Nitrogen equilibrium curve

Figure 8.26. Equilibrium curve, optimal operation line, and optimal catalyst curves in an [ammonia] versus temperature plot for two different sets of conditions. Left-hand panel 420 °C, 80 bar, and 2 1 H2 N2 right-hand panel 450 °C, 200 bar, and 3 1 H2 N2. The crossing between the optimal catalyst curve for specific nitrogen bonding energy and the...

The equilibrium curve and the optimal operation line are again plotted in an ammonia concentration versus temperature plot for each of the two sets of conditions in Fig. 8.26, but now together with the optimal catalyst curves for a few selected nitrogen bonding energies. The right-hand panel also shows the operating line, and it is now possible to estimate which catalyst should be where in the reactor. 

Curve (u) indicates that benzoic acid melts at about 122°C. Under 200 psig nitrogen pressure [curve (b) the melting-point endothermic peak remains unchanged while the boiling point is elevated to 378°C. In order to avoid sublimation and evaporation and to ensure equilibrium conditions, the samples were run in a small hermetically sealed aluminum pan which contained a small hole ( 0.002 in.) punched in the top to equalize the pressure. 

I Adsorption equilibrium data for the system oxygen/nitrogen/active carbon. Presented in a triangular diagram using mass fractions as the concentration scales i9= — 150°C, p = 1 bar). A, B State points of active carbon loaded with pure oxygen and pure nitrogen, respectively. Curve A.. E.. B Locus of the state points of active carbon loaded with gas mixture. 

Finally, in addition to the liquid nitrogen and liquid oxygen - enriched streams from the pressure to the low-pressure column, there is a third liquid air fraction (k) from the pressure to the low-pressure side. This flow is adjusted such that the operating line and the equilibrium curve, as shown in the McCabe-Thiele diagram of the low-pressure column, move closer together. This reduces the irreversibility of the rectification and increases the O2- and Ar-yield. 

So far we have dealt with weU-defined, intuitively obvious phases gas, liquid solid. But chemical engineers deal with other, less intuitive phases of considerable technical interest and economic importance, for example gases and vapors adsorbed onto solids. Figure 11.21 shows, as an example the equilibrium curve (always called an adsorption isotherm or isotherm in the adsorption literature) for nitrogen adsorbed on zeolite at a temperature well below room temperature, but far above the critical temperature of nitrogen (126.2 K). 

Figure 1. The shape of the potential curve for nitrogen in a correlation-consistent polarized double-zeta basis set is presented for the variational 2-RDM method as well as (a) single-reference coupled cluster, (b) multireference second-order perturbation theory (MRPT) and single-double configuration interaction (MRCl), and full configuration interaction (FCl) wavefunction methods. The symbol 2-RDM indicates that the potential curve was shifted by the difference between the 2-RDM and CCSD(T) energies at equilibrium.

Figure 2. Equilibrium concentrations in mole fractions of selected compounds at 500°K. and 1 atm. with composition of 40% oxygen, the indicated percentage of carbon, and the rest hydrogen. To this basic composition is added an amount of nitrogen equal to the amount of carbon. The nitrogen remains primarily as N2 but produces significant quantities of some interesting compounds. The free energy of carbon in the system equals that of graphite at the composition indicated by the arrow. At this point solid carbon would be precipitated if it could be formed there is no inflection of the curves at this point. The asphalt threshold is shown as a sharp inflection, sharpest of all for the aromatic and related heterocyclic compounds. If an atmosphere such as this were to condense, there would be about 1 molecule of glycine per droplet of condensate (6).

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