Figure 7. Methanol mole fraction contour maps in the microchannel
methanol steam reformer reactor that comprises a plurality of process
and heat exchange microchannels.
The hydrogen mole fraction contour maps are illustrated in Figure 8 for
the microchannel reactor that comprises a plurality of process and heat
exchange microchannels. An interfacial layer containing one or more
active metals or alloys can be deposited on the engineered shape to
provide catalytic functionality. An intermediate interfacial layer may
be deposited between the metal substrate and the catalyst containing
interfacial layer to enhance structural integrity of thus formed outer
catalyst containing interfacial layer. An important factor that commonly
used to describe reactor reforming capacity of a tubular reactor is the
heat transfer rate. Surface heat flux is referred to as the rate of heat
energy transfer through the reactor walls for a given tube surface area,
while the volumetric heat flux is referred to the rate of heat energy
transfer through the reactor walls for a given tube interior volume.
Smaller diameter catalytic reactors can offer several advantages, for
example improving heat transfer from external heat source to reaction
mixture in the tube, enhancing tube life-time by reducing thermal
gradients, reducing metal material use, and being applicable for compact
steam reformer systems. To achieve similar production capacity as steam
methanol reformer plants, small diameter tubular reactors require a
plurality of tubing components in series and much higher space velocity.
It is challenging for direct catalyst coating on tubing wall to achieve
high methanol conversion due to limitation of catalytic surface area and
coating delamination at high operating temperature and large temperature
gradient across tube wall. The catalyst inserts, structured monoliths
can be configured with a single layer metal sheet stamped with a
plurality of peaks and grooves. Peaks on metal sheets serve as geometry
support to prevent structure deformation and create multiples of open
channels for reactant gas flow, while grooves on metal sheets provide
open windows for gas communications between each layer of the monoliths.
The present design allows for the efficient use of metal foil comprising
plurality of designed patterns on its surface, rolled into a multi-layer
spiral shaped like a compact foil cylinder and catalyzed to serve as a
catalyst insert in a high aspect ratio reactor. The designed patterns
establish open gas channels between each of the rolled layers. This
unique geometry accelerates gas mixing and the large surface area of
metal foil provides a high catalytic active surface area.