Air Products, in collaboration with the University of North Dakota Energy and Environmental Research Center (EERC), is testing its Sour Pressure Swing Adsorption (Sour PSA) process that separates syngas into an hydrogen-rich stream and second stream comprising of sulfur compounds(primarily hydrogen sulfide)carbon dioxide (CO2), and other impurities. The adsorbent technology testing that has been performed to date utilized syngas streams derived from higher rank coals and petcoke. Using data from experiments based on petcoke-derived syngas, replacing the conventional acid gas removal and separation process (e.g., Rectisol® or Selexol™) with Sour PSA is estimated to reduce the capital cost for CO2 capture by 20 percent. For this scoping study, Air Products will conduct experiments using a two-bed Sour PSA unit with syngas produced from the gasification of powder river basin (PRB) coal in EERC's fluidized bed gasifier. Testing syngas streams from lower rank coals is of critical importance because they contain tars, ash, and a variety of impurities that could reduce the adsorbent lifetime. Measurements of adsorbent characterization and PSA unit performance over time will be collected and analyzed. In addition to pressure swing adsorption, the adsorbent system will be operated in thermal swing adsorption (TSA) mode. The results from PSA and TSA testing will help determine if a PSA alone, or a combination of TSA and PSA, will provide a more optimized operation. The results of this testing will be used to generate a high-level pilot process design, and to prepare a techno-economic assessment to evaluate the applicability of the technology to process low rank coals, which make up such a large amount of the total domestic coal supply.
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