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A constant pressure, mixed gas permeation testing skid was deployed at the National Carbon Capture Center to test membrane performance when continuously exposed to slipstream postcombustion flue gas. Small, laboratory scale membranes can be loaded for testing and the degree of automation allowed the skid to be run unattended for several weeks at a time. In this report, we share our experience in commissioning the skid and quantifying CO2, N2 and O2 permeances of several membranes during the first round of testing. Dense films of polydimethylsiloxane and poly(bistrifluoroethoxyphosphazene) were tested with flue gas for approximately 20 hours each. In addition, we successfully tested four thin film composite hollow fiber membranes made by a dip coating process, consisting of porous Torlon hollow fibers coated with a selective layer of poly(bistrifluoroethoxyphosphazene) or its mixed matrix with a metal organic framework SIFSIX-Cu-2i filler particles. Initial results suggest the polydimethylsiloxane showed comparable results to the literature data, but the coated hollow fiber membranes have lower CO2 permeances relative to N2 or O2 permeances compared to their performance under idealized, dry, contaminant-free mixed gas conditions. While quantification of H2O permeance was performed, we found it was affected by concentration polarization even with small membrane area and a low stage cut.

The aerosols from CO2-depleted flue gas at the National Carbon Capture Center (NCCC) Pilot Solvent Test Unit (PSTU) and Slipstream Solvent Test Unit (SSTU) were measured in real-time using a Dekati Electric Low Pressure Impactor (ELPI+™). The coal-fired flue gas is provided by Alabama Power's Gaston Power Plant Unit 5. The utilization of ELPI+™ for aerosol research in postcombustion CO2 capture is very important due to its quick response time with size classification as low as 6 nm under transient conditions observed at the NCCC. Different process changes have been quantified at the PSTU and SSTU by multiple tests using the ELPI+™. The performance of smooth and sintered collection plates during dynamic process changes has been investigated. Between separate tests, upstream at unit 5, a new baghouse was installed. The aerosols measured at SSTU, before and after the baghouse installation, are compared. PSTU measurements demonstrated sample sensitivity to transient intercooler start-up conditions and dilution gas temperatures. During the tests, the typical concentration ranged from 106 to 107 cm−3. The aerosol's counter median diameter (CMD) for the sintered plates are lower (47–60 nm) compared to the normal plates (89–130 nm). The optical images indicate that sintered plates soak up all of the collected aerosols. The aerosol number concentration showed a significant drop after the baghouse installation. These results are promising and will enable the development of process control strategies to mitigate solvent losses and reduce operation and maintenance expenses.

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