Hydrodynamics of bubbling fluidized bed for adsorption of CO2 with KOH/K2CO3

The aim of this study is to assess the performance of carbon dioxide (CO2) capture in a bubbling fluidized bed using a proper adsorbent. A mixture of potassium hydroxide (KOH) and potassium carbonate (K2CO3) adsorbents was used as bed materials, which provide proper kinetic and fluidization behaviours. The adsorbents consisted of two different mean particle sizes: size 1 is composed of K2CO3 with mean particle size of 335 mu m and KOH with mean particle size of 197 mu m; whereas, size 2 contained the K2CO3 with mean particle size of 605 mu m and KOH with mean particle size of 197 mu m. The weight fraction of KOH in both sizes was 0.3 g/g (30 mass%). The pressure fluctuations of the bed were measured and characterized in a time domain. The effects of several hydrodynamic parameters (i.e., superficial gas velocity, aspect ratio of bed, and particle size distribution of the adsorbent mixture) on CO2 adsorption were investigated. The results showed that the larger bubbles caused an improvement in solid mixing in the bed and consequently enhanced the CO2 capture capacity. Fluidization of the adsorbents mixture with narrower distribution (size 1) led to the formation of larger bubbles and an improvement of mixing in the bed. Therefore, size 1 adsorbent exhibited a higher CO2 capture capacity compared to a wider distribution of (size 2) adsorbent. Furthermore, the bubble size is increased with an increase in the aspect ratio of the bed leading to a better mixing in the bed.