Numerical study of flow maldistribution and depressurization strategies in a small-scale axial adsorber

Flow maldistribution and local high velocity in an axial adsorber is numerically studied to investigate the potential occurrence of sorbent pulverization and uneven utility. A considerable maldistribution induced by the entrance effect and local high velocity caused by rapid gas discharge during depressurization is observed. Three types of gas distributors and different depressurization strategies are then proposed and studied to determine their capabilities to create uniform velocity profiles. Results show that locating the predistributor in the dead zone is critical to flow distribution. The maldistribution factor (Mf) can decrease to a minimum of 0.055 when a perforated inlet plenum is used with a conventional distributor. In addition, the internal ring can effectively reduce wall effects. Moreover, both gas expansion and desorption have a significant influence on the evolution of local velocity during depressurization. In this step, local high velocity can possibly exceed incipient fluidization velocity and cause attrition and pulverization of the sorbent. To a certain extent, employing methods to control the depressurization rate is necessary. Applying linear depressurization (\(p = 101,325 - p_{AD} /t_{DP} \times t + p_{AD}\)) or downward convex conic depressurization (\(p = p_{AD} - \sqrt {\left( {p_{AD} - 101,325} \right)^{2} /t_{DP} \times t}\)) can reduce local high velocity, and thus, improve flow conditions.