Figure 2. Hydrogen mole fraction contour maps in the integrated
combustion-reforming reactor in which combustion chambers are in direct
thermal contact to reaction chambers for an endothermic steam-methanol
reforming reaction.
The chemical enthalpy profiles along the length of the integrated
combustion-reforming reactor are illustrated in Figure 3 in which
combustion chambers are in direct thermal contact to reaction chambers
for an endothermic steam reforming reaction. The inlet and outlet of the
combustion chamber are in fluid communication with combustion fuel and
combustion exhaust channels, respectively, and the inlet and outlet of
the reformation chamber are in fluid communication with reformation fuel
and reformation products channels, respectively. The combustion fuel
channel is disposed along the axis on a side of the combustion chamber
opposite the reformation chamber. The reformation fuel channel is
disposed along the axis on a side of the reformation chamber opposite
the combustion chamber. The reformation products channel is disposed
outside the reformation fuel channel with respect to the axis and on the
side of the reformation chamber opposite the combustion chamber, and the
combustion exhaust channel is disposed outside the reformation fuel
channel with respect to the axis and on the side of the reformation
chamber opposite the combustion chamber. The combustion catalyst
comprises a porous matrix arranged such that sufficient mixture flows
through the catalyst to maintain combustion at a temperature of at most
about 548 K. The composition in the combustion chamber is reacted to
produce sufficient heat to sustain the micro-combustion process without
energy input. The combustion of a combustion fuel in a combustion
chamber is maintained so as to transfer heat from the combustion chamber
to the reforming chamber. The temperature difference between the
combustion chamber and the reforming chamber is at most about 80 K. A
composition comprising fuel and oxidant is passed into a combustion
chamber and, simultaneous to the step of reacting steam and methanol,
the fuel and oxidant in the combustion chamber are reacted to produce
heat. The reforming chamber and the combustion chamber are separated by
a thermally conductive layer. Heat is transferred from the combustion
chamber to the reforming chamber. The average thermal transport distance
from the combustion chamber to the reforming chamber is 0.8 mm or less.
This thermal transport distance is measured from the area within a
combustion zone where combustion occurs. The above aspect of the design
is typically associated with at least one of the following
characteristics: at least 80 percent of the fuel is oxidized in the
combustion chamber and the thermal efficiency of the method is at least
8 percent; hydrogen gas production of at least 60 standard cubic
centimeters per minute hydrogen per cc of steam reformer volume; or
hydrogen gas production of at least 0.8 standard cubic centimeters per
minute hydrogen per cubic centimeter of device volume. The design
provides a method of steam reforming that includes: passing a
reformation gas through a reforming chamber, maintaining combustion of a
combustion fuel in a combustion chamber so as to transfer heat from the
combustion chamber to the reforming chamber. The reforming chamber is
configured such that the volume of the chamber increases as a function
of distance from a reaction chamber inlet; and reformation gas and
products expand as they pass through the reforming chamber. A thermally
conductive wall is disposed between the combustion chamber and the
endothermic reaction chamber. The combustion catalyst is disposed on a
side of the endothermic reaction chamber such that, during operation,
heat from a combustion reaction on the combustion catalyst is
transferred along the length of the reforming chamber. Length is the
direction of a chamber that is parallel to flow through the chamber.
Length, height and width are mutually perpendicular. Relatively short
deviations in the direction of flow, such as flow from the tube toward
and down the separator plate does not change the direction of length
which is determined by the primary direction of flow through or past a
catalyst. This aspect excludes parallel plate type configurations where
a significant component of heat transfer is perpendicular to length. In
this method, a fuel combusts on the catalyst and generates heat in the
combustion chamber.