Regenerative autothermal catalytic steam reformer
A compact steam reformer produces hydrogen to power a fuel cell, such as can be used in a vehicle. The steam reformer includes a first channel, at least partly coated with a steam reforming catalyst, and a second channel, at least partly coated with a combustion catalyst, the channels being in thermal contact with each other. Heat from the combustion is used in the steam reforming reaction. In another embodiment, the gas streams feeding the reforming and combustion channels pass through a valve which reverses the gas streams periodically. The combustion channel becomes the reforming channel, and vice versa, so that carbon deposits in the former reforming channel are burned off. This arrangement enables the reforming reaction to continue indefinitely at peak efficiency.
1. A steam reformer comprising:
a) an elongated reactor having a thermally conductive partition which divides the reactor into first and second channels, both channels being coated with catalysts which are suitable for promoting both combustion and steam reforming reactions, the reactor having an inlet end and an outlet end,
b) an inlet valve connected to direct a first stream comprising fuel and air, and a second stream comprising fuel and steam, into said channels at the inlet end, wherein in a first valve position, the first stream is directed into the first channel and the second stream is directed into the second channel, and wherein in a second valve position the first stream is directed into the second channel and the second stream is directed into the first channel,
c) an outlet valve connected, at the outlet end, to direct gas streams from said first and second channels into conduits for combustion products and reformed products, wherein in a first valve position, the outlet valve directs gas from said first channel into said conduit for combustion products and directs gas from said second channel into said conduit for reformed products, and wherein in a second valve position, the outlet valve directs gas from said first channel into said conduit for reformed products and directs gas from said second channel into said conduit for combustion products, and
d) means for simultaneously switching positions of said inlet valve and said outlet valve such that both of said valves are in a same position.
2. The steam reformer of claim 1 , wherein the switching means includes a measuring device connected to measure a concentration of a component in said conduit for reformed products, the measuring device comprising means for controlling the inlet and outlet valves in response to said concentration.
3. The steam reformer of claim 2 , wherein the measuring device also comprises means for computing a time interval between valve operations, and for adjusting a flow of steam in response to said time interval.
4. The steam reformer of claim 1 , wherein the catalysts in said first and second channels are made from a same material.