Hydrogen to nitrogen ratio

Essential for synthesis considerations is the abiUty to determine the amount of ammonia present ia an equiUbrium mixture at various temperatures and pressures. ReHable data on equiUbrium mixtures for pressures ranging from 1,000 to 101,000 kPa (10 —1000 atm) were developed early on (6—8) and resulted ia the determination of the reaction equiUbrium constant (9). Experimental data iadicates that is dependent not only on temperature and pressure, but also upon the ratio of hydrogen and nitrogen present. Table 3 fists values for the ammonia equilibrium concentration calculated for a feed usiag a 3 1 hydrogen to nitrogen ratio and either 0 or 10% iaerts (10). 

Table 3. Equilibrium Percent of Ammonia for a Gas Containing a Hydrogen to Nitrogen Ratio of 3 1 at Various Pressures...

The gas composition is optimized with DOFs outside the CO2 scrubbing system with regard to inert composition (methane and argon) and hydrogen to nitrogen ratio since the levels of these components affect downstream (ammonia synthesis) reaction kinetics. Improved kinetics at lower inert levels are achieved at the expense of using more fuel or feedstock, since lower inerts can be achieved by firing the primary... 

Adjust Hydrogen to Nitrogen Ratio. The optimum ammonia synthesis reaction rate depends on several factors including pressure, temperature, H2-to-N2 molar ratio, and catalyst activity. Therefore the H2-to-N2 molar ratio is adjusted to suit the requirements in ammonia synthesis. This adjustment occurs before the compression step. 

Gas purification PSA with adjustment of the hydrogen to nitrogen ratio. Carbon dioxide removal (optional) in a low pressure MDEA wash on the offgas from PSA unit. Methanation upstream of the synthesis gas compressor. 

Reforming with the stoichiometric amount of process air (i.e. the amount of air required to give a hydrogen to nitrogen ratio of 3.0 at the ammonia synthesis converter inlet without dedicated installations for adjustment of the gas composition). Steam to carbon ratio about 3.3 low methane leakage (approximately 0.3% dry). 

Gas purification is by conventional shift conversion followed by a physical carbon dioxide removal (e.g. Selexol) and final purification in a cryogenic unit. The hydrogen to nitrogen ratio of the synthesis gas at the cryogenic unit inlet is 1.0-1.8. 

Final purification and adjustment of the hydrogen to nitrogen ratio in a cryogenic unit. 

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