ANFO (or AN/FO, for ammonium nitrate / fuel oil) is a widely used explosive mixture. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied The oil used is most often No. 2 fuel oil, or diesel fuel, but sometimes kerosene or even molasses). Fuel oil is a fraction obtained from Petroleum Distillation, either as a distillate or a residue Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum Kerosene, sometimes spelled kerosine in scientific and industrial usage is a Combustible Hydrocarbon liquid Molasses or Treacle is a thick Syrup by-product from the processing of the Sugarcane or Sugar beet into Sugar.
It is by far the most widely used explosive in coal mining, quarrying, metal mining, and civil construction: it accounts for an estimated 80% of the 6,000,000,000 pounds (2,700,000 metric tons) of explosive used annually in North America. Coal mining is the extraction or removal of Coal from the Earth by Mining. A quarry is a type of open-pit mine from which rock or Minerals are extracted Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body It also sees service in improvised explosive devices, where it is also known as a fertilizer bomb. An improvised explosive device ( IED) is a Bomb constructed and deployed in ways other than in conventional Military action [1]
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Chemistry
ANFO under most conditions is considered a high explosive; it decomposes through detonation rather than deflagration and with a high velocity. An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Detonation is a process of Supersonic Combustion in which a Shock wave is propagated forward due to energy release in a reaction zone behind it Deflagration (Lat de + flagrare, "to burn down" is a technical term describing subsonic Combustion that usually propagates through Thermal conductivity Explosive velocity is the Velocity at which the shockwave front travels through a detonated Explosive. It is a tertiary explosive consisting of distinct fuel and oxidizer phases and requires confinement for efficient detonation and brisance. Tertiary explosives, also called blasting agents', are so insensitive to shock that they cannot be reliably detonated by practical quantities of Primary explosive An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound Brisance is a measure of the rapidity with which an Explosive develops its maximum Pressure. Its sensitivity is relatively low; it generally requires a booster (e. An explosive booster acts as a bridge between a low energy Explosive and a low sensitivity (but typically high energy explosive g. , one or two sticks of dynamite, as historically used, or, in more recent times, Tovex) to ensure reliable detonation. Dynamite is an explosive based on the explosive potential of Nitroglycerin, initially using Diatomaceous earth (kieselgur US Spelling kieselguhr Tovex (also known as Threnchrite, Seismogel, and Seismopac) is a Water gel explosive that has several advantages over traditional Dynamite The explosive efficiency associated with ANFO is approximately 80% of TNT, also stated as (0. Trinitrotoluene ( TNT) is a Chemical compound with the formula C6H2(NO23CH3 8) TNT equivalency. The most efficient mixed AN explosives using fuels other than fuel oil can exceed (1. 6) TNT equivalency.
The basic chemistry of ANFO detonation is the reaction of ammonium nitrate (NH4NO3) with a long chain hydrocarbon (CnH2n+2) to form nitrogen, carbon dioxide and water. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Water is a common Chemical substance that is essential for the survival of all known forms of Life. In an ideal stoichiometrically balanced reaction, ANFO is composed of approximately 94. Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry is the Calculation of Quantitative (measurable 3% AN and 5. 7% FO by weight. The normal ratio recommended is 2 quarts of fuel oil per 50 pounds of ammonium nitrate. [2] In practice, a slight excess of fuel oil is added, as underdosing results in reduced performance while overdosing merely results in more post-blast fumes. Thus, as recommended by the Wisconsin Conservation Department, while avoiding producing excessive yellow smoke, a ratio of "2. 5 to 3 quarts of fuel oil per 50 pounds" of ammonium nitrate "produces excellent results". The quart is an imperial and US customary unit of Volume equal to a quarter of a Gallon. [2] When detonation conditions are optimal, the aforementioned gases are the only products. In practical use, such conditions are impossible to attain, and blasts produce moderate amounts of toxic gases such as carbon monoxide, hydrogen sulfide, and oxides of nitrogen (NOx). Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric The term nitrogen oxide typically refers to any Binary compound of Oxygen and Nitrogen, or to a mixture of such compounds Nitric
Industrial use
Ammonium nitrate is widely used as a fertilizer in the agricultural industry. Fertilizers ( also spelt fertiliser are chemical compounds given to Plants to promote growth they are usually applied either through the soil for uptake by plant Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture In many countries its purchase and use is restricted to buyers who have obtained the proper license. This restriction is primarily because it is an attractive and simple component used in the production of fertilizer bombs by terrorists.
In the mining industry, the term ANFO specifically describes a mixture of solid ammonium nitrate prills and No. A prill is a small aggregate of a material most often a dry sphere formed from a melted liquid 2 fuel oil (heating oil. Fuel oil is a fraction obtained from Petroleum Distillation, either as a distillate or a residue ) In this form, it has a bulk density of approximately 840 kg/m3. Bulk density is a property of powders granules and other "divided" solids especially used in reference to Soil. The density of individual prills is about 1300 kg/m3, while the density of pure crystalline ammonium nitrate is 1700 kg/m3. It is notable that AN prills used for explosive applications are physically different from fertilizer prills; the former contain approximately 20% air. These voids are necessary to sensitize ANFO: they create so-called "hot spots". [3]
AN is highly hygroscopic, readily absorbing water from air. Hygroscopy is the ability of a substance to attract Water Molecules from the surrounding environment through either absorption or Adsorption It is dangerous when stored in humid environments, as any absorbed water interferes with its explosive function. AN is also water soluble. When used in wet mining conditions, considerable effort must be taken to dewater boreholes. A borehole is the generalised term for any narrow shaft drilled in the ground either vertically or horizontally
Other explosives based on the ANFO chemistry exist; the most commonly used are emulsions. An emulsion ( IPA: /ɪˈmʌlʃən/ is a mixture of two Immiscible (unblendable liquids They differ from ANFO in the physical form the reactants take. The most notable properties of emulsions are water resistance and higher bulk density.
The popularity of ANFO is largely attributable to its low cost and high stability. In most jurisdictions, ammonium nitrate need not be classified as an explosive for transport purposes; it is merely an oxidizer. An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound Many mines prepare ANFO on-site using the same No. 2 diesel fuel that powers their vehicles, although heating oil (No. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum 2 fuel oil), which is nearly identical, may cost less than No. 2 diesel fuel. Many fuels can theoretically be used; however, the low volatility and cost of No. 2 fuel oil makes it ideal.
Disasters
Unmixed ammonium nitrate can decompose explosively and has been responsible for industrial disasters such as the Texas City disaster in Texas City, Texas in 1947 and the Ryongchon disaster of Ryongchon, North Korea in 2004. The Texas City Disaster of April 16, 1947, started with the mid-morning fire and detonation of approximately 2300 tons of Ammonium nitrate on board the Texas City is a city located in Galveston County Texas, a county in the U The Ryongchŏn disaster was a Train disaster that occurred in the town of Ryongchŏn, North Korea near the border with China on April Ryongch'ŏn is a ''kun'' (county in North P'yǒngan Province North Korea, at the mouth of the Yalu River. North Korea is the commonly used short form name for the Democratic People's Republic of Korea (or DPRK) a State located in East Asia, However, it is considered a somewhat inefficient explosive as it exhibits only (0. 44) TNT equivalency.
Terrorist use
ANFO has occasionally been used in terrorist bombings. First used in 1970 by student protesters at the University of Wisconsin-Madison, who learned how to make and use ANFO from a Wisconsin Conservation Department booklet entitled Pothole Blasting for Wildlife,[2][4] the ANFO car bomb was soon adopted by the IRA, such as in the 1993 Bishopsgate bombing. A car bomb is an explosive device placed in a car or other Vehicle and then detonated. The Provisional Irish Republican Army (Óglaigh na hÉireann ( IRA; also referred to as the PIRA, the Provos, or by some of its supporters as the The Bishopsgate bombing occurred on 24 April 1993 when the Provisional Irish Republican Army (IRA detonated a Truck bomb in London's financial district It has also seen use by groups such as the FARC, ETA, and various Palestinian terrorists. The Revolutionary Armed Forces of Colombia – People’s Army (Fuerzas Armadas Revolucionarias de Colombia – Ejército del Pueblo also known by the Acronym of eu '''Euskadi Ta Askatasuna''' or ETA ( Basque for "Basque Homeland and Freedom" ˈɛːta is an illegal armed Basque nationalist Separatist Palestinian people or Palestinians ( الشعب الفلسطيني, ash-sha`b al-filasTīni; الفلسطينيون, al-filasTīnīyyūn A more sophisticated variant of ANFO (with nitromethane as the fuel called ANNM) was used in the 1995 Oklahoma City bombing. Nitromethane is an Organic compound with the chemical formula CH3NO2 The Oklahoma City bombing was a domestic terrorist attack on April 19 1995 aimed at the U Improvised bombs made with agricultural-grade AN are less sensitive and less efficient than the explosive-grade variety.
References
- ^ Jo Thomas. "Jury to Be Picked in 2d Oklahoma Bomb Trial", The New York Times, 1997-09-29. Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar Events 522 BC - Darius I of Persia kills the Magian usurper Gaumâta securing his hold as king of the Persian Empire.
- ^ a b c Mathiak, Harold A. (1965). Pothole Blasting for Wildlife. Wisconsin Conservation Department, Madison, Wisconsin 53701, 11.
- ^ It was found by the IRA, in response to using low brisance AN fertilizers, that "hot spots" can be created by blending powdered sugar into the ANFO mixture, effectively sensitizing the mixture to mining-standard prilled ammonium nitrate effectiveness in which the interaction of the detonation front with a spherical void concentrates energy. Brisance is a measure of the rapidity with which an Explosive develops its maximum Pressure. Blasting-grade AN prills are typically between 0. 9 and 3. 0 mm in diameter.
- ^ Mike Davis, Buda's Wagon: A Brief History of the Car Bomb (Verso: New York, 2007): 53.
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