A revised definition of dynamic adsorption coefficient for characterizing activated carbon instead of retention bed

Abstract

Activated carbon (AC) retention beds are widely used in nuclear facilities, removing radioactive contaminants from exhaust air. Dynamic adsorption coefficient (DAC) is the core parameter to quantify the performance. Its definition has not been unified and it is affected by the geometry of the retention bed, the presence, the flow rate, and the concentration of adsorbate. So, DAC is currently a parameter characterizing the adsorption performance of the retention bed instead of the AC. In this regard, the definition of DAC should be revised, stripping away the influence of other factors. In this study, a 1D model for the AC column, a 2D model for blank piping, and a mathematical model for retention factor is developed. All are validated with simulations and experiments based on the “pulse dynamic method”. They are used to analyze the factors affecting DAC quantitatively in detail, including the direct effect of blank piping, the indirect effect of blank piping by affecting the pulse height into the column, and the effect of krypton concentration distribution in the column. Finally, an improved definition of DAC characterizing AC instead of retention bed is given. This definition can be used as a reference for scholars who formulate relevant standards.