Ammonium nitrate porous

Ammonia from coal gasification has been used for fertilizer production at Sasol since the beginning of operations in 1955. In 1964 a dedicated coal-based ammonia synthesis plant was brought on stream. This plant has now been deactivated, and is being replaced with a new faciUty with three times the production capacity. Nitric acid is produced by oxidation and is converted with additional ammonia into ammonium nitrate fertilizers. The products are marketed either as a Hquid or in a soHd form known as Limestone Ammonium Nitrate. Also, two types of explosives are produced from ammonium nitrate. The first is a mixture of fuel oil and porous ammonium nitrate granules. The second type is produced by emulsifying small droplets of ammonium nitrate solution in oil. 

Uses. A soluble form of magnesium nitrate is used as a fertilizer ia states such as Florida where drainage through the porous, sandy soil depletes the magnesium (see Fertilizers). Magnesium nitrate is also used as a prilling aid in the manufacture of ammonium nitrate. A 0.25—0.50% addition of magnesium nitrate to the process improves the stabHity of the prills and also improves durabHity and abrasion resistance. 

Some commercial electrodes are supplied with a double junction. In such arrangements, the electrode depicted in Fig. 15.1(h) is mounted in a wider vessel of similar shape which also carries a porous disc at the lower end. This outer vessel may be filled with the same solution (e.g. saturated potassium chloride solution) as is contained in the electrode vessel in this case the main function of the double junction is to prevent the ingress of ions from the test solution which may interfere with the electrode. Alternatively, the outer vessel may contain a different solution from that involved in the electrode (e.g. 3M potassium nitrate or 3M ammonium nitrate solution), thus preventing chloride ions from the electrode entering the test solution. This last arrangement has the disadvantage that a second liquid junction potential is introduced into the system, and on the whole it is preferable wherever possible to choose a reference electrode which will not introduce interferences. 

As noted above (p. 36), the ammonium nitrate used for these explosives should be porous and should retain 7% of the oil without tendency to segregate on standing. A further requirement in modem practice is that the mixture, when blown into boreholes by compressed air, should break down to give a proportion of fine powder which increases both the density of loading and the sensitiveness of the mixture (see p. 141). 

Another improvement consisted of preparing low density explosives (L.D. explosives) which contain ammonium nitrate in the form of bulky, porous crystals... 

The ease of detonation of ammonium nitrate is greatly influenced by its density. This was studied in detail by Fukuyama [36]. He prepared porous ammonium nitrate. The porous state appears at the transition points of 125 and 84°C when cooled. After the transition, the salt reserves its normal, less porous state. By rapid cooling the porous state can be preserved. 

PRILLS. Small, round, or adcular aggregates of a material, usually a fertilizer, that are artificially prepared, In tlie explosives field, prills-and-oil consists of 94% coarse, porous ammonium nitrate prills and 6% fuel oil,... 

Dynamite is a much safer and more controllable explosive, and is made by absorbing nitroglycerin in porous material such as sawdust or diatomaceous earth. Dynamite has largely been replaced by cheaper explosives containing ammonium nitrate as the principal ingredient. 

Sasol in South Africa produces a porous, prilled ammonium nitrate (PPAN) that finds its widest application in a mix with fuel oil. This mixture is used as an explosive and is commonly known as ANFO (Ammonium Nitrate Fuel Oil). Standard PPAN contains randomly distributed closed pores of an uncontrolled variable size and quantity. Sasol also makes EXPAN by using a patented process where polymeric microspheres are entrained uniformly in individual prills. Surfactants are added prior to the prilling process to ensure that the microspheres are evenly distributed in the prill. The addition of these microspheres (or encapsulated gas bubbles) reduces and controls prill density to desired levels. This improves the sensitivity and performance of the explosive while retaining the desirable properties of the standard prills (mechanical strength, oil absorption and free-flowability)106. 

Ammonium nitrate / fuel oil (ANFO) explosives are a mixture of 94% AN and 6% fuel oil. They are low-cost explosives that are used for coal and metal mining, quarrying and construction. Low density prills are used because they are porous and absorb the fuel oil. ANFO is safe to handle and easy to make240. 

One of the more critical feed properties in the case of ammonium nitrate prilling is the moisture content of the melt. Evaporation of the melt to nearly 100% solids produces hard, non-porous prills. Larger water contents yield porous, less dense prills. 

SASOL in South Africa produces a porous, prilled ammonium nitrate (PPAN) that finds its widest application in a mix with fiiel oil. This mixture is used as an explosive and is commonly known as ANFO (Ammonium Nitrate Fuel Oil). Additional details about PPAN are given in Reference 106. 

Ammonium nitrate is hygroscopic and readily soluble in water (the saturated solution contains about 65% NH4N03). Transitions from one crystal form to another take place at + 125.2 °C = 257.4°F, +84.2 °C = 183.6°F, +32.3 °C = 90.1 °F and -16.9 °C = +1.6°F. The product shows a great tendency to cake. The difficulties therefore involved are avoided by transformation into Prills. Ammonium nitrate is marketed as dense prills and as porous prills. Both can be introduced in industrial explosives after milling except ANFO blasting agents, which need unmilled porous prills. 

Mixtures of porous ammonium nitrate prills with liquid hydrocarbons, loaded uncartridged by free pouring or by means of -+ Air Loaders are extensively used under the name ANFO blasting agents. 

Non-cartridged commercial explosives which can be poured into boreholes, mostly ammonium nitrate explosives containing anticaking agents. When ammonium nitrate became commercially available as - Prills (porous pellets), ANFO blasting agents could also be utilized in the free-flowing form -> also Pellets. 

Fig.3.93 shows the data on the sensitivity of ammonium nitrate, which is an important explosive material. There is a difference in the sensitivity level between crystalline and prilled ammonium nitrate (AN (Prill)), which has many holes in the porous grains that make it more sensitive. The porous prills do not explode completely at a PETN equivalent 1.2g, but they do in the 50/60 steel tube test with an initial explosive booster of 50 g of RDX. 

Safety explosives for mining are produced from anuuonium nitrate. Owing to its low explosion temperature in mixtures with NaCl, the temperature is not high enough to set off the much-feared firedamp. For greater explosive power, for example, for mining (rock explosives), porous-priUed ammonium nitrate containing approximately 6% diesel oil is used. 

The treatment of ADUF by reverse osmosis [13] was found to be useful in concentrating activity in small volume while making a larger volume of the decontaminated effluent for direct disposal after required dilution. Porous cellulose acetate membranes were used in plate module configurations. The concentration of ammonium nitrate in the permeate stream is not very different from that of the contaminated retentate. With the addition of flocculating aids, the decontamination factors in the range of 1000 with VRFs in the range of 100 were achieved. 

Grubb [62J drew attention to the importance of the intimacy of mixing ammonium nitrate with fuel oil by using fine and porous particles of ammonium nitrate and Clark et al. [63] described the use of micro-prilled ammonium nitrate of less than 20 mesh size. They found the AN -FO made of such ammonium nitrate can readily detonate but the rate of detonation is limited by characteristic low bulk density — the consequence of micro-prills. 

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