Ammonium nitrate processes

Let us first segregate the two sources forming the feed to the incinerator. As can be seen from the source-sink mapping diagram (Fig. 9.20), the gaseous emission from the ammonium nitrate process (R2) is within the acceptable zone for the incinerator. Therefore, it should not be mixed with R] then separated. Instead, the ammonia content of Ri should be reduced to 0.10 wt% then mixed with R2 to provide an acceptable feed to the incinerator as shown by Fig. 9.20. The task of removing ammonia from Rj to from 1.10 wt% to 0.10 wt% is identical to the case study solved in Section 9.3. Hence, the solution presented in Fig. 9.18 can be used. 

Figure 10.1. Ammonium nitrate process sketch. (Reproducedby permission of Wiley-VHCH)...

Figure 10J.UCB ammonium nitrate process. (Reproduced by permission ofWiley-VCH)... 

Bovens, J.L. and van Hecke, F., The Carnit Ammonium Nitrate Process, Kemira SA, The International Fertiliser Society, Proceeding 320, 1992 (www.fertiliser-society.org/Proceedings/Prc320.HTM). 

Fig. 22.20. Ammonium nitrate process sketch. (Courtesy of Wiley-VCH. 295. Zapp, K.H.., Ammonium Compounds, in Ullmann s Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH Co., Weinheim, Germany, June 15, 2000.)...

Figure lOJ-2 Block diagram for sequential modular simulation of ammonium nitrate process. 

Fig. 2. Flowsheet of the process for recycling water, ammonia and nitrates from condensates in ammonium nitrate processing...

Gel-type ion exchangers are much less resistant to osmotic shock than macroporous ones. For example, after the application of 70 cycles of osmotic shock (by treating sulfonic acid resins alternatively with 76% HNOg and wastewater from an ammonium nitrate processing plant), the number of cracked beads in the case of a gel-type resin (Wofatit KPS) was 78.3%, but for macroporous resins the number varied from only 1.2% (Amberlite 200) to 7.6% (Duolite C26) [24]. Similar results have been obtained for anion exchangers. Thus, the number of the... 

Bovens, J. L., and F. van Hecke. 1992. The CARNIT Ammonium Nitrate Process, Paper presented at the Fertiliser Society Meeting, London, England. 

As it appears from Table 4.2, CC bond fragmentation is a very fast process with electrofugal groups such as disubstituted a-alkoxy cation or (substituted) a,a-dialkoxy cations, and the CSi bond cleaves very quickly. CH bond cleavage is a much slower process, in the cases discussed occurring only as a nucleophile-assisted (in this case by cerium ammonium nitrate) process. Notice that the data refer to... 

This can be prepared by the controlled reduction of a nitrite (nitrate(lll)) or nitrate. Cautious heating of ammonium nitrate gives dinitrogen oxide by an internal oxidation-reduction process ... 

The urea produced is normally either prilled or granulated. In some countries there is a market for Hquid urea—ammonium nitrate solutions (32% N). In this case, a partial-recycle stripping process is the best and cheapest system. The unconverted NH coming from the stripped urea solution and the reactor off-gas is neutralized with nitric acid. The ammonium nitrate solution formed and the urea solution from the stripper bottom are mixed, resulting in a 32—35 wt % solution. This system drastically reduces investment costs as evaporation, finishing (priQ or granulation), and wastewater treatment are not required. 

Urea processes provide an aqueous solution containing 70—87% urea. This solution can be used directiy for nitrogen-fertilizer suspensions or solutions such as urea—ammonium nitrate solution, which has grown ia popularity recentiy (18). Urea solution can be concentrated by evaporation or crystallization for the preparation of granular compound fertilizers and other products. Concentrated urea is sohdified ia essentially pure form as prills, granules, flakes, or crystals. SoHd urea can be shipped, stored, distributed, and used mote economically than ia solution. Furthermore, ia the soHd form, urea is more stable and biuret formation less likely. 

The Bachmann process, used in the United States and in some European countries, is a simplification of a series of complex reactions. In this process, a solution of one part hexamine in 1.65 parts acetic acid, and a solution of 1.50 parts ammonium nitrate dissolved in 2.0 parts nitric acid and 5.20 parts acetic anhydride are used. The reaction may be summarized as ... 

In the commonly used Welland process, calcium cyanamide, made from calcium carbonate, is converted to cyanamide by reaction with carbon dioxide and water. Dicyandiamide is fused with ammonium nitrate to form guanidine nitrate. Dehydration with 96% sulfuric acid gives nitroguanidine which is precipitated by dilution. In the aqueous fusion process, calcium cyanamide is fused with ammonium nitrate ia the presence of some water. The calcium nitrate produced is removed by precipitation with ammonium carbonate or carbon dioxide. The filtrate contains the guanidine nitrate that is recovered by vacuum evaporation and converted to nitroguanidine. Both operations can be mn on a continuous basis (see Cyanamides). In the Marquerol and Loriette process, nitroguanidine is obtained directly ia about 90% yield from dicyandiamide by reaction with sulfuric acid to form guanidine sulfate followed by direct nitration with nitric acid (169—172). 

Fig. 18. TVA-type cogranulation process with preneutralizer, as used for production of granular mixed fertilizers. Feed materials such as ammonium sulfate, ammonium nitrate, urea, superphosphates, sulfuric acid, and potash are used.

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. 

Hard rock mining of these ore bodies requkes drilling and blasting with ammonium nitrate and dynamite. After blasting, the ore is reduced in size with a drop ball and then loaded on tmcks for transportation to the processing plant. Mica, quartz, and feldspar concentrates are separated, recovered, and sold from the hard rock ore. 

When this reaction was first discovered, a considerably higher (ca 1300°C) temperature was required than that used in the 1990s. Thus, until Haber discovered the appropriate catalyst, this process was not commercially attractive. As of this writing (ca 1995), the process suffers from the requirement for significant quantities of nonrenewable fossil fuels. Although ammonia itself is commonly used as a fertilizer in the United States, elsewhere the ammonia is often converted into soHd or Hquid fertilizers, such as urea (qv), ammonium nitrate or sulfate, and various solutions (see Ammonium COMPOUNDS). 

Ammonium nitrate is normally classified as an oxidizing agent. The pure salt is not classed as an explosive because it is difficult to detonate. Spark, flame, or friction do not cause detonation, and ammonium nitrate is relatively insensitive to shock. However, a variety of substances, such as chloride and oil, are known to sensitize the material, so manufacturers strive to eliminate such substances from their processes. 

Manufacture. Historically, ammonium nitrate was manufactured by a double decomposition method using sodium nitrate and either ammonium sulfate or ammonium chloride. Modem commercial processes, however, rely almost exclusively on the neutralization of nitric acid (qv), produced from ammonia through catalyzed oxidation, with ammonia. Manufacturers commonly use onsite ammonia although some ammonium nitrate is made from purchased ammonia. SoHd product used as fertilizer has been the predominant form produced. However, sale of ammonium nitrate as a component in urea—ammonium nitrate Hquid fertilizer has grown to where about half the ammonium nitrate produced is actually marketed as a solution. 

Three steps are essential to ammonium nitrate manufacture neutralization of nitric acid with ammonia to produce a concentrated solution evaporation to give a melt and processing by prilling or granulation to give the commercial soHd product. 

Vacuum flash processes, which operate under the atmospheric boiling point of the solution, include the Uhde—LG. Farbenindustrie process and the closely related Kestner process (22). In these, ammonia, nitric acid, and recirculated ammonium nitrate solution are fed into the neutralizer. Hot solution overflows to an intermediate tank and then to a flash evaporator kept at 18—20 kPa (0.18—0.2 atm) absolute pressure. Partial evaporation of water at this point cools and concentrates the solution, part of which is routed to evaporation. The rest is circulated to the neutralizer. 

Graining, flaking, and spraying have all been used to make soHd ammonium nitrate particles. Most plants have adopted various prilling or granulation processes. Crystallized ammonium nitrate has been produced occasionally in small quantities for use in specialty explosives. The Tennessee Valley Authority developed and operated a vacuum crystallization process (25), but the comparatively small crystals were not well received as a fertilizer. 

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