CH4 CH4 d

where AF£H4 is the total amount of consumed methane in the differential reactor element, AFCHj is the amount of methane reacted at the catalyst surface by mass transport, and 9 is a corrective factor which accounts for the reaction rate (q>=0 only mass transfer, <p>0 faster reaction, <p=oo the reactant is completely consumed in the differential element of reactor).

A more sophisticated version of the model has also been developed and compared with the approximate one. On this purpose, without changing its original philosophy, the model has been generalized considering the different effects associated with the heat transfer in packed beds, and expressing the effective thermal conductivity as a function of these effects [1,9]. In particular, some more realistic assumptions have been introduced in the complete model, as specified in the following:

• evaluation of mass transfer coefficient for each component, instead of constant value used before;

• both temperature and concentration variations have been calculated in the radial as well as in the longitudinal direction;

• thermal dispersion and irradiation effects have been considered.

Results and discussion

The results obtained by the model are represented in Figs.1-3. In particular, Fig.l shows the behaviour of the concentration and temperature profiles along the longitudinal direction of the reactor relatively to the case when the radial effects are neglected (approximate model). Fig.2 shows the profiles obtained by the model when the radial effects are taken into account (complete model). At last, in Fig.3 the longitudinal temperature profiles obtained by the two versions of the model are compared with experimental results.

Reactor dimensionless length

■*■ CH4 + H20

0 0

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