Trim Bed for adsorption of heavy aromatics

[1946ladjal]

Hi evreybody;
I am newly involved in Linear Alkyl Benzene project for designing a new petrochemical unit,However, based on simplified Process Flow Diagram of Removal Heavy aromatics adsorption beds unit, there is a trim bed adsorption between the 02 main adsorption beds A & B. This trim bed is used only, if I am not wrong, during displacment phase for regeneration of the Saturated one A or B.
Please could anyone tell me what is exactly the purpose of this trim bed., Can we remove it and make main absorbers bigger?

Please find attached the simplied drawing

 

[georgeverghese]

Suspect the trim adsorber is used during the adsorption step. So it may be a 2 stage adsorption, with some trim benzene injected into the product from the main adsorber before trim adsorption.
The trim adsorber may (or may not be) be filled with an adsorbent which has higher affinity for both easy to adsorb and more difficult to adsorb heavy aromatics or di olefins that may have have leaked past the upstream di olefins to mono olefins conversion DEFINE unit. So the easy to adsorb components are removed in the main adsorber and the more difficult to adsorb components separated in the trim unit.
If it was all done in a single adsorber, the easy to adsorb components would fully saturate the adsorbent, leaving the more difficult to adsorb components still in the product stream.
Could the trim benzene injection be for enabling alkylation of the benzene with unremoved di olefins so that it gets removed in this trim adsorber ? So there may be 2 beds in this trim adsorber, the upstream one for alkylation of residual di olefins and a downstream bed for alkyl aromatics removal ?

 

[1946ladjal]

Thanks Georgeverghese for this explaination