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The most common system for adsorption and ion exchange is the fixed bed process in which the adsorbent is being held in a stationary column.
The principle of SepTor Continuous Counter Current adsorption is explained below by evaluating the adsorption process in a fixed bed.
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When a feed solution (φL) is being fed to a fixed bed vessel containing a resin, an adsorption or ion exchange reaction will take place. (Animation courtesy of Xendo Manufacturing) |
During a continuous application of feed solution to the vessel, the adsorption or separation process moves as a front from the top to the bottom of the resin bed in the stationary vessel. This front that gradually moves through the bed is called the Mass Transfer Zone or active zone (MTZ).
For any set of parameters, such as the velocity of the feed flow, the particle size of the adsorbent, viscosity of the feed, temperature etc., this front or zone has a certain length, i.e. the “Mass Transfer Zone Length “ (MTZL). This MTZL usually comprises a very small part of the total length of the fixed bed vessel (the total resin bed length).
While the MTZ is gradually moving through the resin bed, it is only a small portion of the total resin bed that is active in the working zone. Thus one remaining big portion of the resin bed is exhausted resin (the adsorbent in the top part of the vessel is in equilibrium with the process fluid). The other part that is not yet exposed to the active ingredient in the feed solution is fresh resin. Both of these remaining resin portions are sitting idle, and here no activities are taking place.
Hence it the actual separation process takes place in only a small part of the columns resin volume.
When the MTZ has reached the exit of the adsorbent bed, the bed becomes saturated and needs to be washed and regenerated before it can be put in an adsorption operation again.
Since the washing and regeneration process consumes a certain amount of time, the continuous processing in a fixed bed will require a total of at least 2 to 3 beds.
| Compared to the fixed bed process, SepTor continuous counter current adsorption aims to freeze the MTZ in the adsorption and elution sections. This is executed by physically rotating the adsorbent in small columns counter current in the opposite direction of the process fluids. (Animation courtesy of Xendo Manufacturing) |
This approach ensures optimal adsorbent utilization and leads to a far more efficient, compact and economical separation process as compared to a fixed column system.
For additional information please contact info(at)septor.nl
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