Regeneration cycle, cracking

Check the softener for adequate salt and run it through a regeneration cycle to ensure that the correct level of brine is drawn into the resin bed. The resin may lack adequate capacity due to fouling or cracking, or it may have been partially lost down the drain. Alternatively, the softener may be undersized. 

Pilot plant tests were made in a cyclic fixed fluidized bed unit over a range of conditions. Catalyst-to-oil ratio was varied from 3 to 5 and WHSV was varied from 32 to 53, inversely. The reactor temperature was held at 975°F for the cracking and steam stripping cycles, and at 1200°F for the regeneration cycles. After regeneration, carbon on catalyst was effectively zero. 

Next, reactors may be designed to accommodate rapid deactivation-regeneration cycles. The best example is catalytic cracking where coke deposition is so fast that decay takes only minutes. Since, in this case, the feed is the precursor to coke, treatment or guard chambers are not practical. The only solution is to use fluidized beds, which provide reaction and regeneration in a continuous cycle. Other cases are slurry and moving bed reactors, w hen deactivation is not so rapid. 

The catalyst is employed in bead, pellet, or microspherical form and can be used as a fixed bed, moving bed, or fluid bed. The fixed-bed process was the first process used commercially and employs a static bed of catalyst in several reactors, which allows a continuous flow of feedstock to be maintained. The cycle of operations consists of (/) the flow of feedstock through the catalyst bed (2) the discontinuance of feedstock flow and removal of coke from the catalyst by burning and (J) the insertion of the reactor back on-stream. The moving-bed process uses a reaction vessel, in which cracking takes place, and a kiln, in which the spent catalyst is regenerated and catalyst movement between the vessels is provided by various means. 

The H2S comes out with the reactor products, goes through the product-recovery system of the FCCU, and eventually goes to a Claus plant for sulfur recovery. The metal oxide adsorbent recirculates with the spent cracking catalyst back to the regenerator for the next SO adsorption cycle. 

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