Urea-ammonium nitrate fertilizer

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. 

Nitrogen solutions consist of fertilizer product combinations, eg, ammonium nitrate —ammonia, urea—ammonium nitrate—ammonia, urea—ammonium nitrate, and urea—ammonia solutions. Mixed fertilizers cover a broad range and can be loosely defined as fertilizers which contain chemically mixed nitrogen, phosphoms, and potassium (N—P—K). Examples are ammonium phosphate—potash mixtures and ammonium phosphate nitrates. 

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 major end use of ammonia is the fertilizer field for the production of urea, ammonium nitrate and ammonium phosphate, and sulfate. Anhydrous ammonia could be directly applied to the soil as a fertilizer. Urea is gaining wide acceptance as a slow-acting fertilizer. 

Cotterill [100] studied the effect of ammonium nitrate fertilizer on the electron capture or nitrogen specific gas chromatographic determination of Triazine plus other types of herbicide (Atrazine(2-chloro-4-ethylamino-6-isopropylamino, 1,3,5 triazine), Simazine (2-chloro-4.6 bis ethyl amino 1,3,5 triazine), Linuron (3,4,-chlorophenyl-l-methoxy-l-methyl urea), Metribuzin, Triallate and Phorate) residues in soil. 

Table 4.1 gives the use profile for ammonia. It can be applied directly for fertilizer or made into other nitrogen-containing compounds used for fertilizer such as urea, ammonium nitrate, ammonium phosphate, ammonium sulfate, and nitric acid. Overall approximately 80% of ammonia has an end use as fertilizer. Explosives, a second important end use, made from ammonia are ammonium nitrate and, via nitric acid, the nitroglycerin used in dynamite. Chemical intermediates include acrylonitrile and caprolactam, which eventually go into fibers. 

Oxamide, This diamide is sparingly soluble in water and insoluble 111 various organic solvents. It melts at about 350°C, with accompanying decomposition. Because of the low solubility in water, the compound is granulated and used as a slow-release nitrogen fertilizer. Conventional nitrogen ferdlizers such as ammonium sulfate, urea, ammonium nitrate, and ammonium phosphate, are soluble in water, and thus are easily lost as... 

Urea is used as a solid fertilizer, a liquid fertilizer and miscellaneous applications such as animal feed, urea, formaldehyde resins, melamine, and adhesives. Presently, the most popular nitrogen fertilizer is a urea-ammonium nitrate solution. Urea-formaldehyde resins have large use as a plywood adhesive. Melamine-formaldehyde resins are used as dinnerware and for extra-hard surfaces (Formica ). The melamine is synthesized by condensation of urea molecules. 

World demand for nitric acid will continue to be largely dependent upon demand for solid ammonium nitrate fertilizer and nitrogen fertilizer solutions that incorporate ammonium nitrate. Since the early 1980 s, urea has been displacing ammonia nitrate as a fertilizer. The resulting reduction in demand for nitric acid has been partially offset by the increased use of ammonium nitrate in explosives and by the growth in production of polyurethane foams and nylon-6,6. World nitric acid production declined by about 5% between 1987 and 1999, but it is projected to increase marginally by 2005. The declines occurred mainly in the former Soviet Union, Eastern Europe and Western Europe. Production increases occurred mainly in the United States and Africa91,104. Nitric Acid production in the United States is listed in Table 9.11. 

Production of fertilizer grade AN is concentrated mainly in Europe and North America. Apparent demand in the United States was 18% below the 1998 level of 10 billion tons. This was mainly due to weakness in the fertilizer sector. US production of urea-ammonium nitrate (UAN) solutions also dropped significantly (from 3.8 million tons in 1998 to 2.9 million tons in 2001) from 1999 to 2001. In 2001 US ammonium nitrate capacity remains well in excess of domestic requirements as the industry operated at less than 70% of nameplate US capacity. Table 10.1 summarizes US supply and demand240. 

Mention was made earlier of the significant quantity of nitrogen applied to farmlands in the form of urea-ammonium nitrate solution and aqua ammonia. Since the late 1950s, there has also been a growing practice of applying mixed fertilizers (NP and NPK) in fluid form. In fact, the growth of the fluids market paralleled bulk-blended products. In 2002/03 about 25 million mt of fluids was produced and corresponded to 7 percent of the world production. North America, and Europe are major markets for fluids. Fluids are also used in high-value crops in some countries of the Middle East and Latin America. 

The consumption of ureaform in the United States is approximately 75,000 tons/year, not including that formed in compound fertilizers from solutions. Most of the production goes into compound fertilizer for specialty uses, such as for lawns, flower gardens, and golf courses. The wholesale price of ureaform per unit of nitrogen is about three times that of urea, ammonium nitrate, or ammonium sulfate. 

In 1997 about 85% of ammonia production was consumed for fertilizers. Ammonia is either converted into solid fertilizers (urea ammonium nitrate, phosphate, sulfate) or directly applied to arable soil. 

The consumption in the USA in 1996 was 3.83 10 t N, of which 83% was used in fertilizers. Half of the consumption in fertilizers was utilized in liquid fertilizers e.g. in urea-ammonium nitrate. solutions, the rest being used in solid fertilizers. 7% of urea was utilized for animal nutrition and 6% for urea-formaldehyde resins, glues and melamine. In the period between 1984 and 1996 there was a reduction in urea capacity in Western Europe of 39% to 2.5 10 t/a N (Table 2.2-7). 

Urea-Ammonium Nitrate Solutions. An important fertilizer is the urea-ammonium nitrate solution which makes up 20% of the nitrogen fertilizer market. This fertilizer utilizes the unusually high solubility between urea and ammonium nitrate (Table 3.15), which allows for a high nitrogen content, low nitrogen cost, and ease of handling. The solution also can contain herbicides since they can be easily added to the solution. However, these solutions are corrosive, so corrosion inhibitors are added such as ammonium thiocyanate, sodium arsenite, sulfonate OA5, or trace ammonia. 

The largest and most significant use of ammonia and ammonium compounds is the agricultural application of fertilizers. Ammonia and ammonium compounds used as fertilizer represent 89% of the commercially produced ammonia, with plastics, synthetic fibers and resins, explosives, and other uses accounting for most of the remainder (Kramer 2002). Direct uses of ammonia as fertilizer can be broken down into the following categories anhydrous ammonia, 30% urea/ammonium nitrate solutions, 24% urea, 17.5% ammonium nitrate, 5% ammonium sulfate, 2% other forms, 2.5% and multiple nutrient forms, 19% (Kramer 2000). Most ammonium compounds and nitric acid, which are produced from anhydrous ammonia, are used directly in the production of fertilizers. 

The primary use of ammonium nitrate is the manufacture of fertilizers. In 2005, about 2 million metric tons (2.2 million short tons) of ammonium nitrate fertilizer was used in the United States. The compound is added to soil to provide the nitrogen that plants need to grow. It may he used by itself or in combination with another nitrogen-rich compound, urea, in a mixture known as UAN. 

Markets. Industrial use of ammonia varies according to region. For example, industrial usage represents 20% of the ammonia production in the United States and Western Europe, 10% in the USSR, 1—10% in Asia, and 5% in Latin America and North Africa (79). Fertiliser ammonia consumed domestically in most countries is converted to straight or compound fertilizers such as urea, ammonium nitrate, diammonium phosphate, and various grades of mixed fertilizers. However, almost 29% of ammonia nitrogen in the United States is consumed as direct application material. The use of nitrogen solution such as urea and ammonium nitrate (UAN) has also become popular in the United States and the USSR. 

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