The Ammonia Oxidation Process

TABLE 4.3. Modem Nitric Acid Plant Design. 

Catalyst gauze supported on high-chrome steel mesh. Burners can be operated at absorber pressure in lOP/POP plants. 

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Figure 3.27 Conversion of NHj (open symbols) and selectivity to N2O (closed symbols) for the ammonia oxidation process on Pt catalyst. Micro reactors A1 (A), A2 ( ), A3 ( ), B ( ) and C ( ) were used (see Table 3.1) [98].

The arc is spread into a disc by an electromagnet. Operated in Norway, using hydroelectric power, from 1905 to 1930, when it was made obsolete by the ammonia oxidation process. In the United States it was first used in 1917. 

The oxidation of NO to NO2, which is an important step in the manufacture of nitric acid by the ammonia-oxidation process, is an unusual reaction in having an observed third-order rate constant (k o in ( rm) = kso Oc02) which decreases with increase in temperature. Show how the order and sign of temperature dependence could be accounted for by a simple mechanism which involves the formation of (NO)2 in a rapidly established equihbrium, followed by a relatively slow bimolecular reaction of (NO)2 with O2 to form NO2. 

In the DSN process, nitrogen tetroxide, N2O4 obtained from ammonia oxidation is absorbed by concentrated nitric acid in the presence of air or oxygen to yield pure nitric acid. Alternatively, N2O4 may be separated from the product gases of the ammonia oxidation process by refrigeration and then is treated with dilute nitric acid in air or oxygen. 

Devices for compressing gases are used extensively in the chemical industry (see "High Pressure Techniques"), eg, in the manufacture of nitric acid by the ammonia oxidation process Compressors for transferring gases and vapors may be divided into vacuum pumps or exhausters (when the gas is below atmospheric pressure) and into fans, blowers, boosters and ax . I compressors (when the gases are above atmospheric pressure)... 

Researchers returned to the oxidation of ammonia in air, (recorded as early as 1798) in an effort to improve production economics. In 1901 Wilhelm Ostwald had first achieved the catalytic oxidation of ammonia over a platinum catalyst. The gaseous nitrogen oxides produced could be easily cooled and dissolved in water to produce a solution of nitric acid. This achievement began the search for an economic process route. By 1908 the first commercial facility for production of nitric acid, using this new catalytic oxidation process, was commissioned near Bochum in Germany. The Haber-Bosch ammonia synthesis process came into operation in 1913, leading to the continued development and assured future of the ammonia oxidation process for the production of nitric acid. 

During World War 1, the intense demand for explosives and synthetic dyestuffs created an expansion of the nitric acid industry. Many new plants were constructed, all of which employed the ammonia oxidation process. This increased demand served as the impetus for several breakthroughs in process technology. These included ... 

Recent developments in the ammonia oxidation process have included efforts to reduce catalyst losses in the process. Platinum recovery filters have been installed at various stages in the process. Gold/palladium gauze filter pads have been added on the exit side of the catalyst bed, inside the reactor/converter units. These filters have reportedly ensured a platinum recovery of 80% (Ref. PT4). Another trend has been for the use of additional filters in the downstream units. These filters are of alumino-silicate construction. 

Qualitative flow diagram for the manufacture of nitric acid by the ammonia-oxidation process. 

Figure 2-1 presents a qualitative flow diagram for the manufacture of nitric acid by the ammonia-oxidation process. Figure 2-2 presents a quantitative flow diagram for the same process. With the information from these two figures, prepare a quantitative energy balance for the process and size the equipment in sufficient detail for a preliminary cost estimate. 

Process technology and chemical engineering as we understand it today began with the successful realization of the technical ammonia synthesis. Continuous production with high space velocities and space yields combined with the ammonia oxidation process developed immediately thereafter enabled chemical industry for the first time to compete successfully with a cheap natural bulk product, namely, sodium nitrate from Chile. The synthesis of ammonia thus became exemplary for all subsequent chemical mass production processes. 

Ch I la sa Itpetre A commercial mineral largely composed of sodium nitrate from the cdiche deposits in Chile. Before the ammonia-oxidation process for nitrates most imported Chilean saltpetre was used... 

The result of the ammonia oxidation process was determined by means of the following gas analyses ... 

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