Method to Imrpove the Start-Up Time of Catalyst Brick in Fuel Processor
Publication Date: 2003-Oct-13
The IP.com Prior Art Database
Computer modeling was used to determine catalyst brick dimensions required to give the quickest start-up of the system. The introduction of thermal disconnects to speed up the start-up time of the WGS catalyst system was also studied.
METHOD TO IMPROVE THE START-UP TIME OF CATALYST BRICK IN FUEL
Computer modeling was used to determine catalyst brick dimensions required to give the
quickest start-up of the system. The introduction of thermal disconnects to speed up the start-up
time of the WGS catalyst system was also studied.
Fuel cell and fuel processor designs present a number of unusual and difficult challenges
to engineers and manufacturers. Gasoline or diesel fuels are favored for many prospective
commercial applications. This is problematic, since fuel cells are far more efficient at burning
hydrogen than the hydrocarbons that comprise gasoline. Fuel processors are used to convert
hydrocarbons into hydrogen-rich fuel for a polymeric electrolyte membrane (PEM) fuel cell.
One of the major technical hurdles to PEM fuel cell commercialization is the need for a
fuel processing system that is light and small enough to fit into the confined spaces of a vehicle.
The system must also be able to perform reliably under highly variable power loads, be capable
of rapid start-up, and deliver a gas stream containing very low levels of carbon monoxide.
Carbon monoxide (CO) is a poison to all existing electro-catalysts employed in PEM fuel cells,
and its presence results in rapid degradation of performance.
The water-gas shift (WGS) reactor is a critical component of the fuel processor. Its
function is to reduce the carbon monoxide concentration to intermediate levels, which can then
be further reduced in a subsequent preferential oxidation step. However, the WGS reactor is the
single largest component in most fuel processors, accounting for one-third of the total mass,
volume, and cost. Commercial catalysts used for water-gas shift reactions are unsuitable for
transportation due to their insufficient reactivity (high weight and volume) and their tendency to
degrade under the severe conditions encountered in an automotive system. Meeting the need for
water-gas shift catalysts is critical to the commercial success of automotive PEM fuel cell
systems. Factors limiting the use of these catalysts in automobiles include the sensitivity of
today's commercial WGS catalysts to temperature fluctuations and exposure to air; size and
weight restrictions; and other operational limitations, such as the need for activation (start-up)
The potential advantages of reducing the start-up time of monolithic reactors in the Water
Gas Shift (WGS) catalyst systems are assessed. Using a monolithic reactor in steam reforming
of hydrocarbons has the advantages of low pressure drop, improved radial heat transfer, fast
response during transients, and high surface to volume ratio. The monolith reactor is typically
shaped as a honeycomb structure made from a ceramic or metallic substrate with numerous
straight parallel channels that have cross- sectional area or cell density varying from 600 to 1200
cells per sq in. Such a structure provides for a...