Ammonium nitrate is a popular fertilizer since it provides half of the N in the nitrate form and half in the ammonium form. The ammonium fraction is taken up by roots or gradually converted to nitrate by soil microorganisms. Many vegetable growers prefer an immediately available nitrate source of plant nutrition and use ammonium nitrate. The very high solubility of ammonium nitrate makes it well suited for making solutions for fertigation or foliar sprays.
Management practices. Nitrate can also be converted to nitrous oxide gas in very wet conditions through the process of denitrification.
For example, potassium compounds like nitrogen-potassium and nitrogen-phosphorus-potassium fertilizers have been used to increase the stability of ammonium nitrate to phase transition and decrease its sensitivity to explosion. Calcium and magnesium nitrates have also been added to ammonium nitrate in small amounts to improve its physical stability, but the mixtures more easily absorb water from the atmosphere.
Calcium ammonium nitrate CAN , prepared from ammonium nitrate and calcium carbonate, is used in some cases as an alternative to ammonium nitrate. Aluminum sulfate has also been used as a drying additive for ammonium nitrate.
While these alternatives have helped, it is important to note that unintended impurities in the manufacturing process may reduce its stability or facilitate explosion. An in-depth analysis of the CAS content collection reveals a few key areas that have begun to emerge in the Intellectual property landscape, outlining efforts to prevent accidental explosion or misuse.
These include advancements around mixtures, coatings, slow release formulations, particle size control, and hygroscopicity approaches that minimize the potential for misuse and increase stability for safer storage. For example, a coating for a fertilizer has been invented that prevents the infiltration of hydrocarbons, such as fuel oil, into the pores of fertilizer, thereby reducing its efficacy as an oxidizer WO Alternatively, hygroscopic approaches have also been explored by adding a key ingredient such as a urea double salt which forms a stable fertilizer with ammonium nitrate US So, some alternatives have emerged that provide users with safe, cost effective options but there are still significant tradeoffs either in safety or nitrogen content, so more innovation is still required.
Although ammonium nitrate is an important fertilizer because of its high nitrogen content, its explosive hazards limits its application, and it has even been banned in some areas. Reducing the concentration of ammonium nitrate, finding alternative compounds and developing safer forms are strategies that may help increase the safety of nitrogen fertilizers. Table 1 lists alternative nitrogenous fertilizers that have emerged as safer options that could provide substitutes to ammonium nitrate.
Unfortunately, the alternative with the highest nitrogen content is anhydrous ammonia, which is a toxic gas at ambient temperature. Other alternatives with high nitrogen content, such as ammonium hydroxide solutions and urea, are attractive due to their low cost and effectiveness; however, they are volatile.
Slow-release formulations of urea, as well as modified lignins and hydrogels, have been developed to overcome this challenge.
Previous disasters have heightened public awareness of the explosive nature of ammonium nitrate, and the consequences of its unsafe storage and use. In response, many regulations, rules and guidelines for ammonium nitrate, especially regarding its storage and handling, have emerged in different areas to improve safety. The primary U. In that instance, Timothy McVeigh used two tonnes of ammonium nitrate to create a bomb which destroyed a federal building and killed people.
Rescue workers search rubble after deadly Beirut blast. Dozens dead and thousands injured in Beirut blast. Image source, Reuters. An ammonium nitrate explosion can release toxic gases. What is ammonium nitrate? How dangerous is ammonium nitrate? Frantic search for survivors of deadly explosion Dozens dead and thousands injured, health minister says. Ammonium nitrate is classified as dangerous goods and all aspects of its use are tightly regulated. For decades, Australia has produced, stored and used ammonium nitrate without a major incident.
This article was originally published on The Conversation. Read the original article. Gabriel da Silva is a senior lecturer in chemical engineering at the University of Melbourne. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science.
What could have caused the explosion?
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