For engine systems in vehicular or other mobile applications where a supply of hydrogen is required, due to challenges related to on-board storage of a secondary fuel and the current absence of a hydrogen refueling infrastructure, hydrogen is preferably generated on-board using a fuel processor. The hydrogen-containing gas from the fuel processor can be used to regenerate, desulfate and/or heat engine exhaust after-treatment devices, can be used as a supplemental fuel for the engine, and/or can be used as a fuel for a secondary power source, for example, a fuel cell.
One type of fuel processor is a syngas generator (SGG) that can convert a fuel into a gas stream containing hydrogen (H2) and carbon monoxide (CO), known as syngas. Air and/or a portion of the engine exhaust stream can be used as an oxidant for the fuel conversion process. Steam and/or water can optionally be added.
The SGG can be conveniently supplied with a fuel comprising the same fuel that is used to operate the engine. Alternatively a different fuel can be used, although this would generally require a separate secondary fuel source and supply system specifically for the SGG.
The SGG converts the fuel into syngas by cracking and reforming the fuel. This is an endothermic reaction and occurs at temperatures typically in the range of 600° C.-1400° C. The reaction temperature is dependent on various things such as: the hydrocarbon fuel being used, oxidant being used, whether or not a catalyst is used, the fuel conversion efficiency, the degree of coke or soot (herein referred as “carbon”) formation and the temperature limitations of components.
The syngas can be beneficial in processes used to regenerate exhaust after-treatment devices. For other applications, for example, use as a fuel in a fuel cell, the syngas stream may require additional processing prior to use. An example of an SGG has been disclosed in U.S. patent application Ser. No. 12/112,784 filed Apr. 30, 2008 (published Nov. 6, 2008 as U.S. Patent Application Publication No. 2008/0274021, entitled “Compact Fuel Processor”), which is hereby incorporated by reference herein in its entirety.
In vehicular or other mobile applications, an on-board SGG should generally be low cost, compact, light-weight, reliable, durable, and efficiently packaged with other components of the engine system. The SGG can be subjected to numerous on/off cycles, transient conditions, fluctuating and/or intermittent demand, extreme temperatures, temperature spikes, extreme thermal gradients and thermal cycling. Some particular challenges associated with the design and manufacture of fuel processors for vehicular or other mobile applications include the following:                (a) Reducing the volume, weight and cost of an SGG.        (b) Reducing thermal stress on components located within an SGG. Such stress can result in material fatigue and premature failure of materials, components and assemblies. Examples include:                    (1) cracking of components manufactured from ceramic materials, for example, a monolith type particulate filter;            (2) cracking of a heat exchanger; and            (3) thermal degradation of a mixing tube.                        (c) Reducing damage to SGG components that can occur during assembly. For example, thermal insulation liners manufactured from a ceramic material, tend to be vulnerable to damage during assembly of the SGG.        
The present fuel processor with improved reactor design, components and materials of manufacture is effective in addressing at least some of the issues discussed above, both in engine system applications and in other fuel processor applications.