Ammonium nitrate fuel oil (ANFO) explosive emulsions are comparatively safe, effective and low‐cost products for mining operations. They consist of a supersaturated ammonium nitrate solution dispersed as droplets in a continuous fuel phase. Here we apply a previously developed bench‐top Nuclear Magnetic Resonance (NMR) Pulsed Field Gradient (PFG) technique to monitor the emulsion droplet size distribution in ANFO explosive emulsions as a function of time stored at an elevated temperature of 50 °C; we thus investigate the subtle effect of adverse storage conditions on emulsion stability. Storage at 50 °C for 12 weeks lead to a ∼60 % increase in mean droplet size, whereas a sample stored at 21 °C experienced no change in mean droplet size. The addition of inert salts (calcium nitrate or sodium nitrate) to the ammonium nitrate solution was also considered in terms of their ability to enable stable storage of the emulsions at 50 °C. An addition of 5 wt% calcium nitrate to the aqueous phase was required to suppress any thermal degradation of the explosive emulsions whilst a much lower dosage of only 1 wt% sodium nitrate was required to realise the same stabilizing effect.

中文翻译：

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惰性盐对炸药热降解的影响

硝酸铵燃料油（ANFO）爆炸性乳剂是采矿作业中相对安全，有效和低成本的产品。它们由以液滴形式分散在连续燃料相中的过饱和硝酸铵溶液组成。在这里，我们使用先前开发的台式核磁共振脉冲场梯度（PFG）技术来监测在50°C高温下储存的ANFO爆炸性乳剂中乳剂液滴尺寸分布与时间的关系。因此，我们研究了不利的储存条件对乳液稳定性的微妙影响。在50°C下存储12周会导致平均液滴尺寸增加约60％，而在21°C下存储的样品的平均液滴尺寸不会发生变化。还考虑了将惰性盐（硝酸钙或硝酸钠）添加到硝酸铵溶液中的能力，以使它们能够在50°C的条件下稳定储存乳液。为了抑制炸药乳剂的任何热降解，需要向水相中添加5重量％的硝酸钙，而实现相同的稳定效果仅需要低得多的剂量的1重量％的硝酸钠。