Plug flow reactors reforming

The main individual reactions that take place in the reformer (e.g., reactions (1), (2) and (5)) will be considered separately from the overall autothermal reaction for two reasons. First, in ATR the reactor can be considered as two plug-flow reactors in series (1) a very fast POX reaction occurs at the top of the catalyst bed and utilizes a small portion of the bed and (2) a slow SR utilizes the remainder of the reactor bed. Therefore, an optimal ATR catalyst must have excellent SR eatalytic properties. Second, there may be situations in which liquid fuels are reformed using only these individual reactions e.g., diesel fuel may be reformed using only SR (reaction (2)) or only by POX (reaction (1)). 

This model accounts for fuel atomization and vaporization, partial oxidation, steam reforming, and anode exhaust combustion. It is asumed that the partial oxidation reaction is very fast and occurs at the top of the catalyst bed along with fuel atomization and vaporization. It is also assumed that the steam reforming initiates after all O2 is consumed in the partial oxidation reaction. Therefore, the reactor will initially be considered as two plug-flow reactors in series. Figure 2 and 3 depict the inlet conditions for the ATR model and results from the model, respectively. 

Figure 3.26 Steam reforming of CH4 [415]. Plug-flow reactor H2O/CH4M, H2O/H2=10, and 0.2 g of Ni/MgAl204 catalyst (with particle diameters in the range of 0.16-0.3 mm) space velocity=l. 7 10 (vol. total feedgas/vol. cat. bed/h). Reproduced with the permission of Elsevier.

The eatalytic activity of anode materials in steam reforming of methane (SR) was tested in a plug-flow reactor at 600-800°C. The flow rate of the reactants (7%CH4+7%H20 in He) was 101/h, contact time was 0.05 s. 

An isothermal, plug flow, fixed bed reforming pilot plant (shown in Fig. 14) was used to generate the kinetic data. The reactor was U shaped and contained roughly 70 ml of catalyst. Five sample taps were spaced along the reactor length to determine compositions over a wide range of catalyst contact times. The reactor assembly was immersed in a fluidized sand bath to maintain isothermal conditions. 

A non-isothermal plug-flow membrane reactor on both sides of the membrane has been developed and applied to the methane steam reforming reaction to produce synthesis gas at high temperatures according to [Oeitel et al., 1987]... 

Table 10.3 provides an example of the cyclic steady-state performance of the SERP concept using a 6 1 H20 + CH4 feed gas at a pressure of 11.4psig and a temperature of 490°C.S1 The process can directly produce an essentially COx-free H2 product (-94.4% H2 + 5.6% CH4), which is suitable for H2 fuel-cell use. The conversion of CH4 to H2 was -73.0%. The table also shows the equilibrium compositions of the H2 product from a conventional plug-flow reforming reactor operating under identical conditions. Both the H2 conversion and product purity were rather poor in the latter case, which demonstrates the advantage of the SERP concept. Theoretical models of the above-described SERP concept and its variations for H2 production by SMR have been developed, and theoretical parametric studies of the process have been conducted by various authors.62,63... 

Prabhu A K, Radhakrishnan R, Oyama S T (1999) Supiported nickel catalysts for carbon dioxide reforming of methane in plug flow and membrane reactors. Appl Catal A Gen, 183,241-252. 

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