Combustion ammonia

Process 3 Ammonia combustion at an intermediate pressure of 2-5 bar and nitrous gas absorption at 7-15 bar... 

Figure 4-3. Ammonia combustion at atmospheric pressure, absorption at gas compressor discharge pressure of 3-12 bar (Process 1, low-pressure combusion).

Figure 4-9. Ammonia combustion at air compressor discharge pressure of 2-5 bar, absorption at nitrous gas compressor discharge pressure of 7-15 bar (Process 3, dual-pressure cycle).

Noble metal loss of about 0.1 wt.-% of the honeycomb rhodium catalyst was observed during 200 h of operation similar effects are also known in commercial ammonia combustion processes [3]. This did not lead to a decrease in catalyst activity as rhodium was the only construction material. 

Nitrogen dioxide, tetroxide and monoxide detonate when they are heated with ammonia. Ammonia combusts in the presence of nitrous oxide. 

Ammonia combusts spontaneously when it is mixed with fluorine. This system has been considered as a propellant for rockets. If ammonia is in the form of an aqueous solution, the mixture detonates as soon as it is formed. 

Due to the narrow safe area in the hydrocarbon-lean zone, operation in the n-hexane-rich zone was preferred. In the latter case, however, feed compositions having high hydrocarbon concentration had to be avoided, in order to hmit the contribution of radical-chain reactions, favoured at high temperature under aerobic conditions. Therefore, operation with a diluted feed was preferred the ballast used for the reaction was helium, in order to allow evaluation of the amount of N2 produced by ammonia combustion. 

CO, while the earbon balance was between 40 and 60% for the catalyst with x=3, and lower than 40% for the catalyst with x=5. On the other hand, the selectivity to N2, formed by ammonia combustion, was much lower than that obtained with Sn/V/Nb/Sb 1/0.2/1/3. Therefore, in catalysts with the greater amount of Sn, most of N was contained in products that were not detected and that contributed to the relevant loss in carbon balance. 

Another important parameter is the selectivity in conversion of NO with respect to ammonia, being always present as a side reaction of ammonia combustion, the minimization of which is a key factor for both process economics and NO efficiency. Related to this aspect, another important parameter is the efficiency of reduction of NO when the ammonia present is less than the stoichiometric value. 

An explosion in the vent of an ammonia combustion plant was attributed to deposition of ammonium nitrite/nitrate crystals. It is considered that the very unstable nitrite acts as a sensitiser to the nitrate, and that explosion is triggered by contact with acid. 

Figure 9.5 illustrates a simplified scheme of the Mitsubishi process. The process includes the recycle of unconverted propane, and the BOC-PSA technology for rejection of N2 the latter is present in the feed, which contains oxygen-enriched air, and is also generated in the reactor by ammonia combustion. The unconverted hydrocarbon is recovered and recycled to the reactor [23fig], One Mitsubishi patent claims the differentiation of ammonia along the catalytic bed [23d], This might... 

Nitrogen(II) oxide from ammonia combustion is reacted with ammonium hydrogen carbonate solution and air ... 

The oxidation of ammonia (combustion) with (excess) atmospheric oxygen to nitrogen(II) oxide (NO) is carried out in the presence of a catalyst at 820 to 950 C either at atmospheric pressure or at pressures up to 12 bar ... 

NO-yield in ammonia combustion is between 94 and 98% depending upon temperature, pressure and flow rate... 

In M/M- and M/H-plants ammonia combustion occurs at comparatively low pressures, the high nitrogen(ll) oxide... 

Air for ammonia combustion has to be carefully prepurified to avoid deactivation of the Pt-catalyst... 

The gas emerging from the absorption column is scrubbed with acid condensate (ca. 2% nitric acid from the ammonia combustion, see Section 1.4.4.2.1), which reduces the nitrous gas concentration to < 200 ppm, and is then vented. The consumption figures for this process are summarized in the adjoining marginal notes. 

Properties Long, colorless needles. D 1.0056, mp 26.5C, bp 264.7C, flash p 266F (130C). Soluble in alcohol, chloroform, hexane, benzene, ether insoluble in liquid ammonia. Combustible. 

Nitric oxide obtained from ammonia combustion is then further oxidized to nitrogen dioxide in a less exothermic step (Eq. 11.38). 

However, an attendant cost of pressure operation throughout the process is nitric oxide yields of only 90-95% from the ammonia combustion stage compared to yields of 97-98% at atmospheric pressure. For this reason atmospheric pressure processes are still viable and continue to operate. To obtain the greater ammonia oxidation efficiencies possible at near atmospheric pressure and to retain the more efficient absorption at elevated pressures many European producers use split-pressure processes [46]. This combination is particularly valuable when ammonia costs are high. However, the ammonia saving has to be balanced against capital costs of split-pressure plants 1.5 to 2 times that of the other two alternatives because of the need for compressors constructed from exotic metals. 

Acids, alkaloids, aluminum. Iodine, oxidizers, strong bases Acids, bases, copper, magnesium perchlorate Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens Alcohols, aldehydes, ammonia, combustible materials, halocarbons, halogens, hydrocarbons, ketones, metals, organic acids... 

Acetylene, acids, alcohols, halogens, hydrazine, mercury, oxidizers, selenium, sulfur Acids, ammonia, combustible materials, fluorine, hydrocarbons, metals, organic materials, sugars... 

Contrary to pure ammonia combustion where the primary source of N2 comes from reactions of NH2 with NO, ammonia doped into methane-air flames is combusted to N2 via the N + NO reaction. 

Additives, inhibition of detonation, 186-90 Air jet surface, I69f Aliphatic flames, formation of aromatic species, 3-16 Allene, rate coefficients for cyclopentadienyl cation reactions, 59t,60t,6lt Ammonia combustion, kinetic mechanism, 93,94f... 

For instance, when the degree of ammonia decomposition is only 29.4%, the yield to acrylonitrile is 58.9% at 93.1% propane conversion, with a feed composition propane/ammonia/oxygen/inert equal to 1.0 1.2 3.0 14.8, at 420 °C and W/F 0.5 g s cc . When the same active phase is diluted in silica by means of the spraydrying procedure, the best yield to acrylonitrile achieved is 52.7% at 430 °C [29e], but the addition of a dopant (Yb, Er, Dy, Nd, etc.) increases the yield up to 55-56%. Dopants also allow the feed of a lower ammonia/propane ratio, for example, 0.8 instead of the stoichiometric 1.0, while reaching in high yield to acrylonitrile with respect to ammonia, and minimizing ammonia combustion [29h]. 

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