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Title: Small-scale cook-off experiments and models of ammonium nitrate

Abstract

Here, we have completed a series of small-scale cook-off experiments of ammonium nitrate (AN) prills in our Sandia Instrumented Thermal Ignition test at nominal packing densities of about 0.8 g/cm 3. We increased the boundary temperature of our aluminum confinement cylinder from room temperature to a prescribed set-point temperature in 10 min. Our set-point temperature ranged from 508 to 538 K. The external temperature of the confining cylinder was held at the set-point temperature until ignition. We used type K thermocouples to measure temperatures associated with several polymorphic phase changes as well as melting and boiling. As the AN boiled, our thermocouples were destroyed by corrosion, which may have been caused by reaction of hot nitric acid (HNO 3) with nickel to form nickel nitrate, Ni(NO 3) 2. Videos of the corroding thermocouples showed a green solution that was similar to the color of Ni(NO 3) 2. We found that ignition was imminent as the AN boiling point was exceeded. Ignition of the AN prills was modeled by solving the energy equation with an energy source due to desorption of moisture and decomposition of AN to form equilibrium products. A Boussinesq approximation was used in conjunction with the momentum equationmore » to model flow of the liquid AN. We found that the prediction of ignition was not sensitive to small perturbations in the latent enthalpies.« less

Authors:
 [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1477438
Report Number(s):
[SAND-2018-6377J]
[Journal ID: ISSN 0737-0652; 664379]
Grant/Contract Number:  
[AC04-94AL85000]
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Energetic Materials
Additional Journal Information:
[ Journal Volume: 37; Journal Issue: 1]; Journal ID: ISSN 0737-0652
Publisher:
Taylor & Francis
Country of Publication:
United States
Language:
English
Subject:
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; ammonium nitrate; cook-off; thermocouple corrosion

Citation Formats

Hobbs, Michael L., and Kaneshige, Michael J. Small-scale cook-off experiments and models of ammonium nitrate. United States: N. p., 2018. Web. doi:10.1080/07370652.2018.1521480.
Hobbs, Michael L., & Kaneshige, Michael J. Small-scale cook-off experiments and models of ammonium nitrate. United States. doi:10.1080/07370652.2018.1521480.
Hobbs, Michael L., and Kaneshige, Michael J. Mon . "Small-scale cook-off experiments and models of ammonium nitrate". United States. doi:10.1080/07370652.2018.1521480. https://www.osti.gov/servlets/purl/1477438.
@article{osti_1477438,
title = {Small-scale cook-off experiments and models of ammonium nitrate},
author = {Hobbs, Michael L. and Kaneshige, Michael J.},
abstractNote = {Here, we have completed a series of small-scale cook-off experiments of ammonium nitrate (AN) prills in our Sandia Instrumented Thermal Ignition test at nominal packing densities of about 0.8 g/cm3. We increased the boundary temperature of our aluminum confinement cylinder from room temperature to a prescribed set-point temperature in 10 min. Our set-point temperature ranged from 508 to 538 K. The external temperature of the confining cylinder was held at the set-point temperature until ignition. We used type K thermocouples to measure temperatures associated with several polymorphic phase changes as well as melting and boiling. As the AN boiled, our thermocouples were destroyed by corrosion, which may have been caused by reaction of hot nitric acid (HNO3) with nickel to form nickel nitrate, Ni(NO3)2. Videos of the corroding thermocouples showed a green solution that was similar to the color of Ni(NO3)2. We found that ignition was imminent as the AN boiling point was exceeded. Ignition of the AN prills was modeled by solving the energy equation with an energy source due to desorption of moisture and decomposition of AN to form equilibrium products. A Boussinesq approximation was used in conjunction with the momentum equation to model flow of the liquid AN. We found that the prediction of ignition was not sensitive to small perturbations in the latent enthalpies.},
doi = {10.1080/07370652.2018.1521480},
journal = {Journal of Energetic Materials},
number = [1],
volume = [37],
place = {United States},
year = {2018},
month = {10}
}

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Figures / Tables:

Figure 1 Figure 1: (a) SITI schematic with small expansion gap filled with AN prills, (b) cross-section of AN in the SITI apparatus showing thermocouple locations and (c) post-ignition SITI debris for various explosives with AN being the least violent.

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Works referenced in this record:

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