(455f) Integration of CFD and Experimental-Based Design and Development of Fluidized-Bed-Reactor-Based Processes

RTI International (RTI) has an active research and development (R&D) program for commercial development of catalyst/sorbents and associated fluidized-bed processes. One of RTI's most successful development projects has been a high temperature transport desulfurization process based on a regenerable ZnO-based sorbent with operating conditions of 370ºC to 550ºC and up to 1,200 psig. The key reasons for using a transport reactor for this application came from the advantages associated with the hydrodynamics, mass transfer, heat transfer, and reaction rate between the gas and solids. The success of this particular project was strongly based on the experimental R&D program completed. However, with the advances in computational fluid dynamics (CFD) modeling, CFD modeling represents a new tool for development of fluidized-bed processes. RTI is rapidly finding opportunities to integrate CFD modeling into its R&D program with the objective of accelerating process development.

Although the transport desulfurization process has been successfully demonstrated in a pilot plant system with syngas from a commercial coal gasifier, potential commercial end users of this technology would like to see a larger scale demonstration of this technology before installing the first commercial system. Test results collected during 3,000 hours of operating the pilot plant system have been used to develop a CFD model for the process. This CFD model is being used to help optimize the design of this larger demonstration unit and the full scale commercial design.

RTI is also developing the Dry Carbonate Process (DCP) to capture CO2 from power plant flue gas. In DCP, an inexpensive, dry, regenerable, solid sorbent is used to effectively capture CO2 from the flue gas in one fluidized-bed reactor and subsequently regenerated in a second fluidized-bed reactor by heating the sorbent. Design of this reactor system is particularly challenging because

? Pressure drop across the reactor must be very low

? Rapid heat transfer to the sorbent is required for both CO2 capture and regeneration

? CO2 capture reaction is exothermic

? Reaction rate for CO2 capture rapidly decreases with increasing temperature

? Regeneration reaction is endothermic

? Removal of large amount of CO2 requires rapid gas-solid mass transfer rates

To address these technical challenges, an integrated R&D effort combining an experimental test program and CFD modeling was initiated. This integrated approach