Ammonia synthesis conversion efficiency

Haldor Topspe s ammonia synthesis technology is based on the S-200 ammonia converter. This is a two-bed radial flow converter with indirect cooling between the beds. Features of the S-200 include efficient use of converter volume and low pressure drop (factors related to the use of small catalyst particles 1.5 to 3.0 mm), and high conversion per pass due to indirect cooling85. 

Assuming the feedstock is methane, which is the major component of natural gas, the theoretical feed requirement would be equivalent to one-fourth of the potential hydrogen production or 16,713 SCF CH /ST NH3(15.2 MM BTU/ST). However, the actual process consumes on the order of 22,420 SCF CHi+/ST NH3 or about 20.4 MM BTU/ST NH3 (LHV). The required quantity of feed depends on the process design criteria chosen for the methane conversion in the reforming section, the efficiency of CO conversion, degree of CO2 removal and the inerts (CHi+ + Ar) level maintained in the ammonia synthesis loop. Thus, the potential hydrogen conversion efficiency of the feedstock in the steam reforming process is about 75%. Table 3 shows where the balance of the feed is consumed or lost from the process. 

If similar processes could be developed at energy conversion efficiency levels that are comparable to the present day SMR-based NH3 synthesis plants, then it would be possible to realize a major reduction in the production costs of ammonia-borane complex. We note that a concept similar to that discussed above has already been developed for nitric acid synthesis process based on boron nitride analogous to the Haber-Bosch route for nitric acid production from NH3. Finally, recent results have shown that unusual parallel behavior exists between hydrocarbons and their corresponding B-N analogues. Thus, hydrogenation of benzene to cyclohexane may also provide a model for the reformation of borazine to other amine-boranes. 

Linde AG Ammonia Light hydrocarbons LCA process simplifies conversion of light hydrocarbons to ammonia. It consists of a modern hydrogen plant, standard nitrogen unit and high-efficiency ammonia synthesis loop 4 NA... 

The pressure of gas was 101.325 kPa. The ammonia synthesis rate was stable after passage of current for 2-6 min and this rate was at least three magnitudes higher than that of conventional catalytic reactor. The conversion of hydrogen was close to 100% which eliminated thermodynamic equilibrium limitation. The main problem of this method is that the conductivity of SCY ceramic is very poor at normal temperature. Even at 570°C, its conductivity is unsatisfied because the current density was smaller than 2 mA-cm and could not be further increased. This limited the efficiency of ammonia synthesis and theoretical research. The use of solid electrolyte with high proton conductivity at low temperature to replace the SCY ceramic may be favorable to decreasing the synthesis temperature and increasing the current density and production efficiency. 

The heat of reaction in ammonia synthesis is 46.22 kJ/mol ammonia at standard temperature and pressure or, in the units most often used in the industry, 1168 Btu/lb or 649 kcal/kg of ammonia. The efficient use of this heat, preferably for the production of high pressure steam, is of major importance in modern ammonia production. In almost all cases, some heat must be removed from the converter to ensure sufficient conversion, and this heat is used either to preheat the feed or for steam production as outlined in Sect. 6.4.3. 

The photoelectrochemical synthesis of amino acids from simple molecules has also been reported. Low efficiencies were observed in the conversion of mixtures of methane, ammonia and water to several amino acids on platinized TiOz Amino acids and peptides were reported when glucose replaced methane as the carbon source in a parallel experiment Higher quantum efficiencies (20-40%) were observed in the conversion of alpha-keto acids or alpha-hydroxy acids to the corresponding alpha-amino acids Moderate levels of enantiomeric selectivity (optical yields of about 50%) were reported when chiral starting materials were employed. Photoinduced Michael-like reactions were observed when alpha, beta unsaturated acids were used as substrates for the amino acid synthesis... 

An efficient synthesis of ( )-quebrachamine is based on the construction of a suitable precursor via ring cleavage of an a-diketone monothioketal (810) (80JCS(P1)457). This monothioketal, available from 4-ethoxycarbonylcyclohexanone ethylene ketal, was fragmented to the dithianyl half ester (811) with sodium hydride in the presence of water. Reaction of (811) with tryptamine and DCC provided an amide which was converted to the stereoisomeric lactams (812) on hydrolysis of the dithiane function. Reduction of either the a- or /3-ethyl isomer with lithium aluminum hydride followed by conversion of the derived amino alcohol to its mesylate produced the amorphous quaternary salt (813). On reduction with sodium in liquid ammonia, the isomeric salts provided ( )-quebrachamine (814 Scheme 190). 

Tetracyclization. The Heathcock group1 has described a remarkably short and efficient synthesis of the skeleton of Daphniphyllum alkaloids (2) by reaction of the dialdehyde 1 with gaseous ammonia and then dissolution in acetic acid at 70°. The yield is 77%, based on the diol precursor to 1. The azadiene a and the imine b have both been isolated and identified. The conversion of a to b is an intramolecular Diels-Alder type reaction. The tetracyclization may well be involved in the biosynthesis of alkaloids such as Daphnilactone A (3). 

Description Ammonia and C02 react at synthesis pressure of 140 bar to urea and carbamate (Fig. 1). The conversion of ammonia as well as C02 in the synthesis section is 80% resulting in an extreme low recycle flow of carbamate. Because of the high-ammonia efficiency, no pure ammonia is recycled in this process. The synthesis temperature of 185°C is low, and, consequently, corrosion in the plant is negligible. 

Description Ammonia and carbon dioxide react at 155 bar to synthesize urea and carbamate. The reactor conversion rate is very high under the N/C ratio of 3.7 with a temperature of 182-185°C. Unconverted materials in synthesis solution are efficiently separated by C02 stripping. The milder operating condition and using two-phase stainless steel prevent corrosion problems. Gas from the stripper is condensed in vertical submerged carbamate condenser. Using an HP Ejector for internal synthesis recycle, major synthesis equipment is located on the ground level. 

The NH3 can then be further converted into nitrate or nitrite or directly used in the synthesis of amino acids and other essential compounds. This reaction takes place at 0.8 atm N2 pressure and ambient temperatures in Rhizobium bacteria in nodules on the roots of legumes such as peas and beans, as well as in other independent bacteria. In contrast to these mild conditions, industrial synthesis of ammonia requires high temperatures and pressures with iron oxide catalysts, and even then yields only 15% to 20% conversion of the nitrogen to ammonia. Intensive efforts to determine the bacterial mechanism and to improve the efficiency of the industrial process have so far been only moderately successful the goal of approaching enzymatic efficiency on an industrial scale is still only a goal. 

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