Bureau of Mines / Minerals yearbook: Metals, minerals, and fuels 1972
Year 1972, Volume 1 (1972)
Briggs, Ted C.
Nitrogen, pp. 881-896 PDF (2.1 MB)
NITROGEN 895 TECHNOLOGY A new processing method increased the polyphosphate content of nitrogen-phosphate fertilizers and increased the length of time that these materials could be stored. The method was developed and commercialized by the Tennessee Valley Authority. The new method consisted of mixing ammonia and superphosphoric acid, in nearly anhydrous conditions and at high temperature, in a pipe reactor. The initial exothermic reaction took place in the pipe at about 650° F and was complete in seconds. About 60% to 65% of the required ammonia was fed into the pipe reactor, and the remaining ammonia requirement was added in the storage tank. The final product was a liquid fertilizer which contained about 10% nitrogen and 34% P205 equivalent. One user of the new process reported that the storage life of this type of fertilizer was increased from 2 weeks to 6 months. The increased storage life was due to the high polyphosphate content produced in the new method, as the polyphosphates sequestered impurities that formerly caused sludge precipitation. An added advantage of the pipe-reactor process was that it accepted, as feedstock, a superphosphoric acid of lower initial polyphosphate content than other methods yet ended up with a higher grade product. Another advantage was that newly designed portable units could be located on farms or in farming areas. In these cases, ammonia and superphosphoric acid were to be fed directly from tank cars and thus eliminated the need for costly corrosion-resistant storage facilities.58 In most industrial caprolactam processes, each ton of caprolactam product was accompanied by 2 to 5 tons of byproduct ammonium sulfate. A new process was developed by Dutch State Mines (DSM) for making cyclohexanone oxime, a key precursor for caprolactam. The DSM process eliminated the production of ammonium sulfate with the oxime and thereby cut the byproduct ammonium sulfate from the overall process by 60%. In classical caprolactam chemistry, a sequence of reactions yield hydroxylammonium sulfate which reacts with cyclohexanone under neutralization with ammonia to form cyclohexanone oxime and about 2.7 times as much ammonium sulfate as oxime. Subsequent processing of the oxime yields additional ammonium sulfate. The D-SM process eliminates a large percentage of the ammonium sulfate by producing hydroxylamine and cyclohexanone oxime in a phosphoric acid buffered reaction. The hydroxylamine solution from the reaction contacts countercurrently with cyclohexanone in the presence of toluene, which acts as a solvent for the oxime produced. Hydrogen ions liberated by the reaction are accepted by the buffer system, and neutralization with ammonia, as in conventional oxime synthesis, is not necessary. The new process was commercialized with the completion of three plants. One of the plants was in Japan, one in Britain, and one in the United States. Combined capacity of the three plants was 210,000 tons per year of caprolactam.5° Azote et Produits Chimiques S.A. of France developed a direct route to pure monoammonium phosphate, from which ammonium polyphosphate and diammonium phosphate could be prepared for agricultural or industrial use. In the process, phosphate rock was treated with nitric acid, and the resulting solution was passed to an extractor. In the extractor, isobutyl alcohol separated out the phosphates. After purification to remove calcium salts, the solution was neutralized with ammonia. The heavy phase from the resulting mixture was cooled and filtered to yield pure ammonium phosphate. The secondary stream contained calcium and ammonium nitrate. Upon recovery of the isobutyl akohol, the calcium was removed as the carbonate and the ammonium nitrate solution was sent to a fertilizer prilling tower.6o A range of new thermoplastic materials, based on nitrile resins, was developed by Imperial Chemical Industries, Ltd., of England for the production of bottles for soft drinks and wine as well as for film and foil for packaging oxygen-sensitive food products. Bottles made from these nitrogen-containing resins were said to be ~Chemical Engineering. Pipe Reactor Improves N—P Fluid-Fertilizers. V. 79, No. 18, Aug. 21, 1972, p. 60. ' 5Damme, J., J. T. Van Goolen, and A. H. Dc Rooij. Cyclohexanone Oxime Made W,thout Byproduct (NH4)2SO4. Chem. Eng., v. 79, No. 15, July 10, 1972, pp. 54—56. "Browning, Jon E. French Processes Paraded. Chem. Eng., v. 79, No. 22, Oct. 2, 1972, p. 34.
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