Ammonium nitrate production neutralization

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. 

In pressure-neutralized processes, the neutralizer usually operates at 4-5 atm and 175°-180°C. Nitric acid is fed to the neutralizer at a usual concentration range of 50%-60%. In some cases it may be preheated with byproduct steam. Ammonia is fed to the neutralizer in gaseous form. If it is available in liquid form, it is vaporized in a heat exchanger by steam or air. If. air is used the cooled air may be used to cool the prilled or granulated ammonium nitrate product. The neutralizer may be operated at a low pH (3-4) to avoid ammonia loss, and more ammonia may be added later to adjust the pH to 7. The concentration of the solution from the neutralizer is usuaDy in the range of 80%-87% ammonium nitrate. It is evaporated further by using steam from the neutralizer to a concentration of 94%-98%. In many plants, a final evaporator-concentrator is used to increase the solution concentration to 99.5%-99.8%. 

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. 

The term manufacture also includes coincidental production of a toxic chemical (e.g., as a byproduct or impurity) as a result of the manufacture, processing, use, or treatment of other chemical substances. In the case of coincidental production of an impurity (i.e., a chemical that remains in the product that is distributed in commerce), the de minimis limitation, discussed on page 11, applies. The de minimis limitation does not apply to byproducts (e.g., a chemical that is separated from a process stream and further processed or disposed). Certain listed toxic chemicals may be manufactured as a result of wastewater treatment or other treatment processes. For example, neutralization of acid wastewater can result in the coincidental manufacture of ammonium nitrate (solution). 

There has been a trend toward the production of ammonium phosphates in powder form, Concentrated phosphoric acid is neutralized under pressure, and the heat of neutralization is used to remove the water in a spray tower. The powdered product then is collected at the bottom of the tower. Ammonium nitrate/ammonium phosphate combination products can be obtained either by neutralizing mixed nitric acid and phosphoric acid, or by the addition of ammonium phosphate to an ammonium nitrate melt. 

Oxidation of 3,4-dihydropyrimidin-2(l //)-oncs (DHPMs) with ceric ammonium nitrate (CAN) in acetic acid resulted in ethyl 2,4-dioxo-6-phenyltetrahydropyrimidin-5-carboxylates as the major product. However, DHPMs undergo a regioselective oxidation with CAN in the presence of sodium hydrogencarbonate in neutral aqueous acetone solution to yield ethyl 6-meihyl-4-aryl(alkyl)pyrimidin-2(l //)-one-5-carboxylates. A mechanism involving a nitrolic acid intermediate has been suggested.72... 

Defluorinated Phosphate Rock. There is substantial production of defluorinated phosphate rock for fertilizer use in Japan (about 100,000 mt/year). Ground, high-grade rock is mixed with small proportions of sodium carbonate or sulfate and wet-process acid. The mixture is calcined at a temperature of 1350°C in an oil-fired rotary kiln 45.0 m in length and 2.7 m in diameter. The product contains 38-42 percent P205 of which more than 90 percent is soluble in neutral ammonium nitrate solution and is an effective fertilizer on acid soils. During the production of defluorinated phosphate rock, substantially all fluorine is driven off. Sodium bifluoride (NaHF2) is recovered as a byproduct. A similar product is made in the United States, but it is mainly used for animal feed supplement. 

Direct N-nitration of secondary amines by nitric acid is possible only for weakly basic amines. The more basic amines can be nitrated under neutral conditions widi reagents such as dinitrogen pentoxide and nitronium tetrafluoroborate, but nitrosamines are significant by-products. The nitrate ester CF3CMe20N02 has been recommended as a nonacidic nitrating agent for secondary amines which avoids the problem of contamination of the products by A(-nitrosamines piperidine and pyrrolidine were nitrated in yields of 75% and 72%, respectively. Amides and imides are efficiendy N-nitrated using ammonium nitrate in trifluoroacetic anhydride. ... 

Hood.) After standing another 30 nainutes, the reddish-brown mixture is neutralized with solid ammonium nitrate and the ammonia is allowed to evaporate. The residue is extracted with water and then boiled with 200 ml. of Ibjo ethanol. The ethanolic solution is filtered hot to remove a small amount of undissolved anthracene, and the filtrate is cooled to precipitate 13.5 g. (76%) of 9,10-dihydroanthra-cene. The product melts at 104-105°. 

Case l Ammonia-Poor. In this case there is insufficient NH3 to neutralize the available sulfate. Thus the aerosol phase will be acidic. The vapor pressure of NH3 will be low, and the sulfate will tend to drive the nitrate to the gas phase. Since the NH3 partial pressure will be low, the NH3-HNO3 partial pressure product will also be low so ammonium nitrate levels will be low or zero. Sulfate may exist as bisulfate. 

The ICI process is an example of neutralization at atmospheric pressure. Nitric acid feed is preheated by part of the vapors produced in the neutralizer and is then split into two streams. Recycled, undersized product is dissolved in one stream, conditioning material in the other. The recombined streams are added to a two stage neutralizer along with ammonia and recirculated solution to give 87 to 89% ammonium nitrate feed for evaporation. The C I—Girdler-Cominco process is similar in principle the Pintsch-Bamag (23) process uses a two-stage neutralizer without recirculation. 

For the production of ammonium nitrate there are 4 absorption towers 6]/z feet square by 30 feet high, built of acid brick and filled with spiral tile, 4 coolers, 7 feet by 13 feet by 8 feet high, 4 neutralizer tanks, ii feet by 26 feet by 7 feet high 4 supply tanks ii feet diameter by lo feet... 

In the production of ammonium nitrate through the neutralization process as shown in the diagram, ammonia gas is passed into nitric acid and the solution evaporated until practically all of the water has been eliminated. The reaction involved is essentially as expressed by the equation... 

Nitration with nitric acid in the presence of strong protic acids such as H2SO4, FSO3H, and CF3SO3H or Lewis acids such as boron trifluotide requires subsequent separation of spent acid (due to water formed in the reaction) and neutralization of acid left in the product. One is generally left with a large amount of dilute acid for disposal, which is neutralized in the case of sulfuric-acid-catalyzed nitrations to a mixture of ammonium nitrate and ammonium sulfate. By using a solid acid catalyst most of these environmental problems can be eliminated. The solid acid catalyst is simply separated and recycled for subsequent use. 

In the second method, dilute mixed acid, for example 9 % water mixed acid, is used in the nitration to prepare glycerine dinitrate. After dilution by water, glycerine dinitrate is separated. This is a simple but uneconomical method. The third method was developed by DuPont based on ammonium method [10]. Ammonium is used to neutralize the dilute nitric acid solution to form recoverable ammonium nitrate solution. For glycerine dinitrate without any trinitro esters, one unit of glycerine is dissolved into 3.3 units of nitric acid with the density of 1.5 at 15 °C. The solution will be diluted by one unit of water and neutralized by calcium carbonate. The oily product will be separated out. The small amount of product in water solution will be extracted by ethers. 

In the neutralization section, the nitrogen and phosphorus elements in the NP solution are converted to the form they will have in the product. Correct operation of this section is important because the N P205 ratio of the finial product is controDed here. This control is achieved by mixing NP acid obtained from the CNTH-filters with ammonium nitrate solution and with an... 

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