Figure 3. Effect of temperature on the methanol mole fraction along the
fluid centerline of the process microchannel of the microchannel
methanol steam reformer reactor.
The effect of temperature on the methanol mole fraction on the catalyst
surface is illustrated in Figure 4 along the length of the process
microchannel of the microchannel methanol steam reformer reactor. Steam
reforming reactions are typically performed at temperatures in the range
of 200 °C and 300 °C, and at pressures in the range of 50 psi and 800
psi. Therefore, a steam reformer typically includes, or is in thermal
communication with, a heating assembly. The heating assembly may be
located within the steam reformer, external the steam reformer, or both.
The heating assembly may utilize any suitable heating mechanism or
device to heat the steam reformer to a selected operating temperature.
For example, the heating assembly may include a resistance heater, a
burner or other oxidation unit that produces a heated exhaust stream,
and heat exchange with a heated fluid stream. The heating assembly
includes a fuel stream, which will tend to vary in composition and type
depending upon the mechanisms used to produce heat. For example, when
the heating assembly is a burner or otherwise creates heat by oxidation,
the stream will include a stream of a combustible fuel, such as an
alcohol or hydrocarbon, and a combustible gas, such as hydrogen gas.
When the heating assembly includes an electric resistance heater, then
the stream will include an electrical connection to an electrical power
source. In some cases, the feed stream may be delivered to the steam
reformer at an elevated temperature, and accordingly may provide at
least a portion of the required heat. When a burner or other oxidation
chamber is used, a fuel stream is consumed and a heated exhaust stream
is produced. The feed stream is vaporized prior to undergoing the
reforming reaction, and the heating assembly may be adapted to heat and
vaporize any liquid components of the feed stream.