Explosion Risks during Firefighting Operations in Storage Rooms and the Transport of Ammonium Nitrate-Based Fertilizers
Round 1
Reviewer 1 Report
This manuscript described a method to estimate the explosion risks in storage and transportation of ammonium nitrate. The manuscript overall needs to be significantly improved before it can be published. Here are my comments:
1. I believe the authors' idea was to simulate the real condition of ammonium nitrate storage and transportation, however, it turns out that the experimental section only described ammonium nitrate DSC and heating/flaming test with some mixtures. This experimental design is far from the real conditions where PP and PE containers were used during storage and transportation. For example, the static charge/discharge created during the transportation. The experimental section must be improved to prove the hypothesis.
2. I strongly recommend to use simulation software to create modeling and simulate the real situation during AN storage and transportation and compare with the experimental results. Parameters to be considered (not limited to): temperature, pressure, container material, humidity, sealing during storage; and temperature, container material, humidity, sealing, motion, pressure, static charge during transportation.
Author Response
Dear Reviewer,
we agree with your suggestions, but the cases we describe and all the cases we have read (these were the largest ammonium nitrate disasters in the last 100 years) had a developing fire as the initiator of the explosion (apart from Oppau in 1921 - the initiator was dynamite used there to crush solidified AN). Certainly, in the next article we will analyze the influence of static electricity as the initiator of an explosion.
In all the described cases—as well as in most spectacular catastrophes caused by the explosion of AN mixed with hydrocarbons or other organic or inorganic additives—the activation energy originated from fires. Therefore, this study focuses on the rate of fire development and the associated temperature increase over time (from 2 to 50 °C/min). There may also be other causes of AN mixtures explosion (such as static electricity), and the explosion strength and range may vary due to changing environmental conditions such as pressure, temperature and humidity. The polymers selected for the experiments are materials which the packaging for the transport and storage of AN-based fertilizers is made of. In each of the measurements carried out in open containers, the process proceeded without a sudden increase in pressure and there was no ignition of pure AN with a detonation potential observed.
Best regards
Authors
Reviewer 2 Report
1. 1. Footnotes are not inserted chronologically (sequentially)
For example: Page 5 - line 195 there is literature [15], then on page 6 - line 237 there is [26] and further on page 12 - line 386 is correct [16, 17] p. 14 - verse 475 is [21] and verse 476 is [25] (items 22-24 are cited further)
2. 2. The mathematical symbol given in formula (2) - line 416 p. 12: "air density at temperature T" is not identical (probably due to the difference of computer fonts) with the explanations given (page 13 - line 425)
3. Some links in the bibliography are inactive (as of 6/15/2022) and need updating
Item 2
https://elpais.com/dia-597 rio/2004/03/10/espana/1078873233_850215.html
Item 4
https://www.abc.net.au/cm/lb/3823800/data/oricae28099s-internal-report-into-the-mex-602 ican-explosion-data.pdf
4. Polish legal acts (items 16 and 17) should be translated into English.
Author Response
Dear Reviewer,
Thank you for any tips you have given us by reading the text carefully. We sorted the footnotes as you suggested. As for the symbols used in the formulas, we have used the same symbols in the following explanations. We also checked the links in the bibliography and say they are active, but if the link is split in two in pdf, it doesn't work. Polish legal acts have been translated into English. Thank you again for the positive evaluation of our work.
Authors
Reviewer 3 Report
This article discusses the explosion risks arising during the direct contact of ammonium nitrate (AN) with various polymers such as polyethylene (PE) and polypropylene (PP), often used as storage/transport of AN-based materials. The study has been conducted with series of DSC and thermal decomposition studies in laboratory scale. In addition, risk estimation in real accidents has been performed.
The article is well written, the relevance of the topic is discussed well with real incidents. I recommend minor version.
Suggestion: Although the study on PE and PP was based on real incidents, it would have been better if the study can be expanded to other potential polymers, currently used for packing/storing. In other words, if study on similar materials were reported in literature, that could be reported in table form/ in discussion.
Author Response
Dear Reviewer,
thank you very much for any suggestions with which we fully agree. We also performed tests with other polymers. Conclusions from the research we have conducted ourselves, as well as those that we found in the literature on the subject, we have included in conclusions, in line with your recommendations.
Regards
Authors
Round 2
Reviewer 1 Report
The authors have made changes to the manuscript in terms of language, background and discussion. However, the scientific experimental section as well as the suggested simulation methods were not significantly improved.
Author Response
Dear Reviewer,
Thank you very much for your comments, nevertheless, we wanted to point out that the case of an explosion of ammonium nitrate mixtures caused by static electricity discharge is not widely known.
An analysis of the literature indicated one case where such a cause of the explosion was originally suspected.
On May 16, 1991. an explosion and fire occurred at a fireworks company in Depot. Wisconsin. The explosion and fire resulted in three deaths and two injuries. Only one building on the 43-acre complex sustained damage. ATF assistance was subsequently requested by the Waukesha County Sheriff's Department. Also arriving at the scene to conduct an investigation were the Wisconsin Division of Criminal Investigation, the Arson Bureau. OSHA, the Waukesha County District Attorney's Office. and the State of Wisconsin Bureau of Mine Safety. Static electricity was initially thought to be the cause of the explosion. It was later determined, however. that a manufacturing process being completed by one of the deceased had caused the explosion. The process involved the construction of an experimental 6-inch-diameter aerial shell, which required loading the shell with a break charge consisting of rice powder. This break charge was then surrounded by approximately 1 pound of stars.
Also we know that the pneumatic loading of ammonium nitrate based explosive generates electrostatic charge at a significant rate.
But none of the safety data sheets or guidelines from both national and international regulations for transport (both short and long-distance) or storage of AN mention static electricity as a hazard.
According to Australian sources (https://www.dmp.wa.gov.au/Documents/Dangerous-Goods/DGS_COP_StorageSolidAmmoniumNitrate.pdf):
Powered transfer equipment refers to all powered equipment that may be used to move AN into, within or from a store, and includes forklift trucks, front-end loaders, augers, chainconveyors and belt-conveyors.
The use of suitably designed, constructed and maintained powered transfer equipment is essential where AN is involved in order to reduce the risk of contamination, fire and explosion.
One of the most serious contamination hazards arises where AN comes into contact with combustible liquids, since AN readily absorbs spills such as oil and fuel by capillary action.
Due to the time to send back the next version of the article to MDPI (10 days), we will not be able to develop the suggested simulation.
We specialize in CFD software, Fire Dynamics Simulator (FDS), but he does not take into account the explosion process, nor the effects of static electricity.
Also created at the Technical University of Lodz AWZ program with ExAWZ package, which is a tool to support semi-quantitative risk evaluations at work sites with risk of explosive atmosphere occurrence. The tool employs a modified method of the analysis of protective layers. But it too does not enable the simulations you suggest.
We are not aware of such software that takes into account all the parameters you presented.
Sincerely
Authors
Round 3
Reviewer 1 Report
Authors made sufficient improvements and this article can be published.
