ANS:D - moving bed adsorption

Moving bed adsorption is a separation process in which an adsorbent material is continuously circulated through a column while a fluid stream containing the components to be separated flows countercurrently or cocurrently to the movement of the adsorbent. As the fluid passes through the column, the target components are selectively adsorbed onto the surface of the moving adsorbent particles, allowing for separation from the bulk fluid stream. Here's how moving bed adsorption works:

1. Column Setup: The adsorption column typically consists of a cylindrical vessel filled with adsorbent particles. The adsorbent material is usually in the form of beads, pellets, or granules with high surface area and adsorption capacity.
2. Adsorbent Circulation: The adsorbent material is continuously circulated through the column using a conveyor belt, an auger, or pneumatic conveying systems. As the adsorbent moves through the column, it passes through different zones, including the adsorption zone, desorption zone, and regeneration zone.
3. Fluid Flow: The fluid stream containing the components to be separated is introduced into the column and flows countercurrently or cocurrently to the movement of the adsorbent. The fluid passes through the column and comes into contact with the moving adsorbent particles.
4. Adsorption: As the fluid passes through the column, the target components are selectively adsorbed onto the surface of the adsorbent particles. The adsorbent material captures the components based on their affinity for the adsorbent surface, allowing for separation from the bulk fluid stream.
5. Desorption and Regeneration: Once the adsorbent becomes saturated with adsorbed components, it moves into the desorption zone where the adsorbed components are desorbed from the surface of the adsorbent particles. The desorbed components can then be collected for further processing or disposal. After desorption, the adsorbent moves into the regeneration zone where it may undergo additional treatment, such as heating or purging with a stripping gas, to regenerate its adsorption capacity for subsequent cycles.
6. Continuous Operation: Moving bed adsorption operates in a continuous manner, with the adsorbent continuously circulating through the column and the fluid stream continuously flowing through the column. This allows for efficient separation and continuous production of purified products.

Moving bed adsorption is commonly used in various industries for the purification of gases, liquids, and solutions, as well as for the recovery of valuable components from waste streams. It offers advantages such as high adsorption capacity, efficient mass transfer, and continuous operation.