(274d) Effect of Fuel Sulfur on Reformation of Distillate Fuels

Durability of reforming systems to permit stable, coke-free fuel cell stack operation on reformed, commonly available fuels is a key challenge for developing viable fuel cell power generation systems. Precision Combustion, Inc. (PCI) has demonstrated stable, coke-free operation of an Auto Thermal Reformer (ATR) operating on Tier II diesel for ~1100 hours with reforming efficiency >80% (ratio of LHV of reformate to fuel). A distillate fuel (e.g. Diesel/JP-8) was processed with low water usage. The test demonstrated the feasibility of long-term operation at low S:C while producing SOFC quality reformate (i.e. <10 ppm of higher hydrocarbons). In this paper, PCI will detail the performance of the reformer with various levels of sulfur in the fuel. A sulfur trap was used to remove the H₂S and carbonyl sulfides (COS) formed in the reforming reactor.

The effect of increasing fuel-sulfur on ATR performance was examined and experimental results will be discussed. Sulfur levels in the liquid fuel were increased stepwise from 4 to 500 ppm_w. At each level, the ATR was operated for 50 hours and the reformate analyzed for H₂, CO, higher HC's as well as H₂S and COS. The entire reformate was also chilled to trap condensable products. The separated aqueous and hydrocarbon layers were further analyzed for hydrocarbon content. The study clarified issues surrounding fuel-sulfur and illustrated a viable approach for reformation of higher sulfur logistical fuels (e.g. JP-8). Use of JP-8 with 400 ppm_w naturally occurring sulfur was also examined. The data was compared with that from doped fuel. Detailed analyses of the catalyst and sulfur trap were conducted after the test and will also be presented. This sulfur tolerance information provides a measure of the performance that can be expected under realistic conditions with readily available sorbents.

This information will be required in designing reformation systems for practical fuels and for establishing sulfur cleanup approaches.