This Small Business Innovation Research Phase II project proposes a fundamentally new means for biogas/landfill gas desulfurization that produces negligible waste, allows for sulfur recovery/recycling, and provides annualized operating costs that are fraction of current practice. The proposed process consists of two synergistic components: a novel oxidative sulfur removal (OSR) catalytic reactor that produces elemental sulfur and a polishing adsorbent bed equipped with a unique in-situ bed-life sensor (BLS) that permits optimal adsorbent bed operation and cycling. The OSR catalyst has high contaminant tolerance, high selectivity to elemental sulfur, high activity, and low cost. After the OSR reaction and sulfur condensation, the outlet hydrogen sulfide concentration can be reduced to below 5 ppm at a conversion above 90%. If a polishing adsorbent bed is needed to achieve lower sulfur levels, it will be outfitted with an in-situ BLS that provides real-time adsorbent capacity monitoring to maximize adsorbent utilization. This approach is particularly effective for biogas/landfill gas streams with severe sulfur concentration variations; it reduces annualized operating costs by 50% to 65%, while reducing both solid waste generation (adsorbent consumption) and footprint by a factor of 10 - 30.
The Broader impact/commercial potential of this project, if successful, will drastically change the landscape of biogas/landfill gas utilization by improving desulfurization economics and reducing desulfurization solid waste generation. The low-cost, environmentally benign nature of this process will not only improve the desulfurization efficiency of typical biogas sources, but it will facilitate the development of small-scale and/or high-sulfur-content biogas/landfill gas sources for renewable fuel and energy applications. Moreover, the proposed approach can eliminate large sulfur adsorbent beds for almost all current biogas/landfill gas applications with high outlet sulfur thresholds (i.e. direct heating, power generation and combined heat and power), and shrink the size of desulfurization units for advanced applications with low outlet sulfur thresholds (i.e. fuel cells and GTL). Its small footprint and scalability make this technology favorable for mobile, small-scale applications. Besides biogas/landfill gas, other gas streams including natural gas, associated gas, petroleum gas, and syngas from a variety of sources can be desulfurized using this process. BTL, CTL, GTL, and renewable electric power generation will benefit from the success of this innovation. The proposed innovation directly addresses the energy independence and security of our nation (EISA 2007).
