The influence of packing density on sorption in a calcium chloride-ENG composite-Ammonia bed

The rates of adsorption and desorption in adsorption systems can vary greatly depending on the geometric properties, heat and mass transfer characteristics, and kinetics. If the sorption rates are not optimized, significant increases in the thermal mass can result from increased adsorbent and metal casing, resulting in sub-optimal performance. An experimental investigation of the performance of a calcium chloride-expanded natural graphite composite adsorbent with an ammonia adsorbate for different adsorbent packing densities is conducted. The rates of adsorption and desorption are measured and compared to determine the optimal packing density to minimize the thermal mass and maximize sorption rates. A 2D heat and mass transfer model is developed, and predictions are compared with corresponding experimental results. The experimental results are fit to available correlations in the literature for future use in adsorption system design and optimization. Of the packing densities investigated, 265 ± 13 kg ∙ m − 3 yields the fastest adsorption (at 6 bar and 30 °C) and desorption (at 6 bar and 120 °C) rates with a minimum reaction conversion time of approximately 200 s, while 694 ± 32 kg ∙ m − 3 results in the slowest rates with a minimum reaction conversion time of 750 s. The 2D heat and mass transfer model accurately predicts the uptake within 5% for all packing densities except 700 kg ∙ m − 3 . The results are used to obtain fitting parameters for a well-known model from the literature to predict adsorption and desorption rates. Recommendations for further experiments and coupled heat and mass transfer modeling are made based on the results.