(171f) Ultra Deep Desulfurization Of Transportation Fuels By Adsorption
The major drawback to the use of liquid fuels in fuel cells as a source of hydrogen is their sulfur content. EPA regulations have lowered the sulfur level in the commercial fuels to 30 ppmw S for gasoline and 15 ppmw S for diesel, this makes them ideal fuel for fuel cells in mobile applications. The effective utilization of transportation fuels in fuel cell applications requires removal of refractory sulfur species (organosulfur compounds) to below 0.1 ppm. Low temperature fuel cells (e.g. PEM) require clean (essentially pure) hydrogen feed to prevent the poisoning of the anode catalyst. Even the more robust high temperature fuel cells (e.g., solid oxide fuel cells) are poisoned with low levels of sulfur contaminants. Sulfur removal is critical for fuel cells and adsorption is a promising technology for accomplishing such low levels of sulfur. TDA has developed a sorbent-based fuel desulfurization system that can easily integrate with any fuel cell fuel processor. TDA's adsorbent removes all of the refractory organic sulfur compounds from the fuel, which is still in the liquid phase and reduces the total fuel sulfur content to sub-ppm levels (e.g., less than 0.1 ppmw). In order to increase the utilization of the sorbent and minimize the logistics burden and manpower associated with frequent replacements, the desulfurization system operates in a regenerable manner. The sorbent is regenerated by a mild temperature swing, heating the bed to 350oC to remove the adsorbed sulfur species, which are burned with air and converted to sulfur dioxide (SO2). Complete desorption of the sulfur species ensures full regeneration of the sorbent and enables its reuse after each regeneration.