Hydrogen mole fractions

This situation does not improve greatly with increasing temperature, because the entropy change is small. At 2000 K (1727°C) and 101.3 kPa (1 atm), the hydrogen mole fraction at equihbrium is 0.036 at 3000 K (2727°C) the hydrogen mole fraction is about 0.2 (154). 

The effect of ATR inlet temperature on the outlet reactor compositions for the selected operating conditions (S/C = 1.5, O/C = 0.45) is given in Figure 13. The maximum hydrogen yield can be observed with the selected inlet reactor temperature of 700°C. The value is hydrogen mole fraction is 0.39 for this operating condition. 

Fig. 16. Variation of critical withdrawal rate with hydrogen mole fraction and vessel diameter. Fresh boric acid coated vessels at 500 "C (after Baldwin et al. [21]). y = 0.28 x, 51 mm diam o, 36 mm a, 24 mm v, 15 mm. (By courtesy of The Faraday Society.)...

Initial (t O h and final (t-280 h) product profile are summarized in Table 1. Hydrogen mole fraction was calculated through a carbon and hydrogen... 

A measure used for the performance of the reactor is the dry hydrogen mole fraction, which is is the hydrogen mole fraction of the gas after steam is removed. The dry mole fractions are calculated as ... 

Fig. 11.8. Comparison in dry hydrogen mole fraction with pseudo-homogeneous model (----),one-particle heterogeneous model ( —) and two-particle heterogeneous model (-----) at t = 200 s, standard conditions. Reprinted with permission...

Fig. 11.9. Contour plots of the dry hydrogen mole fraction as function of time and axial position at standard conditions. Reprinted with permission from [11]. Copyright 2007 American Chemistry Society.

Fig 11.11 shows that a dry hydrogen mole fraction above 0.84 only is reached in the first minutes. After that the hydrogen content decreases, and after 50 minutes it is down to just above 70%, which is close to the thermodynamic limit for steam methane reforming without C02-acceptor at these... 

Fig. 11.10. Comparison in dry hydrogen mole fraction at different inlet superficial...

Fig. 11.11. Dry hydrogen mole fraction as a function of axial position at different...

Figure 3. Profiles of Hydrogen Mole Fractions in the Hydrogen Products on Dry and Wet Bases Along the Countercurrent Membrane Reactors for the Synthesis Gases with (1) 18.63% CO from Steam Reforming And (2) 5% CO from Autothermal Reforming...

In Sieverts law, nn is the hydrogen mole fraction in the solution, Ph the partial pressure of hydrogen on this solution and Ks the Sieverts constant. The value of this constant is dependent on the temperature as expressed in Eq. (21). 

Inlet gas velocity, uqq, cm/s Inlet hydrogen mole fraction, Yo CO/H2 inlet ratio, I Pressure, P, MPa... 

Fig. 9. Char mass fraction versus hydrogen mole fraction in polymer.

Figure 3.14 Measurements and simulations in turbulent H2/air catalytic (Pt-coated) combustion in the reactor of Fig. 3.2. Case 1 (plates la-d) = 0.24, Tin = 300 K, / eiN = 15080 Case 2 (plates 2a-d) =0.24, riN = 300 K, / eiN = 30150. Raman-measured (symbols) and -predicted (lines) transverse profiles of mean mole fractions at two axial positions (a) x=85 mm and (b) x=205 mm (H2 squares and dashed-dotted lines HjO circles and dashed lines). The thick solid lines through y—0 in (b) are the predicted transverse gradients of the mean hydrogen mole fraction at the wall, (c) LIF-measured and (d) -predicted 2D OH maps. The color bars provide predicted OH in ppmv and the vertical arrows in (c) and (d) define the location of homogeneous ignition (X g). Adapted from Appel et al. (2005) (with permission).

The hydrogen in the anode feed of reformate-based systems is typically diluted with CO2 and (in case of POX or ATR) nitrogen. As a consequence, the hydrogen mole fraction at the anode inlet is rarely higher than 0.3 (vs. 75 percent in the case of a direct hydrogen system). This decreases the ideal potential of the cells and increases the concentration-related losses. 

Figure 4. The results of a step-up in feed hydrogen mole fraction (A) snow overshoots and much longer transients than the reverse step-down experiment (B) for Catalyst I...

The hydrogen mole fraction in the pipe line, yuupipe... 

The feed mixture consists of hydrogen and methane only. This assumption is justified by the high methane concentration (82%) in natural gas. As a result, the hydrogen mole fraction in the permeate is overestimated. 

Fig. 10.3 Specific cost, optimum permeate pressure, Hj purity in the permeate and membrane area at the optimum condition as the function of recovery feed pressure, 40 bar feed hydrogen mole fraction 30%, temperature 25°C. (From [1])...

Example 1.5.3 Consider the thermal diffusion separation of a gas mixture of H2 and N2 initially present with a hydrogen mole fraction Xif in a two-bulb cell. The volumes of the two bulbs are Vi and V2. Let the uniform temperature of the two-bulb cell be changed so that the bulb of volume V] now has a temperature Ti while the other one is at T2 (Ti > T2) (Figure 1.1.3, example 111). Assuming that this is a case of close separation such that Xn Xj/ we obtain... 

Fig. 1L8 Comparison of the dry hydrogen mole fraction predicted for the SE-SMR process with the pseudo-...

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