Measurements and Prediction of Ash Deposition in a Cyclone-Fired Boiler Operating under Variable Load Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The presented study was prepared correctly and in detail. I recommend the article for publication in its current form.

Author Response

Thank you so much for your time reviewing our study and for your encouragement! Best regards!

Reviewer 2 Report

Comments and Suggestions for Authors

1. A good and deep introduction is needed. There are a few review papers for ash deposition with the applications for different models (Kleinhans etc. 2018, DOI: 10.1016/j.pecs.2018.02.001, Cai etc. 2018, DOI: 10.1016/j.apenergy.2018.08.084, Niu etc. 2016, DOI: 10.1016/j.pecs.2015.09.003, ), which compared the differences between models and which was suitable for different fuels. And the authors should not just cite most of their references and should cite the most relevant references. 
2. All the tables in this paper should be adjusted to the requirements of this journal.
3. Please provide the operating conditions of the boiler for different simulations
4. For the ash deposition, the mineral transformation is critical, so please add the ICP results for the fuels and ash samples
5. In Line 158, the B/A formulation is wrong, please revise it.
6. In Table 2, why the content of SiO2 and SO3 in the fuel is larger than that in deposit ash?
7. In Line 177, revise the wrong citation
8. In Figure 2, revise the title of the Y-axis as readers cannot understand what it means
9. In Line 254, Stk number is only applicable when Stk<0.14, please provide the values of different parameters
10. In Line 260, there are several sets of a b c d for the impaction efficiency for different fuels, why do you think you choose the right one?
11. There are also different viscosity models for different fuels and ashes, the authors should compare the models and do experiments for the viscosity models to validate which is suitable for your situations, please refer to the references in Point 1.
12. In Figure 11, why the capture efficiency of fine particles is 100%? In actual situations, this should not happen
13. This paper is tried to measure and predict the ash deposition in a boiler, but the authors just provide the information of temperature and velocity with different loads from simulation. Please also provide the experimental results for comparison.  Please also provide the temperature and velocity profile of CFD results of different loads for the whole boiler
14. The authors just provides simple discussion for the prediction of ash deposition. There are several prediction methods which is more accurate for the impaction efficiency, sticking efficiency, and particle rebound and particle removal behaviors. The authors should try to compare different models to find a suitable one for their cases, and not just used a simple correlation for this paper. And please also provide the experimental results of ash deposits from the probe, such as particle size distribution, mass variations, morphological behaviors, mineralogical behaviors and transformation behaviors for different situations.

Comments on the Quality of English Language

please revise the mistakes in the comments above

Author Response

Kindly see attached file. Thank you!

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This article examines the ash deposition behaviour in an industrial coal furnaces by means of a cfd model and accompanying measurements with a deposition probe.
The approach (ansys fluent lagrangian particle post-processor with a probabilistic sticking model based on a critical viscosity and particle kinetic energy) is well established since more than 10 years and far from novel. Most of the conclusions are already well-known facts. Yet, the last point - that even slight temperature variations may have large influence on deposition ratios is in my opintion still underpresented in the literature (albeit already published elsewhere).
Together with the impression that this work is well crafted and structured, full-scale cfd examinations of ash deposition are still not too common, I still suggest this article for publications.

While the readability is very high, the article seems to lack polishing. Figure vary in layout, tables lack units and some figures are of low quality. Therefore I recommend a publication after minor revisions with emphasis on the form.

Thank you for giving me the opportunity to review this article. Its nice to see ongoing work in this interesting field of ash deposition cfd modelling in industrial boilers!

Please take these comments and questions in consideration for the revisions:
l. 91 - In my opinion, the explanations regarding the CSPI-CT tool should be removed: The "slagging index" or other information from this "tracker" are not discussed any further or set in relation to cfd results other than that they could benefit from this research. Since there are no references included, the nature of the tracker remains unclear. So does the term "successfully operating" (l. 91). In total, this section sounds more like a presentation of a commercial product with limited connection to the actual article.
l. 143 - How is the surface temperature of the probe determined? From calculations, i.e. a heat balance or measurements at the probes surface?
l. 150 / Figure 1: In my opinion, a more detailed description and/or presentation of the probe is needed in order to potentiall allow a reproduction of this work. Fig 1b is not helpful, especially considering the shades of gray & white
l. 150 / Figure 1: Of course, a completely vertical orientation of the geometry and a removal of the ANSYS-typical background would improve the quality by a lot. If someone prints the article (I know its 2023, but still...), these color gradients will lead to a messy result
l. 159 / Table 1: These numbers do not add up to 100%, please check or provide an explanation. Please provide the underlying method of analysis or standard test.
l. 160 / Table 2: How was the ash deposition determined? Which standard test was used? The ash production temperature of the parent fuel should be stated. The sum of constitutens is not 100%, why is that? You state that SEM-EDS is used in order to "measure" the chemical composition. Is that true for the analysis of the original fuel ash as well? Since this method delivers indicative results at best (high dependency of the location of measurement, high error due to peak analysis), are you confident of providing the exact numbers? Or did I misread this section and a XRD-analysis was performed (which is more standard for fuel ash analysis?)
l. 160 / Table 2: The provided number of digits varies from column to column (e.g. SiO2) and line to line
l. 160 / Table 2: Was the ash composition similar for all load conditions? Wouldn't you expect changes with respect to the furnaces load (temperature, residence times ,...)?
l. 198: Unfortunately, the number and location of cyclones cannot be understood from Fig 1a at all. I suggest a better presentation of the boiler's geometry and features.
l. 206 / Table 3: kilogams should be abbreviated as "kg" instead of "Kg"). I would expect half the coal mass flow for 50% load in comparison to 100% load. Why is this not the case?
l. 208 / Table 4: I strongly suggest including the stoichiometric air-to-fuel ratio (maybe even replacing the AFR), since it appears as more common to me.
l. 230: The "Resonableness" remains unclear to the reader and quite arbitrary, especially since your cfd predictions were validated with other, not further explained "predictions" (from where? by who?). Please explain how (and based on what) one could consider a cfd result as "reasonable" or "not reasonable".
l. 269: Please explain the criterion for a "reasonable well" agreement between measurements and cfd simulations.
l. 294 / Table 5: Remove the term "complete" since the table mentions many, but not all settings in ANSYS Fluent for the complete setup of a case.
l. 282 and l. 292: please provide physical units for the critical viscosity. Is it Pa-s?
section 2.2: You should include the resulting viscosity-temperature plot(s) for you ash since Urbain and similar model calculations not trivial. This will increase the reproducibility of your research and is helpful for the interpretetion of the modeling results
l. 380: Remove comma after (COV)
l. 413 / Table 10: Please include a unit for the probe diameter; please assure you use the same number of digits for each parameter (cf. total boiler ash flow)
l. 413: How many trajectories were calculated? Since each trajectory represents a fraction of the total mass flow, the number of trajectories is important for spatial resolution and accuracy of the results
l. 456: Please use "h" as unit for unit instead of "hr"
l. 490: Remove space before "decoupled"
l. 535: The article mostly uses mu_critical, while in Nthe Nomenclature section it is called mu_c

l. 542: Why is there no [1]?
l. 559: References [10] and [11] use different spellings of the same names
l. 563: What does "(Air Ingress: 7.5 – 22.5%)" mean?

References in general:
- Different citation styles are used, sometimes the title is marked with " or “, sometimes not.
- The year  of publications is sometimes included in brackets, sometimes without. The position of the year varies (e.g. [13])
- Inconsistent use of spaces in the references, e.g. after "vol." or "p."
- Inconsistent abbreviations of first names or initials
- some more inconsistensies regarding abbreviations of journals, use of dots after the list of authors and a few more

Please address these issues. Thank you and best regards.

 

Author Response

Kindly see attached file

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The issues were addressed. I recommend publication

Author Response

Thank you for your time and comments!