A Compact, Regenerable, Hot Syngas Desulfurizer for Coal-Based Advanced Energy Systems

摘要

Advanced energy systems require new, more demanding syngas processing schemes. Solid oxide fuel cells (SOFCs) in particular place stringent requirement on the selection of a suitable high temperature sorbent since they operate at 650 to 800°C and require that fuel gases be cleaned to < 1 ppmv total sulfur. GTI, with a long history of sorbent development and state-of-the-art platforms for advancing emerging energy systems, has teamed up with Tufts University to develop a compact, regenerable hot syngas desulfurizer for coal-based advanced energy systems. The desulfurizer is based on the use of fully regenerable sulfur sorbents (single or mixed oxysulfides of the lanthanide group of elements), which are capable of removing any amount of H_2S in the fuel gas to sub-ppm levels at temperatures as high as 800°C [M. Flytzani-Stephanopoulos, M. Sakbodin, Z. Wang, Science 312, 1508-1510 (2006)]. The unique characteristic of this class of sorbents is their capability to maintain long-term usefulness by relying on reversible adsorption, rather than bulk sulfur removal by chemical reaction, as the mechanism for desulfurization as well as regeneration of the sulfided sorbent surface for re-use. GTI's current main focus is on advancing these promising sorbents towards practical implementation as honeycomb monoliths that can be integrated into solid oxide fuel cells for regenerative desulfurization of fuel gas derived from the gasification of Illinois coal. GTI will work closely with Tufts and a commercial sorbent/catalyst vendor (such as Haldor-Tops?e A/S or Süd-Chemie) to manufacture the leading sulfur sorbents in the form of honeycomb monoliths (inert support matrix such as cordierite with the sorbent material coated as a thin layer on the channel walls). The procured materials will be characterized and their desulfurization performance and regenerability demonstrated with a gas mixture simulating an Illinois coal-derived fuel gas. A state-of-the-art Pressurized Fixed-Bed Reactor (PFBR) facility is available for this project. Parametric tests will be performed to evaluate the effects of several key process variables, including temperature (650 to 800°C), space velocity (up to 1,000,000 h~(-1)), H_2S content (up to 10,000 ppmv), COS co-adsorption (up to 750 ppmv), reactor pressure (up to 20 bar), and regeneration gas. In parallel, support studies and tests in thermogravimetric analyzers and micro-reactors will be conducted at Tufts that will contribute to the fundamental understanding and further development of these materials. Test results will be used to prepare a preliminary design package for a benchr scale reactor system capable of processing up to 1,500 standard cubic feet per hour (SCFH) of coal-derived fuel gas on a continuous basis.