Methane reforming results

The production of hydrogen from steam methane reforming results from the following two reversible steps ... 

Unlike the methane steam reformer, the autothermal reformer requires no external heat source and no indirect heat exchangers. This makes autothermal reformers simpler and more compact than steam reformers, resulting in lower capital cost. In an autothermal reformer, the heat generated by the POX reaction is fully utilized to drive the SR reaction. Thus, autothermal reformers typically offer higher system efficiency than POX systems, where excess heat is not easily recovered. 

Steam reformers are used industrially to produce syngas, i.e., synthetic gas formed of CO, CO2, 11-2, and/or hydrogen. In this section we present models for both top-fired and side-fired industrial steam reformers by using three different diffusion-reaction models for the catalyst pellet. The dusty gas model gives the simplest effective method to describe the intermediate region of diffusion and reaction in the reformer, where all modes of transport are significant. This model can predict the behavior of the catalyst pellet in difficult circumstances. Two simplified models (A) and (B) can also be used, as well as a kinetic model for both steam reforming and methanation. The results obtained for these models are compared with industrial results near the thermodynamic equilibrium as well as far from it. 

If mixture 1 is now considered, it can be seen that it contains 19% methane but only approximately 3% water. The methane and water are expected to react at the fuel cell anodes via the steam reforming reaction. The large excess of methane will result in almost complete depletion of the water content of the fuel gas. It is this depletion of the water content and not the hydrogen concentration that leads to an increase in the Nemst voltage and hence to improved performance of the fuel cells. 

Methane and air were fed to the reactor with an O/C ratio of 1.0 and additional steam at different S/C ratios. The reaction was performed under atmospheric pressure and a nitrogen flow was maintained on the permeate side. The results obtained with the membrane were compared with others generated with the same reactor type without a catalytic membrane in the temperature range 400-575 °C, which is low for methane reforming [51]. 

In an autothermal reforming process, lOOOkmol/h of methane at 20°C is compressed to 10 bar, mixed with 2500 kmol/h of saturated steam and reacted with pure oxygen to give 98% conversion of the methane. The resulting products are cooled and passed over a medium-temperature shift catalyst that gives an outlet composition corresponding to equilibrium at 350°C. 

The metallic nature of pardally poisoned phases was studied by benzene hydrogenation. The samples were obtained by stopping the in situ poisoning when the activity, a, in methane reforming decreased to values of 0.1 to 0.4. Some of these results are shown in Table 3. where it is evident that the metallic nature of the active phase has been significantly affected. The ratio between methane reforming rate and benzene hydrogenation rate is almost constant. 

To further illustrate typical Prox performance, results are shown from tests done with an 02/C0 ratio of 1 1 and a reactor space velocity of 440,000 h using a representative shifted reformate from an autothermal methane reformer (CO 500-10,OOOppm 02 1000-20,000ppm H20 = 32% H2 = 32% C02 = 14% ... 

M0O2, which is inactive for methane reforming similar XRD results were seen in the case of a-WC, which was converted to WO2 during the reaction. However, when the reaction was carried out at elevated pressure no deactivation was seen, and the M02C and WC catalysts were stable for the duration of the experiments (>140 hours). Furthermore, no traces of M0O2 or WO2 could be seen in the XRD patterns of the post-reaction samples, and no carbide phase changes were observed. 

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