Dynamic Modeling of Ammonia Removal with Phosphoric-Acid-Treated Activated Carbon

This paper describes the initial development of a dynamic model of ammonia removal by chemisorption using Ammonasorb II (Calgon Carbon), a phosphoric-acid-treated activated carbon. The model is being developed using a commercial adsorption modeling software product (Aspen Adsorption™). An adsorption isotherm equation was derived based on aqueous solution chemistry and compared to measured ammonia capacities for Ammonasorb II under wet conditions. Predicted capacities using the measured phosphoric acid content of one carbon and parameters derived from solution chemistry show good agreement with measurements over a range of ammonia concentration. Both solution-phase and solid-phase equilibrium simulations were performed in support of the isotherm development. Using the dynamic model, a preliminary overall linear mass transfer coefficient was estimated by fitting available ammonia breakthrough data. Additional data are needed to more fully describe and validate the dynamic performance behavior. The model development is directed at sizing trace contaminant control beds for low volume applications such as spacesuits and suit loops where dynamic performance is critical.