Equilibrium reformate composition

Figure 3 shows the equilibrium reformate composition at different temperatures based on stationary process flow sheet simulations (ChemCAD ). The flow rate ratio of AOG to propane has been kept constant at a calculated (0/C)Ref of 1.82. Hydrocarbon conversion is almost complete for reforming temperatures above 700 C. The fraction of H2 and CO is greater than 60 Vol.-%. Soot formation is inhibited above 720 °C for the distinct operation conditions. 

Table 5.7 shows the equilibrium reformate composition at four different O/C and S/C ratios as calculated from the data provided by Seo et al. [66]. The equilibrium composition of the reformate after water addition (provided as mol water per mol of... 

Table 5.7 Equilibrium reformate composition as achieved by steam supported partial oxidation (0/C= 1.2) and autothermal reforming (O/C = 0.88) of methane gas compositions are provided after the reformer and after water addition plus water-gas shift equilibrium at 250°C.

Equilibrium gas compositions (on a dry basis) for steam reforming of hexane are given as a function of temperature, pressure, and feed steam-carbon ratio in Figure 5. In the range of variables studied, the carbon dioxide content is almost independent of temperature, pressure,... 

The reforming properties were also examined in view of thermodynamic equilibrium calculation. Figure 17.12 shows equilibrium gas composition under the condition of S/C = 0.88 at 900 °C as a function of O2/CH4 ratio. Actual O2/CH4 ratio was estimated to be 0.264 from CH4 input and oxygen permeation flux values shown in Table 17.1. The observed gas composition seems to show a good agreement with thermodynamically calculated values. A small deviation of H2 concentration seems to originate from an accuracy of the Q-mass spectrometer. 

Figure 3. Reformate composition for combined steam-/dry-reforming of propane at different equilibrium temperatures, (0/C)Ref= 1.82...

Figure 3.9 Thermodynamic equilibrium gas composition and reformer adiabatic temperature versus air ratio (X) for gasoline reforming [7] feed temperatures were 400°C for air, 200°C for steam and 20°C for the fuel left, S/C = 0 right, S/C = 0.7.

Figure 4.5 Thermodynamic equilibrium gas composition for methanol steam reforming versus S/C ratio reaction temperature, 280°C pressure, 5 bar [46].

The principle of Le Chatelier shows that when the pressure applied to a gaseous system is increased, dre equilibrium composition will chairge in order to reduce tire number of gaseous molecules. In the case of tire steam reforming of metlrane, the partial pressures of methane and steam will increase as the pressure is increased. In the water-gas reaction, where tire number of molecules is the same on both sides of the equation, the effect of increasing... 

Table 4.3 Equilibrium composition in the steam-reforming reaetion at 900 K as afunetion of pressure (molar fraetion)...

Direct thermal decomposition of methane was carried out, using a thermal plasma system which is an environmentally favorable process. For comparison, thermodynamic equilibrium compositions were calculated by software program for the steam reforming and thermal decomposition. In case of thermal decomposition, high purity of the hydrogen and solidified carbon can be achieved without any contaminant. 

Fig. 7 Thermodynamic equilibrium compositions on dry basis for the steam reforming of ethanol. All species are in gas phase. Initial concentrations of CO, CH4, CH3CHO are taken as zero in the calculation.

The product composition from the fuel reformer generally consists of 35 to 40% H2 and 6 to 10% CO balanced with H20, C02, and N2 [39], The CO is further reduced to 2 to 3% by HT WGS and then down to <0.5% CO with LT WGS. It is not possible to reduce the concentration of CO down to a few ppm with LT WGS because of equilibrium constraints. This has to be done with preferential oxidation of CO in the last step. However, owing to the development of high-temperature PEMFC... 

For the 15% of the fuel that is not utilized in the cell reaction we shall simply employ the reforming reaction. To the resulting gas composition, we will then impose the water gas shift equilibrium. 

Recent fuel processor performance is summarized in Table 4. The fuel processors were operated at atmospheric pressure, and the water and methanol feed mixture was about 60 wt % methanol. The typical composition of the reformate stream was 72— 74% hydrogen, 24—26% carbon dioxide, and 0.5—1.5% carbon monoxide on a dry gas basis. The carbon monoxide levels were significantly below equilibrium (5.4% at 350 °C), but they still require additional cleanup for use in fuel cells. The fuel processor efficiency was calculated using eq 5 and was reported to be greater than 80%. It is interesting to note that increasing the power 5-fold, from 20 to 100 W, only resulted in a 50% increase in volume and a 33% increase in mass. 

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