4. Conclusions
The present study relates to a unique method for performing reversible
endothermic, exothermic reactions, and competing reactions. The method
comprises flowing reactants through a reaction channel in thermal
contact with a heat exchange channel, and conducting heat in support of
the reaction between the reactants and fluid flowing through the heat
exchange channel to substantially raise or lower the temperature of the
reactants as they travel through the reaction channel. Particular
emphasis is placed upon how to provide improved conversion and
selectivity in chemical reactions, provide chemical reactor systems that
are compact, and provide thermally efficient chemical reactor systems.
The major conclusions are summarized as follows:
- Microchannel technology is capable of high heat and mass transfer
coefficients between a bulk reaction fluid and the catalytic heat
exchange surface.
- Carbon monoxide output from the fuel processor is controlled over the
operating range of the processor by varying the water-methanol ratio,
the amount of air added to the reactor, and the speed of the
recirculating fan to respectively drive the reaction equilibrium,
oxidize the carbon monoxide and maintain the required heat transfer
within the processor.
- When the reaction in the reaction chamber is a reversible exothermic
reaction, heat is generated in the reaction chamber and transferred to
the heat exchange fluid to cool the reactants as they proceed through
the reaction chamber.
- Microchannel reactors offer less resistance to heat and mass transfer
thus creating the opportunity for dramatic reductions in process
hardware volume.
- While a steam reforming catalyst in the form of a powder or pellets is
appropriate in larger devices, diminished performance may result when
using the steam reforming catalyst in the form of a powder or pellets
in miniature devices and reactors.
- The steam reforming catalyst contains a suitable amount of at least
one metal oxide and cerium to contribute to high methanol conversion
properties.
- The shift reaction increases hydrogen yield while reducing carbon
monoxide, which is a poison for the proton-exchange membrane fuel cell
anode.
- Microchannel reactors offer the advantage of exceptional heat exchange
integration and can be utilized for approaching optimum temperature
trajectories for exothermic, reversible reactions.