(113f) Transport Coefficients in Commercial Beads Measured Using a Thermal Frequency Response Method

Transport coefficients are needed in the design of vacuum swing adsorption processes for air separation. In this contribution we present a novel use of the dual piston pressure swing adsorption (DP-PSA) apparatus, demonstrating its use as a thermal frequency response system.

The method relies on inserting fast response thermocouples (0.25 mm) in commercial beads (1 mm) used in the production of oxygen. With only 3 beads inserted in the DP-PSA unit, the volume modulation produces concentration fluctuations that are not affected by adsorption. Therefore the measured pressure and temperatures can be used to determine the thermal frequency response curves up to 1 Hz.

Operation with different gases allows to determine the mass transfer and heat transfer coefficients at different pressure levels. Helium can be used to determine the relevant heat transfer parameters in the range 0.1 Hz to 1 Hz, where rapid cycling induces a temperature variation in the gas phase due to compression and expansion. Nitrogen is then used with the heat transfer parameters chosen to be consistent with the values found for helium. Finally, air is used to verify the response for a mixture.