3D-PRINTED STRUCTURED ADSORBENTS FOR MOLECULAR SEPARATION

摘要

Most adsorbents are produced as porous, micron-sized powder materials and are thus not suitable to be directly used in adsorption processes. In order to avoid excessive pressure drop during flow of gas or liquid streams through a packed bed of adsorbent, these powders are shaped into larger particles or structured adsorbents. Extrudates, beads or pellets with a size of several millimeters are widely used in industrial processes. The most important disadvantages of such particles include the relatively large pressure drop they generate at high flow rates and the presence of mass transfer limitations as a result of slow diffusion of molecules to the core of the particles. A trade-off between these two effects limits the possibilities to optimize packed bed adsorptive separation processes; e.g. decreasing pellet size allows to reduce mass transfer limitations but this in turn leads to larger pressure drops. In practice, bed geometry (length/width of the packed bed) is adapted to limit pressure drop. Nevertheless, classical packed beds are not ideal for processes in which very short cycle times or very high gas or liquid velocities are required.