Unexpected Attention of Non-nuclear Blasts in 2020

Ammonium nitrate salt (NH₄NO₃) is a white crystal solid, highly soluble in water. It is predominantly used as a high-nitrogen fertilizer in agriculture and also a component of explosive mixtures in mining, quarrying, and civil construction. Generally, the ammonium nitrate is produced by neutralizing nitric acid (HNO₃) with ammonia (NH₃) (Figure 1). The process involves the various unit process operations including (a) solution formation and concentration, (b) solid formation, (c) finishing, (d) screening and coating, and (e) product bagging or bulk shipping [1].

Figure 1. Synthesis of ammonium nitrate salt and structure.

In the early 20^th century, disasters are turned to regular happening in the manufacturing of ammonium nitrate, but more recent. Lebanon’s main capital Beirut was rocked on 4^th August by an explosion that has killed at least 220 people and injured 6000 and 3,00,000 people homeless by using or misusing 2,750 tonnes of ammonium nitrate (Equivalent to around 1,155 tonnes of trinitrotoluene (TNT)) [2]. This collection has been stored for 6 years at a port warehouse [Figure 2].

Figure 2. The most powerful non-nuclear explosives in 2020.

During the past, the chemical has caused furthermore, for serious industrial disasters. For example, a major blast (in 1921) occurred at a BASF multinational chemical company in Ludwigshafen, in the Rhineland-Palatinate state of Germany. Around 400 metric tons of ammonium sulfate and ammonium nitrate mixture were exploded, killing 559 people and injuring 1,977 people. In the blast, the plant was destroyed which could be heard as far as Munichcity, around 300 kilometers away. In 2015 (12th August), ammonium nitrate explosions tore through container storage at the port of Tianjin station [3]. Eight hundred metric tons of the chemicals were said to have been processed in a warehouse for hazardous materials along with other items. The blast has killed 173 people, 8 missing, and 798 non-fatal injuries. Out of 173 fatalities, 104 were firefighters. An explosion of ammonium nitrate occurred at the West Fertilizer Company storage and distribution facility in West, Texas, Fifteen people were killed, more than 160 were injured, and more than 150 buildings were destroyed. Investigators confirmed that the material exploded was ammonium nitrate in 2013 [4].

What are the possibilities to explore long-stored ammonium nitrate (AN):

Manufactured as little beads that, resemble the cooking salt, ammonium nitrate (AN) is cheap to buy and usually safe to handle, but, the main problem is its storing place. AN explosion is caused due to the very rapid decomposition of the material. In principle, the decomposition of ammonium nitrate will produce some reaction products, which can be toxic and hazardous by nature. These include not only nitric acid and ammonia but also various oxides of nitrogen, with massive amounts of nitrogen oxides.

 Ammonium nitrate first dissociates to NH₃ and HNO₃ with 2.18 kJ g⁻¹ heat absorption; at elevated temperature, HNO₃ decomposes to •OH and NO₂ with a molecular homolysis; •OH reacts with NH₃ to produce •NH₂ and H₂O, and •NH₂ is oxidized by NO₂ to form N₂O and H₂O [5].

Nitrogen dioxide (NO₂) is a red, bad-smelling gas. Images from Beirut reveal a distinct reddish color to the plume of gases from the blast (Figure 3) due to NO₂ gas may be liberated from the AN blast.

Figure 3. Sourced from BBC News.

Especially mucous membranes, AN can be an irritant and would be toxic if ingested in sufficient quantities [6], but the latter seems to be highly improbable. Thus, there are numerous extremely serious concerns about explosions, the toxicity alone is not a primary concern. Pure ammonium nitrate is not an explosive on its own. It is classified as an oxidizer under the United Nations classification of dangerous goods. If it is mixed with ingredients like fuel or some other contaminants, or with some other external factors, it became very explosive.

We have suggested that ammonium nitrate is a chemical which can be highly dangerous but only under certain circumstances. The safest way to take care of a safer circle, ammonium nitrate needs to be stored in a tightly sealed container. Otherwise, it can coalesce into a large, solid mass that can absorb enough moisture to liquefy.

References:

1. Environmental Inorganic ChemistryforEngineersbook written by James G. Speight.
2. https://en.wikipedia.org
3. 2015's biggest insured disasters Archived 13 April 2016 at the Wayback Machine 30 March 2016.
4. West Fertilizer Company Fire and Explosion (15 Fatalities, More Than 260 Injured), Report 2013-02-I-TX, U.S. Chemical Safety and Hazard Investigation Board, Washington, 2016.
5. Yi Wang, Xiaolan Song, and Fengsheng Li ACS Omega 2019, 4 (1), 214-225.
6. Wexler, P., ed., Encyclopedia of Toxicology, 3rd ed., Academic Press, London, 2014.

 Blog Written By

Dr. S. CHANDRASEKAR

Institute for Advanced Study

Shenzhen University, China

Editors

Dr. A. S. Ganeshraja

Dr. K. Rajkumar

Reviewers

Dr. Y. Sasikumar

Dr. S. Thirumurugan