(17b) Characterization of a New Glid-Arc Plasmatron On-Board Reformer for An Integrated Solid Oxide Fuel Cell Auxiliary Power Unit

The non-equilibrium Glid-Arc Plasmatron device for hydrocarbon reforming into synthesis gas was developed over a decade ago and its capabilities are well known [1-3]. Some of these capabilities include fast start time, wide dynamic range of operation (with fuel input rates spanning 0.1 to 3 g/s), small and compact physical dimensions, and low electrical power consumption. The GA-Plasmatron is capable of reforming a wide variety of hydrocarbon fuels including methane, propane, and liquid fuels such as, gasoline, diesel, bio-diesel, and JP-5. Reforming results using spray liquid Diesel fuel have shown that the Glid-Arc Plasmatron is capable of producing H2 and CO yields up to 50% and 60%, respectively. Conversion rates as high as 80% are reported in some cases and this includes some additional light hydrocarbons, such as methane, ethylene, and ethane that are produced as byproducts of the reforming process. A lack of sensitivity to sulfur is an additional benefit of using plasma-assisted reforming technologies, since sulfur is known to have adverse effects alternate reforming technologies, such as steam reforming catalysts.

In this investigation, a new GA-Plasmatron device has been developed to operate as part of an integrated system with a solid oxide fuel cell (SOFC) to create a complete plasma-assisted on-board auxiliary power unit (APU). The GA-Plasmatron APU system recycles part of the SOFC anode gas exhaust stream and recuperates heat from the exhaust at temperatures near 850C using an internal heat exchanger. By recycling heat and a portion of the SOFC exhaust, it is possible to limit the amount of external air used as an oxidant, promote endothermic steam reforming reactions, and increase the overall quality and heating value of the reformate stream. The composition of the SOFC exhaust stream was 5.7% H2, 34.5% H2O, 6.8% CO, 36.3% CO2, 16.7% N2 and was created under laboratory conditions using several mass flow controllers and a water evaporation system. Low sulfur Diesel fuel was used in initial trials and was evaporated and premixed with the preheated SOFC recycle stream just before it entered the plasma reaction chamber. The total recycle stream flow rate was varied as was the oxygen-to-carbon (O/C) ratio and the H2O/C ratio. Preliminary results show some improvement over traditional POX results and are comparable to steam reforming results obtained using traditional catalysts.

References

[1] L. Bromberg et al., Compact Plasmatron-boosted hydrogen generation for vehicular applications. Int. J. Hydrogen Energy, 24, (1999).

[2] L. Bromberg et al., Experimental investigation of plasma assisted reforming of methane I: steady state operation. PSFC/JA-05-10.

[3] A. Lutz et al., Thermodynamic analysis of hydrogen production by partial oxidation reforming. Int. J. Hydrogen Energy, 29, (2004).