as feed size, temperature and pressure, residence time, heating rate, reactor configuration as well as the presence of catalytic medium”.

Authors should have explained how reactor operative conditions influence the composition of pyrolysis products.

Line 62: Authors write “large quantities of carbon monoxide (CO, 0%)”. Authors should have verified the correctness of 0%

Lines 69-70: Authors write “tyre derived oil has the potential to be used as automotive fuel after removal of contaminants”. Authors should have specified which contaminants are present.

Materials and methods:

Authors should have explained the equations before to put them into the main text.

Authors should have inserted tables and figures ordered by increasing numbers.

Authors should have explained better equipment cost equations. Why for example the purchase equipment cost is defined in three different ways? This is clear for Eq.4 and Eq. 5 but not for Eq. 1. Where is C1 used in the analysis? What does standard design limit represent?

Line 107-121: Authors should have added the unit of measure in the nomenclature

Authors should have improved the quality of Figure 1. It is not clear what is present in the ordinate axis.

Authors should have introduced a single table rather than table 2 and table 3 in which equipment are ordered in alphabetical order. Since different unit of measures are currently used in table 2 and 3, a conversion should have been applied.

Results and discussions:

Line 199: Authors write that “further purification of carbon black is required to improve its marketing”. Authors should have specified what does it mean further purification.

Lines 222-223: Authors write that “The emissions from the reactor burners are chemically treated using a gas absorption process”. Authors should have given more details on this process.

Table 9: Authors write in the caption “Total plant energy requirement”. However, the unit of measure used is for power. Furthermore, an energy efficiency is reported. Authors should have explained how they calculated it. What is the available fuel energy? How is total supply calculated? Authors should have explained better in materials and methods.

Table 11: Authors consider in the analysis “Telephone line”. Is it an important voice of cost?

Lines 277-287: Authors should have explained the economic feasibility analysis in the section of methods. Furthermore, Authors should have explained or defined all the terms they use.

Lines 291-292: Authors write “this is due to the business ending its capex loan repayment period after year 4. visible and show a trend of not intersecting anywhere during the project life”. It is not clear what Authors mean.

Line 306: Authors write “Figure 2(b) provides the sensitivity analysis of the project”. However, where is the sensitive analysis?

Author Response

Dear reviewer

Firstly I would like to thank you for taking your time to read through my work and providing your critics there after.

Thank you,

N Nkosi

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

I am sorry but I cannot understand if and how the authors answered the questions. there is no point to point answer on the comments, just general changes.

Author Response

Improve introduction to provide sufficient background and include all relevant references

The introduction has been improved to include the following: the significant of study, the broader identification of the study to international communities was highlighted, the study objectives were clearly outlined and the significance of the studied literature was included.

Improve the research design

The layout of the paper was significantly improved by relocating some of the sections as to make the work more cohesive.

Improve description of methods

All the used equations were clearly defined in their order of appearance and their use in the costing data.

Improve presentation of results

The obtained results were further explained, and the tables and figures were simplified to improve clarity and understanding.

Improve conclusions and they should be supported by results

Conclusions were minimized to only be relative to the obtained results.

The manuscript deals with an interesting matter nevertheless it needs extensive reorganization before possible submission

points

1) what does it mean the development of a... model? a model for what?

We figured that the reviewer is referring to the topic, thus we have added they type of model in question.

The reference was removed. I concur with the reviewer that normally we do not insert references in the abstract.

3) why you say two problems? it is not really valid

The authors have rephrased the beginning of the sentence in question.

4) you state The study objectives were achieved through literature research, site visits, telephonic 19 and personal interviews and questionnaires you never really mentioned the study objectives. also how telephone interviews can help the business model you show here?

The study objectives are further defined to highlight the significance of the work. With the regards to the questionnaires, that was work done as part of a different section of the Masters. However, for this work, no questionnaires were conducted hence the study methodology was redefined to remove questionnaires as a study methodology.

5) you need in the abstract but also in the introduction to show why this reasearch is also important for an international audience eg if it can be incorporated elsewhere

The authors fully agree with the reviewer, including other international countries that can potentially adopt the same approach will help broaden the research. We have included three developing countries from different continents that can benefit from this work. We have also included the current status quo of each country regarding waste tyre management and their planned way forward.

6) I dont think that you quote the references correctly eg it is not Muzenda, E. (2014) but Muzenda (2014) etc... please see the instructions of the journal and abide by them exactly

The correct referencing style has been corrected and applied throughout the document

The significance of the literature that was studied is clearly outlined.

8) it is ubrupt to start with the paragraphs gas fraction and liquid fraction. please link them with the previous paragraph

The paragraphs have been linked to make the work more cohesive.

9) you state however, the large quantities of carbon monoxide (CO, 0 vol%) and
63 carbon dioxide (CO2, >5 vol%) hinders its blending with natural gas (2.41 vol % CO and 1.15 vol % 64 CO2) how can they be large quantities if they are 0?

There was a typo with regards to the reported figures, however, the reporting has been rectified.

10) why BTX (benzene, toluene, xylenes) is a valuable chemical? I think it is a pollutant. please elaborate

BTX compounds play a critical role in the production of chemicals, dyes plastics and synthetic fibres, their markets are projected to upsurge at a compound annual growth rate of 5.9% from 2019 to 2027. For this business model, BTX will only be considered as a possible revenue. It will not be part of the daily production streams.

11) you state all major equipment are available and the Detailed (Quotation) Estimates, with 5 10 % precision, is based on complete plant designs, acquired quotations for all equipment and detailed construction costs [23] this sentence is not understandable. please rephrase in English

The three different estimation methods have been rephrased and summarized to be more simplified and understandable

12) I think that 30% error margin is quite high for the Order of Magnitude Estimate. why it was used? please elaborate

The order of magnitude costing method was utilized due to the lack of data and documented information regarding waste tyre pyrolysis in South Africa. The operating of pyrolysis plants is still in its infancy stages in South Africa. Also, the currently existing pyrolysis facilities are independently owned and ideally protect their intellectual property. Hence, I felt that the best approach was to use well documented estimation methods.

13) I am not sure I understand how the correction factor in table 5 is calculated please elaborate

The correction factor is not calculated, it was duplicated from a book used to cost some of the equipment

Figure 1 and all other irrelevant figures were removed as to promote better understanding of the work. The correction factor table was duplicated as it is from a book. We have also obtained permission from the publisher to re-use the table. Table 2 and 3 were omitted from the work, however, We included the source/reference used to cost all the major equipment in table 4.

Table 7 and 8 were relocated under material and method. All the lengthy tables were condensed to include only relevant data. The telephonic and telephonic interviews were only used as reference to validate certain statements.

As mentioned previously, the questionnaires were part of another section of the Master’s and did not feature in this work. Thus, all data relating to questionnaires has been omitted.

17) in discussion you state

Waste tyre pyrolysis in South Africa

why is this chapter relevant here? what it has to do with your bussiness model? please shorten and keep only the relevant data that you utilized here or that you can compare with your data also the manuscript needs editing by a fluent english speaker

The waste tyre pyrolysis in South Africa section has been condensed and relocated to form part of the introduction.

Reviewer 4 Report

The paper was improved respect to previous submission by the Auhtors. However, some recommendations are suggested:

Introduction:

Authors should correct “30-40MJ N/m-3” with “30-40MJ/Nm-3”.

Materials and methods:

The section 2.1 “Waste tyre pyrolysis in South Africa” should be reported in the Introduction section as 1.2 section.

In line 131 Authors should correct the “grades)” with “grades”.

Authors should verify lines 164-165.

Figure 1. Authors should explain why hot air is fed into the pyrolysis chamber. Maybe is it putted into a heat exchanger that exchanges heat with the fluids in the chamber?

Lines 225-232. Equations should be introduced and defined in the text.

Table 3. Authors should add in the caption the acronyms ft, fp and fm used in the nomenclature.

Results and discussion:

Lines 264-265. Authors should explain the P&ID and the process in accordance to the number reported in the drawing. Furthermore, Authors should comment mass and energy balances of Table 5.

Table 6. Authors should correct the caption “Total plant energy requirement” with “Total plant power and energy requirements”

Table 6. Authors should correct “Yearly power requirements” with “Yearly energy requirements”

Figure 3. Authors should explain with the gas absorption tower is in parallel with the exiting line from the pyrolysis reactor. How flue gases are divided from pyrolysis gases in the reactor?

Table 5. Authors should specify the pressure and temperature conditions at which volume flows are calculated.

Table 5. Authors should explain what Qin e Qout are.

Authors should insert table 7 after line 320.

Table 7. Authors should correct “Power” with “Energy”, specifying what form of energy.

Figure 4a. Authors should insert only operating costs, net cash flow e revenues in order to improve the understanding. Furthermore, Authors should explain better why the netw cash flow is negative until the 8 year. Considering equation 9 and with the data of revenues and operating costs in the figure is not clear why a negative value occurs. Are maybe present other operating costs?

Figure 4a and 4b. Authors should improve the quality of the figure

Author Response

Improve the presentation of the results

The result have been improved to include a P&ID, material and energy balances and the graphs have been simplified.

The paper was improved respect to previous submission by the Auhtors. However, some recommendations are suggested:

Introduction:

Authors should correct “30-40MJ N/m-3” with “30-40MJ/Nm-3”.

The authors concur with the reviewer and the mistake has been rectified.

Materials and methods:

The section 2.1 “Waste tyre pyrolysis in South Africa” should be reported in the Introduction section as 1.2 section.

The section 2.1 “Waste tyre pyrolysis in South Africa” has been relocated to form part of section 1.2

In line 131 Authors should correct the “grades)” with “grades”.

The inappropriately placed bracket has been removed.

Authors should verify lines 164-165.

The definitions and explanations used were obtained from a reference book, however, the different cost estimation methods have been simplified to clearly distinguish the differences between the three methods.

Figure 1. Authors should explain why hot air is fed into the pyrolysis chamber. Maybe is it putted into a heat exchanger that exchanges heat with the fluids in the chamber?

This section is explained in the process description, section 3.2. Basically, pyrolysis is an endothermic reaction and thermal energy is required to initiate the decomposition of tyre chips.

Lines 225-232. Equations should be introduced and defined in the text.

The authors believe that the above has already been done.

Table 3. Authors should add in the caption the acronyms ft, fp and fm used in the nomenclature.

The acronyms have been added in the table 3 caption.

Results and discussion:

Lines 264-265. Authors should explain the P&ID and the process in accordance to the number reported in the drawing. Furthermore, Authors should comment mass and energy balances of Table 5.

The process description, section 3.2, has been included and explained in accordance with the process streams in the P&ID, Also, comments on the mass and energy balances have been included.

Table 6. Authors should correct the caption “Total plant energy requirement” with “Total plant power and energy requirements”

The caption has been corrected

Table 6. Authors should correct “Yearly power requirements” with “Yearly energy requirements”

That section of the table has been corrected

Figure 3. Authors should explain with the gas absorption tower is in parallel with the exiting line from the pyrolysis reactor. How flue gases are divided from pyrolysis gases in the reactor?

The gas absorption tower will not be in parallel with the exit flue gas line, the gas will enter at the bottom of the tower, this has been rectified in the P&ID

Upon commencement of the process, the system will be a closed loop. The non- condensable gases will be recycled back to the reaction chamber and only upon the completion of the process will the flue gas be removed from the system

Table 5. Authors should specify the pressure and temperature conditions at which volume flows are calculated.

The process conditions (temperature and pressure) have been included in the mass and energy balances.

Table 5. Authors should explain what Qin e Qout are.

Qin and Qout have been defined

Authors should insert table 7 after line 320.

Table 7 has been relocated to the suggested position

Table 7. Authors should correct “Power” with “Energy”, specifying what form of energy.

Power rephrased to “electrical energy”

Figure 4 (a) has been simplified to only include operating costs, net cash flow and revenues only. The depreciation % has been omitted from figure 4(b) due to the same trend depicted by the parameters, however, the depreciation % is shown in table 8.

Revenues are flowing into the business (seen in figure 4 (a) and table 8), however, the cumulative amounts (net cash flow) remains negative until the initial investment required to design, build and start-up the plant is paid off. Also, the net cash flow was be used to indicate the projected plant life.

Figure 4a and 4b. Authors should improve the quality of the figure

Showing lesser parameters on the same plot has de-cluttered the figures and improved their visibility.

Round 3

Reviewer 3 Report

Ι understand that a lot of work has been put in this research but this is a technical report not a scientific paper. I would prefer to refrain from the reviewing procedure for this round.