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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)

Page 895

 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
 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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