2. Methods
In the present study, a catalytic reactor employs an un-partitioned
exothermic catalytic reaction channel and multiple cooling conduits
passing through the exothermic catalytic reaction channel. An oxidation
catalyst is deposited on the exterior surfaces of the conduits within
the exothermic catalytic reaction channel. This placement of the
catalyst allows the oxidation catalyst to be backside cooled by any
fluid passing through the cooling conduits. Backside cooling means that
at each location where an oxidation catalyst is deposited on one surface
of a wall no oxidation catalyst is deposited on an adjacent or opposite
surface in contact with the cooling fluid, and a portion of the heat
generated by reaction on the oxidation catalyst is conducted through the
substrate to the adjacent or opposite surface that is in direct contact
with the cooling fluid [67, 68]. The catalytic reactor can be made
in numerous configurations with the following common elements [69,
70]. A casing forms the outer boundary, which can be of any shape. The
reactor casing can be a single fabricated component, or can consist of
two or more components joined together. Two or more conduits are placed
within the casing such that one fluid stream can traverse an
un-partitioned channel, the exothermic catalytic reaction channel,
defined by the interior surface of the casing and the exterior surfaces
of the conduits, and a number of separate fluid streams can traverse the
passages defined by the interior surfaces of the conduits, without
mixing occurring between fluid in the exothermic catalytic reaction
channel and fluid in the conduits’ interior passages. A heat transfer
relationship exists between the fluid in the exothermic catalytic
reaction channel and the fluids in the conduits’ interior passages.
The structure of the integral heat exchange is represented physically in
Figure 1 in which the catalytic reactor employs an arrangement of
catalyzed and non-catalyzed substrate passages for providing passive
cooling of the catalytic reactor. Such cooling permits the catalyst to
function with higher reaction temperatures than otherwise possible. By
applying a catalytic coating to a fraction of the walls of the parallel
passages of a combustion catalyst substrate, the uncoated passages act
to cool the common walls exposed to the reacting flow in the coated
passages. Accordingly, the present design is directed to a catalytic
reactor unit, which comprises the combination of a substrate composed of
a plurality of generally parallel passages open at their opposite ends
and exposed to a heated flow of fuel and air mixture therethrough and
selected ones of the passages being coated with a catalyst and others of
the passages being free of the catalyst so as to provide the substrate
with an arrangement of catalyzed passages in which the mixture is
catalytically reacted and non-catalyzed passages in which the mixture is
substantially not reacted but instead provides passive cooling of the
substrate. The substrate is composed of a plurality of intersecting
walls defining the generally parallel passages being aligned in rows and
columns. The walls have sections which border and define the respective
passages. Each wall section is in common with two adjacent passages and
has a pair of oppositely-facing surface regions, one of which is exposed
to one of the two adjacent passages and the other exposed to the other
of the two adjacent passages. The solid catalyst can have various forms
and compositions and can be the types used to oxidize fuels in the
presence of molecular oxygen. The catalyst can be in the form of
relatively small, solid particles of various sizes and shapes, often in
sizes below about one inch in the largest dimension, with a plurality of
such particles being arranged together to form one or more catalyst
masses or beds in the combustion zone. The catalyst is preferably of
larger form and has a skeletal structure with gas flow paths
therethrough.